The adsorptive removal of Cr(VI) using magnetic nanohybrid of Fe3+-TMSPT-MNPs as a novel adsorbent has been investigated. In this regards, magnetic Fe3O4 nanoparticles (MNPs) were synthesized by the sol-gel method and then modified by 3-(trimethoxysilyl)-1-propanethiol and ferric chloride. The structural features of the produced materials were characterized by means of XRD, N2 adsorption-desorption, FT-IR, VSM and SEM. Central composite design (CCD) under response surface methodology (RSM) was applied to design of the experiments to maximize Cr(VI) removal from aqueous solutions. More specifically, the effects of pH, temperature, chromium ion concentration and sorbent dosage were investigated on the chromium adsorption. A total of 20 sets of experiments were designed by the software to achieve maximum removal efficiency (R). The significance of the independent variables and model were tested by the analysis of variance (ANOVA). The best local maximum values for pH, Cr(VI) concentration and sorbent dosage were found to be 4.28, 30 mg.L-1 and 2 g.L-1, respectively, that yielding maximum R of 62.10%. Furthermore, the obtained value for desirability was equal to 0.945. The results indicated that the equilibrium data are well fitted by the Freundlich model. Additionally, the kinetic data are analyzed by the pseudo-second-order model very well with high correlation coefficient. The thermodynamic study illustrated the feasibility, spontaneous and exothermic nature of the adsorption process.
