Biodegradation of three xanthates with different carbon chains in flotation wastewater.
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75% confidenceThis study investigated the biodegradation of three xanthates in a membrane biofilm reactor, achieving over 98% removal of all xanthates with corresponding COD removals of 62-90%. The results showed that different microorganisms were involved in the degradation of each xanthate, and that the branched isopropyl group of one xanthate slowed down its oxidation. The study provides insights into the biodegradation of xanthates in flotation wastewater.
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Abstract
Xanthates are widely used collectors in sulfide ore flotation, but pose ecological risks due to their toxicity and the releasing of carbon disulfide (CS 2 ). This study systematically investigated the biodegradation of three representative xanthates-potassium amyl xanthate (PAX), potassium butyl xanthate (PBX), and potassium isopropyl xanthate (PIX)-in an oxygen-based membrane biofilm reactor (O 2 -MBfR). The O 2 -MBfR achieved over 98 % removal of all xanthates across surface loadings up to 6000 mg-COD/m 2 ·d, with corresponding COD removals of 62-90 %. While PIX exhibited slightly lower COD removal due to the slower oxidation of its branched isopropyl group, functional gene analyses revealed the co-enrichment of alcohol and sulfur oxidation genes (adh, ALDH, soxABC/XYZ, fccAB) and C-S bond cleavage genes (cynT, ssuD). Metagenomic and metatranscriptomic results showed that Pseudomonas and Rhodanobacter predominated in PIX degradation, whereas Thiobacillus, Zoogloea, and Ottowia were mainly involved in PAX and PBX oxidation. Monod kinetics indicated that PIX had the highest maximum specific degradation rate (33.85 mg/gVSS/h) and lowest sCOD decay rate constant (0.29 h -1 ), reflecting strong microbial affinity but limited mineralization. Continuous-flow treatment of real flotation wastewater achieved > 98 % xanthate and ∼85 % COD removal, confirming system robustness. These findings provide mechanistic insight into the structure-dependent biodegradability of xanthates and demonstrate the feasibility of O 2 -MBfR technology for sustainable treatment of flotation wastewater.