Adsorption of malachite green from aqueous solutions by magnetic graphene nanocomposite

The entry of chemical compounds into the environment is considered a serious threat to humans and other living things. One of these compounds is malachite green, which enters water resources and causes problems for humans and public health. The use of Nano sorbents is a new, high-performance method for removing pollutants from aquatic environments. Graphene, due to its unique properties, is one of the materials that can be used to remove some materials. In this study, graphene was prepared from rice straw residue, which is considered as a waste material, and then magnetized by heat solvent method. SEM, BET, Raman and FTIR analysis were performed to detect and evaluate the properties of the synthesized nanocomposites. The nanocomposite was then investigated to remove malachite green from aqueous solutions in a batch system. Effective factors in adsorption such as pH, adsorbent amount, contact time, initial concentration of malachite green and temperature were investigated. The results showed that the maximum adsorption capacity is 993.33 at concentrations of 50 mg/L and the adsorbent is 5 mg/L for 20 minutes. Also, two types of isothermal adsorption models of Freundlich and Langmuir were investigated and since the correlation coefficient of Langmuir model was higher than Freundlich model. Various models have been developed to evaluate the rate of adsorption process. In this study, pseudo-first-order and pseudo-second-order kinetic models were used. Due to the higher detection coefficient of the pseudo-second-order model, the rate of malachite green adsorption process on G/Fe3O4 was well matched with the pseudo-second-order model. Also, thermodynamic studies showed that the adsorption process is spontaneous and the adsorbent collides with malachite green is random. In this study, four types of solvents were investigated. The adsorption-desorption process was repeated over 5 cycles, with a slight reduction in adsorption capacity and the removal efficiency of malachite green from these steps. Finally, considering the suitable adsorption capacity of the synthesized G/Fe3O4 nanocomposite as well as the adsorption capacity of the adsorbent, it can be concluded that this adsorbent can be a suitable adsorbent for removing malachite green from aqueous solutions.