Preparation and characterization of chitosan/clay composites and their adsorption applications

In this study, by using different crosslinked and acrylic acid ratio chitosan/bentonite/acrylic acid CBA composites (CBA1, CBA2, CBA3, CBA4, CBA5) were synthesized and used for adsorption of MG, MB dyes and Cu(II), Ni(II) heavy metals. Effects of contact time, temperature, initial concentration and pH on adsorption mechanism were investigated. Kinetic data were evaluated by pseudo-first, pseudo-second order and Weber-Morris intraparticle mass tansfer and pore diffusion models and kinetic coefficients were determined. Kinetic model was confirmed by magnitudes of correlation coefficients. Pseudo-second model was founded as best model for adsorption of MG, MB dyes and Cu(II), Ni(II) metal ions on all composite surfaces so, by using kpi activation energies (Ea) were calculated. Langmuir and Freunlich models that commonly used were examined for isotherm data calculations and by investigation adsorption equilibrium, isotherm coefficiens were calculated for these models. According to magnitude of correlation coefficiens, Langmuir isotherm model was founded as most usefull isotherm model therefore, by use of determined b-Langmuir coefficients and Van' t Hoff equation adsorption free enthalpy (ΔG), entalphy (ΔH) and entropy (ΔS) parameters were calculated. In order to determine synthesized composites (CBA1, CBA2, CBA3, CBA4, CBA5) and adsorption mechanisms of dyes and heavy metal ions on composite surfaces, FTIR (for functional groups), SEM (for surface morphologies) and TGA-DTA (for thermal behaviors) techniques were used before and after adsorption process.