Adsorption of dyes and humic acid from water using chitosan‐encapsulated activated carbon

The adsorption isotherms and rates of two dyes and humic acid from aqueous solutions onto chitosan‐encapsulated activated carbon (CEAC) beads were measured at 30 °C. Such beads were prepared by mixing different weight percents of cuttlefish‐based chitosan (100%, 80%, 67%, and 55%) and rice‐based activated carbons. It was shown that the isotherms of dyes and humic acid were well fitted by the Freundlich equation. The adsorption capacity and rate could be enhanced when activated carbon was encapsulated with chitosan. Four simplified kinetic models including the pseudo‐first‐order equation, pseudo‐second‐order equation, intraparticle diffusion model, and the Elovich equation were tested to follow the adsorption processes. The adsorption of dyes was best described by the Elovich equation, but that of humic acid was best described by the intraparticle diffusion model. The kinetic parameters of each best‐fit model were calculated and are discussed in this paper. © 2002 Society of Chemical Industry     

生物膜新工艺吸附Cu2+动力学研究

The biosorption of copper(Ⅱ) ions onto biofilm was studied in a batch system with respect to the temperature, initial pH value and biofilm sorbent mass. The biomass exhibited the highest copper(Ⅱ) sorption capacity under the conditions of room temperature, initial pH value of 6.0 and the sorbent mass 8 g. The experimental data were analyzed using four sorption kinetic models, the pseudo-first order, the Ritchie second order, the modified second order and the Elovich equations to determine the best-fit equation for the sorption of metal ions onto biofilm.omparing with the sum of squared-errors, the results show that both the Ritchie second order and modified second order equations can fit the experimental data very well.     

生物膜新工艺吸附Cu2+动力学研究

The biosorption of copper(R) ions onto biofilm was studied in a batch system with respect to the temperature, initial pH value and biofilm sorbent mass. The biomass exhibited the highest copper(R) sorption capacity under the conditions of room temperature, initial pH value of 6.0 and the sorbent mass 8 g. The experimental data were analyzed using four sorption kinetic models, the pseudo-first order, the Ritchie second order, the modified second order and the Elovich equations to determine the best-fit equation for the sorption of metal ions onto biofilm.Comparing with the sum of squared-errors, the results show that both the Ritchie second order and modified second order equations can fit the experimental data very well.     

Equilibrium and kinetics of copper ions removal from wastewater by ion exchange

The removal of copper ions from wastewater by ion exchange has been studied using an iminodiacetate resin.The capacity of the resin for the copper ions has been determined to be 2.30 mmol·g~(-1) by measuring the equilibrium isotherm at 25 °C and initial pH value of 3.5 where the final equilibrium p H value is 5. An analysis of equilibrium isotherm models showed that the best fit model was the Langmuir–Freundlich. The kinetics of the ion exchange process have been investigated and four kinetic models have been tested namely: Ritchie model, pseudo-second order model, pseudo-first order model and the Elovich model. The pseudo-second order model provides the best fit to the kinetic data.     

Removal of zinc ions from aqueous solution using a cation exchange resin

The present study is concerned with the mass transfer and kinetics study of zinc ions removal from aqueous solution using a cation exchange resin packed in a rotating cylindrical basket reactor. The effect of various experimental parameters on the rate of zinc ion removal, such as initial zinc ion concentration, packed bed rotation speed and temperature has been investigated. In addition to find a suitable equilibrium isotherm and kinetic model for the zinc ion removal in a batch reactor. The experimental isotherm data were analyzed using the Langmuir, Freundlich and D–R equations. The equilibrium data fit well in the Langmuir isotherm. The experimental data were analyzed using four sorption kinetic models, pseudo-first and second-order equations, the Elovich and the intraparticle diffusion model equation, to determine the best fit equation for the biosorption of zinc ions onto purolite C-100 MH resin. Results show that the Elovich equation provides the best correlation for the biosorption process.     

Biosorption of Zinc from Aqueous Solutions by Rice Bran: Kinetics and Equilibrium Studies

Abstract

Rice bran, an agricultural by‐product, was used for the removal of zinc ions from aqueous solution. The work considered the determination of zinc‐biomass equilibrium data in batch system. These studies were carried out in order to determine some operational parameters of zinc sorption such as the time required for the Zinc‐biosorbent equilibrium, the effects of biomass particle size, pH, and temperature. The results showed that pH has an importance effect on zinc biosorption capacity. The biosorbent size also affects the zinc biosorption capacity. The sorption process follows pseudo‐second‐order kinetics. The intraparticle diffusion may be the rate‐controlling step involved in the adsorption zinc ions onto the rice bran up to 30 min. The equilibrium data could be best fitted by the Langmuir sorption isotherm equation over the entire concentration range (40–160 mg/dm³). Thermodynamic parameters, such as ΔG°, ΔH°, ΔS°, have been calculated. The thermodynamics of zinc ion/rice bran system indicate spontaneous and endothermic nature of the process.     

Adsorption of cadmium (II) and copper (II) ions from aqueous solution using chitosan composite

The binary chitosan/silk fibroin composite synthesized by reinforcement of silk fibroin fiber into the homogenous solution of chitosan in formic acid was used to investigate the adsorption of two metals of Cu(II) and Cd(II) ions in an aqueous solution. The binary composite was characterized by Fourier transform infrared and scanning electron microscopy. The optimum conditions for adsorption by using a batch method were evaluated by changing various parameters such as contact time, adsorbent dose, and pH of the solution. The experimental isotherm data were analyzed using the Freundlich and Langmuir equations, indicated to be well fitted to the Langmuir isotherm equation under the concentration range studied, by comparing the correlation co‐efficient. Adsorption kinetics data were tested using pseudo‐first‐order and pseudo‐second‐order models. Kinetics studies showed that the adsorption followed a pseudo‐second‐order reaction. Due to good performance and low cost, this binary chitosan/silk fibroin composite can be used as an adsorbent for removal of Cu(II) and Cd(II) from aqueous solutions. POLYM. COMPOS., 2013. © 2013 Society of Plastics Engineers     

Etude de l'élimination des ions Cu (II) de la solution aqueuse par sorption sur la zéolithe a study of the removal of Cu (II) from aqueous solution by sorption on Zeolite A

The objective of this study is to present the results of removal of copper by the method of sorption on zeolite A. The batch experiments were conducted for both the kinetics for the sorption isotherms. The experimental variables studied were pH, contact time at different initial concentrations, the amount of sorbent, temperature and stirring speed. The sorption capacity depends on the pH and mass of sorbent, but the temperature and stirring rate showed no influence. Several mechanisms of retention of copper on the zeolite could be competitive (ion exchange, complexation or precipitation and sorption). The modeling of experimental data on kinetics showed that the model of pseudo‐second order describes satisfactorily the sorption on the zeolite, and that the limiting step of the speed distribution intraparticle. Statistical analysis of the constants for Langmuir‐Freundlich equation has shown that this model seems most appropriate to describe this phenomenon of sorption, which indicates the heterogeneity of the surface sorption of the zeolite. Copyright © 2011 Canadian Society for Chemical Engineering     

Adsorption isotherms,kinetic, and desorption studies on removal of toxic metal ions from aqueous solutions by polymeric adsorbent

Adsorption of Cd(II), Co(II), and Ni(II) on aminopyridine modified poly(styrene‐alt‐maleic anhydride) crosslinked by 1,2‐diaminoethane as an ion exchange resin has been investigated in aqueous solution. Adsorption behavior of these metal ions on the resin was studied by varying the parameters such as pH (2–6), adsorbent dose (0–4.0 g/L), contact time (0–240 min), and metal ions concentration (20–300 mg/L). Adsorption percentage was increased by increasing each of these parameters. The isotherm models such as: Langmuir, Freundlich, Temkin, and Dubinin–Radushkevich were used to describe adsorption equilibrium. The results showed that the best fit was achieved with the Langmuir isotherm equation, yielding maximum adsorption capacities of 81.30, 49.02, and 76.92 mg/g for Cd(II), Co(II), and Ni(II), respectively. The pseudo‐first‐order, pseudo‐second‐order, and intra‐particle diffusion kinetics equations were used for modeling of adsorption data and it was shown that pseudo‐second‐order kinetic equation could best describe the adsorption kinetics. The intra‐particle diffusion study revealed that external diffusion might be involved in this case. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41642.     

Synthesis of chitosan beads as boron sorbents

Parameters, such as pH, temperature, initial boron concentration, adsorbent dosage, and ionic strength, affecting boron adsorption onto chitosan beads were examined in this study. The following values were obtained as the optimum conditions in our studied ranges: pH 8.0, temperature = 308 K, amount of chitosan beads = 0.15 g, initial boron concentration = 4 mg L⁻¹, and ionic strength = 0.1 M NaCl]. The adsorption kinetics were also examined in terms of three kinetic models: the pseudo‐first‐order, pseudo‐second‐order, and intraparticle diffusion models. The pseudo‐second‐order kinetic model showed very good agreement with the experimental data. Intraparticle plots seemed to have two steps and indicated multilinearity. Equilibrium data were evaluated with nonlinear and linear forms of the Langmuir and Freundlich equations. The experimental data conformed to the Freundlich equation on the basis of the formation of multilayer adsorption. To characterize the synthesized chitosan beads, we used Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM) analyses. As shown by FTIR analysis, the boron species may have interacted with the NH₂ groups on chitosan. Microparticles of about 5 μm appeared in the SEM micrographs of the chitosan beads. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Elovich equation and modified second‐order equation for sorption of cadmium ions onto bone char

The removal of cadmium ions from water by sorption onto bone char has been studied. Bone char, traditionally used for colour removal in sugar refining, is produced by the carbonisation of animal bone. Batch experiments were carried out to study the effects of initial cadmium ion concentration and bone char mass on the sorption rate. The experimental contact data were analysed using the Elovich model, previously used to describe the kinetics of gas adsorption on solids, and the Ritchie model, a modified second‐order kinetics equation. Initial analysis of the data, using the Ritchie model, was poor and therefore a modification was incorporated to make the Ritchie model predictions correlate the experimental data more accurately. Both the Elovich and modified Ritchie equations accurately predict the sorption capacity of cadmium on bone char, however, the sorption kinetics, derived from the differential forms of the two equations, were correlated better using the Elovich equation. © 2000 Society of Chemical Industry     

Preparation and characterization of porous chitosan–tripolyphosphate beads for copper(II) ion adsorption

Porous chitosan–tripolyphosphate beads, prepared by the ionotropic crosslinking and freeze‐drying, were used for the adsorption of Cu(II) ion from aqueous solution. Batch studies, investigating bead adsorption capacity and adsorption isotherm for the Cu(II) ion, indicated that the Cu(II) ion adsorption equilibrium correlated well with Langmuir isotherm model. The maximum capacity for the adsorption of Cu(II) ion onto porous chitosan–tripolyphosphate beads, deduced from the use of the Langmuir isotherm equation, was 208.3 mg/g. The kinetics data were analyzed by pseudo‐first, pseudo‐second order kinetic, and intraparticle diffusion models. The experimental data fitted the pseudo‐second order kinetic model well, indicating that chemical sorption is the rate‐limiting step. The negative Gibbs free energy of adsorption indicated a spontaneous adsorption, while the positive enthalpy change indicated an endothermic adsorption process. This study explored the adsorption of Cu(II) ion onto porous chitosan–tripolyphosphate beads, and used SEM/EDS, TGA, and XRD to examine the properties of adsorbent. The use of porous chitosan–tripolyphosphate beads to adsorb Cu(II) ion produced better and faster results than were obtained for nonporous chitosan–tripolyphosphate beads. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Sorption kinetics for the removal of dyes from effluents onto chitosan

The ability of chitosan, a biosorbent obtained by the processing of waste seafood shells, to remove five acid dyes from effluents has been studied. Chitosan is a deacetylated bio‐polymer of chitin. The effect of varying initial dye concentration on the rate of adsorption has been investigated. The rate data have been analyzed using three kinetic models, namely, a pseudosecond order, the Ritchie modified second order, and the Elovich models. The sorption kinetics of Acid Green 25, Acid Orange 10, Acid Orange 12, Acid Red 18, and Acid Red 73 onto chitosan can be best correlated by the Elovich equation. The kinetic model was determined in accordance with the agreement between the rate equations and the differentiation of kinetic equations. The values of rate constants for the three models are in the range of 0.003–2.230, 0.004–0.237, and 0.0173–405 for the pseudosecond order, the Ritchie modified second order and the Elovich models, respectively. The sensitivity analysis, by plotting the reciprocal of the rate, Z_L = (d_q/d_t)^?1 against time, is used to identify the true kinetic model. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Evaluation of new chemically modified coconut shell adsorbents with tannic acid for Cu (II) removal from wastewater

The adsorption of Cu (II) from aqueous solutions using coconut shell modified powder was investigated in batch experiments. The surface charge of the adsorbent was determined. The points of zero charge (PZC) of the adsorbents (pH_PZC) were 4.5, 2.0, and 2.0 to raw coconut (RC), raw coconut alkalized (RCA), and coconut shell modified with tannic acid (TCA) adsorbent, respectively. Batch experiments were performed under kinetic and equilibrium conditions. The kinetic data were analyzed using a pseudo second‐order, and Elovich equation. Adsorption equilibrium data were investigated using the Langmiur, Freundlich, Temkin, and Dubinin–Raduschevich (D–R) isotherm models. It has been found that chemically modified coconut shell (TAC) affected performance when compared with unmodified coconut shell (RC). Kinetic studies showed that the adsorption followed a pseudo‐second‐order rate model. Biosorption kinetics of Cu(II) on the adsorbent TCA was rapid such that almost 90% of Cu(II) were adsorbed within 80 min. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40744.     

Thermodynamic,kinetic, and equilibrium studies on phenol removal by use of cashew nut shell

Adsorption of phenol from aqueous solution onto cashew nut shell (CNS) was investigated to assess the possible use of this adsorbent. The influence of various parameters such as contact time, phenol concentration, adsorbent dose, pH, and temperature has been studied. Studies showed that the pH of aqueous solutions affected phenol removal as a result of decrease in removal efficiency with increasing solution pH. The experimental data were analysed by the Langmuir equation. Equilibrium data fitted well with the Langmuir model with maximum monolayer adsorption capacity of 5.405 mg/g. Thermodynamic parameters such as ΔG°, ΔH°, and ΔS° have also been evaluated and it has been found that the sorption process was feasible, spontaneous, and exothermic in nature. The pseudo‐first‐order and pseudo‐second‐order kinetic models were selected to follow the adsorption process. Kinetic parameters, rate constants, equilibrium sorption capacities and related correlation coefficients, for each kinetic model were calculated and discussed. It was shown that the adsorption of phenol could be described by the pseudo‐second‐order equation, suggesting that the adsorption process is presumable a chemisorption. The CNS investigated in this study showed good application potential for the removal of phenol from aqueous solution.     

The use of Jatobá bark for removal of cationic dyes

In this work, the application of Jatobá bark (the waste product of medicinal plant processing) in removal of the cationic dyes Methylene Blue, Crystal Violet and Rhodamine B from aqueous solution was studied in a batch system. The effect of contact time, pH and temperature on dye removal was investigated. An increase in pH from 2 to 10 was accompanied by an increase in the amount of dye adsorbed. The equilibrium sorption data fitted to the Langmuir, Freundlich and Langmuir–Freundlich equations were investigated. The Langmuir–Freundlich isotherm exhibited the best fit with the experimental data and the maximum adsorption capacities at room temperature being 211.5, 89.5 and 69.4 for Rhodamine B, Methylene Blue and Crystal Violet, respectively. The kinetic sorption was evaluated by the pseudo‐first‐order, pseudo‐second‐order and intraparticle diffusion models. It was observed that sorption follows the pseudo‐second‐order kinetic model. The thermodynamic parameters for the sorption process were also determined. The spontaneous and endothermic nature of adsorption was obtained based on the negative value of free energy (ΔG) and the positive value of enthalpy (ΔH). The results indicate that Jatobá bark could be used as a low‐cost material for the removal of cationic dyes from wastewater.     

Nickel and cobalt sorption on anaerobic granular sludges: kinetic and equilibrium studies

The kinetics and equilibria of sorption of the divalent metal ions cobalt and nickel onto anaerobic granular sludge are described. Single component and binary equimolar systems were studied at different pH values (pH 6, 7 and 8). The kinetic modelling of metal sorption by anaerobic granular sludge has been carried out using Lagergren equations. On fitting the experimental kinetic data both in first‐ and pseudo‐second‐order equations, the regression analysis of a pseudo‐second‐order equation gave a higher r² value, indicating that both external mass transfer and intra‐particle diffusion are involved in the sorption process. The experimental isotherm data were analysed using the Langmuir, Freundlich and Redlich–Peterson equations. The Redlich isotherm, a combination of the Langmuir and Freundlich equations, was found to have the highest regression correlation coefficients at pH 7. At pH 8, the Langmuir mechanism dominated for cobalt and nickel adsorption. In contrast, at pH 6, the Freundlich equation gave a better correlation coefficient which suggests a more heterogeneous adsorption at that pH. The maximal adsorption capacity of the granular sludge, as determined by the Langmuir equation, for cobalt or nickel in single systems (8.92 mg g^?1 Co TSS; 9.41 mg g^?1 Ni TSS, pH 7) compared with binary systems (8.06 mg g^?1 Co TSS; 8.43 mg g^?1 Ni TSS, pH 7) showed no great difference in the accumulation of these metals onto granular sludge. Copyright © 2004 Society of Chemical Industry     

Preparation and characterization of higher degree‐deacetylated chitosan‐coated magnetic adsorbent for the removal of chromium(VI) from its aqueous mixture

Chitosan (90% deacetylated) coated magnetic adsorbent prepared by coprecipitation method to remove Cr(VI) from its aqueous solution. The experimental studies depicts that the predominant option for removal of Chromium by adsorption from its aqueous phase using Magnetic‐Chitosan (MC). The subsequent physical, chemical, and magnetic properties of MC were characterized by X‐ray powder diffraction, scanning electron microscopy, Fourier transform infrared spectrometer, vibrating sample magnetometer. The influence of batch process parameters such as contact time, initial concentration, pH, and coexisting anions were investigated. The Box‐Behnken experimental design in response surface methodology was performed to design the experiment optimal operating conditions. The maximum percentage reduction of Cr(VI) is 96.3 that was obtained by magnetic chitosan with the optimal operating conditions of 149.53 mg/L at pH of 5.32 at the contact time of 80 min and at the temperature of 303 K. The average diameter of the magnetic chitosan was calculated from X‐ray diffractometer analysis as 24.5 nm. The equilibrium adsorption isotherm models such as Langmuir and Freundlich and the adsorption kinetics such as pseudo first order, pseudo second order and intra‐particle diffusion kinetic model were analyzed. The experimental data's suited for the best fit with the Langmuir isotherm model and pseudo first order kinetic model. It also revealed that Cr(VI) adsorption on MC is intrinsically exothermic and spontaneous. The magnetic chitosan was also used to investigate for the removal of Cr(VI) from the real water sources such as surface, underground, and tannery wastewater. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45878.