Enhanced interfacial microbial degradation of n-hexane-contaminated waste gas using a novel magnetic silicone oil

Two-phase partitioning bioreactors have addressed the challenges of treating waste gases contaminated with hydrophobic volatile organic compounds (VOCs), primarily by improving mass transfer. However, the efficient recovery of the non-aqueous phase remains a significant issue. In this study, a novel magnetic silicone oil, designated KH602, was developed as a non-aqueous phase medium in a two-phase partitioning air-lift bioreactor for the treatment of gaseous n-hexane. KH602 improved the oil/water partition coefficient by 1.402-fold compared to conventional silicone oil. When used in the bioreactor, KH602 increased the elimination capacity by 33.3 % at an inlet concentration of 500 mg·m^-3. KH602 also promoted microbial extracellular polymer secretion, with protein content increasing by 25 %. It stimulated a higher proportion of activated cells and enhanced their capacity to utilize n-hexane metabolic intermediates, particularly esters, which showed a 117.9 % increase. Biomass was enriched at the oil-water interface, facilitating the mass transfer of n-hexane via a "gas-oil-biological" pathway. Additionally, microbial genera with known or potential n-hexane degradation capabilities, including Mycobacterium and Gordonia, were enriched. These findings offer theoretical insights and technical support for the efficient treatment of hydrophobic VOCs.