Coupling quinoline degradation with Fe redox in clay minerals: A strategy integrating biological and physicochemical processes

Quinoline is a common hazardous pollutant especially in fossil-fuel related wastewaters. Various approaches including biological degradation and physicochemical treatments (e.g., advanced oxidation processes, AOPs) have been applied for quinolone removal, however individual efficiency of these methods was usually not desirable. Here we reported that quinoline could be extensively degraded by combining biodegradation and AOPs during Fe redox cycling in the clay minerals. Four microbial consortia containing diverse functional groups of bacteria were successfully enriched from industrial coking wastewater, which were capable of reducing Fe(III) in nontronite (NAu-2) when coupled with quinoline degradation, with rates higher than those under other anaerobic condition (e.g., nitrate or sulfate reduction). Subsequent aeration of reduced Fe(II) in NAu-2 produced center dot OH that non-selectively oxidized quinoline. Quinoline was largely sorbed by Fe(III)-containing clay but desorbed when Fe(III) was bio-reduced, making Fe-bearing clay an easily recyclable substance for quinoline treatment. Quinoline was transformed into diverse products through several pathways during Fe(III) bioreduction and Fe (II) oxidation. Overall, our results suggest that Fe-rich clay mineral plays an important role in biological and chemical degradation of quinoline.