MODIFIED PLANTAIN PEEL AS CELLULOSE-BASED LOW-COST ADSORBENT FOR THE REMOVAL OF 2,6-DICHLOROPHENOL FROM AQUEOUS SOLUTION: ADSORPTION ISOTHERMS,KINETIC MODELING,AND THERMODYNAMIC STUDIES

In this study, the feasibility of using modified plantain peel to remove 2,6-dichlorophenol from iaqueous solutions was investigated under batch mode. The effects of physical factors such as initial 2,6-dichlorophenol concentration, contact time, biosorbent particle size, biosorbent dosage and temperature on the removal process were evaluated. The results showed that biosorption of 2,6-dichlorophenol was dependent on these factors. The equilibrium biosorption data were analyzed by the Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich (D-R) adsorption isotherm models. The four tested isotherm models provided good fits to the experimental data obtained at 30°C; however, the Freundlich isotherm model provided the best correlation (R² = 0.9874) of the experimental data. The maximum monolayer biosorption capacity (Q _max ) was found to be 14.25 mg/g. The biosorption kinetics data of 2,6-dichlorophenol were analyzed by pseudo-first-order, pseudo-second-order, Elovich, intraparticle diffusion, and liquid film diffusion models. The five kinetic models fitted well to the biosorption kinetic data; however, the pseudo-second-order kinetic model gave the best fit when the biosorption mechanism was controlled by film diffusion. Thermodynamic quantities such as standard Gibbs free energy (ΔG°), standard enthalpy (ΔH°), standard entropy change of biosorption (ΔS°), and activation energy (E_a) were evaluated, and it was found that the biosorption process was spontaneous, feasible, endothermic in nature and of dual nature, physisorption and chemisorption; however, the physisorption process was dominant. Therefore, modified plantain peel has potential for application as an effective bioadsorbent for removal of 2,6-dichlorophenol from aqueous solution.     

Adsorption of Cr(VI) ions onto poly(ethylene glycol dimethacrylate‐1‐vinyl‐1,2,4‐triazole)

Poly(ethylene glycol dimethacrylate‐1‐vinyl‐1,2,4‐triazole) [poly(EGDMA‐VTAZ)] beads (average diameter = 150–200 μm) were prepared by copolymerizing ethylene glycol dimethacrylate (EGDMA) with 1‐vinyl‐1,2,4‐triazole (VTAZ). Poly(EGDMA‐VTAZ) beads were characterized by swelling studies and scanning electron microscope (SEM). The adsorption of Cr(VI) from solutions was carried at different contact times, Cr(VI) concentrations, pH, and temperatures. High adsorption rates were achieved in about 240 min. The amount of Cr(VI) adsorbed increased with increasing concentration and decreasing pH and temperature. The intraparticle diffusion rate constants at various temperatures were calculated. Adsorption isotherms of Cr(VI) onto poly(EGDMA‐VTAZ) have been determined and correlated with common isotherm equations such as Langmuir and Freundlich isotherm models. The Langmuir isotherm model appeared to fit the isotherm data better than the Freundlich isotherm model. The pseudo first‐order kinetic model was used to describe the kinetic data. The study of temperature effect was quantified by calculating various thermodynamic parameters such as Gibbs free energy, enthalpy, and entropy changes. The dimensionless separation factor (R_L) showed that the adsorption of metal ions onto poly(EGDMA‐VTAZ) was favorable. It was seen that values of distribution coefficient (K_D) decreasing with Cr(VI) concentration in solution at equilibrium (C_e) indicated that the occupation of activate surface sites of adsorbent increased with Cr(VI). © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Adsorption of Cu(II) and Cr(VI) onto Treated Shorea dasyphylla Bark: Isotherm,Kinetics, and Thermodynamic Studies

The efficacy of treated Shorea dasyphylla bark for Cu(II) and Cr(VI) adsorption was assessed in a batch adsorption system as a function of pH, agitation period, and initial metal concentration. The equilibrium nature of Cu(II) and Cr(VI) adsorption was described by the Freundlich, Langmuir, and Dubinin-Radushkevich isotherms. The maximum monolayer capacities of treated Shorea dasyphylla bark, estimated from the Langmuir equation were 184.66 and 42.72 mg/g for Cu(II) and Cr(VI), respectively. The experimental results were fitted using pseudo-first order, pseudo-second order and intraparticle diffusion kinetic models; the pseudo-second order showed the best conformity to the kinetic data. Thermodynamic parameters such as enthalpy change (ΔH°), free energy change (ΔG°) and entropy change (ΔS°) were determined by applying the Van't Hoff equation. The adsorption of Cu(II) and Cr(VI) onto treated Shorea dasyphylla bark was found to be spontaneous and exothermic. The adsorption mechanism was confirmed by means of Fourier transform infrared (FTIR) and Energy dispersive X-ray (EDX) spectroscopy. The dimensionless constant separation factor (R _L), indicated that treated Shorea dasyphylla bark was favorable for Cu(II) and Cr(VI) adsorption.     

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.     

Removal of Basic Blue 3 by sorption onto a weak acid acrylic resin

A weak acid acrylic resin was used as an adsorbent for the investigation of Basic Blue 3 (BB3) adsorption kinetics, isotherms, and thermodynamic parameters. Batch adsorption studies were carried out to evaluate the effect of pH, contact time, initial concentration (28–100 mg/g), adsorbent dose (0.05–0.3 g), and temperature (290–323 K) on the removal of BB3. The adsorption equilibrium data were analyzed by the Langmuir, Temkin, and Freundlich isotherm models, with the best fitting being the first one. The adsorption capacity (Q_o) increased with increasing initial dye concentration, adsorbent dose, and temperature; the highest maximum Q_o (59.53 mg/g) was obtained at 323 K. Pseudo‐first‐order and pseudo‐second‐order kinetic models and intraparticle diffusion models were used to analyze the kinetic data; good agreement between the experimental and calculated amounts of dye adsorbed at equilibrium were obtained for the pseudo‐second‐order kinetic models for the entire investigated concentrations domain. Various thermodynamic parameters, such as standard enthalpy of adsorption (ΔH^o = 88.817 kJ/mol), standard entropy of adsorption (ΔS^o = 0.307 kJ mol^?1 K^?1), and Gibbs free energy (ΔG^o < 0, for all temperatures investigated), were evaluated and revealed that the adsorption process was endothermic and favorable. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Comparison of Basic Dye Crystal Violet Removal from Aqueous Solution by Low-Cost Biosorbents

Abstract

The removal of basic dye crystal violet by low-cost biosorbents was investigated in this study using a batch experimental system. The adsorption of crystal violet onto various adsorbents was solution pH-dependent and the maximum removal occurred at basic pH 10.0. The kinetic experimental data were analyzed using pseudo-first-order and pseudo-second-order equations to examine the adsorption mechanism and the intraparticle diffusion model to identify the potential rate controlling step. These results suggested that the adsorption of crystal violet onto various adsorbents was best represented by the pseudo-second-order equation. The suitability of the Langmuir and Freundich adsorption isotherms to the equilibrium data was also investigated at various temperatures for all four sorbents and the adsorption isotherms exhibited Freundlich behavior. The Freundlich constant K_f was 1.55 for alligator weed, 2.33 for Laminaria japonica, 9.59 for rice bran and 5.38 (mg/g)/(mg/L)^1/n for wheat bran, respectively at adsorbent concentration 5 g/L, pH 10.0 and 20°C. The thermodynamic parameters (ΔH, ΔG, and ΔS) were calculated and the results showed that the adsorption process for various adsorbents was spontaneous, endothermic, with an increased randomness, respectively. The particle size and the reaction temperature exhibited an insignificant impact on the adsorption equilibrium of crystal violet. The adsorbents investigated could serve as low-cost adsorbents for removing the crystal violet from aqueous solution.     

Adsorption of Cr(III), Ni(II), Zn(II), Co(II) ions onto phenolated wood resin

In this study, phenolated wood resin was used an adsorbent for the removal of Cr(III), Ni(II), Zn(II), Co(II) ions by adsorption from aqueous solution. The adsorption of metal ions from solution was carried at different contact times, concentrations and pHs at room temperature (25°C). For individual metal ion, the amount of metal ions adsorbed per unit weight of phenolated wood resin at equilibrium time increased with increasing concentration and pH. Also, when the amounts of metal ions adsorbed are compared to each other, it was seen that this increase was order of Cr(III) > Ni(II) > Zn(II) > Co(II). This increase was order of Cr(III) > Ni(II) > Co(II) > Zn(II) for commercial phenol–formaldehyde resin. Kinetic studies showed that the adsorption process obeyed the intraparticle diffusion model. It was also determined that adsorption isotherm followed Langmuir and Freundlich models. Adsorption isotherm obtained for commercial phenol–formaldehyde resin was consistent with Freundlich model well. Adsorption capacities from Langmuir isotherm for commercial phenol–formaldehyde resin were higher than those of phenolated wood resin, in the case of individual metal ions. Original adsorption isotherm demonstrated the monolayer coverage of the surface of phenolated wood resin. Adsorption kinetic followed the intraparticle diffusion model. The positive values of ΔG° determined using the equilibrium constants showed that the adsorption was not of spontaneous nature. It was seen that values of distribution coefficient (K_D) decreasing with metal ion concentration in solution at equilibrium (C_e) indicated that the occupation of active surface sites of adsorbent increased with metal ions. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 2838–2846, 2006     

Utilization of Raw and Activated Date Pits for the Removal of Phenol from Aqueous Solutions

Activated carbons prepared from date pits, an agricultural waste byproduct, have been examined for the adsorption of phenol from aqueous solutions. The activated carbons were prepared using a fluidized bed reactor in two steps; carbonization at 700 °C for 2 hours in N₂ atmosphere and activation at 900 °C in CO₂ atmosphere. The kinetic data were fitted to the models of intraparticle diffusion, pseudo‐second order, and Lagergren, and followed more closely the pseudo‐second‐order chemisorption model. The isotherm equilibrium data were well fitted by the Freundlich and Langmuir models. The maximum adsorption capacity of activated date pits per Langmuir model was 16 times higher than that of nonactivated date pits. The thermodynamic properties calculated revealed the endothermic nature of the adsorption process. The uptake of phenol increased with increasing initial phenol concentration from10 to 200 ppm and temperature from 25 to 55 °C, and decreased with increasing the solution pH from 4 to 12. The uptake of phenol was not affected by the presence of NaCl salt.     

Adsorption ability of oxidized multiwalled carbon nanotubes towards aqueous Ce(III) and Sm(III)

The aim of the present work was to investigate the adsorption of Ce(III) and Sm(III) onto multiwalled carbon nanotubes (MWCNTs) oxidized with concentrate nitric acid. The effects of solution pH, adsorbent dosage, and contact time were studied by batch technique. Langmuir, Freundlich and D-R isotherms were used to describe the adsorption behavior of Ce(III) and Sm(III) by oxidized MWCNTs, and the experimental results fitted Freundlich model well. The maximum uptake capacities (q _m ) calculated by applying the Langmuir equation for samarium and cerium ions were found to be 89.28 and 92.59 (mg/g), respectively. A comparison of the kinetic models and the overall experimental data was best fitted by the pseudo second-order kinetic model. The calculated thermodynamic parameters (ΔG^o, ΔH^o, and ΔS^o) showed that the adsorption for Ce(III) and Sm(III) is feasible, spontaneous and exothermic at 30–60 °C. Moreover, more than 70% of Ce(III) and Sm(III) adsorbed onto Oxidized MWCNTs could be desorbed with HNO₃.     

Polyamine Functionalized Magnetite Nanoparticles as Novel Adsorbents for Cu(II) Removal from Aqueous Solutions

Three novel magnetic adsorbents were synthesized through the immobilization of di-, tri-, and tetraamine onto the surface of silica coated magnetite nanoparticles. The adsorbents were characterized by XRD patterns, FTIR spectroscopy, elemental and thermogravimetric analysis, magnetic measurements, SEM/TEM, EDX spectroscopy, and N₂ adsorption/desorption isotherms. Their capacity to remove copper ions from aqueous solutions was investigated and discussed comparatively. The equilibrium data were analyzed using Langmuir and Freundlich isotherms. The kinetics was evaluated using the pseudo-first-order, pseudo-second-order, and intra-particle diffusion models. The best interpretation for the equilibrium data was given by the Langmuir isotherm for the tri- and tetraamine functionalized adsorbents, while for the diamine functionalized adsorbent the Freundlich model seemed to be better. The kinetic data were well fitted to the pseudo-second-order model. The overall rate of adsorption was significantly influenced by external mass transfer and intraparticle diffusion. It was observed that the adsorption capacity at room temperature decreased as the length of polyamine chain immobilized on the adsorbent surface increased, the maximum adsorption capacities being 52.3 mg g^?1 for 1,3-diaminopropan functionalized adsorbent, 44.2 mg g^?1 for diethylenetriamine functionalized adsorbent, and 39.2 mg g^?1 for triethylenetetramine functionalized adsorbent. The sorption process proved to be highly dependent of pH. The results of the present work recommend these materials as potential candidates for copper removal from aqueous solutions.     

Lead(II) Adsorption onto Sulphuric Acid Treated Cashew Nut Shell

In this study, sulphuric acid treated cashew nut shell (STCNS) was used as adsorbent for the removal of lead(II) ions from the aqueous solutions. Adsorption studies were performed by varying the solution pH, contact time, and temperature. Experimental data were analyzed by the model equations such as Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich isotherms and it was found that the Freundlich isotherm model fits best with the experimental data at different temperatures studied. The maximum adsorption capacity of lead(II) on STCNS was determined as 408.6, 432, 446.3, and 480.5 mg/g, respectively, at different temperatures (30, 40, 50, and 60°C). The thermodynamic parameters (ΔG^o, ΔH^o, and ΔS^o) were calculated and the thermodynamic properties of lead(II) ions-STCNS system indicate the exothermic process. Adsorption kinetic constants were determined using pseudo-first-order, pseudo-second-order, and the Elovich kinetic models at various temperatures. The adsorption results clearly showed that the adsorption of lead(II) ions onto STCNS followed pseudo-second-order model and the adsorption was both by film diffusion and by intraparticle diffusion. A single-stage batch adsorber was designed using the Freundlich equation.     

Adsorption Profile and Complexing Behavior of Hg(II) Ions onto Polyurethane Foam from Acidic Mixed Solvent System (H2O + Ethanol) Containing Dithizone

A new method has been developed to remove Hg(II) metal ion by preconcentrating onto polyurethane foam (PUF) from acidic mixed solvent system (0.5 N HNO₃ + 25% ethanol) containing dithizone. Batch experiments were carried out to assess adsorption equilibrium and kinetic behavior by varying parameters such as acid concentration, agitation time, aqueous- ethanol ratio, and metal ion concentration. These facilitated the computation of kinetic parameters and adsorption behavior. The optimum conditions of sorption of mixed solvent system are 0.5 mol L^?1 HNO₃ + 25% ethanol containing 1.95 × 10^?4 mol L^?1 of dithizone with 40 minutes of equilibrium time. The kinetic parameters indicate that sorption follows the first-order reaction and intraparticle diffusion process. The obtained data followed the adsorption models. i.e., Freundlich, Langmuir, and Dubinin–Radushkevich (D-R) isotherms successfully. The thermodynamics studies indicate that sorption increases with rise in temperature, entropy driven, and endothermic chemisorption. The nature of the sorption mechanism of Hg(II) ions with dithizone and PUF has been discussed and the composition of the adsorbed complex has been predicted. The effect of different foreign cations and anions has been investigated. The data indicates that only EDTA, thiosulphate, and cyanide are interfering. The method was applied on different synthetic mixtures and saline solution to test the selectivity of the new method for the abatement of Hg(II) ions from mixed solvent system.     

Fabrication and Characterization of SiO2/(3-Aminopropyl)triethoxysilane-Coated Magnetite Nanoparticles for Lead(II) Removal from Aqueous Solution

A novel nano-adsorbent SiO₂/(3-aminopropyl)triethoxysilane-coated magnetite nanoparticles was synthesized for the adsorption of lead ions from water samples. Its structure and magnetic characteristics were characterized, by FTIR, powder X-ray diffraction, scanning electron microscope (SEM), transmission electron microscope (TEM) and vibrating sample magnetometry (VSM). Amino-functionalized SiO₂ coated Fe₃O₄ magnetite nano-adsorbent exhibited superparamagnetic behavior and strong magnetization at room temperature. The efficiency of the nano-adsorbent in separation of the metals was evaluated by adsorption technique. Kinetic data were analyzed using the pseudo-first-order and pseudo-second-order equations. The data fitted very well to the pseudo-second-order kinetic model.The linear Langmuir and Freundlich models were applied to describe equilibrium isotherms and Langmuir model fitted well. The monolayer adsorption capacity was found as 17.65 mg/g at pH 4.0. Thermodynamic parameters such as free energy change (ΔG°), enthalpy change (ΔH°) and entropy change (ΔS°) were also calculated. These parameters showed that the adsorption of Pb(II) onto nano-adsorbent was feasible, spontaneous and endothermic. The amino-functionalized SiO₂ coated Fe₃O₄ magnetic nano-adsorbent shows high adsorption capability for metal ions from aqueous solutions via the chelation mechanisms. The Pb(II) loaded nano-adsorbent can be easily recovered from aqueous solution with magnetic separation and regenerated readily by acid treatment. The product of this work can be used as an effective and recyclable nano-adsorbent for the removal of metal ions in wastewater treatment.     

STUDIES ON THE ADSORPTION OF FURFURAL FROM AQUEOUS SOLUTION ONTO LOW-COST BAGASSE FLY ASH

The present study deals with the sorptive removal of furfural from aqueous solution by carbon-rich bagasse fly ash (BFA). Batch studies were performed to evaluate the influence of various experimental parameters, namely, initial pH (p H ₀), adsorbent dose, contact time, initial concentration, and temperature on the removal of furfural. Optimum conditions for furfural removal were found to be p H ₀ ≈ 5.5, adsorbent dose ≈4 g/L of solution, and equilibrium time ≈4 h. The adsorption followed pseudo-second-order kinetics. The effective diffusion coefficient of furfural is of the order of 10^?13 m²/s. Equilibrium adsorption data on BFA was analyzed by Freundlich, Langmuir, Dubnin-Radushkevich, Redlich-Peterson, and Temkin isotherm equations using regression and error analysis. The Redlich-Peterson isotherm was found to best represent the data for furfural adsorption onto BFA. Adsorption of furfural on BFA is favorably influenced by a decrease in the temperature of the operation. Values of the change in entropy (ΔS ⁰) and heat of adsorption (ΔH ⁰) for furfural adsorption on BFA were negative. The high negative value of change in Gibbs free energy (ΔG ⁰) indicates the feasible and spontaneous adsorption of furfural on BFA.     

Aqueous Phase Adsorption of Cephalexin onto Bentonite and Activated Carbon

The adsorption of cephalexin in aqueous solution has been investigated using bentonite and activated carbon as the adsorbents. Batch kinetics and isotherm studies were carried out to evaluate the effect of contact time, adsorbent dosage, pH, particle size, and temperature. Adsorption equilibrium data were well represented by the Langmuir and Freundlich isotherm models. The adsorption intensity was found to be increased as the aqueous phase pH increased, and had a maximum at pH = 6.1. The pseudo-first order, pseudo-second order, and intraparticle diffusion kinetic models were used to describe the kinetic data. The experimental data fitted very well with the pseudo-second-order kinetic model and also followed the simple external and intraparticle model.     

Coconut (Cocos nucifera) Shell Based Activated Carbon for the Removal of Malachite Green Dye from Aqueous Solutions

The adsorption of malachite green (MG) dye using coconut shell based activated carbon (CSAC) was investigated. Operational factors such as the effect of pH, initial dye concentration, adsorbent dosage, contact time, and solution temperature on the adsorption process were studied. Solution pH strongly affected the chemistry of both the dye molecule and CSAC in solution. Optimum dye removal was obtained at pH ≥ 8.0. Equilibrium was reached in 120 minutes contact time. The Langmuir, Freundlich, and Dubinin–Radushkevich (D-R) isotherm models were used to evaluate the adsorption data. The adsorption data fitted the Langmuir model most with maximum adsorption monolayer coverage of 214.63 mg/g. Pseudo-first-order, pseudo second-order, and intraparticle diffusion models were also used to fit the experimental data. Kinetic parameters, rate constants, equilibrium sorption capacities, and related correlation coefficients, for each model were calculated and discussed. Thermodynamic parameters such as ΔG⁰, ΔH⁰, and ΔS⁰ were evaluated and it was found that the sorption process was feasible, spontaneous, and exothermic in nature. The mean free energy obtained from D-R isotherm suggests that the adsorption process follows physiosorption mechanism. The results showed that coconut shells could be employed as a low-cost precursor in activated carbon preparation for the removal of MG dye from wastewaters.     

Fast Removal of Sr(II) From Water by Graphene Oxide and Chitosan Modified Graphene Oxide

Graphene oxide is a unique material that can be used for adsorption of radioactive waste because it contains various function groups such as epoxide, carbonyl, carboxyl and hydroxyl in addition to its high specific surface area. The as-prepared GO and the modified one (GO-chitosan composite) have been prepared then characterized and used as adsorbent for radioactive metal ions [Strontium, Sr(II)]. The results showed that the prepared materials are efficient adsorbents for removal of Sr(II) from water. The effect of contact time, pH and temperature on adsorption have been studied. The results indicated that the maximum adsorption capacity was about 140 and 179.6 mg/g for GO and GO-chitosan composite respectively. It was found that pH?~?6 and temperature?~?40 °C are the best condition for removal of Sr(II) from water. Two isotherm models (Langmuir and Freundlich) and three kinetic models (Pseudo-first-order, pseudo-second-order, and intra-particle particle diffusion model) have been applied. Based on the calculated isotherm parameters (R²), it can be concluded that Langmuir model fits the adsorption equilibrium data better than Freundlich model, the results also indicated that the second order kinetic model is the best representative for adsorption of Sr(II) on GO, Chitosan and GO-Chitosan. Based on the regressions of intraparticle diffusion model, experimental data showed that the adsorption process involved intraparticle diffusion, which was not the only rate-controlling step.     

Adsorption Characteristics of Sulfamethoxazole and Metronidazole on Activated Carbon

In this work, the removal of two pharmaceuticals i.e., an antibiotic drug, sulfamethoxazole and an antiparasitary drug, metronidazole onto activated carbon from aqueous solutions were studied. Batch adsorption studies were carried out at different pH, adsorbent concentrations, and temperatures. Adsorption isotherms have been modeled by Freundlich, Langmuir, and Dubinin-Raduskevitch (D-R) equations. The adsorption of these drugs was better represented by the Langmuir equation. The effect of the solution pH on the adsorbed amount of SM and MN was studied by varying the initial pH under constant process parameters at equilibrium conditions. The increase in pH of the solutions caused to decrease adsorption of SM and MN on AC. The kinetics of adsorption in view of three kinetic models, i.e., the first-order Lagergren model, the pseudo-second-order model, and the intraparticle diffusion model was discussed. The pseudo-second-order kinetic model describes the adsorption of both sulfamethoxazole and metronidazole on activated carbon. Rate constants for adsorption and desorption, and surface coverage have been evaluated with the help of another approach of the kinetic scheme. The effect of temperature was also studied at the range between 293 and 313 K. Thermodynamic parameters were calculated. The negative value of enthalpy change (ΔH°) indicated the exothermic nature of the adsorption process, and the negative values of free energy change (ΔG°) were indicative of spontaneity of the adsorption process. In this work adsorption behaviour of SM and MN on activated carbon was also evaluated by the data obtained from column experiments.     

Sorption of Al (III) from aqueous solution by fresh macrophyte alligator weed: Equilibrium and kinetics

The removal of Al (III) ions from aqueous solution by locally abundantly low-cost fresh macrophyte, alligator weed, was examined in batch system. Effect of initial solution pH on Al (III) adsorption was investigated and the Al (III) species present in aqueous solution were identified. The main functional groups of the alligator weed were characterized by Fourier transform infrared spectrometer (FT-IR). The equilibrium data fitted to Freundlich and Langmuir isotherms satisfactorily. The pseudo-second-order equation fitted the kinetic data very well. The intraparticle diffusion played an important role in the Al (III) sorption process. Al (III) ions were favorably adsorbed by alligator weed and the values of K_f and 1/n (Freundlich constant) at 25 °C and pH 3.5 were found as 1.9963 (mg/g)/(mg/L)^1/n and 0.7875, respectively, which are comparable to those of granular activated carbon (2.20 (mg/g)/(mg/L)^1/n and 0.8695, respectively).