Simultaneous removal of typical flotation reagent 8-hydroxyquinoline and Cr(VI) through heterogeneous Fenton-like processes mediated by polydopamine functionalized ATP supported nZVI

The heavy metal and organic pollution caused by mining activities keep attracting attention, thus an economic and efficient treatment for combined pollution is pressing. In this study, the simultaneous removal performance of typical organic flotation reagent 8-hydroxyquinoline (8-HQ) and Cr(VI) was investigated via heterogeneous Fenton process induced by a novel polydopamine (PDA) functionalized attapulgite supported nano sized zero-valent iron (nZVI) composite (PDA/ATP-nZVI). Batch experiments showed that PDA/ATP-nZVI had better catalytic reactivity and reduction ability than both ATP-nZVI and nZVI. Under acidic condition, 96.0% of 8-HQ was degraded accompanied with the 42.5% of total organic carbon (TOC) decrease, while 95.8% of Cr(VI) removal efficiency was accomplished by PDA/ATP-nZVI. PDA not only served as redox mediator in expediting electron transfer, but also acted as electron donor that accelerated transformation from Fe(III) to both dissolved Fe(II) and surface Fe(II), which resulted in the increased degradation of 8-HQ. The synergic removal behavior between 8-HQ and Cr(VI) was discussed and the reaction mechanism in the persulfate (PS)-PDA/ATP-nZVI system was also explored. This study developed a highly efficient heterogeneous catalyst, and demonstrated that the PS-PDA/ATP-nZVI system had a potential for remediation of mine environment polluted by both heavy metals and organic flotation reagents. [Display omitted] •PDA/ATP-nZVI was synthesized in one step under acidic condition.•Oxidation of 8-HQ and reduction of Cr(VI) were achieved simultaneously.•PDA/ATP-nZVI had better catalytic reactivity and reduction ability than ATP-nZVI.•PDA accelerated conversion of Fe(III) to both dissolved Fe(II) and surface Fe(II).•SO4•− and •OH were jointly responsible for the 8-HQ degradation.