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In this study, a natural loess soil was evaluated as an adsorbent of Li+ in seawater. Only Li+ was adsorbed preferentially by loess over other cations in seawater despite having the lowest concentration. The adsorption studies of Li+ with loess were assessed using the batch equilibration method. In batch adsorption experiment, the various factors such as agitation time, initial concentration, and amount of dose were investigated. Adsorption isotherm and kinetic studies were performed to quantify the adsorption capacity and adsorption rate of Li+ by loess from seawater. The equilibrium data of adsorption were fitted by using the Freundlich and Langmuir isotherm models. It was seen that the Langmuir isotherm is better in describing the adsorption process of Li+ by loess due to its higher correlation coefficient R2 value. The maximum adsorption capacity of loess for Li+ obtained by Langmuir isotherm was 0.193 mg/g. The pseudo-first-order, the pseudo-second-order, and the intra-particle diffusion kinetic models were employed to analyze the time-dependent adsorption rate of Li+. It was found that the adsorption of Li+ closely follows the pseudo-second-order kinetic model, from which a very accurate estimation of the equilibrium adsorption capacity ( qe,cal) was achieved, as well as the higher R2. Because of its low-cost and high selectivity towards Li+, loess could be probably an applicable adsorbent for the recovery of Li+ from seawater. [ABSTRACT FROM AUTHOR]

This article presents the immobilization of nanostructured biosilica within calcium alginate biopolymer and its potential for the adsorption of Direct Red 12B (DR12B) as an azo dye in batch flow mode reactors. The immobilization of biosilica was performed well according to the images of scanning electron microscopy. Moreover, the results of Fourier transform infra-red analysis confirmed strong binding of dye molecules by surficial functional groups. The adsorption process was pH-dependent and increasing initial pH from 3 to 11 led to the decrease in adsorbed dye from 16.02 to 11.88 mg/g, respectively. Increasing adsorbent dosage from 0.5 to 4 g/L led to decreasing the adsorption of DR12B from 75.13 to 12.10 mg/g, respectively. Among various isotherm models, Langmuir isotherm had the highest correlation coefficient (R2 = 0.9924) with a maximum adsorption capacity of 33.78 mg/g. The value of mean free energy (E = 15.81 KJ/mol) related to Dubinin-Radukevisch (D-R) model demonstrated chemical nature of the adsorption process. The results of kinetic study revealed the fitness of experimental data to pseudo-second order model. The negative values of Gibbs free energy (ΔG°) and enthalpy change (ΔH°) suggested a simultaneous and exothermic adsorption process, respectively. © 2015 American Institute of Chemical Engineers Environ Prog, 34: 1435-1443, 2015 [ABSTRACT FROM AUTHOR]

Activated carbon was prepared from Citrus limettioides seed (CLSC), a novel waste material by chemical modification with sulfuric acid was applied for the adsorption Ni(II) from aqueous solutions. The effect of contact time, pH, adsorbent dose, initial metal ion concentration, and temperature were studied in batch experiments. According to the experimental results, the equilibrium time, optimum pH range, and adsorbent dosage were found to be 3 h, pH = 4.0-8.0 and 1 g L−1, respectively. In addition, raw Citrus limettioides seeds (CLS) were used as adsorbents at the same parameters. Ni(II) removal for CLSC and CLS were obtained 99.00% and 37.00% in turn. The equilibrium data agreed well with Langmuir model, which confirmed the monolayer coverage of Ni(II) ions onto CLS and CLSC. The Langmuir monolayer adsorption capacity of the CLSC was found to be 36.06 mg g−1 which was significantly about 3.5 times greater than that of CLS (10.23 mg g−1) at 300 K. The kinetic data followed pseudo-second order model and intra-particle diffusion was not the sole rate-controlling factor. Surface morphology and structural analysis of CLSC prior to and after adsorption were characterized by SEM and EDX. The presence of hydroxyl, carboxylic, and sulfonic acid groups are confirmed by FTIR spectra. The adsorbents were also tested for the removal of Ni(II) from electroplating wastewater in connection with the reuse and selectivity of the adsorbents. © 2015 American Institute of Chemical Engineers Environ Prog, 34: 1384-1395, 2015 [ABSTRACT FROM AUTHOR]

The aim of the present study is to explore the possibility of utilizing fly ash, loess and activated charcoal for the adsorption of Li in aqueous solution. Batch adsorption experiments were performed to evaluate the influences of various factors like initial concentration, contact time, and temperature. The adsorption data showed that fly ash and activated charcoal are not effective for the adsorption of Li. On the contrary, loess showed much higher adsorption capacity for Li. The adsorption of Li on loess was highly concentration dependent. It was found that the adsorption capacity of loess is favored at a lower Li concentration. At equilibrium, approximately 95% of adsorption was achieved by loess. The equilibrium data were fitted well to the Freundlich isotherm model. The pseudo-second-order kinetic model appeared to be the better-fitting model because it has higher R2 compared to the pseudo-first-order kinetic models. The thermodynamic parameters such as free energy Δ G, the enthalpy Δ H, and the entropy Δ S were calculated. [ABSTRACT FROM AUTHOR]

The article discusses a study on the ability of raw bentonite (RB) to remove azo dye, methyl orange (MO), from aqueous solution and optimization of conditions for its adsorption. The Langmuir and Freundlich adsorption models were used to describe the equilibrium isotherms. The activation energy was calculated at 38.62 kilojoules per molecule, enthalpy of activation was calculated at 36.04 kilojoules per molecule and entropy of activation was calculated at -150.05 joules per molecule K at pH 4.0.