Adsorption of Azo Dye Malachite Green onto Rice Wine Lees: Kinetic and Adsorption Isotherms

The adsorption of malachite green in aqueous solution onto rice wine lees was carried out in detail. The effects of different rice wine lees dosage, solution pH and initial concentration on the adsorption of malachite green by rice wine lees were studied. The experimental results showed that the removal rate of malachite green increases with the increasing dosage of rice wine lees. When the dosage of rice wine lees is 5 g/L, the removal rate within 30 min is 96.22%. At the same time, the removal rate increases as the pH of the solution increases, and the removal rate is higher in an alkaline environment. The kinetic study was performed by the pseudo-first-order and the pseudo-second-order reactions. According to the experimental data, the pseudo-second-order kinetic model better described the adsorption of dye onto rice wine lees, it implies that the predominant process is chemisorption. Besides, the adsorption isotherms were studied by Langmuir model, Freundlich and Temkin isotherm models. The results indicated that the adsorption followed the Langmuir model and the maximum adsorption capacity was 21.505 mg/g. The dye malachite green adsorption onto rice wine lees was monolayer adsorption.