Recoverable magnetic Fe-MOF immobilized carrier to immobilize two microorganisms for reduction of heavy oil viscosity and oilfield wastewater COD

Immobilized microbial technology is a simple, cost-effective, and efficient technique to minimize the difficulty and energy consumption of heavy oil extraction, as well as the COD of oilfield wastewater. In this work, PC- g -Mag(Fe-MOF) was prepared to immobilize microorganisms obtained by grafting lecithin after magnetization using Fe-MOF. The orthogonal tests showed that the optimum temperature for immobilized microorganisms was 38 °C, the optimum pH was 7, the optimum inoculum was 7 % and the desired mineralization level was <20,000 ppm. The viscosity of free and immobilized microorganisms decreased by 61.5 % and 76 %. The recovery efficiency of the carrier with two species of bacteria after 5 cycles of experiments was 87.5 % and 73.2 %, respectively. The removal rate of COD in the 5th time was 69.3 %, the viscosity reduction rate of heavy oil was 61.6 %. The recovery efficiency of heavy oil was increased by 25.09 %. Fe-MOF acts as a biocarrier to immobilize bacteria and enhance the metabolic activity of their microbial communities and improves COD removal from oilfield wastewater and viscosity reduction in heavy oil.