Optimization of Malachite Green Adsorption from Aqueous Solution Using Magnetic Composite Spirulina/Chitosan

The presence of organic dyes in wastewater is one of the special concerns in the environment. Therefore, the treatment of wastewater that contains dyes has great importance for the environment. The use of magnetic adsorbents is a new and highly efficient method to remove dyes from water environments. In the structure of the absorbent, Spirulina algae powder was made into a biopolymer called chitosan. The synthesized adsorbent was characterized by XRD, VSM and FTIR analysis. In order to optimize the process, experimental design software and surface response method were used in the central composite design. The influencing parameters in the adsorption process including solution pH, adsorbent dose, contact time and initial concentration of malachite green dye were investigated. The results of the analysis of variance showed that the effects of the independent variables pH, dose, initial concentration, and time, as well as the square effects of the variables pH, dose, initial concentration, and time, the interaction between pH and initial concentration, the pH to reaction time, the initial concentration to time, and the interaction between dose and time in the model, were significant, as was the pH parameter of the solution, which had the greatest effect among the operating parameters. Freundlich isotherm model was also more capable of describing the equilibrium behavior of the adsorption process. Magnetic composite Spirulina/chitosan was able to remove more than 99% of malachite green from aqueous solution under pH conditions=6.75, adsorbent dose=230 mg/L, initial dye concentration 4 mg/L and time 90 minutes.