Volatile organic compounds (VOCs) are key precursors in the formation of PM2.5 and ozone (O3), playing a critical role in air pollution (Pak et al., 2016, Zhang et al., 2025). VOC emissions originate from a wide range of sources, many of which are closely linked to everyday human activities (Liu et al., 2025). Increasing attention is being paid to VOC pollution, as it poses a serious threat to the atmospheric environment and may have adverse effects on human health (Liu et al., 2022, Robichaud, 2020). The rapid expansion of industrial activities further adds to the potential risks associated with VOC emissions (Bak et al., 2017). VOCs are generally classified into three categories—hydrophilic, weakly hydrophobic, and strongly hydrophobic—based on their octanol–water partition coefficient (Wang et al., 2025b). N-Hexane, a strongly hydrophobic VOC, widely distributed in the environment and can cause severe lung and neurological damage (Chen et al., 2024). These health risks highlight the urgent need for effective treatment strategies targeting the emissions of strongly hydrophobic VOCs such as n-hexane.

Biological purification technology for treating low- and medium-concentration industrial VOCs offers several advantages, including mild operating conditions, environmental sustainability, low operational costs, and ease of implementation (Hu et al., 2016, Li et al., 2023a). It has garnered significant global attention for its potential in industrial applications (Bailón et al., 2009). However, traditional biological methods face limitations when treating strongly hydrophobic VOCs such as n-hexane, primarily due to poor mass transfer efficiency between the gas, aqueous, and biological phases. The development of two-phase partitioning biotechnology has provided a promising solution for the efficient removal of hydrophobic VOCs (Chen et al., 2021).

The introduction of a non-aqueous phase allows hydrophobic pollutants to be adsorbed and dissolved, thereby enhancing mass transfer from the gas phase to the liquid phase and improving removal efficiencies (REs) (Cheng et al., 2016). When the substrate concentration in the aqueous phase is low, the non-aqueous phase can serve as a reservoir, slowly releasing the adsorbed organic compounds to maintain biodegradation (Béchohra et al., 2015). Silicone oil has been widely used as an effective non-aqueous phase due to its strong hydrophobicity, non-toxicity, and resistance to biodegradation (Lu et al., 2025). Previous studies have reported a 25 %–35 % improvement in the treatment of gaseous hydrocarbon pollutants with the addition of silicone oil compared to control setups (Cheng et al., 2020, Dorado et al., 2015, Nourmohammadi et al., 2023). However, the low recovery rate of non-aqueous phase contributes to high operational costs. To address this issue, we previously developed a magnetic silicone oil with strong substrate affinity and easy recyclability, achieving a recovery efficiency of 95.6 % (Li et al., 2023b). Nevertheless, the physicochemical properties of magnetic silicone oils and their role in the biological removal process within the reactor remain insufficiently explored.

In this study, a novel magnetic silicone oil (a silicone oil uniformly doped with magnetic particles, KH602, which could be used to achieve rapid separation of oil and water phases using a magnetic field in the application process, and lead to a promotion in the recycling efficiency and reuse rate of silicone oil) was synthesized using an innovative silane coupling agent N-(β-Aminoethyl)-γ-Aminopropylmethyldimethoxysilane with the aim of reducing costs. Following its characterization, KH602 was applied in a two-phase partitioning air-lift bioreactor for the treatment of n-hexane-contaminated waste gas. The enhancement mechanisms were then investigated by analyzing microbial metabolic characteristics, cellular distribution, and community structure.