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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]

Highlights: [•] Adsorption isotherm of racemic guaifenesin on Chiralcel OD was measured. [•] Adsorption kinetic of racemic guaifenesin on Chiralcel OD was studied. [•] Separation process of racemic guaifenesin was predicted by chromatographic model. [•] Chromatographic model included the column model and extra column dead volume. [ABSTRACT FROM AUTHOR]

In the present study adsorption behavior of methylene blue and rhodamine B from aqueous solution using adsorbent prepared from ' Hyptis suaveolens' (Vilayti Tulsi) was investigated as a function of parameters such as initial concentration, adsorbent dose, pH, contact time and temperature. The adsorption process was pH dependent. The thermodynamic parameters such as $$ {{\Updelta}}G,{{\Updelta}}H \,{\text{and}} \,{{\Updelta}}S $$ were calculated to investigate the nature of adsorption, their values indicate that the adsorption process is favorable. The first-order, second-order and intra-particle diffusion models were used to describe the kinetic parameter. The Freundlich and Langmuir adsorption models were applied to describe the adsorption equilibrium. Column study was conducted for both dyes. [ABSTRACT FROM AUTHOR]

In this work, the effectiveness of native and chemically modified rice bran to remove heavy metal Pb(II) ions from aqueous solution was examined. Chemical modifications with some simple and low-cost chemicals resulted in enhancement of the adsorption capacities and had faster kinetics than native rice bran. Experiments were conducted in shake flasks to monitor the upshot of parameters over a range of pH, initial Pb(II) concentrations and contact times using a batch model study. The sorption capacities q (mg g) increased in the following order: NaOH (147.78), Ca(OH) (139.08), Al(OH) (127.24), esterification (124.28), NaHCO (118.08), methylation (118.88), NaCO (117.12) and native (80.24). The utmost uptake capacity q (mg g) was shown by NaOH-pretreated rice bran. The results showed that, using NaOH-modified rice bran, the chief removal of Pb(II) was 74.54 % at pH 5, primary Pb(II) concentration 100 mg L and contact time 240 min. Equilibrium isotherms for the Pb(II) adsorption were analyzed by Langmuir and Freundlich isotherm models. The Langmuir isotherm model, showing Pb(II) sorption as accessible through the high value of the correlation coefficient ( R = 0.993), showed a q value of 416.61 mg g. The kinetic model illustrated adsorption rates well, depicted by a second order, which gives an indication concerning the rate-limiting step. Thermodynamic evaluation of the metal ion ∆ G was carried out and led to the observation that the adsorption reaction is spontaneous and endothermic in nature. NaOH chemically modified rice bran was a superb biosorbent for exclusion of Pb(II) and proved to be excellent for industrial applications. [ABSTRACT FROM AUTHOR]

Abstract: The adsorption of Pb(II) ions from aqueous solution with ethylenediamine-modified yeast biomass coated with magnetic chitosan microparticles (EYMC) was studied in batch adsorption system. The adsorption of Pb(II) ions increased with the rising pH and a higher adsorption capacity was achieved at the pH 4.0–6.0. The experiment data was well matched by Langmuir model and Freundlich model, while Langmuir model showed the best description. The maximum adsorption capacities obtained by Langmuir model were 121.26, 127.37 and 134.90mgg−1 at 20, 30 and 40°C, respectively. Kinetic studies indicated that the pseudo-second-order model was appropriate to describe the adsorption process and film diffusion maybe governed the rate of the adsorption. Thermodynamic studies revealed that a spontaneous and endothermic adsorption process. The adsorbents, EYMC can be well recovered by 0.1M EDTA. [Copyright &y& Elsevier]

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: Adsorption can be used as a cost effective and efficient technique for the removal of toxic heavy metals from wastewater. Waste materials with no further treatment such as coffee grounds from cafeterias may act as adsorbents for the removal of cadmium. Batch kinetic and equilibrium experiments were conducted to study the effects of contact time, adsorbent dose, initial pH, particle size, initial concentration of cadmium and temperature. Three adsorption isotherm models namely, Langmuir, Freundlich and Dubinin–Radushkevich were used to analyse the equilibrium data. The Langmuir isotherm which provided the best correlation for Cd2+ adsorption onto coffee grounds, shows that the adsorption was favourable and the adsorption capacity found was equal to 15.65mgg−1. Thermodynamic parameters were evaluated and the adsorption was exothermic. The equilibrium was achieved less than 120min. The adsorption kinetic data was fitted with first and second order kinetic models. Finally it was concluded that the cadmium adsorption kinetic onto coffee grounds was well fitted by second order kinetic model rather than first order model. The results suggest that coffee grounds have high possibility to be used as effective and economical adsorbent for Cd2+ removal. [ABSTRACT FROM AUTHOR]

Abstract: Removal of Acid Red 73 (AR 73) and Reactive Red 24 (RR 24) onto modified wheat straw (MWS) from aqueous solutions was investigated. Sorption experiments were carried out as function of MWS dosage, contact time, initial concentration, pH and temperature. Characterizations of MWS were measured and a mass of amine groups were observed in the framework of MWS. The equilibrium sorption data were well represented by the Langmuir isotherm equation, and the calculated thermodynamic parameters indicated a spontaneous and endothermic nature for sorption process. It was shown that pseudo-second-order kinetic equation could best describe the adsorption kinetics. More over, the high maximum sorption capacity (q e max, 714.3mgg−1 for AR 73 and 285.7mgg−1 for RR 24) and low cost (1.24US$kg−1) of MWS provided strong evidence of the potential of MWS for the technological applications of anionic dyes removal from aqueous solutions. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents a study of the removal of ammonium ion from aqueous solutions using natural Chinese (Chende) zeolite. A series of experiments was conducted to examine the effects of solution pH, particle size, contact time, adsorbent dosage, and the presence of other cation- and anion species on ammonium removal. The findings indicated that these parameters named had a significant effect on the removal of ammonium by the zeolite. The effect of other cations on the removal of ammonium followed the order of preference Na+ >K+ >Ca2+ >Mg2+ at identical mass concentrations, and the effect of the presence of individual anions followed the order of preference carbonate>chloride>sulfate>phosphate at identical mass concentrations of ammonium ions. Kinetic analysis showed that the adsorption of ammonium on zeolite at different ranges of particle size well followed the pseudo-second-order model and followed the intra-particle diffusion model only during the initial 60min of the adsorption process. Equilibrium isotherm data was fitted to the linear Langmuir- and Freundlich models with the latter model providing the better description of the process (R 2 =0.991–0.997) compared to the former (R 2 =0.902–0.989). [Copyright &y& Elsevier]

Abstract: The adsorption of methyl orange and methyl violet from aqueous solutions by Phragmites australis activated carbon (PAAC) was studied in a batch adsorption system. The adsorption studies include both equilibrium adsorption isotherms and kinetics. Several isotherm models were investigated and the adsorption isotherm data were best represented by the Temkin isotherms. The kinetic data were well described by the pseudo-second-order kinetic model. The mechanism of the adsorption process was determined from the intraparticle diffusion model. The results indicate that PAAC could be employed as a low-cost alternative for the removal of the textile dyes from effluents. [Copyright &y& Elsevier]

Abstract: A batch system was applied to study the adsorption of methyl violet from aqueous solution by granular activated carbon. The adsorption studies include both equilibrium and kinetics. Equilibrium data were mathematically modeled using the Langmuir–Freundlich isotherm. The equilibrium data were fitted to the isotherm with n =1 very well. Maximum adsorption capacity of 0.095g/g at equilibrium was achieved. The kinetics of adsorption were evaluated by pseudo-first-order and pseudo-second-order models. Also extended geometric method has been applied to estimate the adsorption and desorption rate constants of Langmuir kinetics. By the obtained concentration-independent rate constants, the kinetics of adsorption were modeled by Langmuir kinetics. The stochastic numerical simulation has been applied to simulate the adsorption kinetic data of methyl violet at different concentrations. [Copyright &y& Elsevier]