Highly selective adsorption and biodegradation of emulsified oil by microorganisms embedded in SiO2 hollow sphere bioreactor

Highly efficient elimination and disposal of oils and organic contaminants from water is of great importance for the sustainable development of modern society. In this work, micron-sized "single pore" silica hollow spheres (SHMs) bioreactors were prepared using (W/O/W) ternary-phase microemulsion, and the size of pores was adjusted to the concept of "single-pore" composite microorganism bioreactor, preparation of single-pore silica hollow spheres with an average pore size of 8.572 μm, which enables the SHMs bioreactors to load microorganisms for oils biodegradation. The outer layer was sprayed with a layer of silica nanoparticles with a diameter of 500 nm produced by silane hydrolysis, which encapsulated the inner "single-pore" SHMs to form a core–shell structure (M/Microbe@SHMs). This micro-nano core–shell structure exhibits superhydrophobicity and superlipophilicity, which gives it excellent selective adsorption capacity. Interestingly, M/Microbe@SHMs have excellent emulsion-breaking effects in oil–water separation. In addition to the simultaneous oil/water separation ability, the adsorbed oil and grease can be subsequently degraded to CO2 and H2O by microorganisms' action in the inner layer of M/Microbe@SHMs. Based on this excellent selective adsorption and oil/water separation capacity, while one-step in-situ biodegradation, our microbial bioreactor may have a potential for a wide range of practical applications in wastewater treatment.