Removal of congo red and basic violet 1 by chir pine (Pinus roxburghii) sawdust,a saw mill waste: batch and column studies

The efficiency of chir pine sawdust (CPS) for adsorptive removal of the dyes, congo red (CR) and basic violet 1 (BV), from aqueous solution was evaluated using batch and column studies. The equilibrium was attained in 60 min for CR and 45 min for BV. The adsorption of BV obeyed the Langmuir isotherm model while the Freundlich isotherm fitted the equilibrium data of CR adsorption. The Langmuir monolayer adsorption capacities (Q_o) of CPS for BV and CR were 11.3 and 5.8 g kg^?1, respectively. The kinetic data for CR were best fitted to the Lagergren pseudo-first-order model and for BV to the pseudo-second-order model. The intra-particle diffusion was found to be the rate-controlling step for CR adsorption, while the adsorption kinetics of BV were controlled by both intra-particle and liquid-film diffusion. The thermodynamic parameters indicated that the adsorption process was spontaneous and endothermic in nature. The adsorption activation energy (E_a) for CR (124 kJ mol^?1) implied chemical adsorption while that for BV (5.4 kJ mol^?1) indicated physical adsorption. An increase in the Thomas model constant (K_Th) with increasing flow indicated that for both dyes the mass transport resistance decreased during adsorption. Thus, CPS may be an efficient low-cost adsorbent for decolorization of dye-containing wastewaters.     

Ionic dye adsorption by zinc oxide nanoparticles

The adsorption behaviour of Basic Red 12, Acid Orange 7 and Acid Blue 1 on zinc oxide nanoparticles (ZNP) has been investigated to understand the physicochemical process involved and to explore the possible use of nanoparticles in the treatment and management of textile waste matter. The dye removal capacity of ZNP towards Basic Red 12, Acid Orange 7 and Acid Blue 1 was found to be 15.64, 6.78 and 6.38 mg g^?1, respectively. The adsorption process was pH dependent and optimum pH values of 9.0, 2.0 and 4.0 were obtained for Basic Red 12, Acid Orange 7 and Acid Blue 1, respectively. Equilibrium was established after 1.0 h for all dyes. Langmuir, Freundlich and Temkin isotherm models were applied to the system. The adsorbent ZNP was characterised using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET) and Fourier transform infrared (FTIR) techniques. SEM analysis revealed the noticeable nanoporous morphology of the material. The results of FTIR spectroscopy showed that the process is driven by an electrostatic complexation mechanism. XRD studies revealed the nanocrystalline structure of ZNP. BET surface area measurement suggested a high pore volume and large surface area for the adsorbent. The kinetic measurements suggested pseudo-second-order kinetic processes with high regression coefficients and smaller standard error of estimate values and lower residual sum of squares. The thermodynamic measurements suggested that all processes were exothermic and accompanied by negative values for Δ G⁰, Δ S⁰ and Δ H⁰.     

Low-cost and efficient adsorbent derived from pyrolysis of Jatropha curcas seeds for the removal of Cu2+ from aqueous solutions

Biochar, is a low-cost material that can be used as an alternative adsorbent for the removal of heavy metals. In this study, a low-cost and efficient adsorbent synthesised from Jatropha curcas seeds was used for the uptake of Cu²⁺ from aqueous solutions. The as-prepared adsorbent was characterised by scanning electron microscopy and Brunauer–Emmett–Teller analysis post calcination at 500 °C, its BET surface area and total pore volume were 39.62?m²?g^?1 and 0.049?m³?g^?1, respectively. Subsequently, the effects of initial pH of the solution, contact time, and adsorbent material dosage on the adsorption of Cu²⁺ by the prepared adsorbent were investigated. The as-prepared adsorbent exhibited a high performance, with a maximum adsorption amount of 32.895?mg?g^?1 for Cu²⁺ at pH 5.0 and 25 °C, owing to the presence of ?OH, C=O, C–O, Si-O-Si, and O-Si-O on its surface. The predominant Cu²⁺ adsorption mechanism was assumed to be ion exchange. Notably, the Cu²⁺ adsorption could attain equilibrium within 90?min. In addition, the fact that the Langmuir model was a better fit than the Freundlich model for the isotherm data of Cu²⁺ adsorption by the as-prepared adsorbent suggested that the adsorption of Cu²⁺ was a monolayer adsorption process.     

Removal of Mo(VI) from aqueous solutions using sulfuric acid-modified cinder: kinetic and thermodynamic studies

Removal of Mo(VI) from aqueous solutions was investigated using cinder modified by sulfuric acid. Various parameters such as pH, agitation time, Mo(VI) concentration, and temperature have been studied. The maximum adsorption of Mo(VI) occurred at pH between 4.0 and 6.0. Kinetic studies showed that the adsorption generally obeyed a pseudo second-order model. The activation energy was 31.4?kJ?mol^?1, indicating that the adsorption process was governed mainly by interactions of physical nature. Furthermore, application of Langmuir and Freundlich isotherm models to the adsorption equilibrium data showed that the adsorption behavior obeyed the Langmuir model. The adsorption capacity was found to be 10.8?g Mo(VI)?kg^?1 adsorbent. Finally, thermodynamic parameters such as ΔH ⁰, ΔS ⁰, and ΔG ⁰ were also evaluated, which showed that the adsorption of Mo(VI) on the treated cinder was endothermic, entropy increasing, and spontaneous. In conclusion, the sulfuric acid-modified cinder was shown to be an inexpensive, effective, and simple adsorbent for the removal of Mo(VI) from water.     

Pomegranate husk as an adsorbent in the removal of toxic chromium from wastewater

The use of a new sorbent developed from the husk of pomegranate, a famous fruit in Egypt, for the removal of toxic chromium from aqueous solution has been investigated. The batch experiment was conducted to determine the adsorption capacity of the pomegranate husk. The effects of initial metal concentration (25 and 50 mg l^?1), pH, contact time, and sorbent concentration (2–6 g l^?1) have been studied at room temperature. A strong dependence of the adsorption capacity on pH was observed, the capacity increased as the pH decreased, and the optimum pH value was pH 1.0. Adsorption equilibrium and kinetics were studied with different sorbent and metal concentrations. The adsorption process was fast, and equilibrium was reached within 3 h. The maximum removal was 100% for 25 mg l^?1 of Cr⁶⁺ concentration on 5 g l^?1 pomegranate husk concentration, and the maximum adsorption capacity was 10.59 mg g^?1. The kinetic data were analysed using various kinetic models—pseudo-first-order, pseudo-second-order, Elovich, and intraparticle diffusion equations—and the equilibrium data were tested using several isotherm models, Langmuir, Freundlich, Tempkin, Dubinin–Radushkevich, and Generalized isotherm equations. The Elovich and pseudo-second-order equations provided the greatest accuracy for the kinetic data, while Langmuir and Generalized isotherm models were the closest fit for the equilibrium data. The activation energy of sorption has also been evaluated as 0.236 and 0.707 kJ mol^?1 for 25 and 50 mg l^?1 chromium concentration, respectively.     

Magnetic particles precipitated onto wheat husk for removal of methyl blue from aqueous solution

Magnetic particles prepared via co-precipitation and impregnated onto wheat husk (MN-WH) were used for the removal of methyl blue (MB) from aqueous solution. Experiments were conducted in a batch mode for optimization regarding pH, contact time, adsorbent dose, initial dye concentrations, and temperature. Maximum adsorption (98%) was achieved at pH 5. The adsorption data were fitted into pseudo-first, pseudo-second, intraparticle diffusion, and Elovich equation revealing that adsorption followed pseudo-second-order kinetics. The four most common isotherm models, i.e. the Langmuir, Freundlich, Tempkin, and Dubinin–Radushkevich (D–R), were used to evaluate the data, with the best fit to a Langmuir isotherm (R² = 0.996), followed by a Freundlich isotherm (R² = 0.995), indicating monolayer adsorption of MB on the surface of MN-WH. Thermodynamic parameters calculated from the Van't Hoff equation revealed that the adsorption is exothermic (ΔHº = ?19.7 kJ mol^?1).     

Effects of β-cyclodextrin on adsorption and desorption of carbofuran in soils of divergent texture

Laboratory studies were conducted to determine the adsorption/desorption equilibrium of carbofuran between four divergently textured soils and distilled water and an aqueous solution of 0.01?mol?L^?1 β-cyclodextrin using a batch equilibrium technique. The determined adsorption isotherms for silt loam soils were of L-shaped, for sandy loam soil S-shaped, in agreement with a Freundlich isotherm. In the presence of β-cyclodextrin, the adsorption of carbofuran to the four soils was lower than with distilled water. Positive hysteresis was observed in all soils with distilled water, negative hysteresis when using a solution of β-cyclodextrin as desorbent. The results indicate the potential use of β-cyclodextrin for remediation of pesticide-contaminated soils.     

Steam activation,characterisation and adsorption studies of activated carbon from maize tassels

In this paper, steam-produced activated carbon (STAC) from maize tassel (MT) was evaluated for its ability to remove basic dye (methylene blue MB) from aqueous solution in a batch adsorption process. The equilibrium experiments were conducted in the range of 50–300 mg/L initial MB concentrations at 30°C, for effect of pH, adsorbent dosage and contact time. The experimental data were analysed by Langmuir, Freundlich and Temkin isotherm models of adsorption. Freundlich adsorption isotherm was found to have highest value of R²(R²=0.97) compared to other models of Langmuir and Temkin having (0.96 and 0.95 respectively). STAC has a high adsorptive capacity for MB dye (200 mg/g) and also showed favourable adsorption for the dye with the separation factor (R_L<1) for the dye-activated carbon system. The kinetic data obtained were analysed using pseudo first-order kinetic equation and pseudo second-order kinetic equation. The experimental data fitted well into pseudo second-order kinetic equation, as demonstrated by the high value of R².     

Adsorptive removal of mercury from acid mine drainage: a comparison of silica and maghemite nanoparticles

Mercury adsorption by silica and maghemite nanoparticles (NPs) was studied with the aim of comparing their performance in the remediation of acid mine drainage (AMD) contaminated water. Calculated distribution coefficients (K_d) showed that both NPs are exceptional adsorbents. However, adsorbate coverage per unit area was 30 times higher for maghemite than for silica NPs, despite the latter having a surface area ～15 times greater. Maghemite adsorbed 75% of available Hg compared to 56% by silica, making it a more efficient sorbent than silica under AMD conditions. Kinetics and isotherm data for both adsorbents were fitted by the pseudo-second-order (R² = 1) and the Freundlich (R² ≥ 0.98) models, implying that adsorption to both NP types was by chemisorption. Adsorption increased with NP concentrations and pH and was enhanced in the presence of manganese and sulfate ions although adsorption to silica was inhibited in 1:2 Hg-to-Mn systems. Importantly, trends in simulated wastewater were replicated in actual AMD-contaminated water samples. This study highlights the fact that properties besides surface area and charge of adsorbents determine adsorbent performance, and superior attributes may not always lead to higher adsorption efficiencies.     

Adsorptive removal of rhodamine B from textile wastewater using water chestnut (Trapa natans L.) peel: adsorption dynamics and kinetic studies

Water chestnut peel, an agricultural bio-waste, was used as a biosorbent for removal of rhodamine B (RhB), basic textile dye, from an aqueous solution. The effects of various experimental parameters were studied. The equilibrium data correlated well with a Freundlich isotherm (R² = 0.98–0.99) followed by a Halsey isotherm model (R² = 0.98–0.99) which indicated heterogeneity of the adsorbent surface and multilayer adsorption of RhB dye onto the water chestnut peel waste (WCPW). High correlation coefficients (R² = 0.99) together with close agreement between experimental q_e (0.4–1.7 mg g^?1) and calculated q_e (0.4–2.5 mg g^?1) suggested that the adsorption process followed pseudo-second-order kinetics, with k₂ values in the range of 52–3.4 × 10^?1 g mg^?1 min^?1 at different concentrations. The overall mechanism of adsorption was controlled by both liquid-film and intra-particle diffusions. The negative values of change in Gibb's free energy (?ΔG⁰ = 19.2–29.2 kJ mol^?1) and positive values of change in enthalpy (ΔH⁰ = 30.9–117.6 kJ mol^?1) revealed the process to be spontaneous and endothermic. WCPW was found to be an effective adsorbent for removal of RhB, a cationic dye, from an aqueous solution.     

Removal of Novacron Golden Yellow dye from aqueous solutions by low-cost agricultural waste: Batch and fixed bed study

The present work describes the removal of Novacron Golden Yellow (NGY) dye from aqueous solutions using peanut hulls. The experiments were performed with native, pretreated and immobilised forms of peanut hulls. The effect of various operational parameters (pH, biosorbent dose, initial dye concentration and temperature etc.) was explored during batch study. NGY showed maximum removal at low pH and low biosorbent dose. High initial dye concentration facilitated the biosorption process. Maximum dye removal with native, pretreated and immobilised biomass was found to be 35.7, 36.4 and 15.02 mg/g respectively. The experimental data were subjected to different kinetic and equilibrium models. The kinetic data confirmed the fitness of pseudo-second-order rate law for NGY biosorption. The equilibrium modelling was carried out by Freundlich, Langmuir and Temkin models. The isothermal data of NGY removal were best described by Freundlich adsorption isotherm. Negative values of Free energy change (Δ G⁰) for NGY with native and pretreated biomass depicted the spontaneous nature of biosorption process. In column mode, the effects of bed height, flow rate and initial dye concentrations were optimised. Maximum NGY biosorption (7.28 mg/g) was observed with high bed height, low flow rate and high initial concentration in continuous mode. Bohart–Adams model best fitted to the data obtained from column studies. The results indicated that the peanut hulls could be used effectively for the removal of dyes containing wastewater.     

Kinetic and equilibrium study of Alizarin Red S removal by activated carbon

Activated carbon has been applied for the adsorption of Alizarin Red S (ARS) from the waste water in a batch method to obtain high removal percentage. The influence of variables such as pH, temperature, ARS concentration, mass and size of adsorbent, and contact time on ARS removal percentage was investigated. Different kinetics, thermodynamics, and isotherm models were applied for fitting the experimental data. The adsorption process follows a pseudo second-order kinetic model with R ² of 0.98 and Freundlich, Tempkin, and Dubinin-Radushkevich isotherm models with high determination coefficients (R ²) of 0.91, 0.98, and 0.98, respectively. High enthalpy (positive value), Gibbs free energy (negative value), and high entropy values shows the feasibility and the endothermic spontaneous nature of the removal process.     

Development of chitosan-alginate based biosorbent for the removal of p-chlorophenol from aqueous medium

Removal of p-chlorophenol (pCP) from synthetic aqueous solutions was studied through adsorption on a biosorbent developed from chitosan (CS) and sodium alginate (SA), the natural cationic and anionic polysaccharides, respectively. Chitosan-coated sodium alginate beads were prepared and treated with calcium chloride solution in order to improve the stability as well as hydrophobic character. The resulting beads (CS/CA) were characterized using FTIR spectra, scanning electron microscopy (SEM), and BET surface analysis. The efficiency of this biosorbent in removing pCP from aqueous medium was studied under batch equilibrium and dynamic column flow experimental conditions. The binding capacity of the biosorbent was studied as a function of initial pH, contact time, initial concentration of adsorbate and amount of biomass. The data were fitted to pseudo-first-order, pseudo-second-order, and Weber–Morris models and found that the adsorption process followed pseudo-first-order kinetics. Further, the equilibrium data were fitted to Freundlich, Langmiur, and Dubinin–Radushkevich (D–R) adsorption isotherms and the isotherm constants were evaluated for adsorption of pCP. The maximum monolayer adsorption capacity of CS/CA beads was found to be 127 mg g^?1. Column flow results were used to generate breakthrough curves. The experimental results suggested that the chitosan–calcium alginate blended biosorbent was effective for the removal of pCP from aqueous medium.     

Kinetic,equilibrium and thermodynamic studies for the sorption of metribuzin from aqueous solution using banana peels,an agro-based biomass

Banana peels were employed for the removal of metribuzin from aqueous solution. Sorption in the batch mode was optimized regarding pH, contact time, sorbent dose, initial pesticide concentrations, and temperature. The sorption data were fitted to pseudo-first-order, pseudo-second-order, intraparticle diffusion, Elovich, and liquid film diffusion model, the pseudo-second-order exhibiting best fit (R² = 0.9803). Of the four most common sorption isotherm models (Langmuir, Freundlich, Tempkin, and Dubinin–Radushkevich), the data followed the Langmuir isotherm with highest correlation. The maximum adsorption capacity was found to be 167 mg g^?1. Gibbs free energy, enthalpy, and entropy showed that the sorption was exothermic and spontaneous.     

Effective removal of Cobalt(II) ions from aqueous solutions and nuclear industry wastewater using sulfhydryl and carboxyl functionalised magnetite nanocellulose composite: batch adsorption studies

A new adsorbent sulfhydryl and carboxyl functionalized magnetite nanocellulose composite [(MB-IA)-g-MNCC] was synthesized by graft co-polymerization of itaconic acid onto magnetite nanocellulose (MNCC) using EGDMA as cross linking agent and K₂S₂O₈ as free radical initiator. The adsorption occurs maximum in the pH 6.5. The best fitted kinetic model was found to be pseudo-second-order kinetics. Therefore the mechanism of Co(II) adsorption onto (MB-IA)-g-MNCC follows ion exchange followed by complexation. The Langmuir model was the best fitted isotherm model for the adsorption of Co(II) onto the (MB-IA)-g-MNCC. Simulated nuclear power plant coolant water samples were also treated with (MB-IA)-g-MNCC to demonstrate its efficiency for the removal of Co(II) from aqueous solutions in the presence of other metal ions. To recover the adsorbed Co(II) ions and also to regenerate the adsorbent to its original state 0.1?M HCl was used as suitable desorbing agent. Six cycles of adsorption-desorption experiments were conducted and was found that adsorption capacity of (MB-IA)-g-MNCC has been decreased from 97.5% in the first cycle to 84.7% in the sixth cycle. Recovery of Co(II) using 0.1?M HCl decreased from 93.2% in the first cycle to 79.3% in the sixth cycle.

Abbreviations: T: absolute temperature; q_e: amount adsorbed at equilibrium; q_t: amount adsorbed at time t; CELL: cellulose; Co: cobalt; C_e: concentration at equilibrium; C_HCl: concentration of HCl; C_NaOH: concentration of NaOH; C_A: concentrations of acid; C_B: concentrations of base; W_g: dry weight of composite; W_i: dry weight of MNCC; DS: energy dispersive spectra; EGDMA: ethylene glycol dimethacrylate; Ce: equilibrium concentration; K_L: equilibrium constant; F: Faradays constant; FTIR: Fourier transform infrared spectra; ΔG^o: free energy change; K_F: Freundlich adsorption capacity; 1/n: Freundlich constant; R: gas constant; D: grafting density; EC_o: initial concentration; IA: itaconic acid; IA-g-MNCC: itaconic acid-grafted-magnetite nanocellulose composite; b: Langmuir constant; MNCC: magnetite nanocellulose composite; Q⁰: Maximum adsorption capacity; (MB-IA)-g-MNCC: 2-mercaptobenzamide modified itaconic acid-grafted-magnetite nanocellulose composite; NC: nanocellulose; pH_pzc: Point of zero charge; K₂S₂O₈: potassium peroxy sulphate; k₁: pseudo-first-order rate constant; k₂: pseudo-second-order rate constant; SEM: scanning Electron Microscope; b_s: Sips adsorption capacity; Q_s: Sips maximum adsorption capacity; ΔH°: standard enthalpy change; ΔS°: standard entropy change; A: surface area; σ₀: surface charge density; 1/n_s: surface heterogeneity factor; VSM: vibrating sample magnetometer; V: volume of solution; W: weight of (MB-IA)-g-MNCC; M_composite: weight of the composite; XRD: X-ray diffraction     

Simultaneous removal of Co,Cu, and Cr from water by electrocoagulation

This study provides an electrocoagulation process for the removal of metals such as cobalt, copper, and chromium from water using magnesium as anode and galvanized iron as cathode. The various parameters like pH, current density, temperature, and inter electrode distance on the removal efficiency of metals were studied. The results showed that maximum removal efficiency was achieved for cobalt, copper, and chromium with magnesium as anode and galvanized iron as cathode at a current density of 0.025?A?dm^?2 at pH 7.0. First- and second-order rate equations were applied to study adsorption kinetics. The adsorption process follows second-order kinetics model with good correlation. The Langmuir and Freundlich adsorption isotherm models were studied using the experimental data. The Langmuir adsorption isotherm favors monolayer coverage of adsorbed molecules for the adsorption of cobalt, copper, and chromium. Temperature studies showed that adsorption was endothermic and spontaneous in nature.     

Preconcentration of tin in environmental and biological samples by ion exchange using modified Amberlite XAD-2

Utilization of Amberlite XAD-2 surface modified by covalent immobilization of brilliant green through an azo spacer for adsorptive enrichment of Sn(II) from environmental and biological samples was highlighted. The resulting resin was characterized by Fourier transform infrared spectroscopy, elemental analysis, thermogravimetric analysis, and scanning electron microscopy. The resin retained Sn(II) ions at an optimum pH of 9.5 with a sorption capacity of 40 mg g^?1. The modified sorbent could be reused for 10 cycles without significant changes in sorption capacity. The recovery of Sn(II) was 98% when eluted with 0.1 mol L^?1 ethylenediaminetetraacetic acid. Scatchard analysis revealed that binding sites in the modified resin were homogeneous. The equilibrium adsorption data were analyzed using the Langmuir, Freundlich, Temkin, and Redlich–Peterson isotherm models. The method was applied with satisfactory results for determination of Sn(II) ions in human plasma and sea water.     

Modelling the kinetics and equilibrium properties of cadmium biosorption by river green alga and water hyacinth weed

Cadmium biosorption properties of non-living, dried river green alga from a river source, and water hyacinth weed, Eichhornia crassipes from a lake in Zimbabwe have been investigated. The cadmium uptake was found to depend on initial pH, uptake being apparently minimal at low pH values and increasing with an increase in pH. Cadmium biosorption kinetics by both samples is fast, with 80% of total uptake occurring within 60?min. The effect of initial solution pH and initial cadmium concentration on cadmium biosorption from a cadmium solution has been studied. The data for algal biomass fitted the Langmuir monolayer adsorption isotherm, while the biosorption of the metal by water hyacinth weed fitted the Freundlich adsorption isotherm with 1/n values all less than 1. Maximum metal uptake capacities were recorded using 0.35?g of biomass and a 250?mg?L^?1 cadmium solution at pH 6.5 and at 25°C and these were about 85 and 50?mg?L^?1 for water hyacinth weed and green alga, respectively, showing that water hyacinth weed offered a greater potential for cadmium uptake. The absorption was described by pseudo-second order rate model and the rate constant and equilibrium sorption capacity are reported.     

Removal of heavy metals from aqueous solutions using activated carbon prepared from Cicer arietinum

Removal of Cu²⁺, Cd²⁺, Pb²⁺, and Zn²⁺ from aqueous solutions by activated carbon prepared from stems and seed hulls of Cicer arietinum, an agricultural solid waste, has been studied. The influence of various parameters, such as pH, contact time, adsorbent dose, and initial concentration of metal ions on removal was evaluated. The activated carbon was characterized by FT-IR spectroscopy, X-ray diffraction, and elemental analysis. Sorption isotherms were studied using Langmuir and Freundlich isotherm models. All experimental sorption data were fitted to the sorption models using nonlinear least-squares regression. The maximum adsorption capacity values for activated carbon prepared from Cicer arietinum waste for metal ions were 18 mg g^?1 (Cu²⁺), 18 mg g^?1 (Cd²⁺), 20 mg g^?1 (Pb²⁺), and 20 mg g^?1 (Zn²⁺), respectively. The Freundlich isotherm model fit was best, followed by the pseudo-second-order kinetic model. Desorption studies were carried out with dilute hydrochloric acid for quantitative recovery of the metal ions and for regeneration of the adsorbent.     

Copper(II) ions’ removal from aqueous solution using green horse-chestnut shell as a low-cost adsorbent

The adsorption of copper(II) ions from aqueous solutions by the green horse-chestnut shell was studied in a batch adsorption system. It was determined how the parameters of the adsorption process, such as time, pH, copper(II) ions concentration and sorbent dose, influence the effectiveness of copper(II) ions’ removal. The adsorption process was fast and equilibrium was established about 10?min, and near 95–97% of Cu(II) ions were removed from aqueous solution. Maximum copper(II) ions’ adsorption occurred at around pH 5. The adsorption kinetics are also described, using pseudo-first-order model and pseudo-second-order model of type 1 and 2. A comparison of the kinetics models on the overall adsorption rate showed that the adsorption system was best described by the pseudo-second-order model of type 1 (r²?=?0.999) for all initial concentrations. Another key part of this study was the use of the Freundlich model to determine the adsorption isotherm and the experimental data were in strong correspondence with this model.