Biodegradation of potassium amyl xanthate from mining flotation wastewater with minimal CS2 emission.

The mining industry produces significant volumes of flotation wastewater that contains xanthates, such as potassium amyl xanthate (PAX, C6H11OS2K), that pose toxicity risks to ecosystems and humans. In this study, an oxygen-based membrane biofilm reactor (O2-MBfR) was applied to biodegrade high concentrations (75∼200 mg/L) of PAX; the MBfR achieved > 99% removal of PAX with minimal carbon disulfide (CS2) emission at a PAX surface loading rate of 770 mg/m2-d. The microbial community adapted to changing PAX loading and O2 pressure, and it consistently gave efficient removals of PAX and soluble COD, as well as negligible CS2 emission. Metagenomic sequencing revealed that Mesorhizobium, Zoogloea, Sediminibacterium, Afipia, and Devosia were important genera that contributed in different ways to oxidation of PAX, PAX metabolites, and CS2. PAX degradation began with cleavage of C-O or C-S bonds, which was followed by oxidation of sulfur-containing intermediates. Also, the efficient biodegradation of xanthates offers a potential strategy to avoid flotation tailings caused by flotation wastewater reuse.