Characterized raw Leucaena leucocephala pod (LLP) as biosorbent produced high adsorption of Pb(II) ions in a synthetic aqueous solution

doi:10.21203/rs.3.rs-1495714/v1

Download PDF

Article

Characterized raw Leucaena leucocephala pod (LLP) as biosorbent produced high adsorption of Pb(II) ions in a synthetic aqueous solution

https://doi.org/10.21203/rs.3.rs-1495714/v1

This work is licensed under a CC BY 4.0 License

Version 1

posted

You are reading this latest preprint version

Biosorbent from a plant-based material with characterized properties is important to remove heavy metals hence reduce the impact on humans and aquatic life. This study proposes to remove Pb(II) in a synthetic aqueous solution using characterized plant-based raw Leucaena leucocephala pod (LLP) via adsorption experiment. The effects of pH synthetic aqueous solution and raw LLP dosage on Pb(II) adsorption were investigated. The characteristics of raw LLP before and after adsorption of Pb (II) were also studied. It was found that the highest adsorption capacity of Pb(II) was obtained at pH 5 of synthetic solution with 1.1 mg/g adsorption capacity. Meanwhile, the optimum dosage of raw LLP was 40 g/L at 30 min retention time, resulting in 93% of Pb(II) removal. Optimum removal of Pb(II) using raw LLP in this study was obtained under low retention time of adsorption process compared to other studies using others plant based biosorbent but comparable in terms of heavy metal removal. Raw LLP can be effectively used directly without modification as a biosorbent in removing Pb(II) in industrial waste, hence provides an alternative method for pollutants removal which is safe for the environment and abundantly available.

Leucaena leucocephala pod

biosorption

Pb(II)

characterization

heavy metal removal

Rapid industrialization has affected the world with severe environmental problems especially water pollution from industries, and this has become a global issue of concern. One of the pollutants in wastewater is heavy metals, and they have become a serious environmental problem due to their toxicity and non-biodegradability, which cause health issues. Heavy metal contamination includes toxic arsenic, mercury, nickel, and lead, and it is caused by a variety of 63 industries ¹^,². Heavy metals have a wide range of high atomic weight, particularly those transition metals that are toxic and cannot be processed by living organisms, such as lead (Pb). As, Ag, Sb, Cd, Hg, Pb, are U are among the heavy metals classified as highly toxic even if they are present in low concentrations of about 1.0–10 µg/L ³. Among these highly toxic heavy metals, Pb is a major source found in wastewater, coming from batteries, pigments, paints, petrol, cables, steel, alloys, and plastic industries⁴. The recommended limit for lead in drinking water by the World Health Organization (WHO) is 0.01 mg/L ⁵. When this limit is exceeded in the human system , it can affect almost all organs in the body⁶^,⁷. In Malaysia, high concentration of dissolved Pb was recorded at 32.5 µg/L in tap water at Bandar Sunway, Selangor, Malaysia adjacent to Langat River Basin due to corrosion in the plumbing system in the old building ⁸. This Pb concentration exceeded the maximum limit of the drinking water quality standard of 10 µg/L set by Ministry of Health (MOH) of Malaysia and WHO.

Several physical and chemical processes have been adopted to remove various Pb(II) from wastewaters including filtration, chemical precipitation, coagulation, solvent extraction, ion exchange, adsorption, membrane process, and bioremediation ⁹^,¹⁰. However, these conventional technologies are either expensive, difficult to implement, or inefficient at low concentration of heavy metals (under 100 ppm)¹¹^,¹². Compared to other processes, biosorption can be applied to treat larger volumes of wastewaters due to its high efficiency, ease of operation, availability of a wide range of potential biosorbents, abundant, low-cost biosorbents and natural biopolymers ¹³.

The biosorption process has been emphasized as a promising treatment method for removing toxic metals from liquid effluents because it employs plant-based materials with metal sequestering properties, enhancing the reduction of toxic metal ion concentrations from mg/L to µg/L ¹⁴. A wide range of naturally available materials can be selected as biosorbents to bind and eliminate pollutants from industrial wastewater. Biosorbents can be made from any type of biomass, including plants, animals, microorganisms, and waste from agriculture, factories, and by-products from various industries ¹⁵. The selection of biosorbent material determines its sorption capability¹⁶.

Plant-based or natural polymers are potential biosorbents for the removal of Pb(II). The main advantages of plant-based biosorbents are high porosity, large specific surface area, and easy physical adsorption of heavy metal ions¹⁷. The sorption of Pb(II) by a biosorbent might be attributed to the presence of polar functional groups of lignin, proteins, carbohydrates, and phenolic compounds that have carboxyl, hydroxyl, sulfate, phosphate, and amino groups. These groups have the ability to bind heavy metals by coordination to form complexes with the metal ions in solution ¹⁸. Plant-based biosorbents are abundant and have been proved to be good low-cost biosorbents due to their easy conversion to a value-added product. Moreover, the major advantages of biosorption over conventional separation methods include low cost, high efficiency, minimization of chemical and or/biological sludge, regeneration of biosorbent, no additional nutrient requirement, and possibility of metal recovery ¹⁹. The cost advantage of biosorption technology would guarantee the biosorbents a strong penetration into the market of heavy-metal pollution industries.

Several researchers have made significant contributions in this area, utilizing a number of agro-based materials such as walnut shells ²⁰ , potato peel ²¹, rice straw ²², sesame ²³, and tea waste ²⁴. However, new economical, easily available, and highly effective biosorbents are still needed ²⁵. Morosanu et al. ²⁶ showed that rapeseed waste was able to remove 94.04% Pb(II) at pH 5, with a dosage of 10 g/L, at 60 minutes, and concentration of 50 mg/L. Meanwhile, Taşar et al.²⁷ discovered that peanut shells could remove 63 % of 50 mg/L of Pb(II) in synthetic aqueous solution at pH 5.5, 180 minutes and with dosage of 2 g/L of biosorbent . This studies have discovered that the removal has a long retention time with a low % of Pb (II) removal. This is due to the presence of the functional groups on the surface of biomaterials which cannot guarantee efficient removal of heavy metal ions, because the biosorption process is affected by various factors such as the number of active sites, their accessibility, their chemical state, and their affinity for the targeted metal. Therefore, biosorption efficiency largely depends on the biomass type ²⁸. This is because the functional groups of the lignocellulosic materials are similar, only differing in quantity. However, although their properties are known, differences in the experimental conditions, materials, and methodologies applied in research studies inhibit comparisons in terms of efficiency and complicate consequent decisions regarding the most appropriate plant-based materials for biosorbents.

Leucaena leucocephala (Lam.) is a perennial thornless, tropical plant, with a height of around 8 m. It is in the Fabaceae family and the Mimosoideae subfamily.. Since the trees easily grow in all seasons throughout a year, they are abundantly available in Malaysia, albeit having no commercial use. Therefore, it has potential to be a cheap and readily available material for a biosorbent. A previous study has shown that modified LLP is a capable sorbent for the sorption of Cu(II) ions from aqueous solution ²⁹. The maximum removal percentage of Cu(II) by using modified LLP was obtained at pH 4.94, sorbent dosage of 1.99 g/L, agitation speed of 119.59 rpm, and contact time of 59.55 min. Biosorbents from the family Fabaceae such as flamboyant pod ³⁰ and Sophora japonica pods ³¹ have been tested for removal of Pb(II). However, the time required for Pb(II) removal was more than 1 h and the concentration of Pb(II) was less than 20 mg/L. Therefore, previous research typically only investigated the use of modified LLP to remove Cu(II) from water and wastewater. Furthermore, the available data is limited especially detailed characterization of raw LLP and the effect of pH and dosage on Pb(II) removal. It is therefore, further investigation is needed to explore the characteristic of raw LLP as biosorbent at high Pb(II) concentration to find the minimum time for removal. Thus, the purpose of this study is to characterize the physical and chemical properties of raw Leucaena leucocephala pods and determine the effects of pH synthetic aqueous solution and raw LLP dosage on Pb(II) adsorption in a synthetic aqueous solutions. Proximate and ultimate analysis, porosity analysis, thermogravimetric analysis (TG), Boehm titration, zeta potential, Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM) were also employed to investigate the potential of raw LL pods as biosorbent.

Characterization of raw LLP. Ultimate and proximate analysis. Table 1 shows the results for ultimate and proximate analysis of raw LLP and its comparison with other studies. Elemental analysis results show that raw LLP is mainly composed of carbon (47.6%) and oxygen (38.61%). The hydrogen and nitrogen contents were 6.097% and 2.586% respectively, with no sulfur. The result is similar to those reported by Šoštarić et al. ²⁸, Nuithitikul et al. ³², and Martín-Lara et al.³⁴, who investigated the element composition of raw apricot shells, cashew nut shells, and raw olive stone respectively, which showed high oxygen content. Raw LLP also showed higher ash content as it contains more lignin content. This was confirmed by Sonia and Priya Dasan ³⁵, who found similar data for this finding. This is probably due to sample variety and different biomass sources, reflecting the difference in soil contamination. The proximate analysis in this study in agreement with Šoštarić et al. ²⁸ which found the bulk density of raw LLP is 0.33 g/ml.

Table 1

The ultimate and proximate analysis of raw LLP and its comparison with other studies
Raw material	Ultimate, %					Proximate, %			References
Raw material	C	H	N	O	S	Ash	Bulk density, g/ml	moisture
Raw LLP	47.208	6.097	2.586	38.61	ND	5.5	0.33	2.3	This study
Raw olive stone	52.34	7.11	0.03	40.47	< 0.01	0.37	-	5.43	Martín-Lara et al. (2013)
Cashew nut shells	45.93	5.75	0.62	47.57	ND	-	-	-	(Nuithitikul et al., 2020)
Apricot shells	47.6	6.24	0.12	46.03	ND	1.02	1.15	7.30	(Šoštarić et al., 2018)
Persimmon leaf	57.8	5.4	0.83	35.94	0.03	3.23	-	1.4	(Lee and Choi, 2018)

Biochemical Analysis. The percentages of hemicellulose, lignin, and cellulose present in the raw LLP were 17.677%, 31.2%, and 18.1545%, respectively as shown in Table 2. These results show that the lignocellulosic component of raw LLP mainly consists of lignin, followed by cellulose and hemicellulose. These results agree well with existing studies ³⁶. Arshad and Imran ³⁷ reported that biosorbent consists of lignin, cellulose, and hemicellulose, which make them effective removal metal cation. However, the percentage of each component varies depending on the material source of the biosorbent, plant genetics, the environment where the plant was grown, and processing conditions of the plant ³⁸.

Table 2

Percentual values of the biomass content in the raw LLP and comparison with other studies
Adsorbent	Property					Reference
Adsorbent	Holocellulose,%	Cellulose,%	Hemicellulose,%	Lignin,%	extractive,%	Reference
Raw LLP	35.8313	18.1545	17.6768	31.2	2.5	This study
Flamboyant pods	-	14.7	32.9	48.5	0.4	(di Bitonto et al., 2021)
Flamboyant pods	-	34	35	16.5	11.75	(Oluwasina et al., 2020)
Bauhinia pods	-	37.5	33.5	17.5	10.3	(Oluwasina et al., 2020)
Native apricot shells	74.46	55.23	19.23	22.72	2.56	(Šoštarić et al., 2018)

Fourier transform infrared spectroscopy (FTIR). Figure 2 shows FTIR analysis of (a) raw LLP and (b) Pb loaded with LLP. Table 3 shows peak positions in the FTIR spectrums of raw LLP and Pb loaded with raw LLP, which follows the range given by Pavia et al. ³⁹. Figure 2a shows the spectrum of raw LLP. The broad and intense peak around 3200–3500 cm^− 1 was assigned to the stretching of O–H group, carboxylic acid, and amino groups, in which overlapping bands of O–H and N–H stretching vibrations were observed. Vibrational bands of –OH groups in hydrogen bonded and chemisorbed water, as well as inter and intramolecular hydrogen bonding. This O–H bonding contains polymeric compounds (macromolecular associations), such as alcohols, phenols, and carboxylic acids, which exist in cellulose and lignin. Cellulose connects with hemicellulose or lignin molecules mainly through hydrogen bonds, while the connections between hemicellulose and lignin include both hydrogen and covalent bonds⁴⁰. The absorption band at 2913.95 cm^− 1 could be assigned to asymmetric vibration of C–H stretching due to methyl and methylene groups in the polymers in the biosorbent such as lignin, cellulose, and hemicellulose ⁴¹. The stretching vibration band at 2850 cm^− 1 is due to C–H stretching of aldehyde hydrogen (C–H–O). The stretching vibration band at 1718 cm^− 1 is due to carbonyl group (C = O) stretching from carboxylic acid functional group ⁴². The small peak at 1718 cm^− 1 appears in the spectrum of raw LLP. This peak is due to the stretching vibration of C = O bond (carbonyl group) due to non-ionic carboxyl groups (–COOH, –COOCH₃), and may be assigned to carboxylic acids and ketones. The band at 1607.65 cm^− 1 is attributed to carbonyl groups of ketone which is describe C = O stretching. The peaks at 1315.45 cm^− 1 are due to C–O stretching of carboxylic group. Besides that, the band at 1515.13 cm^− 1 corresponds to aromatic ring for the symmetrical C = C vibration in the lignin component. The observations are in line with the results reported by Md Salim et al. ⁴³ and Ibrahim et al. ⁴⁴. The peaks from 1000 to 1300 cm^− 1 indicate C–O stretching of these functional groups with single oxygen bonds of carboxylic acids, ketone, and alcohols. The sharp peak appearing at 1033.46 cm^− 1 is due to C–OH stretching in cellulose, hemicellulose, and lignin ⁴⁵. The deformation vibrations of the C–H bond in the benzene rings give absorption bands in the 840–730 cm^− 1 range.

Table 3

Peak position in the FTIR spectrums of LLP and Pb loaded with raw LLP
Transmittance peak wave number indicate by the range of samples of wavenumber (cm-1)		Raw LLP	Pb loaded with raw LLP
3400 − 3200	Broad band indicates the carboxylic acid	3310.5	3295
3400 − 3300	Broad band OH groups of alcohol	3310.5	3295
3500 − 3300	N-H stretching for primary amines	3310.5	3295
3000 − 2840	C-H stretching	2913.93	2918.03
2860 − 2700	medium bands of C-H stretching in aldehyde	2852.45	-
1730 − 1700	carbonyl group (C = O) stretch from carboxylic acid	1718	-
1720 − 1708	Aliphatic ketone	1718	-
1670 − 1600	Conjugation of two aromatics rings for C = O.	1607.65	1603.57
1650 − 1580	N-H bending for primary and secondary amines	1607.65	1603.57
1500 − 1400	Deformation C-C bond	1438.05	-
1515	Aromatic ring for the symmetrical C = C vibration	1513.13	-
1400 − 1350	Aldehyde C-H bending vibration	1374.71	1374.71
1400 − 1350	Aldehyde C-H bending vibration	1364.49	1362.45
1300 − 1000	C = O stretching vibration of ether groups (R-O-R)	1096.8	1096.8
	Bending vibration of C-CO-C group of ketone
1320 − 1210	C-O stretching of carboxylic group	1315.45	-
1200 − 1100	Aliphatic ketone
1050 − 1017	Primary alcohol	1033.46	1027.71
840 − 730	The deformation vibrations of the C–H bond	827.07	-
730 − 550	C-Cl bending vibrations	665.64 590.03 510.34	-

Figure 2b for Pb(II)-adsorbed LLP shows that some peaks decreased. The shifts may be attributed to the changes due to bonding of functional group to Pb(II). The broad peaks detected at 1570–1700 cm^− 1 are weaker because of the reduction of the carboxylic acid, ketone, and C–C bond. FTIR spectra of metal Pb(II)-adsorbed LLP show that the peaks expected at 3310.5, 2913.93, 1607.65, 1374.71, 1364.49, and 1033.46 cm^− 1 shifted, respectively, to 3295.16, 2918.03, 1603.65, 1374.71, 1362.45 and 1091. Peaks 2852.45, 1718, 1515.70, 1438.05, 1315.45, 827, and 1163 cm^− 1 disappeared after adsorption. A decrease in transmittance, small deflection, and disappearance of band frequency indicate that there may be interactions due to the exchange of hydrogen ions with Pb(II) and functional groups ^46,47. It is well indicated from the FTIR spectrum of raw LLP that carboxyl and hydroxyl groups were present in abundance. In biopolymers, these groups may function as proton donors; hence, deprotonated hydroxyl and carboxyl groups may be involved in adsorption of Pb(II).

Surface morphology.The SEM micrographs (1500× and 500× magnification) before Pb(II) adsorption are shown in Fig. 3a and b and the micrographs (5000× and 2000× magnification) after Pb(II) adsorption are shown in Fig. 3c and d. Morphological examination by SEM analysis for raw LLP revealed that it is soft-flat shaped with rough pits (Fig. 3a). The cross-section of raw LLP has some distorted pores and the surface of raw LLP has an irregular surface and a fixed shape and size. It also does not have any defined holes (only a few pores on the surface), and it has a small surface area. This is because wax and lignin surround the raw LLP surface as a protective layer ⁴⁸. No significant fine pore development on the surface of the samples was observed Fig. 3b shows the self-assembled structure of cellulose fibers, which is due to the strong interfibrillar attraction between the surface hydroxyl groups. Cellulose also connects with hemicellulose or lignin molecules in raw LLP. Figure 3c and d clearly show that the Pb(II) adsorbed to the raw LLP surface but not deep within the pores as expected. The rough and uneven surface of raw LLP facilitated the adsorption of Pb(II). This result supports the assumption that the pore structure is not the only determining factor influencing the adsorption capacity of heavy metals.

Energy dispersive X-ray analysis (EDAX). Fig. 4 shows the EDAX pattern for raw LLP before and after Pb(II) adsorption. The EDX pattern in Fig. 4a for the raw LLP did not show the characteristic signal of Pb(II), whereas after adsorption, as shown in Fig. 4b, a clear signal of the presence of Pb(II) was observed. Furthermore, the presence of Ca²⁺ and K⁺, which have been shown to be involved in the ion exchange with Pb(II), was indicated in the spectra of unloaded raw LLP. After the adsorption of Pb(II) onto raw LLP, these peaks cations were decreased in the EDX spectrum of Pb(II)-loaded raw LLP. Iqbal et al. ⁴⁹ reported the use of EDAX analysis of grapefruit peel to confirm the mechanism of ion exchange for the removal of Zn(II) from aqueous solutions. The report also noted that the calcium and potassium ions identified in the EDAX spectrum of the fresh grapefruit peel were absent in the peel used for Zn(II) ion adsorption, thus suggesting that these ions may be involved in the ion exchange with the Zn(II) ions. Hence, it could be assumed that Pb(II) was bound to the raw LLP over ion exchange mechanism between Ca²⁺ and K⁺ and Pb(II).

XRF analysis. Table 4 displays the results of the XRF analysis, as well as information on the inorganic chemical composition of raw LLP and Pb(II)-adsorbed raw LLP. Potassium (K) has a significant percentage (14.955%) in raw LLP compared to other inorganic constituents. After the adsorption process, there was a marked reduction of K content in the raw LLP. The elemental composition of the raw LLP is similar to what has been reported by Elhafez et al. ⁵⁰ for rice husk in adsorption of Cu(II) ion. This analysis reveals that K contributes significantly to the adsorption due to the formation of Pb on the raw LLP surface. The XRF analysis show that K percentage was reduced from 14.955–3.781% after adsorption. These results are in line with a recent study ⁵¹, showing that ion exchange mechanism between K⁺ and Pb²⁺ is involved in the adsorption process.

Table 4

XRF of raw LLP and Pb adsorbed with LLP
Adsorbent	Elements
Adsorbent	Al	Si	P	S	Cl	K	Ca	Mn	Fe	Ni	Cu	Cd	Pb
Raw LLP, wt%	0.148	0.229	0.155	0.54	0.884	14.955	4.349	0.696	69.375	6.67	0.264	0.074	1.655
Adsorbed LLP with Pb, wt%	0.128	0.191	0.076	0.366	0.109	3.781	5.331	0.671	64.844	5.37	0.215	0.136	18.782

X-ray diffraction. The XRD patterns of raw LLP before and after adsorption with Pb(II) are shown in Fig. 5. Figure 5 (a) shows a wide broad strong and sharp diffraction peak in the 2θ range of 22.321°–24.403° and a weak peak at 2θ = 14°–16° which indicates crystalline matter. However, the intensity of raw LLP adsorbed with Pb(II) decreased, as shown in Fig. 5 (b). This observation agrees with Pereira et al. ⁵³ who found that biosorbent from carnauba straw and cashew leaf showed an intense peak at about 21.32°, which was attributed to the crystalline structure of cellulose. Gassan and Bledzki⁵⁴ found that chain scissions in cellulose will increase the crystallinity of the cellulose. These findings demonstrate that the cellulose structure is responsible for the adsorption. Salamun et al. (2015) reported that the cellulose molecules are arranged in ordered lattice and most of the OH groups are bonded by hydrogen bond (C–H-O), which can attract Pb(II) ions.

Thermogravimetric analysis (TGA) .Thermal degradation process of raw LLP can be divided into three regions as shown in Fig. 6a. The degradation temperature was obtained from the TG and DTG curves as shown in Table 5. At region I (< 200°C), raw LLP did not undergo significant thermal degradation because of the hydrophilic character of the lignocellulose materials occurred between 25 and 100°C. The weight loss in the first stage was 5.47% (Table 5), which started around 33.91 to 121.69°C to eliminate all moisture. Meanwhile, for region II (200–400°C), which is showed the maxima in the DTG plot (Fig. 6b ) and main thermal degradation stage of raw LLP, are also described in Table 5. Region II also describes the evolution of volatile component. The second region of DTG as shown in Fig. 6b started at 272.91°C, which then reached the highest peak at 332.54°C with weight loss of 47.92%. Region II has overlapping decomposition temperature of hemicellulose, cellulose, and lignin. This is due to hemicellulose degradation (220–315°C), lignin and cellulose decomposition (315–400°C), and lignin degradation (> 450°C) ^{56,57,58,59,60,61}. Comparing the results from previous studies to this study, most of the weight lost in region II occurred at the temperature between 250 and 450°C. The percentage of volatile matter component of raw LLP (47.92%) was lower than those of corn straw (75.02%), corn cob (80.72%), cocoa pod (68.47%), Jatropha cakes (72.53%), moringa cakes (75.08%), Parinari fruit shell (78.17%), and sugar cane bagasse (79.45%) ⁶².

Table 5

Onset temperature (Ton), degradation temperature on maximum weight-loss rate (TMax), weight loss (WL) of raw LLP obtained from the TG and DTG cur
Adsorbents	Region I			Region II				Region III	Reference
Adsorbents	Ton ^oC	T max ^oC	Moisture loss(%)	Ton ^oC	Tend, ^oC	Weight loss (WL)(%)	Tmax ^oC	Weight residue(%)	Reference
Raw LLP	33.91	12.6	5.47	272.91	372.95	47.92	332.54	48.17	This study
Sugarcane bagasse	-	-	-	310	-	58.18	370	26.8	(Sukyai et al., 2018)
Phaseolus vulgaris L. pod	-	-	-	280	-	67.34	380	-	(Raulino et al., 2018)

After 400°C, the decomposition maintained a slow profile where almost all cellulose had been degraded, and the profile can be attributed to the degradation of the remaining lignin. At temperature higher than 380°C, degradation of the remaining lignin occurs and leads to the formation of residue ^63,64. Moreover, residual mass of raw LLP after 400°C was 48.166%. Consistent with the findings of others Dominic et al. ⁶⁵, we found high % residual mass of raw LLP, which corresponds to the protective waxes and layers of lignin in raw LLP. A similar observation was reported by Sukyai et al. ⁵⁶ as shown in Table 5, where unmodified bagasse pulp showed high % of residual mass of 26.8%.

Point of zero charge (pH _pzc ) and Boehm titration.The point of zero charge is defined as the pH at which the biosorbent surface is completely neutral, which is a useful measurement in identifying the best operating conditions (pH levels)⁶⁶. The value of pH_pzc at 4.88 (Table 6) showed predominance of acidic groups on raw LLP surface. This is because raw LLP had acidic surfaces with many oxygenated functional groups, carboxylic, lactonic, and phenolic groups. Based on the biosorbent’s pH_pzc value, it was identified that the biosorbent was primarily acidic in nature; thus, a pH greater than the pH_pzc must be chosen to facilitate the adsorption of the positive Pb(II) by the raw LLP. These results are in good agreement when compared to other studies ^28,67, where the pH_pzc values for Colocasia esculenta (L.) and apricot shells were 3.42 and 4.9, respectively.

Table 6

Boehm titration of the raw LLP and it comparison with other studies
Adsorbent	Surface functional group, mmol/g				pH_PZC	Reference
Adsorbent	phenolic	lactonic	carboxylic	Total acid	pH_PZC	Reference
LLP	0.045875	0.04675	0.14375	0.160614	4.88	This study
Apricot shells	1.14	0.46	0.02	1.2439	4.9	(Šoštarić et al., 2018)

The results for the Boehm titration are given in Table 6. Surface active site analysis revealed that raw LLP contained 0.045875 mmolg^− 1 of phenolic group, 0.04675 mmolg^− 1 of lactone group, 0.14375 mmolg^− 1 of carboxylic group, and a total acidity and 0.236375 mmolg^− 1. As shown in Table 6, the surface of raw LLP have acidic (mostly carboxylic) groups dominating with higher mmolg^− 1. This is in good agreement with the point of zero charge value (4.88) of the biosorbent.

Zeta potential. The zeta potential values for raw LLP are presented in Fig. 7. Raw LLP shows negative zeta potential values within the pH range from 2.0 to 6. The zeta potential for raw LLP decreased from − 1.2 up to − 22.7 mV. As a result, negative charges on the surface of raw LLP could be a good explanation for cationic heavy metal adsorption to them. The carboxylic group on the raw LLP surface is responsible for this significant amount of negative surface charge that dissociates into H⁺(aq.) and COO⁻ (aq.) in the solution. Inglesby et al. ⁶⁸ stated that the increase of magnitude of the negative in the acidic pH is due to the dissociation of functional groups. So, the zeta values of raw LLP remained negative over the entire pH range examined. As the zeta potential decreased, the cell surface becomes more negatively charged, which is favorable for adsorption. This is in agreement with Basu et al. ⁶⁴, which found that zeta potential of cucumber peel decreased up to − 21.0 mV as pH of the suspension increased from pH 2 to 6.

BET analysis and pore size. The nitrogen adsorption–desorption isotherms of raw LLP are shown in Fig. 8. Type III isotherm (IUPAC classification) was observed for raw LLP, indicating that the raw LLP was macroporous.

Table 7 shows BET, total pore volume, external surface area, and average pore width of raw LLP were determined to be 0.6692 m²/g, 0.00269 cm³/g, 1.0063 m²/g, and 175.346 Å, respectively. This indicates that the raw LLP has a low surface area and this is similar to what has been reported in previous studies for some agricultural residues. Pereira et al., ⁵³ and Demirbas⁶⁹ stated that plant-based biosorbents do not have a high surface area. The small pore volume of raw LLP may be due to the structure of cellulose, hemicellulose, and lignin in raw LLP, which may result in fewer pores, which correlates with the results of Bota et al. ⁷⁰ and Asuquo and Martin ⁴¹. This results in raw LLP having wide average pore width due to the macropores, making them suitable for liquid-phase adsorption because it facilitates adsorbate diffusion into the biosorbent structure ^41,71,72. However, it should be noted that the adsorption of heavy metals to raw LLP is not solely dependent on the presence of large surface areas, as porosity is not the only criterion required for good biosorbents. Functional groups such as phenolic, carboxylic, hydroxyl, amines, and ether groups on raw LLP that serve as active sites for adsorption also contribute significantly to their adsorption potential for target heavy metals. These functional groups act as sources of physical and chemical interactions that facilitate adsorption via a number of mechanisms that include hydrogen bonding, electrostatic interactions, and surface complexation ⁴¹.

Table 7

Pore structure of raw LLP
Property	BET Surface Area (m²/g)	Total pore volume cm³/g	External Surface area (m²/g)	Average pore width (BJH), Å
LLP	0.6692	0.00269	1.0063	175.346

Pb(II) adsorption analysis by raw LLP.

Effect of pH on Pb(II) adsorption to raw LLP. Figure 9 shows the adsorption capacity of Pb(II) in synthetic solution at different pH with 50 mg/L of initial Pb(II) concentration and 40g/L raw LLP dosage. Adsorption of Pb(II) on raw LLP increased at pH 3.0 and 4.0; it remained constant up to pH 5 but decreased at pH 6.0 (Fig. 9). The highest adsorption capacity of Pb(II) was 1.1 mg/g obtained at pH 5 of the synthetic solution. This is because the hydrogen ion (H+) concentration influences the removal efficiency of metal ions in the aqueous solution and affects the solubility of Pb(II) in the solution. The protonation of the raw LLP surface leads to the competition between protons and metal ions for the binding sites. The plots in Fig. 9 confirm that adsorption of Pb(II) is strongly influenced by pH, which is explained based on the point of zero charge (pH_pzc). Free Pb(II) ions were the predominant species when the solution pH was below 6.0 ⁷³. The removal percentage increased as the pH of the solution approached 5. In the case of Pb(II) adsorption, most of the active sites such as carboxylic acids were occupied by protons on the raw LLP surface at lower pH. According to Roberts and Caserio⁷⁴, dissociation of acidic functional groups such as carboxylic acids (pKa values of carboxylic acids range from 3.8 to 5.0). When the pH of the biosorbent (raw LLP) rises (pH > pKa), the surface acidic functional groups deprotonate and the negative charge on the biosorbent rises.

Effect of raw LLP dosage on Pb(II) removal. The effect of raw LLP dosage on the removal of Pb(II) is illustrated in Fig. 10 where the dosage of LLP was varied from 8 to 40 g/L at an initial synthetic Pb(II) solution concentration of 50 mg/L at pH 5 and retention time of 30 min. The percentage of Pb(II) removal increased from 85–93.4% with increasing dosage from 8 to 50 g/L. This result could be explained by the fact that for optimum biosorption, extra sites must be available for biosorption reaction, which was achieved by increasing the dosage⁷⁵. The maximum biosorption percentage reached 93.4% at 50 g/L. However, further increase in biosorbent dosage beyond 40 g/L did not result in sufficient improvement in the percentage removal of Pb(II) ions by raw LLP as reported by ⁷⁶. Therefore, the optimum dosage for raw LLP was taken as 40 g/L for subsequent batch experiments.

Comparison study. The performance comparison between LLP and other biosorbents is shown in Table 8. It is clearly demonstrated that the performance of raw LLP on the Pb(II) removal achieved 93% higher than Sophora japonica pods ³¹, Adsononsia digitata ⁷⁷ and peanut shells ²⁷ with 60%, 68% and 65%, respectively for plant based biosorbent. Raw LLP performed better than Adsononsia digitata and peanut shells in terms of Pb(II) removal time, which was 30 min at 93% removal. Aside from that, both experiments on pH effect revealed that LLP is effective for Pb(II) removal at high concentration of 50 mg/L.

Table 8

Comparison of raw LLP with other plant-based biosorbent
Adsorbent	Type of solution	Dosage, g/L	Time, min	Optimum pH	Initial concentration, mg/L	Pb percent removal, %	Refence
Raw LLP	Synthetic	40	30	5	50	93	This study
Sophora japonica pods	Synthetic	5	120	6.0–7.0	5-100	60	(Amer et al., 2015)
Adsononsia digitata	Synthetic	7	120	5.5	25	68	(Chigondo, 2013)
Peanut shells	Synthetic	2	180	5.5	50	65	(Taşar et al., 2014)

Pb(II) was successfully removed using raw LLP in this study where the highest adsorption capacity of Pb(II) was obtained at pH 5 of synthetic aqueous solution with 1.1 mg/g adsorption capacity, and the optimum dosage of raw LLP was 40 g/L only in 30 min with 93% of Pb(II) removal. Raw LLP exhibited good performance for Pb(II) adsorption based on the interactions between Pb(II) ions and functional groups on the surface of the biosorbent, which were confirmed by FTIR analysis. The spectra showed that carboxyl, hydroxyl, and amine groups are involved in Pb(II) ion binding to the raw LLP. The pH at point of zero charge (pH_PZC) was 4.88, while Boehm titration result that the raw LLP biosorbent contained 0.045875 mmolg^− 1 of phenolic group, 0.04675 mmolg^− 1 of lactone group, 0.14375 mmolg^− 1 of carboxylic group, and a negative value for zeta potential, which show a dominance of acidic groups at the biosorbent surface. SEM of the raw LLP showed that it has a nonporous structure with 0.6692 m²/g and 0.00269 cm³/g of BET surface area and total pore volume, respectively. XRD results show the presence of cellulose in raw LLP. TGA and biochemical analyses confirm that the raw LLP biosorbent contained cellulose, hemicellulose, and high lignin content. In conclusion, raw LLP has high potential as biosorbent for for heavy metal removal especially Pb(II), hence safe for the environment due to its natural based biosorbent and abundantly available.

Preparation and characterization of raw Leucaena leucocephala pods (LLP). Raw LLP was collected from a local rural area in Shah Alam, Malaysia. The seeds were separated from the pods and washed using tap water to remove any impurities and then dried in an oven (Froilabo SN: 505137) at 90°C for 48 h. The dried samples were then ground using a blender to produce raw LLP powder. The raw LLP powder was then sieved using a horizontal sieve shaker with 300 µm/200 µm opening sieve plates based on National Renewable Energy Laboratory (NREL) Hames et al. ⁷⁹. The physical appearances of original dried and ground raw LLP are shown in Fig. 1a and Fig. 1b.

Physical and chemical analysis of raw LLP. The ultimate analysis of raw LLP was performed using the standard ASTM E870-82 (2013) to determine carbon (C), hydrogen (H), nitrogen (N), sulfur (S), and oxygen (O) content using CHNS/O analyzer (Flash 2000, ThermoScientific, Italy). Oxygen content was obtained by subtracting the sum of the obtained elemental values from 100% ²⁸.

Ash analysis method was based on ASTM D13174-02 procedure. The ash was obtained after complete combustion of a 1 g sample at temperatures between 450 and 950°C for 4 h. The ash content was calculated using Eq. 1:

% of ash= (weight of ash/weight of biosorbent ) x 100 (1)

For moisture content analysis, 2.0 g of the sample was dried to constant weight at 105°C for 24 h in an oven, allowed to cool, and weighed. The moisture content was calculated using Eq. 2⁶⁴:

Moisture content (%)= \(\frac{ \text{I}\text{n}\text{i}\text{t}\text{i}\text{a}\text{l} \text{w}\text{e}\text{i}\text{g}\text{h}\text{t} \text{o}\text{f} \text{f}\text{i}\text{l}\text{l}\text{e}\text{d} \text{c}\text{r}\text{u}\text{c}\text{i}\text{b}\text{l}\text{e} -\text{F}\text{i}\text{n}\text{a}\text{l} \text{w}\text{e}\text{i}\text{g}\text{h}\text{t} \text{o}\text{f} \text{f}\text{i}\text{l}\text{l}\text{e}\text{d} \text{c}\text{r}\text{u}\text{c}\text{i}\text{b}\text{l}\text{e} }{\text{I}\text{n}\text{i}\text{t}\text{i}\text{a}\text{l} \text{w}\text{e}\text{i}\text{g}\text{h}\text{t} \text{o}\text{f} \text{f}\text{i}\text{l}\text{l}\text{e}\text{d} \text{c}\text{r}\text{u}\text{c}\text{i}\text{b}\text{l}\text{e} - \text{I}\text{n}\text{i}\text{t}\text{i}\text{a}\text{l} \text{w}\text{e}\text{i}\text{g}\text{h}\text{t} \text{o}\text{f}\text{e}\text{m}\text{p}\text{t}\text{y} \text{c}\text{r}\text{u}\text{c}\text{i}\text{b}\text{l}\text{e} }\times 100\)(2)

Bulk density measured by placing 2 g of fiber into a graduated syringe and applying sufficient pressure to pack the content in the syringe while recording the final volume. The bulk density calculated based on Bansal ⁸⁰ using Eq. 3:

Bulk density (%) = (w/v) x 100 (3)

where w is the weight of powder (g) and v is cylinder volume packed with dried powder (mL).

Biochemical analysis. The biochemical properties of the raw LLP were analyzed in terms of its extractive, cellulose, lignin, holocellulose, and hemicellulose content according to TAPPI T 204 cm-97 2007 ^60,81, TAPPI T222 ⁸²., ASTM D 1104–56⁸³, TAPPI T 203⁶⁰, and ASTM D1106-56 ⁸⁴ respectively.

Point of zero charge (pH _pzc ). pH point of zero charge (pHpzc) of raw LLP biosorbent was determined based on Reddy et al. ⁸⁵. First, 100 mL deionized water was boiled for 20 min to eliminate dissolved CO2 and cooled by capping the solution. Next, 0.2 g of raw LLP was placed in 15 mL of the CO2-free water, sealed, and continuously agitated for 48 h at room temperature before measuring the solution’s pH.

X-ray diffraction. XRD patterns were analyzed and recorded using X-ray diffractometer (RIGAKU / XRD D/MAX 2200V/PC) using Cu Kα radiation at the scanning speed of 2°/min with 2θ angle varying in the range of 5°–80° ⁸¹.

Thermogravimetric analysis (TGA). Thermogravimetric analysis (TGA) was performed using a thermogravimetric analyzer (Mettler Toledo, TGA/DSC1 Star System). A sample of 20 mg was weighed and heated from 50 to 800°C at a constant heating rate of 20°C/min in a nitrogen atmosphere ^56,86.

Scanning Electron Microscope (SEM) analysis. The surface morphology and shape of raw LLP was evaluated using scanning electron microscopy (SEM-EDX SU3500) with images at 500×, 1000×, 1500×, and 5000× magnifications. A small amount of each sample was directly mounted on an aluminium holder with a diameter of 12.5 mm using a two-sided adhesive carbon model. The sample was coated with platinum using Sputter Coater, Polaron SC 7620. The prepared samples were introduced into the microscope chamber with a high vacuum.

BET surface areas and distribution of pore sizes. Brunauer–Emmett–Teller (BET) specific surface area, pore volume, and average pore diameter of raw LLP were determined based on N₂ adsorption method at 77 K (Micromeritics 3Flex 3500). The dried and powdered biomass was first degassed at 100°C for 5 h. and then the measurements were done by N₂ sorption method.

Fourier Transform Infrared Spectroscopy (FTIR). Functional group analysis of raw LLP was performed by using Fourier transform infrared (FTIR) following Basu et al. ⁶⁴. The samples were recorded between 4000–500 cm^− 1 in a spectrometer (Perkin Elmer) and then pressed into transparent thin pellets.

X-ray fluorescence (XRF) spectrum analysis. The element composition of raw LLP was determined using X-ray fluorescence (XRF) spectrum analysis (Thermo Finnigan, FlashEA 1112)^{81, 50}. Samples were pelletized to 6 mm masks using wax as binder with a 5g of sample and analyzed to determine the chemical composition of the raw LLP.

Boehm titration. The Boehm titration method was used to characterize functional groups according to the scheme described by Boehm et al.⁸⁷ and Goertzen et al. ⁸⁸.About 1 g of raw LLP was shaken for 24 h, separately, with 50 mL of 0.05 M bases: NaHCO₃, Na₂CO₃, and NaOH. Afterwards, the suspensions were decanted and then filtered with Whatman no. 40 filter paper. The 1 mL filtered solution was titrated with 0.1 M HCL and then back-titrated with 0.05 M NaOH. The endpoint was determined using a phenolphthalein color indicator. The total surface acidity was calculated as moles neutralized by NaOH, the carboxylic acid fraction as moles neutralized by NaHCO₃, and the lactonic group fraction as moles neutralized by Na₂CO₃. The difference between molar NaOH and Na₂CO₃ was assumed to be the phenolic functional group content following Rutherford et al. ⁸⁹.

Zeta potential measurement. Zeta potential of the raw LLP sample was measured over the pH range of 2.0–7.0 by using Malvern Zetasizer Nano ZS (model ZEN3600) and the procedure was executed according to Mukherjee et al. ⁹⁰. About 0.5 g of raw LLP sample was added to 50 mL distilled water and sonicated for 30 min. The resulting solution was filtered using Whatman filter paper No. 1. Supernatants containing microparticles of raw LLP were distributed into vials for zeta potential measurement. The pH of the solutions was recorded immediately after zeta potential of the raw LLP samples was measured. The pH of filtrate was determined by multiple measurements of zeta potential as a function of pH of the solution, adjusted using 1 M HCl or 1 M NaOH.

Preparation of synthetic Pb(II) aqueous solution .Analytical reagent grade of Pb(NO₃)₂ was supplied by R&M Chemicals Sdn. Bhd. and used as synthetic wastewater. Pb(NO₃)₂ powder of 0.16 g was dissolved in 100 mL distilled water in a volumetric flask and shaken for 2 minutes until the Pb(NO₃)₂ powder fully dissolved to produce 50 mg/L concentration of Pb(II) solution.

Biosorption experiment.The adsorption process was initiated by stirring at 120 rpm and continued for 30 min using THZ- 98A mechanical shaker. At the end of the experiment, the flasks were removed from the shaker and the solutions were separated from the biosorbent by filtration through Whatman filter paper no. 4 with 20–25 µm size. The supernatant was analyzed using atomic absorption spectrophotometer (AAS) (HITACHI / AAS Z2000). All the experiments were done in triplicate to ensure repeatability. The method was based on Ngabura et al.⁹² and the calculation was based on Khan et al. ⁹³ as follows:

q_{e =} V (C_i - C_f )/ W (5)

where q_e is the amount of Pb(II) ions adsorbed per specified amount of biosorbent (mg/g), C_i and C_f are initial and final concentrations of Pb(II) ion (mg/L), W denotes the weight of biosorbent (g), and V is volume of solution (L).

The percentage removal of Pb(II) ions was calculated by using the following Eq. 9¹:

Pb(II) removal (%)= (C₀ - C_e) C₀ x 100 (6)

where C₀ is the initial concentration of Pb (mg/L) and C_e is the equilibrium concentration of Pb (mg/L).

Effect of pH. The experiment was carried out for biosorption at a concentration of 50 mg/L of Pb (II) ions and 40 g/L of biosorbent dose in a 25 mL metal solution with pH ranging from 2 to 6. Solution pH value was adjusted using 0.1 M HCl or 0.1 M NaOH.

Effect of biosorbent dosage.Different biosorbent doses ranging from 8 to 50 g/L were used for 25 mL of Pb(II) and Pb(II) solutions in a 100 mL conical flask while maintaining a pH of 5.0, a temperature of 25°C, and Pb(II) ion concentrations of 50 mg/L.

Availability of Data and Materials

All data generated or analysed during this study are included in this published article

Ghaedi, S., Seifpanahi-Shabani, K. & Sillanpää, M. Waste-to-Resource: New application of modified mine silicate waste to remove Pb²⁺ ion and methylene blue dye, adsorption properties, mechanism of action and recycling. Chemosphere 133412 (2021)
Hou, S. et al. Pollution characteristics, sources, and health risk assessment of human exposure to Cu, Zn, Cd and Pb pollution in urban street dust across China between 2009 and 2018. Environ. Int.128, 430–437 (2019).
Zhang, H. Biosorption of heavy metals from aqueous solutions using keratin biomaterials. (2014).
Meitei, M. D. & Prasad, M. N. V. Lead (II) and cadmium (II) biosorption on Spirodela polyrhiza (L.) Schleiden biomass. J. Environ. Chem. Eng.1, 200–207 (2013).
Shrestha, R. et al. Technological trends in heavy metals removal from industrial wastewater: A review. J. Environ. Chem. Eng.9, (2021).
Yogeshwaran, V. & Priya, A. K. Adsorption of lead ion concentration from the aqueous solution using tobacco leaves. Mater. Today Proc.37, 489–496 (2020).
Wani, A. L., Ara, A. & Usmani, J. A. Lead toxicity: A review. Interdiscip. Toxicol.8, 55–64 (2015).
Ahmed, M. F., Mokhtar, M. Bin, Alam, L., Mohamed, C. A. R. & Ta, G. C. Investigating the status of cadmium, chromium and lead in the drinking water supply chain to ensure drinking water quality in malaysia. Water (Switzerland)12, 1–26 (2020).
Carolin, C. F., Kumar, P. S., Saravanan, A., Joshiba, G. J. & Naushad, M. Efficient techniques for the removal of toxic heavy metals from aquatic environment: A review. J. Environ. Chem. Eng.5, 2782–2799 (2017).
Rodriguez-Narvaez, O. M., Peralta-Hernandez, J. M., Goonetilleke, A. & Bandala, E. R. Treatment technologies for emerging contaminants in water: A review. Chem. Eng. J.323, 361–380 (2017).
Witek-Krowiak, A., Szafran, R. G. & Modelski, S. Biosorption of heavy metals from aqueous solutions onto peanut shell as a low-cost biosorbent. Desalination265, 126–134 (2011).
Peng, S. H. et al. Biosorption of copper, zinc, cadmium and chromium ions from aqueous solution by natural foxtail millet shell. Ecotoxicol. Environ. Saf.165, 61–69 (2018).
Alipoyo, J. C., Magoncia, V. E. B., Perido, A. A. M., Gapusan, R. B. & Balela, M. D. L. Optimization of hydrolysis of polyacrylonitrile-kapok fiber composite for the adsorption of lead ions in aqueous solution. Environ. Nanotechnology, Monit. Manag.16, 1–10 (2021).
Al-Qodah, Z., Yahya, M. A. & Al-Shannag, M. On the performance of bioadsorption processes for heavy metal ions removal by low-cost agricultural and natural by-products bioadsorbent: A review. Desalin. Water Treat.85, 339–357 (2017).
Kamarudzaman, A. N. Biosorption of Copper ( II ) and Iron ( II ) using Spent Mushroom Compost as Biosorbent. Biointerface Res. Appl. Chem.12, 7775–7786 (2022).
Fu, F. & Wang, Q. Removal of heavy metal ions from wastewaters: a review. J. Environ. Manage.92, 407–18 (2011).
Cunha, G. da C. et al. Applications of magnetic hybrid adsorbent derived from waste biomass for the removal of metal ions and reduction of 4-nitrophenol. J. Environ. Manage.213, 236–246 (2018).
Pagnanelli, F., Mainelli, S., Vegliò, F. & Toro, L. Heavy metal removal by olive pomace: biosorbent characterisation and equilibrium modelling. Chem. Eng. Sci.58, 4709–4717 (2003).
Reddy, D. H. K., Seshaiah, K., Reddy, A. V. R., Rao, M. M. & Wang, M. C. Biosorption of Pb2+ from aqueous solutions by Moringa oleifera bark: Equilibrium and kinetic studies. J. Hazard. Mater.174, 831–838 (2010).
Najam, R. & Andrabi, S. M. A. Removal of Cu(II), Zn(II) and Cd(II) ions from aqueous solutions by adsorption on walnut shell-Equilibrium and thermodynamic studies: treatment of effluents from electroplating industry. Desalin. Water Treat.57, 27363–27373 (2016).
Guechi, E.-K. & Oualid Hamdaoui. Biosorption of methylene blue from aqueous solution by potato (Solanum tuberosum) peel: equilibrium modelling, kinetic, and thermodynamic studies. Desalin. Water Treat.57, 10270–10285 (2016).
Amer, H., El-Gendy, A. & El-Haggar, S. Removal of lead (II) from aqueous solutions using rice straw. Water Sci. Technol.76, 1011–1021 (2017).
Cheraghi, E. A. E. & Moheb, A. Adsorption of cadmium ions from aqueous solutions using sesame as a low-cost biosorbent: kinetics and equilibrium studies. Int. J. Environ. Sci. Technol.22, 2579–2592 (2015).
Wan, S. et al. Sorption of lead(II), cadmium(II), and copper(II) ions from aqueous solutions using tea waste. Ind. Eng. Chem. Res.53, 3629–3635 (2014).
Pehlivan, E., Altun, T., Cetin, S. & Iqbal Bhanger, M. Lead sorption by waste biomass of hazelnut and almond shell. J. Hazard. Mater.167, 1203–1208 (2009).
Morosanu, I., Teodosiu, C., Paduraru, C., Ibanescu, D. & Tofan, L. Biosorption of lead ions from aqueous effluents by rapeseed biomass. N. Biotechnol.39, 110–124 (2017).
Taşar, Ş., Kaya, F. & Özer, A. Biosorption of lead(II) ions from aqueous solution by peanut shells: Equilibrium, thermodynamic and kinetic studies. Journal of Environmental Chemical Engineering vol. 2 1018–1026 (2014).
Šoštarić, T. D. et al. Study of heavy metals biosorption on native and alkali-treated apricot shells and its application in wastewater treatment. J. Mol. Liq.259, 340–349 (2018).
Patil, A. K., Shrivastava, V. S. & Mahavidyalaya, D. N. Removal of Cu ( II ) Ions by Leucaena Leucocephala ( Subabul ) Seed Pods from Aqueous Solutions. 7, 377–386 (2010).
Abdel Rahman, L. H., Al Farhan, B. S., Abu Dief, A. M. & Megalea Zikry, M. Removal of Toxic Pb(II) Ions from Aqueous Solution by Nano Sized Flamboyant Pod (Delonix regia). Arch. Chem. Res.01, 1–10 (2016).
Amer, M. W., Ahmad, R. A. & Awwad, A. M. Biosorption of Cu(II), Ni(II), Zn(II) and Pb(II) ions from aqueous solution by Sophora japonica pods powder. Int. J. Ind. Chem.6, 67–75 (2015).
Nuithitikul, K., Phromrak, R. & Saengngoen, W. Utilization of chemically treated cashew-nut shell as potential adsorbent for removal of Pb(II) ions from aqueous solution. Sci. Rep.10, 1–14 (2020).
Martín-Lara, M. A., Blázquez, G., Ronda, A., Pérez, A. & Calero, M. Development and characterization of biosorbents to remove heavy metals from aqueous solutions by chemical treatment of olive stone. Ind. Eng. Chem. Res.52, 10809–10819 (2013).
Calero, M., Pérez, A., Blázquez, G., Ronda, A. & Martín-Lara, M. A. Characterization of chemically modified biosorbents from olive tree pruning for the biosorption of lead. Ecol. Eng.58, 344–354 (2013).
Sonia, A. & Priya Dasan, K. Chemical, morphology and thermal evaluation of cellulose microfibers obtained from Hibiscus sabdariffa. Carbohydr. Polym.92, 668–674 (2013).
Vaughan, T., Seo, C. W. & Marshall, W. E. Removal of selected metal ions from aqueous solution using modified corncobs. Bioresour. Technol.78, 133–139 (2001).
Arshad, N. & Imran, S. Indigenous waste plant materials: An easy and cost-effective approach for the removal of heavy metals from water. Curr. Res. Green Sustain. Chem.3, (2020).
Albatrni, H., Qiblawey, H. & Al-Marri, M. J. Walnut shell based adsorbents: A review study on preparation, mechanism, and application. J. Water Process Eng.45, 102527 (2022).
Pavia DL, Lampman GM, K. G. Introduction to Spectroscopy. (Brooks/Cole Thomson Learning, 2001).
Wang, S., Dai, G., Yang, H. & Luo, Z. Lignocellulosic biomass pyrolysis mechanism: A state-of-the-art review. Prog. Energy Combust. Sci.62, 33–86 (2017).
Asuquo, E. D. & Martin, A. D. Sorption of cadmium (II) ion from aqueous solution onto sweet potato (Ipomoea batatas L.) peel adsorbent: Characterisation, kinetic and isotherm studies. J. Environ. Chem. Eng.4, 4207–4228 (2016).
Barka, N., Abdennouri, M., El Makhfouk, M. & Qourzal, S. Biosorption characteristics of cadmium and lead onto eco-friendly dried cactus (Opuntia ficus indica) cladodes. J. Environ. Chem. Eng.1, 144–149 (2013).
Md Salim, R., Asik, J. & Sarjadi, M. S. Chemical functional groups of extractives, cellulose and lignin extracted from native Leucaena leucocephala bark. Wood Sci. Technol.55, 295–313 (2021).
Ibrahim, M. N. M. et al. A novel agricultural waste adsorbent for the removal of lead (II) ions from aqueous solutions. J. Hazard. Mater.182, 377–385 (2010).
Shi, J. & Jian, L. Wood-Forming Tissue of Pinus Koraiensis Under. BioResources7, 3463–3475 (2012).
Deshmukh, P. D., Khadse, G. K., Shinde, V. M. & Labhasetwar, P. Cadmium Removal from Aqueous Solutions Using Dried Banana Peels as An Adsorbent: Kinetics and Equilibrium Modeling. J. Bioremediation Biodegrad.08, (2017).
Karnitz, O. et al. Adsorption of heavy metal ion from aqueous single metal solution by chemically modified sugarcane bagasse. Bioresour. Technol.98, 1291–1297 (2007).
Johar, N., Ahmad, I. & Dufresne, A. Extraction, preparation and characterization of cellulose fibres and nanocrystals from rice husk. Ind. Crops Prod.37, 93–99 (2012).
Iqbal, M., Schiewer, S. & Cameron, R. Mechanistic elucidation and evaluation of biosorption of metal ions by grapefruit peel using FTIR spectroscopy, kinetics and isotherms modeling, cations displacement and EDX analysis. J. Chem. Technol. Biotechnol.84, 1516–1526 (2009).
Elhafez, S. E. A., Hamad, H. A., Zaatout, A. A. & Malash, G. F. Management of agricultural waste for removal of heavy metals from aqueous solution: adsorption behaviors, adsorption mechanisms, environmental protection, and techno-economic analysis. Environ. Sci. Pollut. Res.24, 1397–1415 (2017).
Iqbal, M., Saeed, A. & Zafar, S. I. FTIR spectrophotometry, kinetics and adsorption isotherms modeling, ion exchange, and EDX analysis for understanding the mechanism of Cd2+ and Pb2+ removal by mango peel waste. J. Hazard. Mater.164, 161–171 (2009).
Pereira, J. E. S. et al. Valorization of carnauba straw and cashew leaf as bioadsorbents to remove copper (II) ions from aqueous solution. Environ. Technol. Innov.23, 101706 (2021).
Moreira, A. L. da S. L. et al. Bifunctionalized chitosan: A versatile adsorbent for removal of Cu(II) and Cr(VI) from aqueous solution. Carbohydr. Polym.201, 218–227 (2018).
Gassan, J. & Bledzki, A. K. Thermal degradation of flax and jute fibers. J. Appl. Polym. Sci.82, 1417–1422 (2001).
Salamun, N., Triwahyono, S., Jalil, A. A., Matsuura, T. & Salleh, N. F. M. Acid-vacuo heat treated low cost banana stems fiber for efficient biosorption of Hg(II). RSC Adv.5, 14129–14137 (2015).
Sukyai, P. et al. Effect of cellulose nanocrystals from sugarcane bagasse on whey protein isolate-based films. Food Res. Int.107, 528–535 (2018).
Deepa, B. et al. Structure, morphology and thermal characteristics of banana nano fibers obtained by steam explosion. Bioresour. Technol.102, 1988–1997 (2011).
Donaldson, L. A., W, K. K. Y., Mackie, K. L. & Zealand, N. Ultrastructure of steam-exploded wood. 114, 103–114 (1988).
Basu, M., Guha, A. K. & Ray, L. Adsorption Behavior of Cadmium on Husk of Lentil. Process Saf. Environ. Prot.106, 11–22 (2017).
Alotaibi, M. D. et al. Characterization of natural fiber obtained from different parts of date palm tree (Phoenix dactylifera L.). Int. J. Biol. Macromol.135, 69–76 (2019).
Ranasinghe, S. H., Navaratne, A. N. & Priyantha, N. Enhancement of adsorption characteristics of Cr(III) and Ni(II) by surface modification of jackfruit peel biosorbent. J. Environ. Chem. Eng.6, 5670–5682 (2018).
Titiloye, J. O., Abu Bakar, M. S. & Odetoye, T. E. Thermochemical characterisation of agricultural wastes from West Africa. Ind. Crops Prod.47, 199–203 (2013).
Jahan, M. S., Saeed, A., He, Z. & Ni, Y. Jute as raw material for the preparation of microcrystalline cellulose. Cellulose18, 451–459 (2011).
Basu, M., Guha, A. K. & Ray, L. Adsorption of Lead on Cucumber Peel. J. Clean. Prod.151, 603–615 (2017).
Dominic, M. et al. Green tire technology: Effect of rice husk derived nanocellulose (RHNC) in replacing carbon black (CB) in natural rubber (NR) compounding. Carbohydr. Polym.230, (2020).
Sposito, G. On points of zero charge. Environ. Sci. Technol.32, 2815–2819 (1998).
Saha, G. C. et al. Biosorptive removal of lead from aqueous solutions onto Taro (Colocasiaesculenta(L.) Schott) as a low cost bioadsorbent: Characterization, equilibria, kinetics and biosorption-mechanism studies. J. Environ. Chem. Eng.5, 2151–2162 (2017).
Inglesby, M. K. et al. Surface characterization of untreated and solvent-extracted rice straw. Colloids Surfaces B Biointerfaces43, 83–94 (2005).
Demirbas, A. Heavy metal adsorption onto agro-based waste materials: A review. J. Hazard. Mater.157, 220–229 (2008).
Bota, A. et al. Adsorbents from waste materials. Adsorption3, 81–91 (1997).
Ribeiro, R. F. L., Soares, V. C., Costa, L. M. & Nascentes, C. C. Production of activated carbon from biodiesel solid residues: An alternative for hazardous metal sorption from aqueous solution. J. Environ. Manage.162, 123–131 (2015).
Menéndez-Díaz, J. A. & Martín-Gullón, I. Chapter 1 Types of carbon adsorbents and their production. Interface Sci. Technol.7, 1–47 (2006).
Gupta, S. Sen & Bhattacharyya, K. G. Adsorption of Ni(II) on clays. J. Colloid Interface Sci.295, 21–32 (2006).
Roberts, J. D. & Caserio, M. C. Basic Principles of Organic Chemistry, 2nd ed., W.A. Benjamin, 1977. (W.A.Benjamin, 1977).
Wu, J. et al. Preparation of highly dispersive and antioxidative nano zero-valent iron for the removal of hexavalent chromium. Chemosphere262, (2021).
Reddy, D. H. K., Harinath, Y., Seshaiah, K. & Reddy, A. V. R. Biosorption of Pb(II) from aqueous solutions using chemically modified Moringa oleifera tree leaves. Chem. Eng. J.162, 626–634 (2010).
Chigondo, F. Removal of lead (II) and copper (II) ions from aqueous solution by baobab (Adononsia digitata) fruit shells biomass. IOSR J. Appl. Chem.5, 43–50 (2013).
Hames, B. et al. Preparation of samples for compositional analysis. . Natl. Renew. Energy Lab. (2008).
Hames, B. et al. Preparation of Samples for Compositional Analysis: Laboratory Analytical Procedure (LAP); Issue Date 08/08/2008. (2008).
Bansal, M. Removal of heavy metal pollutants by biosorption using low cost. (National Institute of Technology , Kurukshetra, 2009).
Goldmann, W. M., Ahola, J., Mikola, M. & Tanskanen, J. Formic acid aided hot water extraction of hemicellulose from European silver birch (Betula pendula) sawdust. Bioresour. Technol.232, 176–182 (2017).
Bortoluz, J. et al. Isolation, characterization and valorization of lignin from Pinus elliottii sawdust as a low-cost biosorbent for zinc removal. Cellulose26, 4895–4908 (2019).
Abraham, E. et al. Environmental friendly method for the extraction of coir fibre and isolation of nanofibre. Carbohydr. Polym.92, 1477–1483 (2013).
Li, X. Physical, chemical, and mechanical properties of bamboo and its utilization potential for fiberboard manufacturing. Agric. Mech. Coll.Master of, 76 (2004).
Reddy, D. H. K., Seshaiah, K., Reddy, A. V. R. & Lee, S. M. Optimization of Cd(II), Cu(II) and Ni(II) biosorption by chemically modified Moringa oleifera leaves powder. Carbohydr. Polym.88, 1077–1086 (2012).
Mahmoodi, N. M., Taghizadeh, M. & Taghizadeh, A. Mesoporous activated carbons of low-cost agricultural bio-wastes with high adsorption capacity: Preparation and artificial neural network modeling of dye removal from single and multicomponent (binary and ternary) systems. J. Mol. Liq.269, 217–228 (2018).
Boehm, H. P. Surface oxides on carbon and their analysis: A critical assessment. Carbon N. Y.40, 145–149 (2002).
Goertzen, S. L., Thériault, K. D., Oickle, A. M., Tarasuk, A. C. & Andreas, H. A. Standardization of the Boehm titration. Part I. CO2 expulsion and endpoint determination. Carbon N. Y.48, 1252–1261 (2010).
Rutherford, D. W., Wershaw, R. L. & III, J. B. R. Development of acid functional groups and lactones during the thermal degradation of wood and wood components. Sci. Investig. Rep. (2008) doi:10.3133/SIR20075013.
Mukherjee, A., Zimmerman, A. R. & Harris, W. Surface chemistry variations among a series of laboratory-produced biochars. Geoderma163, 247–255 (2011).
Ngabura, M., Hussain, S. A., Ghani, W. A. W. A., Jami, M. S. & Tan, Y. P. Utilization of renewable durian peels for biosorption of zinc from wastewater. J. Environ. Chem. Eng.6, 2528–2539 (2018).
Ngabura, M., Aslina, S., Azlina, W., Ghani, W. A. & Saedi, M. Utilization of Renewable Durian Peels for Biosorption of Zinc from Wastewater. J. Environ. Chem. Eng.6, 2528–2539 (2018).
Khan, M. A., Ngabura, M., Choong, T. S. Y., Masood, H. & Chuah, L. A. Biosorption and desorption of Nickel on oil cake: Batch and column studies. Bioresour. Technol.103, 35–42 (2012).

No competing interests reported.

Download PDF

Version 1

posted

You are reading this latest preprint version

Characterized raw Leucaena leucocephala pod (LLP) as biosorbent produced high adsorption of Pb(II) ions in a synthetic aqueous solution

Status:

Version 1

Abstract

Figures

Introduction

Results And Discussion

Conclusion

Materials And Method

References

Additional Declarations

Status:

Version 1