Polydopamine Nanoparticles as a New and Highly Selective Biosorbent for the Removal of Copper (II) Ions from Aqueous Solutions

The adsorption and desorption of copper (II) ions from aqueous solutions were investigated using polydopamine (PD) nanoparticles. The nanoscale PD nanoparticles with mean diameter of 75?nm as adsorbent were synthesized from alkaline solution of dopamine and confirmed using scanning electron microscopy and X-ray diffraction analysis. The effects of pH (2?C6), adsorbent dosage (0.2?C0.8?g?L^?1), temperature (298?C323?K), initial concentration (20?C100?mg?L^?1), foreign ions (Zn²⁺, Ni²⁺, Cd²⁺, Fe²⁺, and Ag⁺), and contact time (0?C360?min) on adsorption of copper ions were investigated through batch experiments. The isotherm adsorption data were well described by the Langmuir isotherm model. The maximum uptake capacity of Cu²⁺ ions onto PD nanoparticles was found to 34.4?mg/g. The kinetic data were fitted well to pseudo-second-order model. Moreover, the thermodynamic parameters of the adsorption (the Gibbs free energy, entropy, and enthalpy) were studied.     

A Comparison of Inorganic Solid Wastes as Adsorbents of Heavy Metal Cations in Aqueous Solution and Their Capacity for Desorption and Regeneration

The adsorption capacity of seven inorganic solid wastes [air-cooled blast furnace (BF) slag, water-quenched BF slag, steel furnace slag, coal fly ash, coal bottom ash, water treatment (alum) sludge and seawater-neutralized red mud] for Cd²⁺, Cu²⁺, Pb²⁺, Zn²⁺ and Cr³⁺ was determined at two metal concentrations (10 and 100 mg?L^?1) and three equilibrium pH values (4.0, 6.0 and 8.0) in batch adsorption experiments. All materials had the ability to remove metal cations from aqueous solution (fly and bottom ash were the least effective), their relative abilities were partially pH dependant and adsorption increased greatly with increasing pH. At equimolar concentrations of added metal, the magnitude of sorption at pH 6.0 followed the general order: Cr³⁺????Pb²⁺????Cu²⁺?>?Zn²⁺?=?Cd²⁺. The amounts of previously sorbed Pb and Cd desorbed in 0.01 M NaNO₃ electrolyte were very small, but those removed with 0.01 M HNO₃, and more particularly 0.10 M HNO₃, were substantial. Water treatment sludge was shown to maintain its Pb and Cd adsorption capability (pH 6.0) over eight successive cycles of adsorption/regeneration using 0.10 M HNO₃ as a regenerating agent. By contrast, for BF slag and red mud, there was a very pronounced decline in adsorption of both Pb and Cd after only one regeneration cycle. A comparison of Pb and Cd adsorption isotherms at pH 6.0 for untreated and acid-pre-treated materials confirmed that for water treatment sludge acid pre-treatment had no significant effect, but for BF slag and red mud, adsorption was greatly reduced. This was explained in terms of residual surface alkalinity being the key factor contributing to the high adsorption capability of the latter two materials, and acid pre-treatment results in neutralization of much of this alkalinity. It was concluded that acid is not a suitable regenerating agent for slags and red mud and that further research and development with water treatment sludge as a metal adsorbent are warranted.     

Two-stage Batch Adsorber Design: A Time-Dependent Langmuir Model for Adsorption of Pb2+ and Cd2+ onto Modified Kaolinite Clay

The kinetics of the adsorption of Pb²⁺ and Cd²⁺ by sodium tetraborate (NTB)-modified kaolinite clay adsorbent was studied. A one-stage and two-stage optimization of equilibrium data were carried out using the Langmuir and time-dependent Langmuir models, respectively. Increasing temperature was found to increase the pseudo-second order kinetic rate constant and kinetic data for Pb²⁺ adsorption were found to fit well with the pseudo-second order kinetic model (PSOM) while that for Cd²⁺ were found to show very good fit to the modified pseudo-first order kinetic model (MPFOM). Binary solutions of Pb²⁺ and Cd²⁺ reduced the adsorption capacity of the modified adsorbent for either metal ion with increased initial sorption rate due to competition of metal ions for available adsorption sites. The use of NTB-modified kaolinite clay adsorbent reduces by approximately 72.2% and 96.3% the amount of kaolinite clay needed to adsorb Pb²⁺ and Cd²⁺ from wastewater solutions. From the two-stage batch adsorber design study, the minimum operating time to determine a specified amount of Pb²⁺ and Cd²⁺ removal was developed. The two-stage batch adsorption process predicted less than half the minimum contact time to reach equilibrium in the one-stage process for the adsorption of Pb²⁺ and Cd²⁺ by NTB-modified kaolinite clay adsorbent and requires 0.05 times the mass of the adsorbent for the single-stage batch adsorption at the same operating conditions.     

羟基磷灰石对铅锌矿区土壤吸附Zn2+、Cd2+的影响

为探究羟基磷灰石(HAP)对矿区土壤重金属的固化效果,采用吸附试验,研究施加HAP的铅锌矿区土壤对Cd~(2+)、Zn~(2+)的动力学吸附和等温吸附效果。结果表明:土壤对Cd~(2+)、Zn~(2+)的吸附量随Cd~(2+)、Zn~(2+)初始浓度的增加而增加;在酸性条件下,其吸附量随pH上升而上升;准二级动力学方程能很好地描述两者的吸附过程,土壤吸附能力随HAP的添加量增大而增强;在Zn—Cd共存体系中,当初始浓度为20mg/L时,土壤对Zn~(2+)、Cd~(2+)的吸附无明显差异,2种金属离子竞争力度小,随着初始浓度上升,竞争明显,对Zn~(2+)的最大吸附量能达到单一体系中的79%～87%,而Cd~(2+)的最大吸附量只有单一体系中的57%～72%,Zn~(2+)的竞争力优于Cd~(2+),Zn~(2+)对Cd~(2+)吸附产生严重的抑制。综上可知,HAP能提高矿区土壤的吸附性能,在Zn、Cd污染土壤中,更能提升土壤对Zn~(2+)的吸附固持能力。     

Comparison of Cadmium Ion Adsorption on Various ACTIVATED CARBONS

Studies on the removal of cadmium(II) ions from aqueous solutions by adsorption on various activated carbons [commercial activated carbon (CAC) and chemically prepared activated carbons (CPACs) from raw materials such as straw, saw dust and datesnut] have been carried out with an aim to obtain information on treating effluents containing Cd(II) ions. Factors influencing the adsorption of Cd(II) ions from aqueous solution by ACs have been investigated by following a batch adsorption technique at 30± 1 ^°C. The percentage removal increased with decrease in initial concentration and particle size of CPACs and an increase in contact time, dose and initial pH of the solution. Adsorption process was inhibited by the added electrolytes. The adsorption data were fitted with the Langmuir, Dubinim–Radushkevich and Freundlich isotherms and first-order kinetic equations viz., first-order, Lagergren and Bhattacharya–Venkobachar equations and intra-particle diffusion model. The kinetics of adsorption is first order with intra-particle diffusion as one of the rate determining steps. Thermodynamic parameters were obtained from equilibrium constants measured at 30, 35 and 40 ^°C (Error = ± 1 ^°C). Results of the studies on adsorption of Cd²⁺ ions from simulated wastewater were compared with that of CAC and Tulsion CXO-9(H), a commercial ion exchange resin/cationic resin (CR). Straw carbon showed the maximum adsorption capacity towards Cd²⁺ ions and a high value of rate constant of adsorption. Straw carbon is an alternative low-cost adsorbent to CAC.     

Sorption of Heavy Metals by Canola Meal

The results from this research indicate that canola meal (CM) can be used for adsorption of Zn²⁺, Cd²⁺, Cu²⁺, Pb²⁺and Ni²⁺from aqueous solutions. The order of sorption for these metals in single metal systems was as follows (molar basis): Zn²⁺> Cu²⁺> Cd²⁺> Ni²⁺> Pb²⁺. It was noted that a decrease in the concentration of CM caused a higher metal loading on the meal. Increases in the metal concentration, temperature or pH resulted in increased sorption of the metals by the meal. The systems with identical ratios of CM to Zn²⁺concentrations, regardless of their levels, resulted in the same amount of metal adsorbed per unit weight of meal. The Freundlich isotherm type model was used in this study and was found to fit the experimental equilibrium concentration data of Zn²⁺and Cd²⁺; however, the Langmuir isotherm model fit only the equilibrium data of Zn²⁺. Scanning Electron Microscopy (SEM) and Energy-Dispersive X-ray (EDX) microanalyses revealed that the metal ions were sorbed mainly at the cell wall and only small amounts of ions diffused into the cytoplasm of the CM cells. The Electron Spin Resonance (ESR) tests were inconclusive regarding the direct participation of free radicals in copper sorption.     

Removal of Zn2+ from Aqueous Solution using Castor Seed Hull

The effects of various experimental parameters on adsorption of Zn²⁺ metal ion from its aqueous solution by castor seed hull and also by activated carbon have been investigated using batch adsorption experiments. It has been found that the amount of zinc adsorbed per unit mass of the hull increases with the initial metal ion concentration, contact time, solution pH and with the amount of the adsorbent. Kinetic experiments clearly indicate that adsorption of zinc on both castor hull and activated carbon is a three-step process??a rapid adsorption of the metal ion, a transition phase, and an almost flat plateau. This has also been confirmed by the intraparticle diffusion model. It has also been found that the zinc adsorption process followed pseudo-second order kinetics. The kinetic parameters including rate constants have been determined at different initial metal ion concentration, pH, amount, and type of adsorbent, respectively. The Langmuir and Freundlich adsorption isotherm models have been used to interpret the equilibrium adsorption data. The Langmuir model yields better correlation coefficients. The monolayer adsorption capacities (q _m ) of castor hull and activated carbon have been compared with those for others reported in the literature. The value of separation factor (R _L ) derived from the Langmuir model gives an indication of favorable adsorption. Finally, from comparative studies, it has been found that castor hull is a potentially attractive adsorbent as compared to commercial activated carbon for the removal of zinc from aqueus effluents.     

砖红壤及其矿物表面对重金属离子的专性吸附研究

本文对Ｃｕ＾２＋、Ｚｎ＾２＋、Ｃｏ＾２＋、Ｎｉ＾２＋和Ｃｄ＾２＋在砖红壤、针铁矿、无定形氧化铝和高岭石表面上的专性吸附进行的研究结果表明：ＰＨ是影响重金属离子吸附过程的最重要因素，而表面带电性质对吸附过程的影响不大。砖红壤表面的吸附顺序是Ｃｕ＾２＋〉Ｚｎ＾２＋〉Ｃｏ＾２＋〉Ｎｉ＾２＋≥Ｃｄ＾２＋；针铁矿表面的吸附顺序是Ｃｕ＾２＋〉Ｚｎ＾２＋〉Ｃｄ＾２＋〉Ｎｉ＾２＋〉Ｃｏ＾２＋；而无定形氧化铝和高岭     

Waste-Derived Siliceous Materials as a Novel Sorbent for Removal of Ni2+ from Aqueous Solutions

In the present study, the preparation of sorbent from waste-derived siliceous materials has been investigated for the removal of nickel ion (Ni²⁺) from aqueous solutions. Three types of ashes, i.e., rice husk ash (RHA), palm oil fuel ash (PFA), and coal fly ash (CFA), were used in the preparation of sorbent. Batch studies were carried out to examine the effect of various experimental parameters, i.e., RHA/CFA/PFA ratio in the sorbent preparation, contact time, initial concentration of Ni²⁺, agitation rate, and pH. Among all the ratios of the prepared sorbent, it was found that sorbent containing RHA and PFA gave the highest Ni²⁺ removal efficiency. The optimum conditions for Ni²⁺ removal using RHA/PFA sorbent were obtained at contact time of 30?min, Ni²⁺ concentration of 100?mg/L, agitation rate of 130?rpm, and pH?4. During the optimum condition, more than 90% of Ni²⁺ could be removed in all experiment studies. It was also found that the spent RHA/PFA sorbents had a narrow range of particle size distributions as compared to prepared RHA/PFA sorbent. In addition, the surface morphology of the spent RHA/PFA sorbents had more compact structures.     

Removal of Zn from Aqueous Solutions by Low-Rank Coal

The ability of an immature coal (leonardite) to remove zincfrom aqueous solutions was studied as a function of pH,contact time and concentration of metal solutions.Effective removal of Zn²⁺ was demonstrated at pHvalues of 5–6. Kinetic study showed that the adsorption ofZn²⁺ occurs in two phases: a rapid phase followed by aquasi-equilibrium state attained within the first twohours. The adsorption isotherm was measured at 25 °C, using adsorptive solutions at the optimum pH value todetermine the adsorption capacity.     

Removal of chrome dye from aqueous solutions by fly ash

The ability of fly ash to remove Omega Chrome Red ME (a chrome dye, mostly used in textile industries) from water has been studied. It has been found that low adsorbate concentration, small particle size of adsorbent, low temperature, and acidic pH of the medium favor the removal of chrome dye from aqueous solutions. The dynamics of adsorbate transport from bulk to the solid phase has been studied at different temperatures in light of the adsorption of dye on the outer surface as well as diffusion within the pores of fly ash. The applicability of Langmuir isotherm suggests the formation of monolayer coverage of dye molecules on the outer interface of adsorbent. The thermodynamics of chrome dye-fly ash system indicates spontaneous and exothermic nature of the process. The pronounced removal of chrome dye in the acidic range may be due to the association of dye anions with the positively charged surface of the adsorbent.     

Preparation, Characterization, and Adsorption Behavior of Cu(II) Ions onto Alkali-Treated Weed (Imperata cylindrica) Leaf Powder

The adsorption of Cu(II) ions by sodium-hydroxide-treated Imperata cylindrica (SoHIC) leaf powder was investigated under batch mode. The influence of solution pH, adsorbent dosage, shaking rate, copper concentration, contact time, and temperature was studied. Copper adsorption was considered fast as the time to reach equilibrium was 40–90 min. Several kinetic models were applied and it was found that pseudo-second-order fitted well the adsorption data. In order to understand the mechanism of adsorption, spectroscopic analyses involving scanning electron microscope (SEM) coupled with energy-dispersive spectroscopy (EDS) and Fourier transform infrared (FTIR) spectrophotometer were carried out. Ion exchange was proven the main mechanism involved as indicated by EDS spectra and as there was a release of light metal ions (K⁺, Na⁺, Mg²⁺, and Ca²⁺) during copper adsorption. Complexation also occurred as demonstrated by FTIR spectra involving hydroxyl, carboxylate, phosphate, ether, and amino functional groups. The equilibrium data were correlated with Langmuir, Freundlich, and Dubinin–Radushkevich isotherm models. Based on Langmuir model, the maximum adsorption capacity was recorded at the highest temperature of 310 K, which was 11.64 mg g^?1.     

Use of wollastonite for the treatment of Cu(II) rich effluents

The adsorption technique using wollastonite has been applied for the removal of Cu(II) from aqueous solutions. The low concentration, high temperature and alkaline pH favor the removal of Cu(II). The Langmuir isotherm was used to represent the equilibrium data at different temperatures. The apparent heat of adsorption has been found to be 5.926 Cal mol^?1. The uptake of Cu(II) is diffusion controlled and the mass transfer coefficient is 3.6 × 10^?5 cm s^?1. The maximum removal of Cu(II) in alkaline medium has been explained on the basis of the uptake of hydrolyzed adsorbate species by the active surface sites of adsorbent.     

Adsorptive Potential of 2-Mercaptobenzimidazole-Immobilized Organophilic Hydrotalcite for Mercury(II) Ions from Aqueous Phase and Its Kinetic and Equilibrium Profiles

An organophilic calcined hydrotalcite (OHTC) was prepared by treating calcined hydrotalcite (HTC) with sodium dodecylbenzene sulphonate (an anionic surfactant) to achieve a high loading of thiol functionality through the immobilization of 2-mercaptobenzimidazole (MBI) as a chelating agent. The adsorbent (MBI-OHTC) obtained was characterized using XRD, FTIR, SEM, TG/DTG, surface area analysis and potentiometric titration. The adsorption of MBI-OHTC to remove Hg(II) ions from aqueous solutions was studied as a function of pH, contact time, metal ion concentration, ionic strength and adsorbent dose. The optimum pH range for the maximum removal of Hg(II) was 6.0–8.0. The maximum value of Hg(II) adsorption was found to be 11.63 and 21.52 mg g^?1 for an initial concentration of 25 and 50 mg l^?1, respectively at pH 8.0. The equilibrium conditions were achieved within 3 h under the mixing conditions employed. A reversible pseudo-first-order used to test the adsorption kinetics. The adsorption mechanism consisted of external diffusion and intraparticle diffusion and the intraparticle mass transfer diffusion was predominated after 20 min of experiment. Extent of adsorption decreased with increase of ionic strength. The experimental isotherm was analyzed with two parameters (Langmuir and Freundlich) and three parameters (Redlich–Peterson) equations. The isotherm data were best modeled by the Freundlich isotherm equation. Complete removal (≈100%) of Hg(II) from 1.0 l of chlor-alkali industry wastewater containing 9.86 mg Hg(II) ions, was possible with 3 g of the adsorbent dose at pH 8.0. About 95.0% of Hg(II) can be recovered from the spent adsorbent using 0.1 M HCl.     

Adsorption of Dioxin by Bag Filter + Powdered Activated Carbon

A novel bag filter + powdered activated carbon technique is here proposed to address the low utilization rate of powdered activated carbon and the low dioxin removal rate associated with the conventional activated carbon injection + bag filter technique, better known as the fly ash + activated carbon + bag technique. In this method, dibenzofuran serves as a dioxin simulant. The effect of the adsorption temperature and dibenzofuran inlet concentration on the adsorption performance of activated carbon was studied using a filter cloth adsorption device with an inner diameter of 25 mm, and the adsorption performances of fly ash, activated carbon, and fly ash +5% activated carbon were compared. The results showed that activated carbon exhibited a higher adsorption efficiency and remained highly efficient longer than fly ash +5% activated carbon. When the dibenzofuran inlet concentration was 0.0956 g/m³ (about one million times the concentration of dioxin in the flue gas of incinerated waste), the duration of the high-efficiency (>90%) adsorption of the powdered activated carbon (thickness 1.2 mm) on the filter cloth was over 7 h. These results prove that the replacement of fly ash + activated carbon + filter bag with powdered activated carbon + bag filter can significantly improve the removal efficiency of the dioxin in waste incineration flue gas and the utilization rate of activated carbon.     

KINETICS OF ION EXCHANGE IN SOIL ORGANIC MATTER. IV. ADSORPTION AND DESORPTION OF Pb2+, Cu2+, Cd2+, Zn2+ AND Ca2+ BY PEAT

The equilibria as well as the rates of adsorption and desorption of the ions Pb²⁺, Cu²⁺, Cd²⁺, Zn²⁺, and Ca²⁺ by soil organic matter were determined in batch experiments as a function of the amount of metal ions added to an aqueous suspension of HCl-washed peat. Simultaneous determination of the metal ions and hydrogen ions in the solution by atomic absorption spectrophotometry and pH-measurements showed that the adsorption of one divalent metal ion by peat was coupled with the release of two hydrogen ions. Since this equivalent ion-exchange process causes a corresponding increase of the electric conductivity of the solution, the rates of the adsorption and desorption processes were determined by an immersed conductivity electrode. The distribution coefficients show that the selective order for the metal adsorption by peat is Pb²⁺ > Cu²⁺ > Cd²⁺≌ Zn²⁺ > Ca²⁺ in the pH range of 3·5 to 4·5. The slope of -2, as observed in a double logarithmic plot of the distribution coefficients versus the total solution concentration confirms the equivalence of the ion-exchange process of divalent metal ions for monovalent H₃O⁺ -ions in peat. The absolute rates of adsorption, as well as the rates for the fractional attainment of the equilibrium, increase with increasing amounts of metal ions added. This behaviour is also observed for the subsequent desorption of the metal ions by H₃O⁺-ions. At a given amount of metal ions added, the absolute rates of adsorption decrease in the order Pb²⁺ > Cu²⁺ > Cd²⁺ > Zn²⁺ > Ca²⁺, while the rates for the fractional attainment of the equilibrium decrease in the order Ca²⁺ > Zn²⁺≌ Cd²⁺ > Pb²⁺ > Cu²⁺. The half times for adsorption and desorption were in the range of 5 to 15 sec.     

Equilibrium, Kinetics, and Thermodynamics of Methylene Blue Adsorption by Pine Tree Leaves

The adsorption capacity of pine tree leaves for removal of methylene blue (MB) from aqueous solution was investigated in a batch system. The effects of the process variables, such as solution pH, contact time, initial dye concentration, amount of adsorbent, agitation speed, salt concentration, and system temperature on the adsorption process were studied. The extent of methylene blue dye adsorption increased with increase in initial dye concentration, contact time, agitation speed, temperature, and solution pH but decreased with increased in amount of adsorbent and salt concentration. Equilibrium data were best described by both Langmuir isotherm and Freundlich adsorption isotherm. The maximum monolayer adsorption capacity of pine tree leaves biomass was 126.58?mg/g at 30?°C. The value of separation factor, R _L , from Langmuir equation and Freundlich constant, n, both give an indication of favorable adsorption. The intrapartical diffusion model, liquid film diffusion model, double exponential model, pseudo-first and second order model were used to describe the kinetic and mechanism of adsorption process. A single stage bath adsorber design for the MB adsorption onto pine tree leaves has been presented based on the Langmuir isotherm model equation. Thermodynamic parameters such as standard Gibbs free energy (??G ⁰), standard enthalpy (??H ⁰), and standard entropy (??S ⁰) were calculated.     

Utilisation of Rubber Wood Shavings for the Removal of Cu(II) and Ni(II) from Aqueous Solution

The potential of heat and chemically treated rubber wood shavings (RWS) to remove Cu(II) and Ni(II) was evaluated at bench-scale by varying parameters such as initial Cu(II) and Ni(II) concentrations, contact time and adsorbent dosage. Maximum Cu(II) and Ni(II) uptake was achieved using NaOH-treated RWS after 5 h of contact time, pH 5.0 (Cu), 5.5 (Ni) and 6.0 (mixed-metal solution), initial Cu(II) and Ni(II) of 100 mg L^?1 and RWS dosage of 0.3% (w/v). Point of zero charge (pH_PZC) value of 4.35 suggests the appropriateness of pH range used. Higher Cu(II) and Ni(II) adsorption following NaOH treatment was due to smaller average pore diameter (34.63 Å), higher mesopore content and higher surface negativity charge. EDAX analysis confirmed the presence of Cu and Ni on the surface of the RWS. The importance of carboxyl and hydroxyl functional groups during Cu(II) and Ni(II) removal is supported by the FTIR analysis and good correlation (R ² of 0.96–0.99) with the pseudo-second-order adsorption kinetic model. The results indicate the potential of using RWS as an alternative adsorbent to remove Cu(II) and Ni(II) from industrial wastewaters.     

A Study on Al(III) and Fe(II) Ions Sorption by Cattle Manure Vermicompost

Cattle manure vermicompost has been used for the adsorption of Al(III) and Fe(II) from both synthetic solution and kaolin industry wastewater. The optimum conditions for Al(III) and Fe(II) adsorption at pH?2 (natural pH of the wastewater) were particle size of ≤250?µm, 1 g/10 mL adsorbent dose, contact time of 4 h, and temperature of 25°C. Langmuir and Freundlich adsorption isotherms fitted reasonably well in the experimental data, and their constants were evaluated, with R ² values from 0.90 to 0.98. In synthetic solution, the maximum adsorption capacity of the vermicompost for Al(III) was 8.35 mg g^?1 and for Fe(II) was 16.98 mg g^?1 at 25°C when the vermicompost dose was 1 g 10 mL^?1, and the initial adjusted pH was 2. The batch adsorption studies of Al(III) and Fe(II) on vermicompost using kaolin wastewater have shown that the maximum adsorption capacities were 1.10 and 4.30 mg g^?1, respectively, at pH?2. The thermodynamic parameter, the Gibbs free energy, was calculated for each system, and the negative values obtained confirm that the adsorption processes were spontaneous.     

Removal of Pb2+ Ions from Water by Poly(Acrylamide-co-Sodium Methacrylate) Hydrogels

The application of poly(acrylamide-co-sodium methacrylate) (AAm/SMA) hydrogel for the removal of Pb²⁺ ions from aqueous solutions has been investigated using batch adsorption technique. The extent of adsorption was investigated as a function of pH, adsorbent dose, and temperature. The Fourier transform infrared (FTIR) spectra showed that ?CNH₂ and ?CCOOH groups are involved in Pb²⁺ ion adsorption. The obtained results were analyzed by pseudo-first-order, pseudo-second?Corder, and intraparticle diffusion models using both linear and nonlinear methods. It was found that the Pb²⁺ ion adsorption followed pseudo-first-order kinetics. Nonlinear regression analysis of six isotherms, Langmuir, Freundlich, Redlich-Peterson, Toth, Dubinin-Radushkevich, and Sips, have been applied to the sorption data, while the best interpretation was given by Redlich-Peterson. Based on the separation factor, R _L, the Pb²⁺ ion adsorption is favorable, while the negative values of ?G indicates that the Pb²⁺ ion adsorption on the investigated hydrogel is spontaneous.