Adsorption behaviors of malachite green by using crosslinked chitosan/polyacrylic acid/bentonite composites with different ratios

In this study, by using different quantities of methylenebisacrylamide (MBA) and acrylic acid (AA), chitosan/polyacrylic acid/bentonite composites (CCS/PAA/BNTs) were synthesized and used for the adsorption of malachite green (MG). The fourier transmission infrared spectra, thermogravimetric analysis-differential thermal analysis and scanning electron microscopy techniques were used to determine synthesized composites. The effects of initial concentration, contact time, temperature and pH were investigated. Kinetic studies indicated that, due to the pseudo-second order model, correlation coefficients (R-2 >0.98) were the best fit thus, by using k(ps), the activation energies (E-a) were calculated (19.06, 15.64, 19.49, 8.29, 24.53 kJmol(-1)). The equilibrium data of MG agreed with the Langmuir model. The highest adsorption capacity calculated was found as 384.62-454.55 mgg(-1) for MG adsorption at 298-318 K. Thermodynamic studies demonstrated that MG adsorption was endothermic, caused spontaneous reaction and increased the entropy between 298-318 K. The adsorption reactions of MG were revealed as physisorption (Delta H<80 kJmol(-1)). The optimum pH was found as 6. The CCS/PAA/BNT2 composite indicated the highest adsorption capacity and best thermal stability compared to the other composites. (C) 2019 Elsevier B.V. All rights reserved.