For the purpose of removing methylene blue (MB) from various ecological water samples, a brand-new solid phase micro-extraction in portable syringe system (SPME-PSS) has been developed. A 100 cm long by 5 mm wide column containing 10 mg of Poly(3-hydroxy butyrate)-b-Poly(methyl methacrylate) with Ag nanoparticles (PHB-AgPrici) serving as the adsorbent PHB-surface AgPrici's morphology has been studied using DSC, FT-IR, and SEM-EDX techniques. Adsorption mechanism of MB toward PHB-AgPrici was investigated using isotherms, kinetics, and thermodynamics experiments. To test adsorption and the capacity of PHB-AgPrici for adsorption, Langmuir and Freundlich's isotherms method was utilized. It was anticipated for MB to have a 169.3 mg/g monolayer adsorption capacity (qmax) toward PHB-AgPrici. The proposed sorbent material could successfully be recycled ten times (via adsorption and desorption cycles) without losing any of its capacity for regeneration. A kinetic analysis was also conducted, and it was discovered that the reaction obeyed pseudo-second-order kinetics because of a higher R2 and good qe values. The Kf and 1/n values (1/n > 0.1) further adhered to the favorable nature of adsorption. The G° (-3.7093) and H° (4.40391) values indicate that the reaction should be endothermic, but the S° (25.107698) data indicate that there is unpredictability at the solid solution interface throughout the adsorption phase. A multivariate optimization methodology was utilized to progress a superior considerate of the synergistic connection between the extraction and separation procedures by concentrating on the optimization of extraction parameters. Central composite design (CCD) was utilized for optimization procedure variables of PHB-AgPrici and (cycle of adsorption/desorption) later combining optimization. The recommended technique offers a linear reaction for MB over the range of conc. 10 to 150 µg L− 1 with correlation coefficient ≥ 0.99775. Validity of the desired approach has been confirmed by spiking addition technique. The recommended technique was productively utilized to diverse real water samples. Furthermore, based on the experimental results, a mechanism is proposed for the adsorptive removal of organic dyes with PHB-AgPrici polymer adsorbent.
Research Article
Synthesized of poly(3-hydroxy butyrate)-b-poly(methyl methacrylate) with Ag nanoparticles for removal of methylene blue by multivariate optimization approach
https://doi.org/10.21203/rs.3.rs-2450619/v1
This work is licensed under a CC BY 4.0 License
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Methylene blue
next generation adsorbent.
Solid Phase Microextraction
Multivariate
PHB
Ag NPs
According to experts, pollution from both organic and inorganic sources poses a serious global threat to human survival. High concentrations of synthetic dyes in the water are thought to be detrimental to both humans and aquatic life. Globally, roughly 1000 tons of dyes are consumed annually, and 10 to 15 percent of those colors enter the natural water system without any environmental intervention [1]. Organic and inorganic waste drainage to natural water is an environmental problem that has strained global concern in recent years. Industrial sewages with a high range of destructive chemicals such as heavy metals, pigments, and aromatic dyes, discharge to the aquatic environment including sea, fresh water and cause adverse effect on the earth crust with their direct interaction, which are accountable for pollution of water resources [2–4]. The common chemical contaminants are aromatic compounds that include dyes, polycyclic aromatic rings compounds and derivatives of phenolic compounds are mainly use in industries [5]. It is notable that millions tons of dyes manufacture each year for different purposes in industries such as paper production [6], fabrics [7], sustenance [8], medicines [9]. Only a little amount of dyes in water can be visible and impose toxic effects on aquatic life, [10] and responsible for the low water penetration due to which photosynthetic phenomenon [11, 12]. Long exposer to the dye containing water can cause severe effects on health such as cyanosis, increased heart rate, jaundice, quadriplegia, shock, vomiting, tissue necrosis [13] and rhinitis [14]. Several strict legislation regulations pass by environmental protect agency (EPA) for the dye wastewater particularly from fabric and paper industries [15, 16]. Various techniques were established to eliminate organic dyes from wastewater such as co-precipitation; coagulation [15], oxidation [17], adsorption [18], precipitation [19], ion-exchange [20], flocculation, and membrane separation [9, 21] from industries. Amongst them, adsorptive technique is a vital simple and low cost approach with achieve ultra-deep removal efficiency, large-scale application, no secondary pollution and efficient regeneration ability [22, 23].
Numerous potential adsorbents such as activated carbon, zeolites [24], polymeric materials [25], sawdust [26] and, polymer nanocomposites [27, 28], have been widely used for the removal of dye up to strict EPA regulation and achieve ultra-clean water. Recently, wide-ranging research were done on biopolymer materials. The researcher conclusion that biopolymers have enhanced mechanical characteristic than other polymers systems due to their excellent structural properties. In the last two decades, biopolymers reveal probable applications for example adsorption of heavy metals [29], gas [9], aromatic harmful dyes [30], chemical sensing [31], dye scavenging [32]. In recent decades, due to the economic and ecological advantages, conventional polymers are replacing with biopolymers [33, 34]. Biopolymers such as microbial polyesters, poly (3-hydroxy alkanoates), PHAs, gain much attention. Amongst them, poly-3-hydroxybutyrate (PHB), short chain length member of PHAs, are measured as strong and excellent candidates with vary identical features to synthetic polymers which can be originate from eukaryotic organelles [35, 36].
Akiyama et al. investigate the adsorption activation of different polymer and conclude that PHB offer lower adsorption activation energy compared to other conventional polymer adsorbents. Poly (3-hydroxy alkanoate) microbial derived polyesters (PHA)s are accrued carbon-based materials into bacteria’s cell [37]. Moreover, there are some PHA derivatives to make appropriate for different adsorption activities [38, 39]. The biodegradable PHA derivatives are enormously desirable adsorbents for pollutant adsorption. In our previous study, we investigated solid phase extraction of lead, cadmium and zinc trace metal pollutant adsorption on diethanol amine functionalized PHB [40].
In contrast to the PHBs biopolymer, conventional plastics poly (propylene) [37], poly(ethylene) [37, 41–43], poly(styrene) [37, 44] are non-biodegradable that restrict their uses. PHAs are widely utilized for the adsorption of greenhouse gas [45], and consider a good candidate for the aromatic materials adsorption [44]. In recent decades, industrial scale production of PHB through microorganism gain huge interest and can be potentially utilized as adsorbent due to anionic nature in many reactions.
In this work, PHB biopolymer doped with silver can be synthesized through simple one pot method with specific process conditions. PHB-AgPrici can be efficiently utilized as adsorbents for the elimination of methylene blue dye from real water samples at first time. The adsorption behavior is investigated by using different isothermal models and kinetic studies and multivariate optimization approach.
2.1. Chemicals and reagents
100 mg L− 1 stock solution of methylene blue were prepared in ethyl alcohol (Sigma chemicals). 0.1 mol/L acetate and phosphate buffer solution been utilized to adjust pH in range of 2 to 10. Syringe system established in the lab and used for this study.
2.2. Instrumentation
Methylene blue were analyzed by colorimetric analysis by using Perkin Elmer UV-Vis. Spectrophotometer. FT-IR spectra were characterized by Jasco-430 model, Japan coupled with a (MCT) liquid nitrogen cooling detector used for the characterization of the PHB-AgPrici. SEM, and SEM-EDX analysis of polymer sample performed on FEI Quanta FEG 450 SEM, USA, operated at 200 kV. Differential scanning calorimeter (DSC) curve of PHB-AgPrici was analyzed by differential scanning calorimeter.
2.3. Preparation of ricinoleic acid from castor oil
85.6 g of potassium hydroxide were dissolved in 500mL ethanol and marked the solution as ‘A’. Castor oil (318 g) was dissolved in solution ‘A’ at 67oC under on continuous stirring for 200 min. Subsequently, the solution was cooled up to the room temperature and acidify by adding suitable stoichiometric amount of 1M H2SO4 solution. The upper ricinoleic acid layer was transferred to a separating funnel and three time washed through distilled water. The obtained liquid ricinoleic acid was dried by anhydrous Na2SO4. Yield: 260 g.
2.4. Synthesis of oligomer ricinoleic acid with Ag NPs (AgPrici)
AgNO3 (4.51 g) was solubilized into the ricinoleic acid (78.4 g) with oil thickness 0.62 mm, in a Petri dish (Φ = 20 cm). This solution was exposed to white light (30-Watt lamp) from 10 cm height under atmospheric condition. Oligomer oil nanocomposite was obtained after a month autoxidation [46].
2.5. Synthesis of methacrylated PHB (PHB-MA)
As shown in scheme I, the hydroxylated PHB (PHB-OH) was obtained by refluxing of chloroform solution containing PHB and diethanol amine according to the procedure reported in the cited reference. Hydroxyl ends of PHB were capped with methacryloyl chloride. Briefly, PHB-OH (8.21 g) and triethyl amin (2.90 g) were dissolved in CHCl3 (20 mL). Methacryloyl chloride (4.32 g) was added into this solution continuously stirring for 24 hrs. The reaction mixture was filtered from the side product, triethyl amine hydrochloride [40]. The solution was poured into excess methyl alcohol to precipitates methacrylated PHB (PHB-MA). The obtained polymer was filtered through filter paper and dried under vacuum at 25oC for 24 h.
2.6. Synthesis of PHB-AgPrici
Autoxidized ricinoleic acid is a macroperoxide initiator and it produces thermally free radicals and attach to double bonds of PHB-MA to produce PHB-Prici block copolymer [47]. Before the reaction the complete reaction assemble was purged by introducing argon through needle for about one min. A mixture of PHB-MA (1.20 g) and AgPrici (0.67 g) was dissolved in toluene (2.0 mL) in a reaction bottle under argon. The tightly capped reaction assemble was put into water-bath where the temperature was maintaining at 95 oC for 2h [38, 46, 47]. After the reaction, the compound in continuous stirring was coagulated in methanol. The resultant PHB-AgPrici copolymer was dried in vacuum for whole 24 h at 40oC.
Figure (1a and 1b) shows the FTIR spectra and DSC spectra of the as synthesized PHB-AgPrici copolymer. In addition, PHB-AgPrici was conformed through FT-IR spectroscopy. Peaks at 2975 and 2932 cm-1, as seen in Fig. 1a, are attributed to the vibrational peak of C-H stretching vibration. Indicating the -C = O stretching vibration, which permits the development of PHB-AgPrici copolymer, a strong sharp peak appeared at 1720 cm-1. The Differential scanning calorimeter spectra of as-synthesized PHB-AgPrici was shown in Fig. 1b, revealing the PHB blocks showed melting transition (Tm) at 162 oC and glass transition (Tg) at 52 oC, corresponding to characteristic signals of PHB-AgPrici.
The scanning electron microscope (SEM) and SEM-EDX of the PHB-AgPrici is shown in Fig. 2. The PHB-surface AgPrici's morphology makes it clear that the surface is rough and porous, which may be the reason why methyl blue is attracted to it. According to the elemental analysis of PHB-AgPrici by SEM-EDX, the silver nanoparticle was present (Ag 2.05%) in the block copolymer.
2.7. Adsorption Experiment
All experimental reaction of methylene blue dye adsorption was carried out through 30 mg of PHB-AgPrici copolymer as adsorbent into 15 mL of methyl blue solutions with 30-ppm concentration. Deionized water was used for dilution of stock solution for batch experiment. The purpose of the adsorption tests was to find any variations in the methyl blue's ability to bind to PHB-AgPrici under various circumstances, including pH (3–10), materials dose (10–30 mg), methyl blue conc. (5–30 ppm), and sorption period (10–60 min) at room temp. Physiochemical adsorptive performances were determined in batch-wise flow system. In the initial batch, 30 mg PHB-AgPrici were mixed in 15 mL of 30ppm methylene blue solution with continuous stirring in a flask. After a predetermined amount of time, the methyl blue concentration was measured using a UV-Vis spectrophotometer at 663 nm. Removal effectiveness and adsorption capacity (qe) of the methyl blue PHB-AgPrici adsorbent were calculated at equilibrium applying Equations 1 and 2 respectively.
where Ci is the methyl blue initial conc. and Co is the final conc. after the adsorptive reaction.
The adsorption capacities qe (mg/g) and Ci/Co shows the initial and equilibrium concentration (ppm) of dye. However, volume V and mass W denote as the reaction solution volume in liter and mass grams of the adsorbent, correspondingly [28].
Langmuir and Freundlich isotherms were utilized to determine methylene blue dye adsorption equilibrium. Furthermore, Eq. 3 attributed to Langmuir isotherm whereas for explaining the adsorption behaviors this equation converted to linear in Eq. (4).
$$\frac{{C}_{e}}{{q}_{e}}qe=\frac{{q}_{max}{K}_{L}{C}_{e}}{1+{K}_{L}{C}_{e}}\dots \dots \dots \dots \dots \dots \dots \dots \dots \dots \dots ..\left(3\right)$$
$$\frac{1}{{q}_{e}}=\frac{1}{{K}_{L}{q}_{max}}.\frac{1}{{C}_{e}}\times \frac{1}{{q}_{max}}\dots \dots \dots \dots \dots \dots \dots \dots \dots .\left(4\right)$$
Whereas qmax represent the maximum dye adsorptions capacities (mg/g) of the PHB-AgPrici and KL (L/mg) demonstrations Langmuir isotherms to calculate adsorption behavior of methyl blue on the PHB-AgPrici adsorbent surface. RL the separation factor calculates by Eq. (5).
$${R}_{L}=\frac{1}{{1+{C}_{i}\times K}_{L}}\dots \dots \dots \dots \dots \dots \dots \dots \dots \dots \dots \dots .\left(5\right)$$
Where RL is used to demonstrate the possibility of adsorption on a linear curve (RL = 1.0), to be either beneficial (RL > 0 and 1.0) or unfavorable (RL > 1.0), and linear RL to be irreparable when RL = 0. Eq. contains the linear form of the Freundlich's isotherm Eq. (6).
$$log{q}_{e}=log{qK}_{f}+\frac{1}{n}log{C}_{e}\dots \dots \dots \dots \dots \dots \dots \dots \dots \dots \dots \dots \dots \dots .\left(6\right)$$
The adsorption capacity and intensity of the suggested technique using PHB-AgPrici as an adsorbent for methylene blue are to be determined using the Kf (Freundlich's constant) and 1/n. Adsorptive removal process' positive (1/n is superior than 0.1 and less than 0.5) or unfavorable (1/n is larger than 2) outcomes can also be determined using the 1/n.
2.8. Kinetic study
Pseudo first and pseudo second order kinetics were applying to calculate the rate of methylene blue adsorption on methylene blue using PHB-AgPrici adsorbent as reveals in Eq. (7) and Eq. 8 correspondingly:
Sorption is represented by the symbol qt in time t, and the equilibrium reaction rates are represented by the symbols K1 (min1) and K1 (g mg1 min1). The results of the linear coefficient regression must be used to estimate the best isothermal and kinetic model R2.
2.9. Thermodynamic studies
Thermodynamic studies are to carry out to investigate the spontaneity, possibility and exothermic or endothermic reaction of the adsorption method by using, Gibbs free energy (ΔGo), adsorption entropy (ΔSo) and enthalpy (ΔHo). Difference in Gibbs free energy, enthalpy and entropy of the methyl blue on PHB-AgPrici polymer was evaluated by using thermodynamic equation.
$${\varDelta G}^{^\circ }=-RT\text{ln}(\frac{{q}_{e}}{{C}_{e}})\dots \dots \dots \dots \dots \dots \dots \dots \dots \dots ..(9)$$
$${\text{ln}(\frac{{q}_{e}}{{C}_{e}})\varDelta G}^{^\circ }=\frac{{\varDelta H}^{^\circ }}{R}+\frac{{\varDelta S}^{^\circ }}{RT} \dots \dots \dots \dots \dots \dots \dots \dots \dots ..\left(10\right)$$
$${\varDelta G}^{^\circ }={\varDelta H}^{^\circ }-T{\varDelta S}^{^\circ }\dots \dots \dots \dots \dots \dots \dots \dots \dots \dots \dots .\left(11\right)$$
Whereas T (Kalvin) denotes the temperature at which methyl blue dye is present and R denotes the gas constant, which is 8.314 J/mol. K. The liner plot intercept and slope of ln(qe/Ce) vs 1/T can be used to calculate S° and H°, respectively.
2.10. Portable solid phase micro extraction reaction
Innovative PHB-AgPrici colorimetric sensor based solid phases micro extraction via portable syringe systems has been established to remove methyl blue from a variety of environmental water samples utilizing colorimetric censorship approach by UV-Vis spectrometric. A portable syringe device coupled to a long column (150 cm 5 mm i.d.) that contains 15.0 mg of PHB-AgPrici adsorbent. The SPME-PS system was wash through ethanol before used to avoid undesirable effect on the recovery of the methyl blue analysis. As internal standard 10mL (20ppm) of methyl blue and real water sample were mixed. The pH was maintained through buffer solution. Sample were taking into the PHB-AgPrici based SPME-PS system through pushing up/down the plunger and then back to the beaker which is recognized as one pot one cycle adsorption/desorption system. In this innovative technique, 10 adsorption cycles were used for the adsorptive recovery of methyl blue form the aqueous solution in one-minute time. After the removal of dye on PHB-AgPrici sensor, the adsorbent was simply regenerated in one min by using 2.0 mL of methanol in to the into the SPME-PS system. Subsequently, purged liquid was tested in UV and check the absorbance of blank prepared in the same way.
Multivariate optimization through data screening and surface response procedure
A univariate approach offers understanding regarding different variables and possible interactions. The multivariate technique may have improved sympathetic regarding synergistic connection with separation and extraction methods dealing with extraction and optimization variables. The most common statistical method for screening (PBD) (to identify the key factors to be further investigated) is DOE, which is used in conjunction with plackett-Burman design, response RSM, and CCD for further data interpretation. Three factors—pH (3–11), PHB-AgPrici amount (from 3.0 to 15.0 mg), and adsorption/desorption cycles (from 2.0 to 10)—were used to screen the variables and determine their relative importance for the proposed PBD approach. As shown in Fig. 3, screening out was done using a Pareto chart of identical result, residual plot for responses, and an interaction plot for responses (a, b). Optimization methods were performed by two multivariate techniques such as central composite method and screening of variables through multivariate process, where different reaction variables were optimized for proposed SPME technique. After variables screening, the experimentations were set in a way that few variables have been fixed to be such as the pH (6.0), PHB-AgPrici (mg) (6.0 mg) quantity, cycle of Adsorption/desorption (7 time). After that the overhead fixed variables had been optimized by the CCD application after optimizing. The study of variables and stages was the pH4, 6 and 10; Quantity of PHB-AgPrici (2, 6.0 and 20 mg) and cycle of (Adsorption/desorption) for 2, 7 and 12 times (Table 1). Among the most common design is the CCD quadratic model, which tend to be most utilized designs of CCD. The CCD quadratic model has been utilized for formulating a relation among independent and depending variables of their optimization. Subsequently performing uses, CCD theoretical higher reaction attained by means of quadratic equation. The effect and interaction of these experimental variables were statistically asses by using ANOVA test.
|
Source |
DF |
Adj SS |
Adj MS |
F-Value |
P-Value |
|---|---|---|---|---|---|
|
Model |
15 |
4982.47 |
332.16 |
2.37 |
0.057 |
|
Blocks |
1 |
402.55 |
402.55 |
2.87 |
0.112 |
|
Linear |
4 |
222.49 |
55.62 |
0.40 |
0.808 |
|
pH |
1 |
7.04 |
7.04 |
0.05 |
0.826 |
|
amount of adsorbent |
1 |
18.58 |
18.58 |
0.13 |
0.721 |
|
Temp |
1 |
12.07 |
12.07 |
0.09 |
0.774 |
|
Time |
1 |
171.45 |
171.45 |
1.22 |
0.287 |
|
Square |
4 |
3033.45 |
758.36 |
5.41 |
0.008 |
|
pH*pH |
1 |
1116.67 |
1116.67 |
7.97 |
0.014 |
|
amount of adsorbent* |
1 |
1301.15 |
1301.15 |
9.28 |
0.009 |
|
Temp*Temp |
1 |
23.67 |
23.67 |
0.17 |
0.687 |
|
Time*Time |
1 |
1780.02 |
1780.02 |
12.70 |
0.003 |
|
2-Way Interaction |
6 |
1007.16 |
167.86 |
1.20 |
0.363 |
|
pH*amount of adsorbent |
1 |
39.06 |
39.06 |
0.28 |
0.606 |
|
pH*Temp |
1 |
126.56 |
126.56 |
0.90 |
0.358 |
|
pH*Time |
1 |
76.56 |
76.56 |
0.55 |
0.472 |
|
amount of adsorbent*Temp |
1 |
10.70 |
10.70 |
0.08 |
0.786 |
|
amount of adsorbent*Time |
1 |
736.24 |
736.24 |
5.25 |
0.038 |
|
Temp*Time |
1 |
5.93 |
5.93 |
0.04 |
0.840 |
|
Error |
14 |
1962.33 |
140.17 |
||
|
Lack-of-Fit |
12 |
1937.66 |
161.47 |
13.09 |
0.073 |
|
Pure Error |
2 |
24.67 |
12.33 |
||
|
Total |
29 |
6944.80 |
3.1 Data Screening Strategy
Variables Three factors—pH 2 to 10, the amount of PHB-AgPrici 2.0 to 15.0 milligram, and 2 to 12 cycles (adsorption/desorption)—have been used in screening in order to identify and anticipate their vital importance for the proposed technique employing PBD. As shown in Fig. 3, screening out was applied using a Pareto chart of standardized effect, residual plot for responses, and interaction plot for responses (a and b). Pareto and usual chart have been utilized by the use of FD to discover the maximum noticeable variables are displayed in (Fig. 3a and b). The result indicates that the Amount of PHB-AgPrici (2.0 to 10.0 milligram) and cycle of adsorption/desorption (2.0 to 12 times) has a prominent optimistic influence on the expertise of the proposed technique and had been additionally inspected to optimized by the use of CCD and response surface methodology. The lengths of bar in Pareto chart are probable to absolute value of the projected impact and line in vertical portray 95% of the confidence interval. The reference line influences in above is measured to be noteworthy ones with respect to response. After screen out we attained a lowest t-value (95.0%) of 2.14 and it has been determined that above this value the factor will be extremely noteworthy. The Fig. 3 (a) display normal probability percentages versus internal standardized residuals plot and response optimization of the effect Fig. 3 (b). A straight-line pattern was detected to be trailed main lacking any departure, that additionally representing that the residuals have convincingly common distributions at a given level as shown in Figure. 3 (a and b). These results acquired show that the model is dependable.
3.2. Optimization by CCD
Main variables as pH (2–10), PHB-AgPrici Quantity (2.0 to 10.0 milligram) and of Adsorption/desorption (2.0 to 12 times) by CCD optimization of the RSM in experiments design via statistical tool Minitab. After that to form and comprehend a statistical and graphical relation among variables, independent and dependent both, the CCD quadratic model has been approved for optimizing above variables, follow. The quadratic equation of the CCD was utilized to calculate the maximum theoretical response in Table 2. To show the relationship and contact between the experimental variables, the ANOVA test was used (Table 1). The p-value is higher (> 0.05), which indicates statistically that the proposed mode has a significant impact at the 95% confidence level. P-value (> 0.05) in 95% assurance level statistically presenting noteworthy impact in ANOVA test. Worth of fit of polynomial model equation was conveyed with determination coefficient (R2 = 86.06% and adjusted R2 = 80.84%). For R2 is a measure of variation quantity around mean illuminated by model. Huge adjusted R2 values point out decent correlation between investigational data and fitted model that further conformed statistical significance of the propose model.
Highest response of dependent variables is quantity of PHB-AgPrici (2.0 to 10 milligram) and pH to be mention by the contour exterior plot and 3D exterior by quadratic equation. The 3-Dimensional contour and surface plots had been haggard pH with PHB-AgPrici amount which displayed in Fig. 4 (a and c), however, contour plot and 3D surface plot between pH and time are shown in Fig. 4 (b and d) correspondingly. The curvatures and center of these plots is the representative of their possible contact amongst the objective variables by the projected approach. It was noticed from (Fig. 4a and 4c) that at central attainment a plateau portrays highest recovery % of MB. The highest recovery of MB has attained of studied variables.
3.3. Adsorption isotherms
This study examines an association among the conc. of dye and their accumulating modes on sorbent meso-surface (at constant temperature). MB adsorption were done by the utilization of 10.0 milligram of the adsorbent under optimized condition, about 20 mg/L− 1 was the initial concentration of MB. An adsorption isotherm offers valuable data around adsorption capacity, binding affinity, and bio sorbent surface properties that assist to comprehend the adsorbate binding mechanism with bio sorbent. In this work, two theoretical models, Langmuir and Freundlich's isotherms had been utilized to observe MB adsorption behavior on PHB-AgPrici as displayed in Fig. 5 (A and B). The outcomes are précised in Table 2 exposes Langmuir's isotherm was top fitted meanwhile values of linear regression coefficient (R2) isotherm observed to be greater than that with Freundlich isotherm for both MB that certified the monolayer adsorption on PHB-AgPrici. Maximum adsorption capacity of MB observed to be 169.3 mg/g, correspondingly. The values of separation factor (RL) is also founds to be then one that favor adsorption phenomenon. Langmuir's isotherm defines monolayer adsorption onto PHB-AgPrici surface requiring finate amount of adsorption sites however, Freundlich's isotherm supports that adsorption happens heterogeneous surface of adsorbent.
| a. Isotherm parameters | ||
|---|---|---|
| Type of isotherm | Parameters | MB |
| Langmuir | qmax (mg/g) | 116.6861 |
| KL (L/mg) | 0.055588 | |
| RL | 0.230666 | |
| R2 | 0.99032 | |
| Freundlich | Kf | 9.322449 |
| 1/n | 0.61771 | |
| R2 | 0.95324 | |
| b. Kinetics parameters | ||
| Parameters | MB | |
| Pseudo first order reaction | qe. exp (mg/g) | 46.6 |
| qe. cal (mg/g | 5.2396 | |
| K1 | -0.0006 | |
| R2 | 0.7789 | |
| Pseudo second order reaction | qe. cal (mg/g | 53.37235 |
| K2 (g mg− 1 min− 1) | 0.02274 | |
| R2 | 0.99775 |
3.4. Adsorption kinetics
For the adsorbent adsorption efficiency calculation, for attaining equilibrium time is essential. Diverse solutions of equivalent concentration 30 milligram/Liter MB (10 mL) had been put together in test tube of 10 milliliters than 10 milligram of polymer in all test tube were put in however retained the experimental condition constant for other samples. The samples have shacked for a diverse time intermission of 05, 10, 15, 20, 25, 30 minutes to examine time to equilibrium and determined the variation binding capacity. It was declared that by enhancing in interaction time adsorption greater than before and time of equilibration has been attained within 25 minutes. Diverse kinetic models had been utilized as pseudo-first order, and pseudo-second-order. By application of linear rate equation of pseudo-first and pseudo-second-order, the (K1 & K2) correlation values and rate constants has evaluated (Table 2) correspondingly. The ln (qe–qt) plot vs time produces an correlation coefficients of 0.7789, as shown in Fig. 6a, which specified that sorption of MB on PHB-AgPrici do not follow the pseudo-first order kinetics. The time/qt vs time plot for pseudo second order produces noble correlation coefficients of 0.998. Linear plots of slope and intercept acquired the (K1 & K2) rate constants as shown in Fig. 6b. The R2 (0.998) values demonstrates that pseudo-second-order kinetic is followed by reaction, and reaction relay on the quantities of equally substrate and analysts of pseudo second-order model with probable chemical interface.
3.5. Adsorption Thermodynamics
The adsorption impact of the MB on PHB-AgPrici were took in diverse temperature varies from 298 to 323 K and revealed in Fig. 7. The adsorption got drop by temperature increase. (∆H°) total changes in enthalpy (KJ mol− 1), (∆G°) Gibbs free energy, (∆S°) changes in entropy (KJ mol− 1 K− 1) of MB by use of PHB-AgPrici as adsorbent were evaluated by equation of thermodynamic. Gibbs free energies are (kJ mol− 1), temperature is demonstrated T (K) and equilibrium constant (Kc). ∆H° value was count to be 4.40391 (kJ mol− 1), attributed to endothermic reaction. Whereas, ∆S° achieve as 25.1077 (kJ mol− 1 K− 1), corresponding to the interferences in solid solution throughout methylene blue as given in Table.3.
| Adsorbent | Temp (K) | KL | ΔGo (KJ mol-1) | ΔHo (KJmol-1) | ΔSo (JK-1mol-1) | R2 |
|---|---|---|---|---|---|---|
| 298 | 3.477 | -3.087475535 | 4.40390826 | 25.10769802 | 0.99512 | |
| 303 | 3.551 | -3.192330437 | ||||
| 313 | 3.77 | -3.453423389 | ||||
| 323 | 3.98 | -3.709324586 |
3.6. Selectivity
Real-world samples contain a variety of molecules species that can interfere with the methylene blue lead signal and negatively affect the recommended extraction method's effectiveness. We use 10 mL (30 mg/L) of diversely interfering methylene blue in an analyst ratio experiment to highlight the impact of various interfering ions or compounds. When an ion or molecule affects the signals of the reactant molecules and ions by more than 5%, it is thought to be tolerable. From the aforementioned experiment conducted under ideal conditions, we may deduce that Na+, K+, PO43−, SO42−, CO32−, and NO3− can tolerate levels above the 2000-tolerance limit as measured by the interfering concentration to analyte ratio.
3.7. Removal Activities
The SPME-PSS investigative enactment joined with spectrophotometric technique were effectively examined in optimized conditions of experiment. A linear calibration curve attained (10–100 µg L− 1) concentration range. The LOD of proposed technique were attained to exist in 0.55 µg L− 1 via applying the (3S blank S− 1) subsequent formula, here S signifies blank standard deviations (three times), and S representing calibration curve slope. The RSD repeating nature of the projected technique had been acquired to remain 4.5% with 15.0 µg L− 1 MB. Consistency of projected technique were as well as tested of studied dye at 2 conc. level by spiking standards (3 and 6 µg L− 1) in real water. Acquired % regaining greater than 97% as presented in Table 4, that approves the rationality of the coveted SPME-PSS technique for elimination and MB quantifiable determination.
| Sample | Added (ng/L− 1) | Examined (ngL− 1) | Recovery (%) |
|---|---|---|---|
| .... | ND | …. | |
| Drinking-water | 3.0 | 2.95 ± 0.16* | 99.1 |
| 6.0 | 5.96 ± 0.15 | 99.5 | |
| .... | 1.9 ± 0.12 | .... | |
| Waste water | 3.0 | 4.8 ± 0.15* | 98.2 |
| 6.0 | 7.8 ± 0.18 | 99.0 | |
| .... | ND | …. | |
| Canal water | 3.0 | 2.99 ± 0.17* | 99.9 |
| 6.0 | 5.96 ± 0.16 | 99.6 | |
| .... | ND | …. | |
| River water | 3.0 | 2.90 ± 0.16* | 99.3 |
| 6.0 | 5.98 ± 0.20 | 99.7 | |
| .... | ND | …. | |
| Plastic bottle water | 3.0 | 2.88 ± 0.16* | 96.5 |
| 6.0 | 5.94 ± 0.15 | 97.6 |
3.8. Application to real water samples
Projected SPME-PSS technique has been effectively utilized to quantitatively govern MB in real water (consuming, river, tap, canal, and wastewater) as presented in Table. 4. The outcome discovered that wastewater has somewhat high concentration of MB and nearby is far apprehension about methylene blue in fresh water for wellbeing fact of opinion in the recent works because of their poisonousness [48, 49].
3.9. Adsorptive mechanism of PHB-AgPrici adsorbent
The methylene blue dye adsorption mechanism is characterized through the development of a heterojunction copolymer material. The adsorption of methylene blue molecules undergoes three major steps; (1) synthesis of hydroxylated PHB through methacrylated PHB and diethanol amine, (2) then the loading of oligomer ricinoleic acid with Ag NPs (AgPrici) and create more hydroxal and O− terminal ions for effectively adsorption of methylene blue on the PHB-AgPrici co polymer, (3) through different charge transfer reaction which produce oxidizing and reducing ions and radicals on the surface of PHB-AgPrici polymer which is significantly reactive toward the absorptions of the positively charged sulfur on these O− ions. The successive adsorption mechanism of MB can be shown in Scheme II revealing next generation adsorption capacity and fast reactivity toward organic dye through immense O− terminal ions.
3.10. Comparison of PHB-AgPrici adsorbent for methylene blue removal with other adsorbents
The methylene blue adsorption on the PHB-AgPrici adsorbent was compared with other reported materials in literature and summarized in Table 5. Amongst these adsorbents, PHB-AgPrici polymer reveals highest percentage efficiency in a reasonable reaction time compared to other samples. The adsorbent efficacy of the PHB polymer enhanced by the loading of oligomer ricinoleic acid with Ag NPs which increase hydroxyl and O- terminal ions for the fast and effective adsorption of methylene blue dye and achieved highest percent removal up to 99.5%.
| Material | Sample matrix | Sample volume (mL) | Adsorption capacity (mg/g) | Efficiency/% | Time (min) | Ref |
|---|---|---|---|---|---|---|
| ASAC and CAC | Industrial effluent | 50 | 98 | 98 | 120 | [50] |
| polydopamine microspheres | Waste water | 100 | 90.7 | 98 | 80 | [51] |
| activated carbon | aqueous solution | 500 | 142 | 96 | 60 | [52] |
| graphene | aqueous solution | 855 | 153 | 99 | 40 | [53] |
| Agro-wastes | aqueous media | 100 | 55.4 | 90 | 200 | [54] |
| PHB-AgPrici | Canal water | 15 | 169.3 | 99.5 | 30 | This Study |
A novel and ecological pleasant SPME-PSS was presented as an alternate way for the elimination of poisonous MB in diverse environmental water samples former to measure by spectrometric methods. The core benefit for utilizing SPME-PSS because of their easiness and calmer control than with conventional solid phase methodologies. Variables show imperative part on extraction proficiency of projected SPME-PSS has been taken and optimization was done by utilizing multivariate optimization. The CCD and combined design has been utilized during the experimentation to shade out and optimize of furthermost projecting vital variables show significant part on productivity in extraction in projected technique. We expect the planned technique will be utilized as moveable tool for separation in the elimination and determining diverse ecological contaminants in diverse environmental samples. The present technique consists numerous benefits related with batch techniques and traditional column and lessen the contaminating chance or loss of sample, non-tedious, effortlessly managing and low-priced techniques. R2 and RL values demonstrates the pseudo second order kinetics has been followed by the reaction and is naturally promising. However, Kf and 1/n value designate the MB adsorption on PHB-AgPrici. Endothermic reaction was examined by positive value of ∆H°, while increase in randomness at solid solution interface throughout MB adsorption were determined by value of ∆S°. The concluded data directed that MB was satisfactorily lesser than the concentrated MB contaminant level in water. Because of the toxicity caused by MB to numerous marine creatures even at little concentrations, the severe environmental complications might arise.
Acknowledgments: This work was funded by Tubitak 2221. Rooh Ullah would like to thanks to Tubitak for financial supports. Dr. M. Tuzen thanks to Turkish Academy of Sciences (TUBA) for partial supports.
Conflicts of Interest: The authors declare no conflict of interest.
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Schemes I and II are available in the Supplementary Files section.
No competing interests reported.
- Scheme1.png
Scheme I: The reaction synthesis design of ricinoleic acid, oligomer ricinoleic acid with Ag NPs (AgPrici), methacrylated PHB (PHB-MA) and PHB-AgPrici
- Scheme2.png
Scheme II. Adsorptive mechanism of PHB-AgPrici adsorbent
