Application of in-situ microbubble method on SEP@MnO2/RGO composite membrane for efficient and long-acting treatment of oil field wastewater

Abstract

The treatment of oilfield wastewater has been a problem for oil workers for a long time. Indeed, it is economical, efficient and environmental friendly to treat oilfield wastewater with membrane. However, the contamination and stability of membrane limit the application of membranes. This study focuses on improving the long-term integrated treatment of oilfield wastewater by commercial PVDF membranes in different environments. Sepiolite(Sep)@MnO 2 composites were synthesized by hydrothermal method. SEP@MnO 2 and graphene oxide(GO) were left on the commercial PVDF membrane after vacuum filtration. Then the membrane was subjected to 120 vacuum thermal reduction. The prepared Sep@MnO 2 /RGO composite membrane showed good separation result and flux for different proportion of oilfield wastewater. Moreover, it can remove some common salt (NaCl,MgSO 4 , CaCl 2 , MgCl 2 ) and heavy metal ions (Ni 2+ , Fe 3+ , Cr 6+ ) in oilfield wastewater. Even more valuable, a few addition of H 2 O 2 to oilfield wastewater caused an oxidation reaction and the produced in situ microbubbles greatly enhance the antifouling property of the membrane. After 15 cleaning tests and 12 h of cycling, the membrane still showed strong separation ability. Compared with other oil-water separation membranes reported, this membrane demonstrated a longer and better separation effectively. All the work promotes the application of membrane separation technology in oilfield wastewater treatment. Hopefully, the application of in-situ microbubble method on membrane will solve the problem of membrane pollution in oilfield wastewater treatment. • The membrane can effectively treat the oil field wastewater with heavy metals and salts. • The application of in-situ bubble method on the membrane enhances the anti-fouling property of the membrane. • The membrane is qualified in a table and long-active treatment of oilfield wastewater.