Kinetics,Thermodynamics, and Isothermic Evaluation in Sorption Study of Hazardous Dye Using Sodium Dodecylsulfate Physically Impregnated in Polyester‐Type Polyurethane Foam

Use of polyester‐type polyurethane foam (PUF) is an effective adsorbent for the removal of hazardous dye: crystal violet (CV) from an aqueous solution. In this adsorption study, the formation of hydrophobic ion pair (opposite charge attraction) between the charged species, i.e., cationic (basic) dye CV and anionic surfactant sodium dodecylsulfate (SDS) sorbed onto PUF. Chemical calculations were performed using quantum simulation to understand ion‐pair formation for CV–SDS at the semiempirical PM6 level. Adsorption studies were performed using 200 mg cylindrical PUF with an overhead stirrer in solutions containing varying compositions of the dye–surfactant mixture. The equilibrium thermodynamics and kinetics of the adsorption process were studies by measuring CV dye removal as a function of time and temperature. Results show that the formation of the dye–surfactant ion pair is necessary for effective adsorption onto PUF. Various adsorption isotherms, viz., Langmuir, Freundlich, Temkin, Dubinin–Radushkevich (DRK), Harkin‐Jura, and several kinetic models, viz., pseudo‐first order, pseudo‐second order, Elovich, and Intraparticle diffusion were used to fit the spectrophotometric result. The equilibrium adsorption data fit to the Langmuir isotherm gives the maximum adsorption of PUF as 33.39 mg g^?1 from 200 mL 5.0 × 10^?5 mol L^?1 CV solution at 298.15 K. The kinetics study showed that the overall adsorption process follows pseudo‐second‐order kinetics. The Morris–Weber model suggests that an intraparticle diffusion process is active in controlling the adsorption rate. The Freundlich, Temkin, DRK adsorption isotherms showed that solute dye transfers from solution to the PUF adsorbent surface through physical adsorption. The Langmuir and Harkin‐Jura adsorption isotherms suggest that the adsorbent surface is homogeneous in nature. The thermodynamic data showed that the adsorption process is spontaneous and endothermic with a positive enthalpy change and a negative change in Gibb's energy.     

Removal of basic yellow cationic dye by an aqueous dispersion of Moroccan stevensite

The aim of this study was to investigate the adsorption of basic yellow, a cationic dye, from aqueous solution by natural stevensite, with 104 m²/g of specific surface area. The kinetics and the effects of several experimental parameters such as the pH of the solution, adsorbent dose and initial dye concentration were researched using a batch adsorption technique. The results showed that an alkaline pH favoured basic yellow adsorption and the adsorption reached equilibrium in about 20 min. It was concluded that the adsorption process was governed by the electrostatic interaction. The isothermal data were fitted by means of Langmuir and Freundlich equations, and a monolayer adsorption capacity of 454.54 mg/g was calculated. Finally, a good agreement was found between the pseudo-second order model and the experimental data. A high maximum adsorption capacity was obtained (526 mg/g) and a maximum surface density of ~ 9 dye molecules/nm² was estimated, involving a columnar arrangement of the adsorbed molecules.     

Application of graphene-based adsorbents in the treatment of dye-contaminated wastewater; kinetic and isotherm studies

The adsorption of methylene blue (MB) on graphene-based adsorbents was tested through the batch experimental method. Two types of graphene-based adsorbents as graphene oxide (GO) and reduced graphene oxide (RGO) were compared to investigate the best adsorbent for MB removal. So that optimizing the MB removal for the selected type of graphene-based adsorbent, the diverse experimental factors, as pH (2–10), contact time (0–1440 min), adsorbent dosage (0.5–2 g/L), and initial MB concentration (25–400 mg/L) were analyzed. The conclusions indicated that the MB removal rised with an increase in the initial concentration of the MB and so rises in the amount of adsorbent used and initial pH. Maximum dye removal was calculated as 99.11% at optimal conditions after 240 min. Adsorption data were compiled by the Langmuir isotherm (R²: 0.999) and pseudo-second-order kinetic models (R²: 0.999). The Langmuir isotherm model accepted that the homogeneous surface of the GO adsorbent covering with a single layer. And the adsorption energy was calculated as 9.38 kJ mol⁻¹ according to the D-R model indicating the chemical adsorption occurred. The results show that GO could be utilized for the treatment of dye-contaminated aqueous solutions effectively.     

Removal of methylene blue from aqueous solution by adsorption onto zeolite synthesized from coal fly ash and its thermal regeneration

BACKGROUND: The removal of cationic dyes from wastewater is of great importance. Three zeolites synthesized from coal fly ashes (ZFAs) were investigated as adsorbents to remove methylene blue (MB), a cationic dye, from aqueous solutions. Experiments were conducted using the batch adsorption technique under different conditions of initial dye concentration, adsorbent dose, solution pH, and salt concentration. RESULTS: The adsorption isotherm data of MB on ZFAs were fitted well to the Langmuir model. The maximum adsorption capacities of MB by the three ZFAs, calculated using the Langmuir equation, ranged from 23.70 to 50.51 mg g^?1. The adsorption of MB by ZFA was essentially due to electrostatic forces. The measurement of zeta potential indicated that ZFA had a lower surface charge at alkaline pH, resulting in enhanced removal of MB with increasing pH. MB was highly competitive compared with Na⁺, leading to only a < 6% reduction in adsorption in the presence of NaCl up to 1.0 mol L^?1. Regeneration of used ZFA was achieved by thermal treatment. In this study, 90–105% adsorption capacity of fresh ZFA was recovered by heating at 450 °C for 2 h. CONCLUSION: The experimental results suggest that ZFA could be employed as an adsorbent in the removal of cationic dyes from wastewater, and the adsorptive ability of used ZFA can be recovered by thermal treatment. Copyright © 2010 Society of Chemical Industry     

Radiation synthesis of graphene oxide/composite hydrogels and their ability for potential dye adsorption from wastewater

A high yield of graphene oxide (GO) was chemically synthesized from graphite powder utilizing adjusted Hummer's method. The contents of acidic functional groups in GO were determined using potentiometric titration. Composite hydrogels dependent on graphene oxide/poly(2-acrylamido-2-methylpropanesulfonic acid)/polyvinyl alcohol (GO/PAMPS/PVA) were synthesized utilizing a ⁶⁰Co gamma irradiation source at different doses. The synthesized graphene oxide and composite hydrogels were portrayed via X-ray diffraction, thermogravimetric analysis, and Fourier transform infrared analysis. The morphology of composite hydrogels was characterized by scanning electron microscope. The gel % and swelling % for the prepared hydrogel demonstrated that the swelling % of hydrogel increased with raising AMPS content. Whereas the increment of GO and increasing the irradiation dose lead to a reduction in the swelling %. The influences of pH, GO percentage, initial dye concentration, the adsorbent dosage, contact time, and temperature on the adsorption of basic blue 3 dye were evaluated and the adsorption capacity was 194.6 mg/g at optimum conditions; pH = 6, GO/PAMPS/PVA composite hydrogels with 5 wt% of GO, initial dye concentration = 200 mg/L, adsorbent dose = 0.1 g, solution volume = 50 mL after 360 min at room temperature (25°C). The adsorption of dye onto the GO/PAMPS/PVA composite hydrogels follows Pseudo-second-order adsorption kinetics, fits the Freundlich adsorption isotherm model.     

Polyaniline‐functionalized magnetic nanoparticles for the removal of toxic dye from wastewater

A novel and inexpensive approach was adopted to develop a magnetic nanocomposite for the adsorption of cationic dye from an aqueous solution. This nanocomposite, which was based on a superparamagnetic iron oxide nanocore, was functionalized with a hydrophilic coating of polyaniline (PANI). The nanoparticle size, colloidal stability, surface chemistry, and magnetic properties were studied extensively by transmission electron microscopy, X‐ray diffraction, Fourier transform infrared spectroscopy, and vibrating sample magnetometry. The polymeric functionalized magnetic nanocomposite had an average core size of 20–40 nm and a shell size of 6–10 nm. To evaluate the potential of such nanocomposites for dye adsorption, malachite green (MG) was exposed with different operational parameters, such as the pH, temperature, initial concentration of the dye, contact time, and reusability. The rate of the adsorption followed pseudo‐second‐order kinetics with the adsorption isotherm fit the Langmuir isotherm model well. The maximum adsorption capacity was 240 mg of MG/g of adsorbent. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40840.     

Starch/rice husk ash based superabsorbent composite: high methylene blue removal efficiency

Superabsorbent hydrogels composites based on the biopolymer starch (ST) and rice husk ash (RHA) were successfully developed and tested towards the removal of methylene blue (MB), a cationic dye. RHA content hit the morphology, mechanical and water uptake properties of the composite. Batch adsorption experiments, carried out under pH 5 at 33 °C and with 2000 mg L^?1 as the initial concentration of MB, showed that at 5 wt% RHA the composite exhibited a remarkable adsorption capacity reaching up to 1906.3 mg g^?1 within 60 min. The adsorption kinetics followed the pseudo-second-order model and intraparticle diffusion was involved in this process. The Langmuir adsorption isotherm suggested a monolayer formation and spontaneous process. Thermodynamic parameters confirmed the spontaneity of the adsorption and suggested electrostatic interaction among the cationic dye molecules and the anionic adsorption sites on the adsorbent surface. FTIR analysis confirmed the adsorption process occurs via electrostatic mechanism associated with hydrophobic interactions. The adsorbents showed reusability with slight loss of adsorption capacity in five consecutive adsorption/desorption cycles. These results demonstrate ST/RHA superabsorbent composite as a low-cost, eco-friendly, robust and powerful adsorbent material for wastewater remediation.     

Application of natural hydroxyapatite in the treatment of polluted water: Utilization of dromedary bone as bioadsorbent

In this study, the dromedary bone waste was valorized by the obtainment of hydroxyapatite (HAp) and its application to remove crystal violet (CV) dye from aqueous solution. Fourier transform infrared spectroscopy, X-ray diffraction, elemental analysis X-ray fluorescence spectrometer (XRF), particle size laser analysis, and the point of zero charge pH value (pHpzc) were realized to characterize the natural adsorbent. The capacity of HAp to adsorb CV was measured at different contact times, pH values, and initial dye concentrations. The results showed that the model that better described the experimental data of adsorption kinetics was the pseudo-second-order kinetic model (PSO). Freundlich model well fitted the sorption isotherms. A maximum sorption capacity of 266.66 mg/g of CV dye on natural HAp was obtained. Hence, dromedary bone treated might be valorized as a natural adsorbent for water treatment with low environmental risks.     

Chitosan/polyaniline hybrid for the removal of cationic and anionic dyes from aqueous solutions

Nanostructured chitosan/polyaniline (CH/PANI) hybrid was synthesized via in situ polymerization of aniline in the presence of chitosan. The CH/PANI hybrid was characterized by FTIR spectroscopy, X-ray diffraction, thermogravimetric analysis, and scanning electron microscopy. The CH/PANI hybrid had a nanofibrous structure with an average diameter of 70 nm. This hybrid was employed as an ecofriendly and efficient adsorbent with high adsorption capacity for the removal of Acid Green 25 (AG) and methylene blue (MB) from aqueous solutions. AG and MB were used as anionic and cationic model dyes, respectively. The CH/PANI adsorbent showed high dependence on the pH of the medium with an excellent adsorption performance and regeneration manner. The kinetics and adsorption isotherms were studied. The CH/PANI hybrid follows the pseudo second-order adsorption kinetics and Temkin isotherm model for the adsorption of both AG and MB dyes. This assumes that the enthalpy of dyes molecules decreases with the adsorption on heterogeneous surface with various kinds of adsorption sites and as well as the ability to form multilayers of the dye. Also, intraparticle diffusion was found to play an important role in the adsorption mechanism. The maximum adsorption capacity was found to be 240.4 mg g⁻¹ of AG at pH 4 and 81.3 mg g⁻¹ of MB at pH 11. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47056.     

Thermodynamic and kinetic studies of crystal violet dye adsorption with poly(methyl methacrylate)–graphene oxide and poly(methyl methacrylate)–graphene oxide–zinc oxide nanocomposites

We successfully prepared poly(methyl methacrylate) (PMMA)–graphene oxide (GO) and PMMA–GO–zinc oxide (ZnO) nanocomposites and characterized them using different techniques. The adsorption performances of the as-prepared composites were investigated for crystal violet (CV) dye removal. The contact time as a main factor affecting the adsorption process by adsorbents was studied. Because the adsorption capacity value for CV was found to show no extensive changes after 35 min, 35 min was selected as the best contact time for our system. The adsorption results revealed that the best capacity of CV adsorption onto the PMMA–GO and PMMA–GO–ZnO nanocomposites occurred at pH 12 and 298 K. The respective entropies (−0.208 and −0.168 kJ mol⁻¹ K⁻¹) and enthalpies (−72.86 kJ/mol, and −55.54 kJ/mol) for PMMA–GO and PMMA–GO–ZnO and Gibbs energy revealed that the process of adsorption was exothermic. In addition, the Elovich, pseudo-first-order, intraparticle diffusion, and pseudo-second-order (four types) models were applied to our kinetic study. Our results indicate that CV adsorption onto PMMA–GO and PMMA–GO–ZnO was good with the pseudo-second-order (type 1) and pseudo-first-order models because of the low χ² value and the high correlation coefficient value. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47495.     

Adsorption behavior of cationic dyes on citric acid esterifying wheat straw: kinetic and thermodynamic profile

The kinetic and thermodynamic behaviors of cationic dye adsorption onto citric acid esterifying wheat straw (EWS) from aqueous solution were investigated. Two cationic dyes, methylene blue (MB) and crystal violet (CV) were selected as adsorbates. The kinetic and thermodynamic parameters of dye adsorption were examined with a batch system by changing various experimental factors (e.g. initial pH, EWS dosage, dye concentration, contact time, temperature). The MB and CV removal ratios came up to the maximum value beyond pH 4. The 2.0 g/L or up of EWS could almost completely remove MB and CV from 250 mg/L of dye solution. The adsorption percentages of MB and CV kept above 95% over a range from 50 to 350 mg/L of dye concentration when 2.0 g/L of EWS was used. The isothermal data followed the Langmuir model. The adsorption processes could be described by the pseudosecond-order kinetic model. The dual linear plots of intraparticle diffusion indicated that two intraparticle diffusion steps occurred in the dye adsorption processes. The thermodynamic study indicated that the adsorptions of dyes were spontaneous and endothermic. High temperatures favored the adsorption processes.     

Adsorption of Crystal Violet From Aqueous Solution by Citric Acid Modified Rice Straw: Equilibrium,Kinetics, and Thermodynamics

Rice straw, an abundant, lignocellulosic agricultural residue was thermochemically modified with citric acid to develop a biodegradable cationic adsorbent. The application potential of the prepared adsorbent to remove hazardous Crystal Violet dye from its aqueous solution was investigated. The morphological and chemical characteristics of the adsorbent were established by scanning electron microscopy (SEM), surface area, and porosity analysis by the BET (Brunauer, Emmett, and Teller) nitrogen adsorption method and Fourier transform infrared (FTIR) spectroscopy. Batch adsorption studies were carried out as a function of solution pH, adsorbent dose, initial dye concentration, and temperature, in order to get insights into the effect of these independent parameters on the adsorption process. The Langmuir, Freundlich, and Dubinin–Radushkevich models were used to describe the equilibrium adsorption data. The sorption mechanism was also evaluated in terms of kinetics and thermodynamics. The adsorption equilibrium data was well described by the Langmuir isotherm model. The adsorption process followed the pseudo-second-order rate kinetics. Thermodynamic study showed spontaneous and exothermic nature of the adsorption process.     

Magnetic and K+-cross-linked kappa-carrageenan nanocomposite beads and adsorption of crystal violet

Biopolymer-based magnetic beads, composed of kappa-carrageenan (κ-Car) and Fe₃O₄ nanoparticles, were synthesized. The magnetic beads were prepared through in situ precipitation of Fe²⁺/Fe³⁺ ions in the presence of carrageenan and subsequently treating with K⁺ solution. The structure of magnetic kappa-carrageenan beads (mκ-Carb) was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), vibrating sample magnetometer, and thermal gravimetric analysis techniques. According to SEM micrographs, an undulant and coarse structure with cubic-shaped sections was obtained when the magnetic nanoparticles were incorporated in composition of beads. The TEM image confirmed the formation of magnetic nanoparticles with an average size of 3–7 nm. The synthesized beads were examined as adsorbent to remove crystal violet dye from aqueous solutions. It was found that due to coarse surface, the rate of dye adsorption on magnetic beads can be improved slightly. The experimental adsorption kinetics was analyzed according to pseudo-first-order and pseudo-second-order kinetic models and the adsorption kinetics followed well the pseudo-second-order model. Isotherm adsorption data of dye on beads were modeled according to Langmuir and Freundlich isotherm models. The results revealed that the experimental data have the best fit to Langmuir isotherm model, and maximum adsorption capacity of beads for dye obtained was 84.7 mg/g. The influence of pH on the variation of adsorption capacity of beads for crystal violet was not considerable. The thermodynamic parameters indicated that the adsorption of CV dye on beads is spontaneous.     

Adsorption studies on the removal of Malachite Green from aqueous solutions onto halloysite nanotubes

Halloysite nanotubes (HNTs) were used as nano-adsorbents for removal of the cationic dye, Malachite Green (MG), from aqueous solutions. The adsorption of the dye was studied with batch experiments. The natural HNTs used as adsorbent in this work were initially characterized by FT-IR and TEM. The effects of adsorbent dose, initial pH, temperature, initial dye concentration and contact time were investigated. Adsorption increased with increasing adsorbent dose, initial pH, and temperature. Equilibrium was rapidly attained after 30 min of contact time. Pseudofirst-order, pseudo-second-order and intraparticle diffusion models were considered to evaluate the rate parameters. The adsorption followed pseudo-second-order kinetic model with correlation coefficients greater than 0.999. The factors controlling adsorption process were also calculated and discussed. The maximum adsorption capacity of 99.6 mg g⁻¹ of MG was achieved in pH = 9.5. Thermodynamic parameters of ΔG°, ΔH° and ΔS° indicated the adsorption process was spontaneous and endothermic.     

Removal of methylene blue from aqueous solutions by using cold plasma‐ and formaldehyde‐treated onion skins

In this paper, the use of cold plasma‐treated and formaldehyde‐treated onion skins as a biosorbent has been investigated to remove methylene blue dye from aqueous solutions. The surface characteristics of the treated onion skins were investigated using Fourier Transform–infrared spectroscopy. The influence of process variables such as adsorbent dosage, initial dye concentration and pH were studied. Equilibrium isotherms were analysed by Langmuir, Freundlich, Temkin and Dubinin–Radushkevich isotherm models. The results indicated that the data for adsorption of methylene blue onto onion skins fitted well with the Langmuir isotherm model. The sorption capacities for cold plasma‐treated and formaldehyde‐treated onion skins by Langmuir isotherm were found to be 250 and 166.67 mg/g, respectively. The equilibrium time was found to be 150 min for 50 mg/l dye concentrations. The maximum removals for cold plasma‐treated and formaldehyde‐treated onion skins obtained were 90.94 and 95.54% at natural pH 10.0 for adsorbent doses of 0.15 g/200 ml, respectively. The rates of sorption were found to conform to pseudo‐first‐order kinetics. Results indicated that onion skins could be used as a biosorbent to remove methylene blue dye from contaminated waters.     

Removal of Basic Dye from Aqueous Solution using Cinnamomum camphora Sawdust: Kinetics,Isotherms, Thermodynamics,and Mass-Transfer Processes

Cinnamomum camphora sawdust (CCS) was employed as a cheap and effective biosorbent to remove basic dye from aqueous solutions. The biosorbent was characterized by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FT-IR). Adsorption experiments were carried out in a batch system as a function of initial pH, adsorbent dose and particle size, ionic strength, initial dye concentration, and reaction temperature. The selected basic dye (malachite green) adsorption onto CCS significantly depended on these factors. By comparative kinetic analysis, the rate of sorption was conformed with good correlation to pseudo-second-order kinetics. Equilibrium data were fitted well by Langmuir isotherm with the maximum adsorption capacity of 155.0 mg/g at the temperature of 318 K and pH 7.0 ± 0.1. Thermodynamic parameters proved that malachite green dye biosorption process was spontaneous and endothermic within the investigated temperature range. The mechanism of adsorption was also studied. It was found that the adsorption of malachite green onto CCS was mainly governed by film diffusion. The electrostatic attractions and ionic interactions between malachite green dye and CCS might be responsible for the adsorption process. The comparative investigation suggested that the sawdust could be considered as a potential adsorbent for malachite green dye removal from wastewater.     

Adsorption behavior of Congo red from an aqueous solution on 4‐vinyl pyridine grafted poly(ethylene terephthalate) fibers

In this study, a reactive fibrous adsorbent was prepared through the grafting of 4‐vinyl pyridine monomer onto poly(ethylene terephthalate) (PET) fibers for the removal of Congo red (CR) dye from an aqueous solution with the batch adsorption method. Effects of various parameters such as the grafting yield, pH, treatment time, and initial dye concentration on the amount of adsorption of the dye onto the reactive fibers were investigated. The effective pH was 4.0 for adsorption on grafted PET fibers. The sufficient time to attain equilibrium was 150 min. The maximum adsorption capacity of the reactive fibers for CR was 17.3 mg/g of fiber. The rates of adsorption conformed to pseudo‐second‐order kinetics with good correlation. The adsorption isotherm of CR fit a Langmuir‐type isotherm. The reactive fibers were stable and regenerable by acid and base without loss of activity. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Investigation of Cationic Dye Adsorption from Water onto Acetic Acid Lignin

An adsorbent was prepared from acetic acid lignin (AAL) to investigate the adsorption mechanism of methylene blue (MB) from water. AAL was first deacetylated in NaOH aqueous solution and then fractionated by methanol to prepare adsorbents with various acidic hydroxy groups. The adsorption capacities of MB increased with the increase in initial pH and with the decrease in adsorbent dosage. The results of adsorption kinetics indicated the dye uptake process is a chemisorption. The adsorption capacity of lignin for MB adsorption increased from 18.2 to 63.3 mg g^?1 as AAL was deacetylated and fractionated.     

Microcolumn adsorption studies of acid/basic dyes related to the physicochemical properties of the adsorbent

The adsorptive removal of cationic Methylene Blue and anionic Alizarin Red S was analysed in microcolumn tests. A detailed analysis of the influence of adsorbent surface acidity/basicity, elemental composition, Brunauer–Emmett–Teller area, pore distribution, and point‐of‐zero‐charge pH on breakthrough properties was carried out. The characteristics of the mass transfer zone were used for evaluation of column performance. Four different activated carbons with different physical and chemical properties were analysed. It was concluded that, for adsorbents containing pores smaller than 1.7 times the solute molecular radius, the interactions between surface and solute have the greatest influence on the effective usage of column uptake capacity. A column packed with adsorbent characterised by large enough pores readily removed either anionic or cationic solutes. Partial correlation analysis revealed that the adsorption of cationic dye (Methylene Blue) was more sensitive to adsorbent textural properties in comparison with anionic dye (Alizarin Red S). Maximum column capacities were 3–4 times higher for cationic Methylene Blue than for anionic Alizarin Red S, with values of 494 and 107 mg/g respectively. The higher solubility of Alizarin Red S could be responsible for its lower and more even removal efficiencies. Finally, the surface chemistry of the adsorbent affected how the operating conditions influenced the column performance, as deduced from the opposite effect of flow rate on the adsorption of Methylene Blue by each adsorbent.     

A modified cellulose adsorbent for the removal of nickel(II) from aqueous solutions

A series of adsorption studies was carried out on a glycidyl methacrylate‐ modified cellulose material functionalised with imidazole (Cellulose‐g‐GMA‐Imidazole) to assess its capacity in the removal of Ni(II) ions from aqueous solution. The study sought to establish the effect of a number of parameters on the removal of Ni(II) from solution by the Cellulose‐g‐GMA‐Imidazole. In particular, the influence of initial metal concentration, contact time, solution temperature and pH were assessed. The studies indicated a Ni(II) uptake on the Cellulose‐g‐GMA‐Imidazole sorbent of approximately 48 mg g^?1 of nickel from aqueous solution. The adsorption process fitted the Langmuir model of adsorption and the binding process was mildly endothermic. The kinetics of the adsorption process indicated that nickel uptake occurred within 400 min and that pseudo‐second order kinetics best describe the overall adsorption process. Nickel(II) adsorption, recovery and re‐adsorption studies indicated that at highly acidic pH values the adsorbent material becomes unstable, but in the range pH 3–6, the adsorbent is stable and shows limited but significant Ni(II) recovery and re‐adsorption capability. Copyright © 2006 Society of Chemical Industry