In this work, the adsorption of malachite green (MG) on rattan sawdust (RSD) was studied at 30 degrees C. The results indicated that RSD can be used as a low-cost adsorbent for the removal of MG dye from aqueous solutions. Equilibrium data were analyzed by two isotherms, namely the Freundlich isotherm and the Langmuir isotherm. The best fit to the data was obtained with the Langmuir isotherm. The monolayer adsorption capacity of RSD was found to be 62.71 mg/g. The adsorption kinetics can be predicted by the pseudo-first-order model. The mechanism of adsorption was also studied. It was found that for a short time period the rate of adsorption is controlled by film diffusion. However, at longer adsorption times, pore-diffusion controls the rate of adsorption. The amount adsorbed on the outer surface was estimated from the time where film-diffusion stops controlling the adsorption rate.
In this work, the adsorption of malachite green (MG) was studied on activated carbon prepared from bamboo by chemical activation with K(2)CO(3) and physical activation with CO(2) (BAC). Adsorption studies were conducted in the range of 25-300 mg/L initial MG concentration and at temperature of 30 degrees C. The experimental data were analyzed by the Freundlich isotherm, the Langmuir isotherm, and the multilayer adsorption isotherm. Equilibrium data fitted well with the Langmuir model with maximum adsorption capacity of 263.58 mg/g. The rates of adsorption were found to confirm to pseudo-second-order kinetics with good correlation and the overall rate of dye uptake was found to be controlled by pore diffusion throughout the entire adsorption period. The results indicate that the BAC could be used to effectively adsorb MG from aqueous solutions.
In this work, pumpkin seed hull (PSH), an agricultural solid waste, is proposed as a novel material for the removal of methylene blue (MB) from aqueous solutions. The effects of the initial concentration, agitation time and solution pH were studied in batch experiments at 30 degrees C. The equilibrium process was described well by the multilayer adsorption isotherm. The adsorption kinetics can be predicted by the pseudo-first-order and the modified pseudo-first-order models. The mechanism of adsorption was also studied. It was found that for a short time period the rate of adsorption is controlled by film diffusion. However, at longer adsorption times, pore-diffusion controls the rate of adsorption. Pore diffusion takes place in two distinct regimes, corresponding to diffusion in macro- and mesopores. The results demonstrate that the PSH is very effective in the removal of MB from aqueous solutions.
In this paper, broad bean peels (BBP), an agricultural waste, was evaluated for its ability to remove cationic dye (methylene blue) from aqueous solutions. Batch mode experiments were conducted at 30 degrees C. Equilibrium sorption isotherms and kinetics were investigated. The kinetic data obtained at different concentrations have been analyzed using pseudo-first-order, pseudo-second-order and intraparticle diffusion equations. The experimental data fitted very well the pseudo-first-order kinetic model. Analysis of the temportal change of q indicates that at the beginning of the process the overall rate of adsorption is controlled by film-diffusion, then at later stage intraparticle-diffusion controls the rate. Diffusion coefficients and times of transition from film to pore-diffusion control were estimated by piecewise linear regression. The experimental data were analyzed by the Langmuir and Freundlich models. The sorption isotherm data fitted well to Langmuir isotherm and the monolayer adsorption capacity was found to be 192.7 mg/g and the equilibrium adsorption constant Ka is 0.07145 l/mg at 30 degrees C. The results revealed that BBP was a promising sorbent for the removal of methylene blue from aqueous solutions.
Oil palm trunk fibre (OPTF)--an agricultural solid waste--was used as low-cost adsorbent to remove malachite green (MG) from aqueous solutions. The operating variables studied were contact time, initial dye concentration, and solution pH. Equilibrium adsorption data were analyzed by three isotherms, namely the Freundlich isotherm, the Langmuir isotherm, and the multilayer adsorption isotherm. The best fit to the data was obtained with the multilayer adsorption. The monolayer adsorption capacity of OPTF was found to be 149.35 mg/g at 30 degrees C. Adsorption kinetic data were modeled using the Lagergren pseudo-first-order, Ho's pseudo-second-order and Elovich models. It was found that the Lagergren's model could be used for the prediction of the system's kinetics. The overall rate of dye uptake was found to be controlled by external mass transfer at the beginning of adsorption, then for initial MG concentrations of 25, 50, 100, 150, and 300 mg/L the rate-control changed to intraparticle diffusion at a later stage, but for initial MG concentrations 200 and 250 mg/L no evidence was found of intraparticle diffusion at any period of adsorption. It was found that with increasing the initial concentration of MG, the pore-diffusion coefficient increased while the film-diffusion coefficient decreased.
In this work, the potential feasibility of rice straw-derived char (RSC) for removal of C.I. Basic Green 4 (malachite green (MG)), a cationic dye from aqueous solution was investigated. The isotherm parameters were estimated by non-linear regression analysis. The equilibrium process was described well by the Langmuir isotherm model. The maximum RSC sorption capacity was found to be 148.74 mg/L at 30 degrees C. The kinetics of MG sorption on RSC followed the Lagergren's pseudo-first-order model and the overall rate of dye uptake was found to be controlled by external mass transfer at the beginning of adsorption, while intraparticle diffusion controlled the overall rate of adsorption at a later stage. The results indicated that RSC was an attractive adsorbent for removing basic dye from aqueous solutions.