Synergistic adsorption and reduction of hexavalent chromium using highly uniform polyaniline–magnetic mesoporous silica composite

Abstract

Abstract In this study, a novelly synthesized magnetic mesoporous silica composite with high uniformity and polyaniline (PANI) grafted was successfully applied to highly efficient Cr(VI) removal. With the assistance of high adsorption capacity of protonated PANI and the magnetic mesoporous composite at low pH, Cr(VI) was adsorbed and then reduced to less toxic Cr(III) by PANI. The resultant adsorbent was characterized by TEM and FTIR, nitrogen adsorption–desorption measurements were carried out, and the zeta potentials of the prepared adsorbent were also measured at different pH. The adsorption and synergistic reduction route was particularly deduced by analyzing the existing forms of PANI and Cr by XPS. Pseudo-second-order model could well fit the data obtained from batch Cr(VI) removal experiments for the kinetic study, and Langmuir model well described the sorption isotherms with the maximum adsorption capacity of 193.85 mg/g. Competition from coexisting ions (K+, Na+, Ca2+, Cl−, SO42−, NO3−) was proved to be insignificant. Moreover, the exhausted adsorbent could be well regenerated and kept above 83% removal efficiency in the first three cycles, which demonstrated that it was cost-effective. The results suggested that this novel magnetic adsorbent may offer a simple adsorption and synergistic reduction treatment option to remove Cr(VI) contamination from industrial wastewater and natural water bodies.