Sodium alginate microspheres loaded with purple phosphorus-based immobilized microorganisms for oilfield wastewater purification and heavy oil viscosity reduction

Immobilized microbial technology is a simple, cost-effective, and efficient technique to minimize the difficulty and energy consumption of heavy oil extraction, and the Chemical Oxygen Demand (COD) of oilfield wastewater. In this study, SA@VP-g-L was developed and utilized as a microbial immobilization carrier obtained by grafting lecithin onto purple phosphorus. The unique physicochemical properties of this carrier provide a stable and efficient attachment environment and survival site for microorganisms. Orthogonal tests showed that the optimum temperature for SA@VP-g-L immobilized microorganisms was 38 °C, the optimum pH was 7, the optimum inoculum was 7 % and the desired mineralization level was not higher than 15,000 ppm. Under suitable conditions, the immobilized microorganisms of SA@VP-g-L-immobilized microorganisms showed a COD removal of more than 80 %, the viscosity of heavy oil was reduced by 88.5 %. Displacement experiments indicated that the use of the carrier (SA@VP-g-L) led to an increase of 28.95 % in the heavy oil recovery. This phenomenon was ascribed to the reduction in the COD and the viscosity of the heavy oil within the re-injected water. Therefore, the application of SA@VP-g-L as a carrier to immobilize microorganisms in oilfields can improve the metabolic activity of microbial communities.