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The abundance of gasification char residues which contributed to solid waste management problem is one of the major concerns in biomass gasification industry. This study focuses on synthesizing gasified Glyricidia sepium woodchip based activated carbon (GGSWAC) for the removal of basic green 4 (BG4) dye, evaluating the GGSWAC physicochemical properties and assessing the BG4 adsorption performance in batch and fixed-bed column systems. The optimal conditions of GGSWAC synthesis were at radiation power, time, and impregnation ratio (IR) of 616 W, 1 min and 1.93 g/g, respectively. The surface area (S BET) and total pore volume (TPV) of GGSWAC were 633.30 m2/g and 0.34 cm3/g, respectively. The Fritz–Schlünder best fitted to the experimental data at all temperatures in the isothermal studies, indicating a monolayer adsorption. The kinetic study showed that BG4 adsorption followed Avrami kinetic model. Based on thermodynamic parameters, the adsorption of BG4 dye onto GGSWAC was an endothermic and spontaneous process. In continuous operation, the Thomas and Yoon–Nelson models successfully predicted BG4 adsorption onto GGSWAC. The low production cost of 0.54 USD/kg showed that GGSWAC is economically feasible for commercialization. [ABSTRACT FROM AUTHOR]

Rambutan seeds (Nephelium lappaceumL.)-based activated carbon (RSAC) was prepared using potassium hydroxide (KOH) activation and carbon dioxide (CO2) gasification methods. The adsorbent prepared was characterized using Fourier transform infrared, SEM, proximate analysis, and BET techniques, respectively. The effects of three variable parameters; activation temperature, activation time, and chemical impregnation ratio (IR) (KOH: char by weight) on the preparation of RSAC used for the removal of MG dye was investigated. Based on the central composite design, quadratic and two factor interaction (2FI) models were, respectively, employed to correlate the effect of variable parameters on the preparation of RSAC used for the percentage MG dye removal and activated carbon yield. From the analysis of variance, the most influential factor on each experimental design response was identified. The optimum conditions of MG dye removal by RSAC are: activation temperature (802°C), activation time (1.0 h), and IR (2.4), respectively. The percentage MG dye removal obtained was 91.45% resulting in 22.56% RSAC yield. The percentage error between predicted and experimental results for the removal of MG dye is 2.4%. The effects of operational parameters like pH, initial dye concentration, contact time, and solution temperature were investigated using batch method. Graphical correlations of eight different adsorption isotherm models were carried out. Freundlich isotherm fitted the adsorption data most. The data were also analyzed by the Lagergren pseudo-first-order, Ho Mc Kay pseudo-second-order, Elovich and Avrami kinetic models. Pseudo-second-order kinetic model best represents the kinetic data and the mechanism of adsorption was controlled by both film and intraparticle diffusions. Thermodynamic studies gave negative ∆G° values, indicating that the process of MG dye adsorption onto RSAC was spontaneous. The positive values of ∆H° and ∆S° suggest that the process of dye adsorption was endothermic. [ABSTRACT FROM PUBLISHER]

Activated carbon produced from pomelo peels (PPAC) was tested for its effectiveness in the removal of malachite green (MG) dye from aqueous solution. The PPAC prepared was characterized using TGA, BET, FTIR, SEM, pHpzc, Elemental analysis and Boehm titration, respectively. The extent of dye adsorption was investigated as a function of pH, contact time, adsorbate concentration and solution temperature. Dye removal was pH dependent, resulting in 95.06% removal at pH 8.0. Quantum chemical studies suggested that the cationic MG dye possessed minimal molecular size at planar geometry coupled with high-electrostatic interaction thereby, enhancing the adsorption at high pH. Langmuir, Freundlich and Dubinin–Radushkevich (D–R) equilibrium isotherms were used to fit the adsorption data. Langmuir isotherm fit the adsorption data most with maximum monolayer adsorption capacity of 178.43 mg/g. The kinetic data fitted the pseudo-second-order model with correlation coefficient greater than 0.99. The mean free energyE(kJ/mol) got from the D–R isotherm indicated physisorption mechanism Thermodynamic parameters; Gibbs free energy (ΔG°), enthalpy (ΔH°) and entropy (ΔS°) changes were also calculated, and the values indicated that the adsorption process was spontaneous and endothermic in nature. Regeneration efficiency of spent PPAC was studied using 0.2 M HCl, the efficiency was found to be in the range of 92.71–96.35% after four cycles. The study showed that PPAC can be used as an effective, low cost and environmentally friendly adsorbent for the removal of MG dye from aqueous solution. [ABSTRACT FROM PUBLISHER]

The adsorption of a group of heavy metals namely, Zn2+, Ni2+, and Cd2+onto olive stones activated carbon (OSAC) was carried out in this work. The effects of different reaction parameters, such as the adsorbent dosage, contact time, shaking speed, and initial pH, on pollutant removal efficiency were investigated. Adsorption of Zn2+, Ni2+, and Cd2+was effectively explained by Langmuir and Freundlich isotherms. OSAC efficiently removed 99.03% Zn2+, 97.34% Ni2+, and 94.88% Cd2+at pH 5 and shaking speed 200 rpm. Surface characteristics of the prepared AC were examined by pore structure analysis, scanning electron microscopy, and Fourier transform infrared spectroscopy. The Brunauer-Emmett-Teller surface area, total pore volume and average pore diameter of the prepared AC were 886.72 m2/g, 0.507 cm/g, and 4.22 nm, respectively. The equilibrium data of the adsorption were fitted well to the Langmuir and the highest value of adsorption capacity (Q) on the OSAC was found for Zn2+11.14 mg/g, followed by Ni2+8.42 mg/g and Cd2+7.80 mg/g. A pseudo-second-order model sufficiently described the adsorption kinetics, which indicated that the adsorption process was controlled by chemisorption. The results revealed that the OSAC has the potential to be used as a low-cost adsorbent for the treatment of wastewaters contaminated with heavy metals. [ABSTRACT FROM PUBLISHER]

The adsorption of heavy metals Fe2+, Pb2+, and Cu2+onto olive stone activated carbon (OSAC) was investigated in this study. The effects of different reaction parameters (i.e. adsorbent dosage, contact time, shaking speed, and initial pH) on the pollutant removal efficiency were determined. The adsorption processes of Fe2+, Pb2+, and Cu2+were effectively explained using Langmuir and Freundlich isotherms. OSAC efficiently removed 99.39% Fe2+, 99.32% Pb2+, and 99.24% Cu2+at pH 5 and with 200 rpm shaking speed. The adsorption equilibrium data were best represented by the Langmuir model, and the monolayer adsorption capacities were found to be 57.47, 22.37, and 17.83 mg/g for Fe2+, Pb2+, and Cu2+, respectively. A pseudo-second-order model sufficiently described the adsorption kinetics, which indicated that the adsorption process was controlled by chemisorption. The results revealed that OSAC can be used as a low-cost adsorbent for the treatment of wastewaters contaminated by heavy metals. [ABSTRACT FROM PUBLISHER]

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. [ABSTRACT FROM AUTHOR]

The adsorption of a synthetic textile dye (Remazol Brilliant Black Reactive) on cocoa pod husk-based activated carbon was investigated in batch process. The adsorbent prepared was characterized by gas adsorption surface analysis (Brunauer Emmett Teller, BET), scanning electron microscopy, and Fourier transform infrared spectroscopy. The effects of initial dye concentration, contact time, solution temperature, and solution pH were evaluated. Equilibrium data were fitted to Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich isotherm models, the first being the best with maximum monolayer coverage of 111 mg g-1. Kinetic data were fitted into pseudo-first-order, pseudo-second-order, intraparticle diffusion, and Elovich models; the pseudo second-order model provided the best correlation. Maximum adsorption was observed at pH 7. Standard free energy, standard enthalpy, and standard entropy were also calculated. The adsorption interaction was found to be endothermic and spontaneous. Both the mean free energy of adsorption and the activation energy show that the mechanism is by physisorption. [ABSTRACT FROM AUTHOR]

Abstract: In this work, coffee husk based activated carbon (CHAC) was prepared by physicochemical activation for the removal of Remazol Brilliant Orange 3R (RBO3R) dye from aqueous solution. The effects of dye initial concentration, contact time, solution temperature and pH on RBO3R adsorption were investigated. Result showed that the adsorption of RBO3R was favorable at acidic pH. The adsorption uptake was found to increase with increase in initial RBO3R concentration, contact time and solution temperature. Langmuir isotherm model fitted well the adsorption equilibrium data with monolayer saturation capacity of 66.76mg/g at 303K. The adsorption kinetic was found to follow the pseudo-second-order kinetic model. Boyd plot indicated that the adsorption of RBO3R on CHAC was controlled by film diffusion. The adsorption process was found to be endothermic with the reaction mechanism follows a physisorption process. [Copyright &y& Elsevier]