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The study evaluated the effectiveness of an aquatic plant, Canna indica to remove 2,4,6-Trichlorophenol (TCP) from aqueous solution in a hydroponic set-up. The effects of TCP initial concentration (50–250 mg/L) and solution pH (4–9) on TCP biosorption were investigated. The removal efficiency increased with days and initial concentrations. The optimum removal was obtained at pH 4.0. The equilibrium data obtained were analysed by Langmuir, Freundlich, Temkin, Elovich and Dubinin-Radushkevich isotherm models. The equilibrium time was found to be 20 days. The Langmuir and Freundlich model gave the best correlation with the experimental data. According to Langmuir model, the maximum monolayer biosorption capacity of C. indica for TCP was found to be 52.08 mg/g, at 25 ± 2°C. The adsorption was found to follow the pseudo-first-order kinetics. The intraparticle diffusion model revealed that intraparticle diffusion is not the sole rate-limiting step for the biosorption process. Thermodynamic parameter such as standard free energy (ΔGo) was −2537.697 kJ/mol. This showed that the biosorption process was highly spontaneous and proceeded mainly by chemisorption process. C. indica used in this study is eco-friendly, widely available and offers greater potential for wastewater treatment for removal of chlorinated pollutants such as TCP from aqueous solutions. [ABSTRACT FROM AUTHOR]

Codiaeum variegatum stem powder (CVSP) was used as a low cost, readily available and biodegradable sorbent for decontamination of crude oil from aqueous solution. CVSP was characterized by the FTIR, SEM and BET techniques. The physical characterization of the crude oil showed light crude. Equilibrium isotherm of crude oil uptake was analyzed by the Langmuir, Feundlich, Tempkin, Flory-Huggins and Scatchard models. The Langmuir isotherm gave best fit with regression of 0.995 indicating a homogenous CVSP surface involving monolayer sorption of crude oil, supported by the Scatchard model analysis. The maximum monolayer uptake capacity of CVSP for crude oil was established and compared to other reported sorbents. [ABSTRACT FROM AUTHOR]

A comparison of linear and non-linear regression method for predicting the optimum isotherm was made using the experimental adsorption equilibrium data of Cu(II) onto treated Martil sand (TMS). For this, six error analysis methods were used: the coefficient of determination r 2 , the sum of the squares of the errors, the sum of the absolute errors, the average relative error, the hybrid fractional error function and the Marquardt's percent standard deviation. The error values indicated that non-linear method is a better way to obtain the isotherm parameters describing the Cu(II) adsorption onto TMS. The comparison between different models such as Langmuir, Freundlich, Dubinin-Radushkevich, Temkin, Redlich-Peterson, Koble-Corrigan and Fritz-Schlünder showed that Fritz-Schlünder model was more suitable to describe the equilibrium data. Based on this result and in order to optimize the equilibrium model results for more accurate parameters values, the Fritz-Schlünder equation was modified and called modified Fritz-Schlünder model. As a comparison of such developed modified model to existing mentioned ones, the results showed that the adsorption equilibrium of Cu(II) onto TMS was better described by the modified Fritz-Schlünder model than by others. [ABSTRACT FROM AUTHOR]

In this research, the equilibrium sorption of nickel(II) by inexpensive dead fungal biomass of Aspergillus awamori was explained using the linear and nonlinear regression analysis of Freundlich, Langmuir, Temkin, and Redlich–Peterson isotherms. In the case of nonlinear regression method, the best fitting model was evaluated using six different error functions, namely coefficient of determination (r 2 ), chi-square test (χ2), hybrid fractional error function (HYBRID), Marquardt’s percent standard deviation (MPSD), average relative error (ARE), and sum of the errors squared (SSE). The r2 function was found to be a better option to minimize the error distribution between the experimental equilibrium data and the predicted two-parameter isotherms. In the case of three-parameter isotherm, HYBRID was found to be the best error function to minimize the error distribution structure between experimental equilibrium data and theoretical isotherms. [ABSTRACT FROM AUTHOR]

Removal of polycyclic aromatic hydrocarbons (PAHs) from petroleum refinery wastewater was investigated using spent waste biomass [rice straw (RS) and sugarcane bagasse (SB)] from bioethanol production process as low-cost biosorbents of natural origin. The equilibrium sorption capacity has been significantly improved by increasing the initial PAHs concentration, contact time, and temperature. The biosorption equilibrium of PAHs onto SB and RS was achieved in approximately 180 min with uptake capacity of the three PAHs followed the order: SB > RS at all studied initial concentrations (qeapproximately recorded 3.61, 1.01, and 0.86 mg/g SB and 3.35, 0.77, and 0.73 mg/g RS at initial concentrations of 150, 50, and 50 mg/L for naphthalene, anthracene, and pyrene, respectively). The sorption kinetics data best fitted the pseudo-first-order rate model for naphthalene, and the pseudo-second-order rate model for anthracene and pyrene. The adsorption isotherms of PAHs were in agreement well with Langmuir isotherm model for all three PAHs molecules at different temperatures than Freundlich and Temkin isotherm models, and the adsorption mechanism was dominated by a combination of physical and chemical adsorption. Thermodynamic parameters suggested that the sorption of the three PAHs onto both SB and RS is endothermic and nonspontaneous. [ABSTRACT FROM AUTHOR]

Highlights: [•] Polyphosphazene nanotube as an adsorbent could be facilely synthesized. [•] The adsorbent owns numerous electron-rich N and P atoms and hydroxyl groups. [•] The adsorbent was an efficient and specific adsorbent for the removal of MB. [•] The pseudo-second-order model could be better to describe the adsorption of MB. [•] The MB adsorption onto PZS nanotubes was endothermic and spontaneous. [Copyright &y& Elsevier]

The removal of some of pollutants including catechol, 3-methylcatechol, 3-methoxycatechol, and 2,3-dihydroxybenzoic acid by adsorption onto activated carbon cloth (ACC) at 35.0 ± 0.1°C was investigated. The equilibrium experimental data were fitted to Langmuir, Freundlich, Temkin, Langmuir-Freundlich, and Redlich-Peterson isotherms. Also the kinetic experimental data were fitted to the pseudo-first-order and pseudo-second-order kinetic models. It was found that the pseudo-second-order model describes the kinetic of adsorption better than the other one. By comparing the obtained results with the previously reported data, it can be concluded that ACC is a high efficient adsorbent for removal of phenolic compounds from aqueous solutions. [ABSTRACT FROM AUTHOR]

The adsorption of methyl orange dye from aqueous solution onto penta-bismuth hepta-oxide nitrate, Bi5O7NO3, synthesized by precipitation method, was studied in a batch adsorption system. The effects of operation parameters such as adsorbent dose, initial dye concentration, pH and temperature were investigated. The adsorption equilibrium and mechanism of adsorption was evaluated by Langmuir and Freundlich isotherm and different kinetic models, respectively. The results indicate that adsorption is highly dependent on all operation parameters. At optimum conditions, the adsorption capacity was found to be 18.9 mg/g. The adsorption data fits well with the Langmuir isotherm model indicating monolayer coverage of adsorbate molecules on the surface of Bi5O7NO3. The kinetic studies show that the adsorption process is a second-order kinetic reaction. Although intra-particle diffusion limits the rate of adsorption, the multi-linearity plot of intra-particle model shows the importance of both film and intra-particle diffusion as the rate-limiting steps of the dye removal. Thermodynamic parameters show that the adsorption process is endothermic, spontaneous and favourable at high temperature. [ABSTRACT FROM AUTHOR]

Abstract: The utilization of modified wheat residue (MWR) as sorbent to remove the anionic dye (Reactive Red-24, RR-24) from aqueous solution was studied. MWR was prepared and characterized by specific surface area, SEM, zeta potential, FTIR and elemental analysis. Sorption experiments were carried out as a function of sorbent dosage, pH, contact time and concentration of dye. Results indicated that a mass of amine groups were grafted into the framework of MWR. It was shown that pseudo-second-order kinetic equation could best describe the sorption kinetics. The equilibrium sorption data were well represented by the Langmuir isotherm equation. The maximum sorption capacity of MWR for RR-24 was 200.0mg/g, which showed higher capacity than those of previous work and a similar capacity compared to those of commercial activated carbon. The results indicated that MWR could be employed as an excellent and low-cost sorbent for removal of anionic dye from aqueous solution. [Copyright &y& Elsevier]

Abstract: An activated carbon was prepared from the stalk of the scrap aquatic plant loosestrife, by H3PO4 activation and then was evaluated for its ability to adsorb 2,4,6-trichlorophenol (TCP). The effects of solution pH, agitation time, TCP initial concentration, and temperature on TCP adsorption were investigated. The equilibrium adsorption data of TCP on activated carbon were analyzed by Langmuir, Freundlich and Temkin isotherm models. The Temkin model gave the best correlation with the experimental data. The adsorption was found to follow the pseudo-second-order kinetics. The intraparticle diffusion model was used to determine the mechanism of the adsorption process. Thermodynamic parameters such as standard enthalpy (ΔH o), standard entropy (ΔS o), and standard free energy (ΔG o) were obtained. Adsorption of TCP is exothermic with ΔH o at −12.87kJ/mol. [Copyright &y& Elsevier]

Abstract: The adsorption of chromium (VI) ions from aqueous solution by ethylenediamine-modified cross-linked magnetic chitosan resin (EMCMCR) was studied in a batch adsorption system. Chromium (VI) removal is pH dependent and the optimum adsorption was observed at pH 2.0. The adsorption rate was extremely fast and the equilibrium was established within 6–10min. The adsorption data could be well interpreted by the Langmuir and Temkin model. The maximum adsorption capacities obtained from the Langmuir model are 51.813mgg−1, 48.780mgg−1 and 45.872mgg−1 at 293, 303 and 313K, respectively. The adsorption process could be described by pseudo-second-order kinetic model. The intraparticle diffusion study revealed that film diffusion might be involved in the present case. Thermodynamic parameters revealed the feasibility, spontaneity and exothermic nature of adsorption. The sorbents were successfully regenerated using 0.1N NaOH solutions. [ABSTRACT FROM AUTHOR]

Abstract: Wheat residue based anion exchanger (WR-AE) was prepared by ETM (epichlorohydrin–triethylamine method), which is the reaction of wheat residue (WR) with epichlorohydrin and triethylamine in the presence of ethylenediamine and N,N-dimethylformamide. Characterization of WR-AE was measured, including BET surface area, SEM, zeta potential, nitrogen content and FTIR analysis. Batch experiments and statistical analysis were conducted to study its ion-exchange property for phosphate from aqueous solutions. Filter bed experiment was conducted for the regeneration test. The characteristic results validated the increased amine groups in WR-AE and its maximum sorption capacity (Q max, mmolg−1) of phosphate was 1.80±0.06mmolg−1. More over, the WR-AE regenerated in both NaCl and HCl solutions can be repeatedly used in several sorption–desorption cycles without any significant loss of the sorption capacities. [Copyright &y& Elsevier]

Equilibrium isotherms of Cr(VI) uptake by tobacco-leaf residues, under controlled solution pH and temperature, were obtained with batch uptake experiments. Batch uptake kinetics under different initial Cr(VI) concentrations was also obtained. The results showed that Cr(VI) uptake capacities of the tobacco-leaf residues were up to 113.2 mg g-1 (dry wt). The uptake capacity was found to be dependent on solution pH and the maximum values were obtained at a pH of around 1.0. On the other hand, the effect of temperature the uptake capacity was found to be small. All equilibrium isotherms were well correlated with the standard Langmuir equation. Kinetics profiles showed that the uptake process was fast, and equilibrium was reached within 30 minutes of mixing contact. The role of polyphenols in Cr(VI) biosorption was studied and the results indicated that complex formation with Cr(VI) may be an important mechanism for Cr(VI) removal. The study indicated that abundantly available tobacco-leaf residues can be used as efficient biosorbent materials for Cr(VI) removal from wastewater. [ABSTRACT FROM AUTHOR]

Abstract: The separation of quaternary mixtures of lactobionic acid, lactose, sorbitol and fructose using a gel-type ion-exchange resin loaded with H+, K+ and Ca2+ ions has been investigated. This separation is relevant in order to improve the productivity of lactobionic acid obtained from the enzymatic reaction catalyzed by Glucose–fructose oxidoreductase and glucono-δ-lactonase enzymes. Measurement of the single-component equilibrium isotherms for all four species was carried out in a preparative column packed with the selected resin at temperatures of 293, 313 and 333K using the frontal analysis and column adsorption–desorption method. Mass transfer coefficients for all species at different temperatures have been estimated by solving the dynamic model of the chromatographic column. From pulse tests of single-component and mixture solutions, the K+ loaded resin was found to be suitable for this quaternary separation. The unfavourable adsorption isotherm for the lactobionic acid is described by the anti-Langmuir model. Other compounds have shown linear equilibrium in the concentration range up to 130gL−1. Binary and quaternary fixed-bed experiments were well described by the dynamic model using the parameters obtained from the single-component adsorption data. [Copyright &y& Elsevier]

Abstract: Batch experiments were conducted to study the biosorption characteristics of a cationic dye, Malachite Green (MG), onto aerobic granules. Effects of pH, aerobic granule dosage, contact time and solution temperature on MG biosorption by aerobic granules were evaluated. Simultaneity the thermodynamic analysis was also performed. The results showed that alkaline pH was favorable for the biosorption of MG and chemisorption seemed to play a major role in the biosorption process. Kinetic studies indicate that MG biosorption on aerobic granules in the system follows the pseudo-second order kinetics. The equilibrium time was 60min for both 50 and 60mg/L and 120min for both 70 and 80mg/L MG concentrations, respectively. Moreover, the experimental equilibrium data have been analyzed using the linearized forms of Langmuir, Freundlich, and Redlich–Peterson isotherms and the Langmuir isotherm was found to provide the best theoretical correlation of the experimental data for the biosorption of MG. The monolayer biosorption (saturation) capacities were determined to be 56.8mg of MG per gram of aerobic granules at 30°C. Thermodynamic analysis show that biosorption follows an endothermic path of the positive value of ΔH ∘ and spontaneous with negative value of ΔG ∘. [Copyright &y& Elsevier]

Abstract: Comparison analysis of linear least-square method and non-linear method for estimating the isotherm parameters was made. Comparison analysis was made using the experimental equilibrium data of safranin onto rice husk at a solution temperature of 305K. Sorption data were fitted to Freundlich, Langmuir and Redlich–Peterson isotherm equations. All the three isotherm equations showed a better fit to the experimental data. The results show that non-linear method could be a better way to obtain the isotherm parameters. Redlich–Peterson isotherm is a special case of Langmuir isotherm when the Redlich–Peterson isotherm constant g was unity. [Copyright &y& Elsevier]

Abstract: Comparison analysis of linear least square method and non-linear method for estimating the isotherm parameters was made using the experimental equilibrium data of safranin onto activated carbon at two different solution temperatures 305 and 313K. Equilibrium data were fitted to Freundlich, Langmuir and Redlich–Peterson isotherm equations. All the three isotherm equations showed a better fit to the experimental equilibrium data. The results showed that non-linear method could be a better way to obtain the isotherm parameters. Redlich–Peterson isotherm is a special case of Langmuir isotherm when the Redlich–Peterson isotherm constant g was unity. [Copyright &y& Elsevier]