Characteristics of amine surfactant modified peanut shell and its sorption property for Cr(VI)

Modified peanut shell (MPS) was prepared by amination reaction with peanut shell (PS) as the starting material. The sorption of Cr(VI) oxyanions on MPS in static and column tests were investigated. In addition, the sorption isotherm and kinetic models were applied to confirm the sorption capacity and the sorption mechanisms. BET surface area analysis showed the physicochemical characteristics of the samples. The results of zeta potential, Fourier transform infrared (FT-IR) and Raman spectra analysis illustrated that chemical adsorption and ion exchange are the potential sorption mechanism. The static sorption test showed that the maximum sorption capacity (qmax) of MPS for Cr(VI) increased with temperature, which indicated that the Cr(VI) sorption process was endothermic. The saturated sorption capacity of Cr(VI) in the column sorption test was 138.34 mg·g−1, which accounted for 93.9% of the qmax at 25 °C. The regeneration capacity of MPS was evaluated using HCl solution as an eluent. The high regeneration efficiency (82.6%) validated the dominance of the ion exchange mechanism in the Cr(VI) sorption process with Cl− ions displacing Cr(VI) oxyanion on MPS. The Langmuir isotherm model showed a higher correlation coefficient than the other adsorption isotherm models. And in the kinetic study, a pseudo-second-order model fit the data best.