Simultaneous removal of Cr(VI) and orange G6 by polyaniline/attapulgite supported nano zero-valent iron activate persulfate

In this paper, the polyaniline/attapulgite composite supported nano zero-valent iron (nZVI/PANI/ APT) composites were synthesized by one-step oxidation using Fe3+ as oxidant and iron source. nZVI/PANI/APT was used as a catalyst to activate persulfate (Ps) for the simultaneous removal of Cr(VI) and orange G6 (OG6) from aqueous solutions. The main factors (different composite materials, pH value, Ps concentration, etc.) affecting the removal performance of Cr(VI) and OG6 were evaluated as well. The experimental results revealed that the nZVI/PANI/APT composites can effectively remove Cr(VI) and OG6 simultaneously at a relatively low Ps concentration, the removal efficiencies of Cr(VI) and OG6 were 99.7% and 99.4% after 60 min, respectively. PANI/APT as the supporter matrix could decrease the aggregation of nZVI and increase its reactivity. A good synergistic effect between Cr(VI) reduction and OG6 oxidation was achieved by nZVI/PANI/APT combined Ps system. nZVI not only can be as a reductant for removal Cr(VI) and OG6 but also play as a catalyst to activate Ps and generate radicals for the degradation OG6. The presence of persulfate could not significantly decline nZVI reactivity for Cr( VI) reduction but remarkably promote OG6 oxidation. Moreover, kinetic and thermodynamic analyses were used to study the removal process, and the possible removal mechanism of Cr(VI) and OG6 was discussed by using the UV-Vis spectrum and liquid chromatography-mass spectrometry techniques. The nZVI/PANI/APT-persulfate heterogeneous Fenton system combines the nZVI reduction with the Fenton-like oxidation, which can be used for the treatment of industrial wastewater containing heavy metal ions and organic dyes.