MXene based immobilized microorganism for chemical oxygen demand reduction of oilfield wastewater and heavy oil viscosity reduction to enhance recovery

The high energy consumption drawbacks of thermal recovery of heavy oil are becoming increasingly apparent, contrary to the goal of being green, environmentally friendly and low carbon. In this work, a carrier was designed for the immobilization of Bacillus subtilis using lecithin(PC)-modified magnetized Ti 2 C 3 MXenes (PC- g -Fe 3 O 4 /Ti 2 C 3 ) for heavy oil exploitation, which effectively reduced the chemical oxygen demand (COD) of oilfield wastewater and viscosity of heavy oil. According to orthogonal tests, the ideal temperature for immobilizing Bacillus subtilis was 38 °C, the ideal pH was 7, the desired mineralization was less than 20,000 ppm, the COD removal rate was over 80 %, and the heavy oil's viscosity was reduced by 77.5 %, and the carrier could be recycled and reused. As the results of the displacement experiment showed, the microbial oil drive with the carrier (PC- g -Fe 3 O 4 /Ti 2 C 3 ) could enhance the recovery of heavy oil by 28.39 %, which was due to the reduction of COD and viscosity of the heavy oil in the reinjection water. So, PC- g -Fe 3 O 4 /Ti 2 C 3 has excellent potential for use in the oil field because it is very effective, affordable, and ecologically benign.