Adsorption of Dyes Using From Blue Crab Shells

Abstract The aim of this work was to evaluate the adsorption capacities of the acidic dye Congo red (CR) and the basic dye malachite green (MG), which are hazardous to the environment and human health in aquatic environments, using chitosan obtained from blue crab shells, considered as waste. By first extracting chitin and then chitosan from blue crabs, the maximum adsorption capacities of these dyes in aquatic solutions were investigated. Parameters such as pH, contact time, initial concentration of MG/ CR, and temperature were analyzed. Characterization of the adsorbent was performed using Fourier-transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The FTIR findings showed that hydrogen bonds and C = O and N-H bending contributed to the adsorption of MG / CR. The equilibrium data were analyzed with Langmuir and Freundlich isotherms, and kinetic models were applied. The highest maximum adsorption capacities were 68 mgg⁻¹ for CR at 25⁰C and 140 mgg⁻¹ for MG at 45⁰C. The thermodynamic parameters indicated that adsorption was spontaneous and endothermic for MG and exothermic for CR, respectively. These results show that MG dye has a higher adsorption capacity compared to CR using chitosan derived from blue crab shells.