PVDF microfiltration membranes modified with AgNPs/tannic acid for efficient separation of oil and water emulsions

Treatment of oil/water mixture, especially oil/water emulsions, is of great significance in the protection of both the environment and living creatures. Herein, in this work, we reported a two-step strategy to enhance the hydrophilicity and underwater oleophobicity of PVDF microfiltration membranes using tannic acid (TA, a nature plant polyphenol) and AgNO3 solutions. After coating by Ag nanoparticles (AgNPs)/TA (0.4 mg/ml Ag+, 0.2 mg/ ml TA), the PVDF membrane exhibited high hydrophilicity for a short immersion time (10.35 s) of a water droplet (V=5 mu l, initial WCA=19), underwater superoleophobicity (UOCA=161) and antifouling property and thus, high-efficiency oil/ water emulsions (SDS/kerosene/water emulsion) separation could be realized. Compared with Fe/TA-PVDF (0.4 mg/ml Fe2+, 0.2 mg/ml TA, initial WCA=21 and UOCA=156) and Cu/TAPVDF (0.4 mg/ml Cu2+, 0.2 mg/ml TA, initial WCA=31 and UOCA=147), the AgNPs/TA-PVDF in our work possessed best hydrophilicity and underwater superoleophobicity. In addition, the AgNPs/TA-PVDF could maintain its hydrophilicity, underwater superoleophobicity and mechanical property after rinsing tests and scratch resistance tests.

Automated summary

In this study, a two-step strategy using tannic acid (TA) and AgNO3 solutions was employed to enhance the hydrophilicity and underwater oleophobicity of PVDF microfiltration membranes. The coated membranes exhibited high hydrophilicity, underwater superoleophobicity, and anti-fouling properties, enabling efficient separation of oil/water emulsions.