Hydroxyapatite (HAp)/β-tricalcium phosphate (β-TCP) as a porous composites were prepared by a solgel process. We got a gelatin that was burned at 50-80 oC form HAp/β-TCP. Mixed powder was ultrasonically dispersed in an aqueous solution containing an optimum amount of Ring-openingmetathesis polymerization (ROMP) was used for the preparation of a poly(d,l-lactide-co-glycolide Acid hydrogel polymer -functionalized polymer suitable for solid-phase extraction of metal ions from aqueous solutions. Resins were prepared by the copolymerization of the functional monomer. After the sol-gel process. Then, the nano-composite materials were employed as absorbents for removal of zinc ions from aqueous solutions. The adsorption behaviors of nano-composites were studied also. Experimental results revealed that the n-HAP/PLGA-β-TCP had greater adsorption capacity than nHAP/ β-TCP , and poly(d,llactideco-glycolide Acid played an important role for the adsorption of Zn(II) ions. Moreover, the adsorption isotherms were all well described by the Langmuir and Freundlich models, The adsorption of metal ions can be explained the effect of composites recycle on the adsorption process on the cations by the Langmuir and Freundlich models effect and show the fitting of Zn(II) adsorption of correlation coefficient the Freundlich model is more suitable than Langmuir model.ste your essay in here. Hydroxyapatite as a nature bone from Animal , β-Tricalcium phosphate as prepared from nature bone after calcination at a different temperature , washing from ethanol and water deionized ,dried in the microwave at 50 0 C ,obtained a white powder from nano-[PO4 ]-3 .Figure.1.Show the structure of PLGA(polymer) .Concentrations of polymer and nano-biomaterials were determined by using Atomic Absorption spectrophotometer. Model 210 VGP,USA.,pH measured by CG-820 Schott Gerate pH-meter.1.0 g Hydroxylapatite, Ca10(PO4)6(OH)2, has a solubility constant at 2.07×10-33 powder for calcium phosphate was dissolved in 100 cm3 of H2O. Was mixed with the nHAP solution, and the mixture was stirred for 20 min at 60 ◦C. Then, nHAP-n-β-TCP was obtained by co-precipitation of the mixture of the nano-composites and the zinc ions compounds in the presence of 1.0 mol dm−3 sodium hydroxide solution and the final pH of the solution was 10.06±0.03 after co-precipitation. And then, the prepared nano sphere composites were suspended in aqueous solution for crosslinking, and left standing for 4-4.5 h at room temperature under continuous stirring. At last, the final product was washed with distilled water for several times until pH reached to neutral, and stored for further application. nHAP/PLGA-β-TCP was synthesized approximately by the same method as nHAP-βTCP, except for the addition of PLGA. In the mixture of nano-composites and the zinc salts, 0.5 g PLGA powder was added under strong stirring. The PLGA blended nano sphere composites were obtained by the same co-precipitation technique. Subsequently, the nanosphere composites were crosslinked as usual. There after the final products were washed and stored for further applications. Characterization of nHAP-β-TCP and nHAP/PLGA-β-TCP Fourier transform infrared spectroscopy (FTIR) The FTIR spectra of nHAP, β-HAP and PLGA were recorded using a Fourier transform infrared spectrometer (Spectrum BX 11,Perkin Elmer 5 Model). All the samples were prepared as KBr tablets, and the range of the scanning wave numbers was 400–4000 cm−1. Scanning electron microscope (SEM) The SEM images of nHAP,nβ-TCP and PLGA were taken with a scanning electron microscope (SEM “JEOL JSM 6360LA”, Japan). The acceleration voltage was 25.0 kV.
Adsorption methods
Adsorption of Zn(II) at different initial solution pH The effect of different initial solution pH to the adsorption of Zn(II) by n HAP-β-TCP and n HAP /PLGA-n β-TCP were investigated. The range of pH was 6.03–8.22, and the initial concentration of Zn(II) ions in aqueous solution was 250 mg dm−3. n-HAP-β-TCP and n-HAP /PLGA- β-TCP were weighed and immersed in Zn(II) solutions with different initial pH under continuous stirring at room temperature for 24 h. The Zn(II) concentrations were analyzed with 2% Triton X-100 as developing agent at a wavelength of 520 nm. The amount of adsorption, q (mg g−1), was calculated according to the following equation(1): ………..1 ( ) 0 m C C V q e Where C0 and Ce (mg dm−3) are the initial and final Zn(II) concentrations, V (dm3) is the volume of the Zn(II) ions solution, and m (g) is the weight of the polymers PLGA in the dried adsorbents.
Adsorption equilibrium experiments
The adsorption equilibrium experiments of n HAP-β-TCP and n HAP/PLGA-β-TCP were carried out at 25 0C and pH 6.08±.0.03. The initial concentration of Zn(II) was ranged from 40 to 800 mg dm−3. The nano-composite adsorbents were weighed and immersed in Zn(II) solutions with various 6 initial concentrations under continuous stirring for 24 h, respectively. The same analysis method as mentioned above has been employed to detect the initial and final Zn(II) concentrations by by UV– visible spectrophotometer. The amount of adsorption was calculated based on Eq. (1). Kinetics adsorption The kinetics adsorption experiments were also measured at 25◦C and pH 6.08±0.03. The initial Zn(II) concentration of solution is 76.3 mgg−1. nHAP-nβ-TCP or n-HAP/ nβ-TCP-PLGA was weighed and immersed in Zn(II) solutions under continuous stirring. In calculated time periods, 3×10-3 dm3 of sample solution was taken out and filtrated to analyze the Zn(II) concentration (Cti). At the same time, and the same amount of deionized water is added into the bulk solutions to keep the volume of the solutions constant. The adsorption of Zn(II) ions at time ti, q(ti,) (mg g−1), was calculated from the following equation ……………….2 ( ) 1 0 0 1 ( ) m C C V V q s i ti C t ti i Where C0 and Cti (mg dm−3) are the initial Zn(II) concentration and the concentrations at time ti (min), respectively. V0 and Vs (dm3) are the initial volume of the Zn(II) solution and that of the bulk solution taken out every time for Zn(II) concentration analysis, respectively. Here, Vs is equal to 3×10-3 dm3. m (g) is the weight of the polymers in the dried adsorbents.
Recycling and Desorption procedures
Recycling experiments
The utilizing of the nano-composites nHAP-βTCP/PLGA and repeated the procedure of adsorptiondesorption procedure. After the first batch reaction of nano-calcium phosphate/polymer(dimer) was washed by deionized water to removal the raffinat acid and was dried by oven vaccum at 600C , in the preparation for next adsorption of zinc ions and the capacities of adsorption-desorption of the nano-biomaterials for Zn(II) ions were determination by ICP-MS.The recovery of nHAPTCP/PLGA 7 nano-composites was used three-seven recycles of adsorption-desorption process and the results which indicate that the weight losses in the activity of the nano-composites, for the first seven recycles the composition will be negligible.
Results and discussion
Preparation of nHAP-nβ-TCP and nHAP/PLGA- nβ-TCP The preparation processes for nHAP – nβ-TCP and nHAP / PLGA/ nβ-TCP by solid-state reaction-step method, co-precipitation of the mixture containing PLGA polymers in NaOH solutions, were described in the supplementary material in Figures.2a,2b. XRD pattern and FTIR Spectrum of Hydroxyapatite powder from animal bone. Insert Figure.1. Preparation of Poly Lactic-co-Glycolic Acid (dimer) Insert Figure.2a .XRD pattern of Hydroxyapatite powder from animal bone Insert Figure.2b. 8 FTIR Spectrum of Hydroxyapatite powder from animal bone Characterization of adsorbent . Figure.2c. Show the FTIR spectra of nature bone (Raw-Material), HAP and synthetic β-TCP at 20% concentration of Ca10(PO4)6(OH)2 and 30% Ca3(PO4)2 for comparison. Shows the Figure.1c. The most complicated and apparent spectrum. Insert Figure.2c. FTIR Spectrum of Hydroxyapatite powder with β-TCP at 20% concentration of Ca10(PO4)6(OH)2 and 30% Ca3(PO4)2from animal bone Scanning electron microscope analysis The SEM micrographs of synthesized HAp nanopowder from animal scale and β-TCP sources (βCa3(PO4)2) is a synthetic, completely inorganic compound.from figures 3a and 3b. SEM for nanocomposites/ polymer before and after removal of zinc ions. Insert Figure.3a SEM for nano-composites/polymer Before removal of Zn(II) Insert FigureSEM for nano-composites/polymer after removing of Zn(II) Adsorption Experiments The experiments of batch adsorption were carried out on the removal of zinc ions to study the thermeodynamics,kinetics, and mechanism. In the experiments of kinetic, studies of the batch adsorption and were carried out by shaking 0.2g of nHAPTCP with 100 mL of different concentrations of zincr ions solution (100–400 mg/L) at the initial solution pH (6.03) and at the temperature of 323 K for different contact times from 10 min to 60 min in a rotary shaker (100 mL Erlenmeyer flasks) at the agitation speed of 200 rpm. At Predefined time, the flasks were withdrawn from the rotary shaker and the residual of zinc ions concentration in the solution was measured by AAS. The percentage removal of zinc ions was estimated by using the following equation: Re % ……………………….(1) 0 0 C C C moval e In the isotherm experiments, 0.2 g of biomaterial resin and 100 mL of different zinc ions concentrations (100–400 mg/L) were taken in a series of 100 mL Erlenmeyer flasks. The flasks were shaken in a rotary shaker (150-200 rpm) for about 60 min at the initial solution pH and at the temperature of 323 K. The amount of zinc ions loaded onto the nano-biomaterial composites resin at equilibrium, qe (mg/g), was estimated by using the following relationship: ……………………………(2) 0 V m C C q e e 10 where C0 and Ce are the initial and final zinc ion concentrations in the solution (mg/L), respectively. The amount of zinc ions loaded onto the biomaterial resin at time t, qt (mg/g), was estimated by the following relationship: where C0 is the concentration of zinc ions in the solution at equilibrium (mg/L). The experimental data obtained from the studies of equilibrium adsorption were used to test the different adsorption isotherm models such as Langmuir and Freundlich, to know the types of adsorption technique such as chemical or ionexchange). Studies of the thermodynamic, 0.2 g of biomaterial resin and 100 mL of various initial zinc ions concentration (100–400 mg/L) was shaken in a rotary shaker (150-200 rpm) and the optimum conditions with diufferent temperatures (from 323 to 343K). The percentage removal of zinc ions according applying the equation (1). Characterization of the nHAP and β-TCP/PLGA The capacity of adsorption of the adsorbent mainly depends upon the pore size of the surface modification and porosity and also the chemical reactivity of the functional[P-O] groups present on its surface. The different chemical functional groups present in the adsorbent were observed by the FTIR analysis. The FTIR spectrums of the nHAP and βTCP/PLGA were shown in the Figures 1b and 1c. The FTIR spectra of the nano-hydroxyapatite was shown in Figure 1b. The intense peak at 3630 cm21 was due to OH stretching vibrationof water and stretching vibration of phosphine. Presence of carboxlic groups was confirmed by PLGA/β-TCP bending vibration for C-O at 1480 cm21 and CPO stretching vibration at 1100 cm21. Presence of H2O was also confirmed by its bending vibration at 1480 cm21. The peaks at 3523 and 3996 cm21 were due to PC=O vibration of alkyl group. The CH2 bending vibration occurred at 1480 and 1354 cm21. The intense peak at 620 cm21 was due to PCO stretching vibration of ether groups. So, the IR spectra reveal C–O (1480–1125 cm−1), ethyl –CH2 (2300 cm−1), and –OH stretching vibrations (3600– 4000 cm−1). The band located at 620 cm−1 is attributed to the asymmetric vibration of PO4 3−. The crosslinking of the scaffolds with glutaraldehyde shows the main absorption peak at 1620 cm−1 . It 11 has been also proposed that the crosslinking with glutaraldehyde can make the samples more hydrophobic as amino groups are blocked with aliphatic chains Effect of contact time The effect of contact time is an important role of selecting a wastewater treatment, where the time decreased for wastewater disposal should be measured. As shown in Figure.4.The sorption of Zn(II) onto the n-CaHAP/β-TCP was very rapid and equilibrium was reached within 3 min, where the removal 98.9% from Zn(II). A further increase in contact time has no effect on the removal percent.Figure. 4 showed that a longer of mixing time, a higher displacement of biomaterial/PLGA. For about first 3 minutes, Zinc ions adsorbed was same. From 3 minute to 7, concentration Zn(II) adsorbed was on the decrease due to not achieving equilibrium between amount of Zn(II) adsorbed onto HA/β-TCP/PLGA and amount of Zn(II)ions remaining in the solution. As a result, active side of adsorbent biomaterial was not fully bind Zn(II)ions. At 8 minutes in a stirring, it happened optimum contact time of Zinc ions adsorption. It showed that amount of Zinc ions adsorbed by biomaterial and remained in the solution were in equilibrium. biomaterial as adsorbent has bond zinc ions from solution to its surface active side. At contact time between adsorbate and adsorbent for 8 minutes could remove zinc ions in solution by concentration 10 mg L-1 until 9.267 mg L-1. After 8 minutes till 12 minutes, ability of biomaterial to adsorb zinc ions decreased. Amount of ions solution adsorbed decreased because binding of function groups on the surface of adsorbent and zinc ions was lower, so the zinc ions stayed in the solution. As a longer the contact time of adsorption, so the inconsistency between particle of adsorbate and adsorbent was larger. Insert Figure. 4 Effect of Contact Time in Znic ions Removal 12 Effect of adsorbent Dosage: Figures (5a,b) show the adsorption of Zn(II) as a function of dosage of nano HA/nano-β-TCPwith polymer PLGA. Increasing by the adsorbent dose the percentage of Zn(II) removal increases , but adsorption density , the amount adsorbed per unit mass, decreases .It’s far comfortably understood that the number of to be had adsorption sites increases by increasing the adsorbent dose and it therefore outcomes in an increase in the percentage of two cations adsorbed .The decrease in adsorption density with an increase within the adsorbent dose is specifically because of un saturation of adsorption sites through the adsorption method [17] . Another explanation may be the inter-particle interaction, including assemblage as a result of high adsorbent dose, which include assemblage would lead to a decrease in the total surface area of the adsorbent and on an increase in diffusional path duration[18]. The adsorption equilibrium data have been analyzed by various isotherm models, such as Langmuir and Freundlich, isotherm models, to investigate the adsorption mechanism further Langmuir model is based on the assumption that adsorption sites are identical and energetically equivalent, only monolayer adsorption occurs in the process[19]. It can be represented as follows: . ……………………..3 1 max max q C q q b C e e e Where qe is the amount of Zn(II) ions adsorbed at equilibrium (mg g−1), Ce is the liquid-phase Zn(II) concentration at equilibrium (mg dm−3), qmax is the maximum adsorption capacity of the adsorbent (mg g−1), and b is the Langmuir adsorption constant (dm3 mg−1), respectively. Freundlich isotherm model is based on the assumption of an exponentially decaying adsorption site energy distribution[20] .It is applied to describe heterogeneous system characterized by a heterogeneity factor of n. The Freundlich model is expressed as 13 follows: log log ………………………4 1 log e e f C K n q Where Kf is the Freundlich isotherm constant, and n (dimensionless) is the heterogeneity factor. The experimental adsorption data linear based on the a forementioned isotherm models. The parameters obtained were all listed in Table 1. the correlation coefficients (R2) of the linear form for Langmuir model were much closer to 1.0 than those of other models, the coefficients for Freundlich was ˃1. According to Langmuir model, the calculated maximal Zn(II) uptakes of nHAP-nβ-TCP and nHAP/PLGA- nβ-TCP were quite close to their corresponding experimental data as shown in. Table.1.Freundlich and Langmuir isotherms of the composites. Insert Table( 1 ) Langmuir and Freundlich, adsorption isotherm model for the adsorption of zinc ions onto the HATCP/PLGA. From the insert in figure.5., it was found that the Langmuir theoretical curves is the best of the experimental data. They all revealed that Langmuir model proposed the most satisfactory description on the Zn(II) adsorption by both nano-composites adsorbents, indicating the homogeneous surface of the two types of nano-hydroxyapatite adsorbents and the monolayer coverage of Zn(II) ions. For further analysis on the adsorption process, a dimensionless constant, RL, which reflects the essential characteristic of Langmuir model, can be obtained from the constant b[21] . Insert Figures.5a,b. 14 Adsorption of Zn(II) as a function of dosage of nano HA/nano-β-TCP with polymer …………….(5) 1 1 0 bC RL 3.4. adsorption Isotherms The adsorption of isotherm to describe the interactive behaviors between the solutes and adsorbents and lighten the properties and affinity of the adsorbent [21]. In this work, The Zn(II) adsorption isotherms of both nHAP and nβTCP composites were measured at 25◦C and pH 6.03, which were presented in Figures.5a,b.It is depecits that the removal of zinc ions decreased with increase initial zinc ions concentration. The equilibrium adsorption capacity(mg g-1) increased with increase initial ions concentration. Zinc ions concentration decreased from removal 99.83% to 92.72% this can be attributed to the saturation of avialuble active sites on the biomaterial resin above a certain concentration of zinc ions. Increasing in the equilibrium capacity of adsorption from 48.832 to 568.792 mg/g and due to the higher adsorption rate. Applying Langmuir [22] and Freundlich[23] adsorption isotherm models and used to analyze to the effect of initial zinc ions concentration values to produced in figure.4. show the non linear form Langmuir adsorption isotherm model to give equation. …………………………. 1 L e m L e e K C q K C q (6) The non linear form Freundlich adsorption isotherm reach to the equation ………………………………. 1/ n e f e q K C (7) 15 Insert Figure.5a .Langmuir theoretic curves Insert Figure 5b. Adsorption Isotherm curves Adsorption Isotherms for zinc ions concentration KL is the Langmuir constant and related to the affinity of the zinc ions to the biomaterial resin(L/mg), Ce is the concentration of zinc ions in the equilibrium solution (mg/L), C0 initial concentration of zinc ions ,Kf is the freundlich constant( mg/g)(L/mg1/n) and to form bonding energy and n is a measure of the deviation from linearity of adsorption( g/L), R is the gas constant (8.314 J/mol K). T,Tempereature 0C. Kinetics Adsorption Kinetic adsorption data were treated with pseudo-first-order kinetic model[24]. ( )……… 1 e t e k q q dt dq (8) Where qe and qt refer to the amount of adsorbent for nano-biomaterial adsorbed(mg/g) at equilibrium and a different time (t) min,respectively, and K1 is the equilibrium rate constant of pseudo-first-order sorption(1/min). Integration of equation(8). For boundary conditions t=0 ,t and qe =0 to qt gives. ………. 2.303 1 t k q q q e t e (9) Which is the integrated rate law for the pseudo-first-order kinetic model in equation 9. To obtain a linear form …………….. 2.303 log( ) log 1 t K q q qe t e (10) 16 The slope and intercept of the plot of log(qe –qt ) against t were used to determine at first-order rate constant, k1 in figure(6a), the first-order equation of legergen does not fit well with the whole range of contact time and is generally applicable over the initial phase of the adsorption process[24,25]. Kinetic data were further treated with the pseudo-second-order kinetic model according to equation. ( ) ………………………. 2 2 e t t k q q dt dq (11) For integration of this equation k2 is the equilibrium rate constant of pseudo-second-order adsorption(g/mg min). The boundary condition at t=0 to t and qt =0 to qt gives the following ……………………. 1 1 2K t q q qe t e (12) Which is integrated rate law for a pseudo-second-order reaction in equation y1 can be rearranged to obtain a linear form. …………………………. 1 1 2 2 t q K q q t t e e (13) The slope and intercept of the plot of t/qt against t were used to calculate the second order kinetic model, K2 in figure (6b). It is more likely to predict the behavior over the whole range of adsorption for the case of chemisorptions mechanism as the rate determining step[24-28]. From table(2) : Study of the different initial concentration of adsorbent by the pseudo-second-order for adsorption model has a high value of R2 ˃ 99.98%. From figures(6a,b): The depicts that the effect of contact time on the removal of Zn(II) ions and the equilibrium adsorption capacity(qe). It was showed that the removal of Zn(II) ions and equilibrium adsorption was increased with increase in contact time within 30 min of the equilibrium time 17 adsorbed onto composites at the same figure(6a). Show the residual time between nHA/βTCP with polymer PLGA and Zn(II) ions gives the lower removal of Zn(II) ions and the equilibrium adsorption capacity is highly removal of Zn(II) particles. The effect of equilibrium time data were used to the effect of pseudo-firest order [26 ] and pseudosecondorder in kinetic equation [ 28-31]. The results were shown in figures 6a,b respectively. Figure 6a,b. Adsorption kinetics and mechanism (Zinc ions concentration 50-300 mg/L, pH 6.03, nan0-biomaterials dose 0.2 g, volume of sample100 mL, equilibrium time 30 min and temperature 290C). Insert figures 6a,b Insert Table( 2 ) comparision between the pseudo-first order and pseudo-second order kinetic models for adsorption of znic ions onto biomaterials/polymer. Thermeodynamic study Thermeodynamic parameters play an important a vital role in the effect on the temperature for removal of zinc ions as shown in figures(7a,b). Effect of temperature on to removal of Zinc ions. 18 Insert figures 7a,b Figure7a,b. Thermodynamic study (Zinc ions concentration 100–400 mg/L, pH 6.03±0.03, nature apatite dose 70 g, volume of sample 100 mL, and equilibrium time . This figure depicts that the concentration of zinc ions decreased with increasing temperature indicates that the exothermic nature of adsorption of zinc ions onto the biomaterial resin and the maximum zinc ions removal at reached temperature at 270C. Thermeodynamic utilizing behavior of ions adsorption onto resin, thermeodynamic parameters Δ0G change in free energy,ΔH0 change in enthalpy and ΔS0 change in entropy according equation(14) ΔG0=-RTln(Ce)/C0)……………………………….14 R=gas constant(8.3145/mol/L),CAe adsorbed amount of zinc ions onto new nanobiomaterial( nHATCP/PLGA). From equations can be calculated ΔG0,ΔH0 and ΔS0 values. Insert Table( 3) The negative values of ΔG0 indicates that the adsorption of zinc ions onto the biomaterial resin of ΔH0. As a negative value indicates that the adsorption of zinc ions onto new resin is exothermic reaction. Study of the Recycling and Recovery Adsorbent: The recovery and reuse of the nano-composite nHAPβTCP/PLGA would decrease processing costs and may be recovery and reusing of nano-biomaterials composites after Zn(II) ions extraction from aqueous solution. The ability of recycle and reuse of nano-composites nHAPβTCP/PLGA. The application of reuse or recycle of nano-composites play an important role in the reusability of the 19 nano-composites was investigated by seven cycles for adsorption –desorption/capacity. Table(4): Show the effect of the number of Zinc(II) ions solution cycles., from this table.4. The nano-composites could be recycled above 6 times, and the adsorption capacity from 1st -7st 30.78 and 18.67 from adsorption- desorption respectively, so the result that indicate to the nanocomposites and can be used of the adsorbent application, for the removal of Zn(II) ions from aqueous solution and the nano-composites for the inexpensive and the recycle of adsorbent for waste solution treatment. From figure.4. Show the initial and final adsorption capacity for Zn(II) ions solution. Table(4):Recovery and Reuse Adsorbent.
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