Recyclable Magnetic Nickel Ferrite-Carboxymethyl Cellulose-Sodium Alginate Bio-Composite for E�cient Removal of Nickel Ion from water

In wastewater treatment, magnetic bio-composites are frequently investigated as an adsorbent due to their great capacity for adsorption and affordability. In this current work, an attempt has been made to develop spinel nickel ferrite carboxymethyl cellulose composite (NiFCMC) and modi�ed its surface by alginate polymer to form NiFCMC-Alg. composite. Several techniques were utilized to characterize these adsorbents including (FTIR), XRD (X-Ray Diffraction), FE-SEM, EDS (energy-dispersive spectra), TGA (thermogravimetric analysis), VSM and pH zpc . These adsorbents were explored to check their potentiality to remove Ni (II) ions in aqueous medium on various parameters such as contact time, initial metal ion concentration, pH, adsorbent dose and temperature. The optimum equilibrium time noticed was 180 minutes at pH 8 with adsorbent dose of 0.1 g. Results of kinetic studies showed best �t result for Lagergren pseudo second order model. Likewise, the Langmuir isotherm model also showed good agreement with maximum adsorption capacities 47.84 mg/g, 60.24 mg/g for NiFCMC and NiFCMC-Alg. respectively. Calculated thermodynamic parameters con�rmed spontaneous nature of adsorption process. The regeneration e�ciency of both adsorbents was studied for �ve cycles. This study has shown that NiFCMC and NiFCMC-Alg. can be a good substitute for removing Ni (II) ions in aqueous medium.


Introduction
Water pollution is one of the major environmental problems globally with the rapid industrialization, urbanization and intensi ed agricultural practices that need much attention of the researchers worldwide.
The primary reason behind water contamination is direct disposal of e uents without treatment into water bodies by textile, dyes and tanning industries, painting, mining, petrochemical and fertilizer/ pesticides industries [1], [2].Heavy metals are especially harmful and tend to accumulate in human bodies and pose severe health issues.Therefore, their removal from the waste water is necessary.Different traditional approaches and methodologies such as coagulation, ltration, precipitation, ion exchange, solvent extraction etc. have been explored for the removal of heavy metals [3].Due to certain drawbacks of these techniques, enormous research efforts are made to develop e cient and cost effective adsorbents as alternative to these conventional methods.From the literature review, it is indicated that adsorption is a promising technique as it is simple, effective, cost effective and less time consuming is frequently employed to eliminate the certain heavy metals from waste water [4], [5].
Nickel belong to group of heavy metals which is mainly produced from waste water of industries involved in mining, metalworking, and storage battery production etc. [6].Being toxic metal, it cause respiratory and digestive disorders, skin problems and carcinogenesis [7].Because of its ill-effects, WHO and U.S.E.P.A. have set upper permitted limits for Ni in drinking water and waste water at 1 ppm and 0.02 ppm respectively [8].
A cellulose derivative called carboxymethyl cellulose (CMC) is an anionic polymer that is water soluble containing hydroxyl (-OH) and carboxylic (-COOH) functional groups which act as binding sites for divalent actions [9].Alginate is a linear polysaccharide obtained from brown algae.It is made up of residues from D-mannuronic acid (M) and L-guluronic acid (G) that are covalently bound to one another and contain carboxylic groups.It proved to be e cient and economical adsorbent in waste water treatment application [10], nanomaterials like magnetic nanoparticles, graphene, carbon nanotubes were known to be reported for adsorption and mechanical properties with impregnation with polysachharide [11], [12].The focus of adsorption research has been on to the incorporation of polysaccharides with Fe 3 O 4 as adsorbent due to simple method of preparation, large surface area and high e ciency [13].
Though nano ferrites proved to be good adsorbents but due to lesser stability and performance in aqueous medium, their surface are modi ed by doping, surfactant treatment and polymer coating to enhance their performance [14].Heavy metal ions including Ni (II), Cd (II), Pb (II), and Cu (II) are the subject of continuing research by using modi ed chitosan and calcium alginate [15], 2007), cellulosehydroxyapatite beads [16], spent coffee grounds composite beads [17] and Magadiite materials [18] and alginate on hemp bers [19] has been done.Various composites /blend of CMC modi ed by biopolymers and synthetic polymers have been reported for the removal of heavy metal ions.The removal of SA/CMC blend for turmeric extract [20], As (III, V) by using zero-valent stabilized starch and CMC [21], Eu (III) by magnetic CMC composite [22], iron Cr (VI) by SA/CMC beads [23], U(VI) by polyaniline/CMC beads [24], Cu (II) removal by polyacrylic acid/CMC [25], Mn(II), Pb(II) and Cu(II) by magnetic SA/CMC composite hydrogel [26] and Cu(II) and Cr(II) by SA/CMC/ yash zeolite sphere [27] has also been reported.
In this work, an attempt has been made to remove Ni (II) ion by spinel nickel ferrite carboxymethyl cellulose composite and modifying its surface further with alginate polymer in aqueous medium.The removal of nickel ion by these adsorbents is less reported as per literature review.The synthesis of composite at normal conditions was easiest and least expensive technique.The cost-effectiveness of the adsorbents was proven by exploring the regeneration and reusability of adsorbents up to six adsorptiondesorption cycles.

Material
All the chemicals reagents used in the study were of analytical grade.Nickel chloride, ferric chloride, hydrazine hydrate, diethyl oxalate, Nickel sulphate, sodium citrate, potassium iodide, dimethyl glyoxime, hydrochloric acid, ammonia, sodium alginate (food grade, 91%), CaCl 2 , Hydrochloric acid was available for purchase from Loba Chemie Ltd.India.Carboxymethyl cellulose (CMC) was synthesized in laboratory from the cellulose extracted from corn cob.

Nano Nickel Ferrite (NiF) Synthesis
Spinel nickel nano metal ferrites (NiFe 2 O 4 ) were synthesized via low temperature combustion.Using this approach, hydrous solution of nickel chloride and ferric chloride were mixed with the prepared oxalyldihyrazide (ODH) compound in stoichiometric ratio of 1:2:4.Resulting solution was then concentrated on a water bath at 90 o C for two hours and annealing of the concentrate was done in a mu e furnace at 600 o C for three hours to have the nished product labelled as Nickel ferrite, which is brown in colour [14], [28].

Surface modi cation of nano nickel ferrite with carboxymethyl cellulose (CMC) and Sodium Alginate
The composite of nano nickel ferrite with CMC was prepared via cross linking method.The CMC used was prepared by alkalization and etheri cation of cellulose extracted from corn cob-an agricultural waste in our previous work [29].In distilled water, CMC sodium salt was dissolved (2%, 50mL) and 1g spinel nano ferrites were dissolved in 10 ml distilled water separately and added to it and stirred for 2 hours.
Using a syringe needle, the mixture was added to a solution containing 5.5g in 100 ml of 0.5M CaCl 2 .
After 24 hours, the composite thus formed was ltered, rinsed with distilled water and nally dried at 50 o C [30]- [32].
The surface modi cation of CMC-Ni spinel nanoferrites was done with polymer sodium alginate (Na-alg).
In this process, 1:1 of CMC (2%) and spinel ferrite of respective transition metal was mixed and stirred uniformly for 15 minutes.The sodium alginate 4% solution was made by combining sodium alginate with distilled water agitated by heating at 50 o C and was then added to the above mixture.Mixture was allowed to stir for 2 hours and introduced into a solution containing 0.5M CaCl 2 (5.5g in 100 ml) with a syringe needle.The composite was ltered after 24 hours, washed and dried at 50 o C [30]- [32].

Characterization
FTIR spectrophotometer (Shimadzu 8400S) was used to characterize NiF, NiFCMC, and NiFCMC-Alg.By using a scanning electron microscope (SEM) with an EDS detector (JEOL JSM-7610, EDS: OXFORD EDS LN2), the surface morphology was investigated.The thermal stability of adsorbent was determined by thermo gravimetric analysis (TGA) (Perkin Elmer TGA 4000).The crystallite structure was calculated by using X-ray diffraction.pH (XRD, Bruker D8), pH of Point zero charge (pH zpc ) was a calculated by solid addition method.Magnetic properties were determined by a Vibration Sample Magnetometer VSM-7400.

Adsorption Studies
The adsorption behavior of NiFCMC and NiFCMC-Alg.adsorbents was calculated by Batch adsorption method.In the present method, a de ned adsorbent amount (0.1g) and a known concentration of NiSO 4 .6H 2 O (100 mg/L) were mixed in several conical asks and then shaken in a thermostatic shaker for three hours at 150 rpm.Samples were taken after a set period of time, and the solution's reduced concentration was estimated by measuring absorbance using UV spectrophotometer (Model: Shimadzu, 8400 S) by producing more intense colour by using dimethylglyoxime [33].
The stock solution for NiSO 4 .6H 2 O was prepared by adding 4.479g in 1000 mL.The reagents used for the procedure were prepared as follows: 1. HCl solution (0.5N): 50 mL of concentrated HCl was diluted to 1000 mL with distilled water.2. Sodium Citrate solution: To make this solution, 125 g of sodium citrate (Na 3 C 6 H 5 O 2 .2H 2 O) was dissolved in 500 mL of distilled water.
3. Iodine Solution (0.005N): 20 g of potassium iodide (KI) was dissolved in 5mL distilled water.To this solution, 6.4 g of iodine crystals were dissolved and solution was diluted to 1000 mL with distilled water.
4. Dimethylglyoxime (DMG): 1 g of dimethylglyoxime was dissolved in 100 mL of concentrated ammonia followed by addition of 100 mL of distilled water.
Procedure: In 50 mL volumetric ask, 1 mL of aliquot of Ni (II) ion sample not containing more than 2 µg/ mL of solution was taken.To this solution, 20 mL of 0.5 N HCl was added, followed by addition of 10 mL sodium citrate solution, 2 mL of iodine solution and 4 mL of dimethylglyoxime solution.The solution in titration ask was made 50 mL with distilled water and allowed to stand for 20 minutes for the colour to develop.The absorbance of this solution was measured at max of 470 nm by UV-spectrophotometer.
The equations ( 1) and ( 2) were used to evaluate Q e adsorption capacity (mg/g) and percentage removal of Ni (II) ions respectively [14].
Where, C o , C t and C e are concentrations (in ppm) of metal ion solution at initial time, time t and at equilibrium, V states metal ion solution volume (in litre) and m is mass of adsorbent (in g) [14], [34].

Regeneration Studies:
After studying the adsorption behavior, the predetermined quantity of utilized adsorbent was employed for regeneration.It was done by treating 1g of used adsorbent with 100 ml of 0.1N HCl in conical ask for 1hour on thermostatic shaker at 150 rpm.In order to reuse the adsorbent, it was ltered, washed and dried.The Eq. 3 was used to calculate the percentage regeneration e ciency of NiFCMC and NiFCMC-Alg.[14].

Amountofmetalionadsorbedinnthcycle
Figure 1 shows FTIR spectra of NiF, NiFCMC and NiFCMC-Alg.composites in the range between 4000 − 400 cm − 1 .The strongest peak is associated with the metal-oxygen band in the tetrahedral site appeared at 500-600 cm − 1 and the peak at 400-450 cm-1 is attributed to metal-oxygen band in the octahedral sites which con rmed formation of a spinel metal ferrite [14].The peak at 1593-1595 cm − 1 and 1420 cm − 1 of sodium alginate corresponds to symmetric and asymmetric COO-stretching vibration of carboxylate group.The strong adsorption peaks at 3306-3310 cm − 1 corresponds to hydroxyl (-OH) group stretching and 2912 cm − 1 for aliphatic -CH stretching of the ether group resulting from carboxymethylation of cellulose.The spectral bands at 1323-1325 cm − 1 corresponds to C-O stretching and > CH-O-CH 2 stretching of saccharide appeared at 1020-1037 cm − 1 in the spectra of NiFCMC and NiFCMC -Alg.which con rmed that sodium alginate has been attached on the surface of NiFCMC [35], [36].

D= (4)
where, D represents crystalline size, is X-ray wavelength, β is broadening peak and θ is diffraction angle.Average crystallite size of NiF, NiFCMC and NiFCMC-Alg was calculated as 21nm, 25.63nm and 38.42nm.

Field Emission Scanning Electron Microscopy (FESEM)
Figure 3 (a, b and c) shows the SEM images of NiF, NiFCMC and NiFCMC-Alg.respectively.The crystalline structure of nickel ferrite, which is also indicated by the XRD pro le, was con rmed by the particles' appearance as aggregates of homogeneous grains with spherical shapes.The average size range of nickel ferrite was found to be 0.549 µm and in case of NiF-CMC it was 3.5µm.It indicated that the size of NiFCMC was larger than uncoated NiF and the surface became more porous.Further in NiFCMC-Alg.composite, the cross-section showed interior with more porosity on the surface [27].  1 along with its atomic and weight percentages.The percentage of carbon content increased in CMC and CMC-Alg composites as compared to pure metal ferrites as revealed by the results.It con rmed that sodium alginate and carboxymethyl cellulose were adhered to the nickel ferrite surface.

Thermogravimetric Analysis (TGA)
By the technique of thermo gravimetric analysis, thermal stability of the NiF, NiFCMC, NiFCMC-Alg.was investigated.The sample was heated in air atmosphere with temperature ranged from range 30 to 800°C having heating rate 10°C/minute.Figure 5 shows TGA of NiF, NiFCMC, NiFCMC-Alg.
A weight loss of 6-10% was observed at temperatures about 100°C, which may be caused by evaporation of trapped moisture in the samples.Around 250°C, additional weight loss of 4-8% was observed for NiFCMC and NiFCMC-Alg while 10-21% weight loss at 450 o C in NiFCMC and NiFCMC-Alg.composite.The degradation and breakdown of organic functional groups of polymeric chain in the composite may be the cause of this weight loss.No further weight loss was noticed up to temperature 600-800°C [38], [39].These results suggested that in 1 g of composite around 0.193 g of CMC and 0.245g of CMC-sodium alginate was attached.

Vibration Scanning Magnetometry (VSM)
Magnetic properties were calculated by measuring magnetization of sample as a function of applied magnetic eld. Figure 6 (a, b and c) depicts the measurement from which a mild magnetization saturation of 0.59 emu/g, 0.43 emu/g and 0.21emu/g was established for NiF, NiFCMC and NiFCMC-Alg.
respectively.This was attributed to presence of Fe 3 O 4 nanoparticles.As a result of polymerization, the slight increase in mass of NiFCMC and NiFCMC-Alg.may be the cause of reduced magnetization [24].

pH of Point Zero Charge (pH PZC )
The pH zpc of prepared material represents the pH value at which net surface charge of adsorbent is nil.
Solid addition method was employed for calculating the pH zpc of magnetic composite (Li et al., 2011).The calculated values of pH pzc For NiFCMC and NiFCMC-Alg composite the computed values of pH pzc were 6.8 and 7.7 respectively.It revealed that the magnetic composite's surface would have net positive charge below this pH and net negative charge above this pH [14], [40], [41].

Effect of Contact Time
The adsorption behavior depends upon time.For studying this effect, Ni (II) ion solution with known concentration (100mg/L) and known volume (50 mL) were taken along with xed amount of adsorbent in Erlenmeyer asks for xed temperature in thermostatic shaker.The asks were removed from shaker at xed time interval and reduced concentration of metal ion was noted by UV-spectrophotometer (Shimadzu UV -1800).
Figure 8 illustrates effect of contact time on removal percentage, concentration (Ct) for Ni (II) ions.It was evident that at the initial stage, the removal percentage was rapid and attained equilibrium after passage of time.This resulted from more available empty sites on the adsorbent's surface and with the passage of time, vacant sites got totally occupied and the rate of adsorption decreased until it reached equilibrium [14], [42].

Effect of Adsorbent Dose
Figure 9 represents the effect of adsorbent dose on removal percentage for NiFCMC and NiFCMC-Alg.To study this effect, a solution of known Ni (II) ion concentration (100 mg/L) with varying adsorbent dose (0.1 g to 0.5 g) was taken.The graph clearly showed an increase in removal percentage from 41.77 to 57.57% for NiFCMC and 75.22 to 95.78% for NiFCMC-Alg.withincreased amount of adsorbent.The number of active sites increased together with the dose of adsorbent that cause the rise in removal percentage [14], [43].The optimum adsorbent dosage in the study was kept at 0.5 g.

Effect of pH
The pH of solution has direct effect upon adsorption behavior of adsorbent as pH affects the charge on the surface of adsorbent.The experiment was carried at various pH levels from 2-10 which have 0.1 g adsorbent dose and xed concentration of 100 mg/L of Ni ion solution for equilibrium time of 3 h to explore the impact of pH. Figure 10 represents the effect of pH on the removal percentage of Ni ion solution for NIFCMC and NiFCMC-Alg.The maximum removal percentage was 43.55% for NiFCMC and 69.23% for NiFCMC-Alg respectively at pH 8 and further decreased.
The NiFCMC-Alg.composite behaved ionic above point zero charge value (pH zpc = 7.7) and at low pH, the electrostatic attraction was lesser.Because at lower pH value, there was higher amount of H + ions in aqueous solution and H + ions and Ni (II) ions engaged in competition to adhere to the adsorbent surface.
Smaller H + ions bind to the empty site more quickly, while Ni (II) ions interact less electrostatically with the adsorbent surface.Since surface charge density decreased as electrostatic interaction between molecules of adsorbent and metal ion increased, the degree of adsorption increased as pH increased.

Adsorption Kinetics
Adsorption kinetics de ne the adsorption behaviour with respect to time.Numerous kinetic models were investigated including Lagergren pseudo rst order, pseudo second order, Elovich model and Weber-Moris intra particle diffusion model [44], [45].These models were tted with data from adsorption investigations with regard to time and general linear equations were given in Table 2.In the Table 2, Q e and Q t represents adsorption capacities (mg/g) of metal ion at equilibrium state and time 't'.k 1 (min − 1 ) and k 2 (mg/g /min) are rate constant of Lagergren pseudo rst order and Lagergren pseudo second order kinetics respectively.(g/mg/min) signi es the rate of chemisorption at initial stage and β (g/mg) de nes the desorption constant for Elovich model.K is the intra particle diffusion rate constant.
Table 3 provides a summary of the various adsorption constants related to various models.On the basis of a comparison of the calculated correlation coe cients (R 2 ) values, the tness of various kinetic models was determined.Adsorption will be a physical process if the data meet pseudo rst order kinetics while chemisorption will be the adsorption behaviour if the data t the pseudo second order kinetics model effectively [42].From the data it was revealed the data was most well t by the Lagergren pseudo- second order model, which had the greatest R 2 value among the various kinetic models.It implied that the Ni ion and adsorbent's adsorption behaviour was chemical in nature.
The Weber Morris intra-particle diffusion model, which is described by Eq. 5, was used to analyze the adsorption behaviour [14], [42].
Where, K int denotes the rate of intra particle diffusion.Plot between Q t versus t 0.5 determines the diffusion behaviour.A straight line must pass through the origin if that step is the sole one that determines rate.The plot is not linear and line is not passing through the origin in case of both adsorbents as shown in Fig. 11 (d).It showed that there are other elements besides intra particle diffusion that have an impact on the adsorption rate [42].

Effect of Concentration
Ni (II) ion solution at various concentrations (100 to 300 mg/l) was used for studying adsorption.From Fig. 12, it was found that with increased initial concentration of metal ion solution, adsorption capacity of both adsorbents increase and maximum at 300 mg/L.On increasing the metal ion concentration, there are more interactions occur between adsorbate and adsorbent [14].However, with increased concentration of the solution, there showed a decrease in % removal of Ni (II) ion.This might be because as the concentration of metal ions rises, fewer active sites become available on surface of the adsorbent.
At various temperatures, the impact of concentration was investigated.The adsorption behaviour of metal ion increased with increase in temperature in case of both adsorbents.It was due to the reason that with increase in temperature, the adsorbate and adsorbent interact more readily [14].The temperature rise cause an increase in number of pores which increases the surface area of the adsorbent and speeds up the adsorption process [42].

Adsorption Isotherms
Under equilibrium conditions, the adsorption behaviour was studied by numerous adsorption isotherms models like Langmuir, Freundlich, Temkin and Dubinin-Radushkevich (D-R).Table 4 provides the general linear equations with various isotherm assumptions.
In the Table 4, Q (mg/g) represents Langmuir adsorption capacity, b represents Langmuir constant, K f represents Freundlich constant, B = RT/b T is used for heat of adsorption, A is for equilibrium binding constant (l/g), T denotes absolute temperature (Kelvin), b T is for Temkin isotherm constant (J/mg), Qm is D-R adsorption capacity (mg/g), K represents D-R isotherm constant and ε is for Polanyi potential (KJ/mol) respectively.The slope and intercept of the graphs shown in Fig. 13 were used to compute values of different constants.Different adsorption isotherm models correlation coe cients (R 2 ) were compared and it was observed that the R 2 value of the Langmuir isotherm model was higher than those of the Freundlich, Temkin, and D-R models as computed in the Table 5 and the Langmuir model provided the greatest t for the adsorption data.NiFCMC and NiFCMC-Alg were found to have Langmuir adsorption capabilities of 47.84 and 60.24 mg/g, respectively.
The following equation de nes R L (separation factor), one of the important parameters linked to the Langmuir adsorption isotherm [14], [42]: where C o is the maximum initial concentration of adsorbate.According to the computed value of R L , if R L >1 then the adsorption is unfavourable; R L = 1 denotes the adsorption is linear, 0 < R L <1 suggests favourable adsorption and R L =0 signi es the adsorption is irreversible.
Langmuir adsorption process was advantageous in the current study, as evidenced by the value of R L being in the range of 0-1.
Adsorption energy in the D-R model is determined using the following equation to predict the kind of adsorption.[14], [42]: If, predicted energy of adsorption is below 8 KJ/mol, in that scenario chemisorption will occur; otherwise physical adsorption will occur.Table 5 showed the calculated value of adsorption energy more than 50 KJ/mol for NiFCMC and more than 100 KJ/mol for NiFCMC-Alg.adsorbent revealed that chemisorption occurred in the current study.To study the adsorption thermodynamics of adsorbent different thermodynamic equations are used.
According to Van't Hoff [14] 8 (9) According to Gibb's Helmholtz equation Table 7 contains the various adsorption thermodynamic parameters that were determined.For both adsorbents, calculated values for ΔH o and ΔS o were found to be positive indicating the endothermic nature of the adsorption process and the interaction between adsorbate and adsorbent was strong.The calculated value ΔG o was negative, indicating the spontaneous nature of adsorption process [42].

Mechanism of Adsorption
Observations from the current investigation have led to the development of a general mechanism, which is depicted in Fig. 15.The modi cation of surface of nickel ferrite by carboxymethyl cellulose (CMC) and alginate plays signi cant role for adsorption of Ni (II) ions from aqueous solution.As surfaces of CMC and alginate contain a variety of functional groups like -OH and -COOH in their long chain structure which acts as active sites for adsorption to occur.There is electrostatic interaction between the adsorbate and the adsorbent molecules due to presence of various kinds of functional groups on surface of magnetic composite.Because -OH and -COOH functional groups are present, the surface of the adsorbent becomes slightly negative on which positively charged Ni (II) ions get attached and removal e ciency got enhanced.This favoured the chemisorption process.

Conclusion
Carboxymethyl cellulose and alginate were used to modify magnetic nickel ferrite in the current study and used as adsorbent for the removal of Ni (II) ions from the aqueous medium.The batch adsorption approach was adopted.Under ambient conditions, the magnetic NiFCMC and NiFCMC-Alg.were synthesized and veri ed by FTIR spectra.The spinel crystalline structure was revealed by XRD analysis before and after surface modi cation.FESEM showed that the average size of NiF and NiFCMC was 0.549 µm and 3.5µm respectively whereas EDS (Energy Dispersive Spectra) of NiF, NiFCMC and NiFCMC-Alg.con rmed about the elemental composition of these adsorbents.The adsorption behavior was studied for various parameters i.e.; effect of contact time, adsorbent dosage, initial metal ion concentration, pH and temperature.Studies on kinetics of adsorption showed that the Lagergren pseudosecond order model t the adsorption data more accurately indicating the chenisorption behaviour.Out of various isotherm models, the Langmuir adsorption isotherm, which demonstrated homogeneous monolayer adsorption, best t the data.For NiFCMC and NiFCMC-Alg, respectively, the highest adsorption capacities were reported to be 47.84 mg/g and 60.24 mg/g.The negative value of ΔG o indicated spontaneous nature of adsorption process.Up to six cycles of regeneration of the magnetic composites were tested, proving that the adsorbents are both economical and environmentally bene cial.
Regeneration e ciency is an important component to de ne the performance and cost effectiveness of adsorbent after recycling.In the present study, NiFCMC nad NiFCMC-Alg.composite were regenerated with 0.1N HCl as desorbing solvent.The regeneration e ciency was studied upto six cycles.Regeneration e ciency and % weight loss for both adsorbents are shown in Table 8 and Fig. 16.It was evident from the table that regeneration e ciency % for NiFCMC and NiFCMC-Alg.after six cycles was still 81.3% and 77.2%.The weight loss after six cycles of adsorption-desorption was also studied after six cycles and a loss of 18.7% and 22.8% weight for NiFCMC and NiFCMC-Alg.adsorbent was reported respectively.The results revealed that NiFCMC and NiFCMC -Alg.composite was suitable cost effective alternative for the removal of Ni (II) ions from aqueous medium.

4 .
Energy Dispersive Spectra (EDS) EDS spectrum of NiF, NiFCMC, NiFCMC-Alg composites are shown as Fig.4(a, b and c) which represents distinct peak for each of constituent elements.The elemental makeup of each sample is shown in Table
and listed the adsorption capabilities of several types of adsorbent along with the current investigation for Ni (II) ions based on the literature review and it was evident that both adsorbents has better removal e ciency for Ni(II) ions from aqueous medium.
distribution equilibrium constant (dimensionless); R is universal gas constant (8.314J/K/mol, T is absolute Kelvin temperature, C o and C e signi es the initial and equilibrium concentration of mg/l).Slope and intercept of linear plot of InK d vs 1/T are used to compute the values of H o and S o as shown in Fig.14.

Figure 9 Effect
Figure 9

Figure 12 Effect
Figure 12

Table 3
Calculated values of constants of different kinetic models for NiFCMC and NiFCMC-Alg.

Table 4
General linear equation of adsorption isotherm models with assumption and their graphical forms

Table 5
Calculated values for different adsorption isotherm constants of NiFCMC and NiFCMC-Alg.

Table 6
Comparison of adsorption capacity of several adsorbents with Ni (II) ions

Table 7
AdsorptionThermodynamic parameters calculated values in Ni (II) ion system

Table 8
Regeneration performance of adsorbent NiFCMC and NiFCMC -Alg.composite Regeneration Cycle Regeneration E ciency for Wt.loss % of adsorbent after six cycle