Experimental design, modeling and mechanism of cationic dyes biosorption on to magnetic chitosan-lutaraldehyde...

Magnetic separation of toxic dyes has become a potential and effective method in wastewater treatments. In present research, a facile in situ one step co-precipitation synthetic approach is used to develop water-dispersible Fe₃O₄/Chitosan/Glutaraldehyde nanocomposites (MCS-GA) as an efficient adsorbent for the removal of Crystal Violet (CV) from aqueous solution. The physicochemical properties of the MCS-GA were investigated using FTIR, SEM, TEM, XRD, BET, and VSM techniques. 5-level and 3-factors central composite design (CCD) combined with the response surface methodology (RSM) was applied to investigate the statistical relationships between independent variables i.e. initial pH, adsorbent dosage, initial dye concentration and adsorption process as response. The optimal values of the parameters for the best efficiency (99.99%) were as follows: pH of 11, the initial dye concentration of 60 mg L^-1 and MCS-GA dosage of 0.817 g L^-1, respectively. The adsorption equilibrium and kinetic data were fitted with the Langmuir monolayer isotherm model (q_max: 105.467 mg g^-1, R²: 0.996) and pseudo-second order kinetics (R²: 0.960). Thermodynamic parameters (R² > 0.941, ΔH°: 690.609-896.006 kJ mol^-1, ΔG°: -1.6849 to -13.4872 kJ mol^-1, ΔS°: 0.168-0.232 kJ mol^-1 K^-1) also indicated CV adsorption is feasible, spontaneous and endothermic in nature. Overall, taking into account the excellent efficiency, good regeneration and acceptable performance in real terms, MCS-GA can be introduced as a promising absorbent for dyes removal from the textile wastewater.