Preparation of nickel@polyvinyl alcohol (PVA) conductive membranes to couple a novel electrocoagulation-membrane separation system for efficient oil-water separation

Efficient separation of oil-in-water emulsion remains a decisive step for success of oily wastewater treatment. To achieve this goal, a novel strategy regarding combining membrane separation with in situ electrocoagulation based on sacrificial anodes and cathodic hydrogen evolution via conductive metalized fabric membrane was proposed. As a key component of this novel coupling system, nickel functionalized fabric membrane with high hydrophilicity and electrical conductivity (electrical resistance of ∼2 Ω cm−1) was successfully prepared via a low-cost and facile route, including steps of PVA (polyvinyl alcohol)/Ni coating and autocatalytic electroless Ni plating. The optimized conductive membranes exhibited high permeate flux (19.3 × 105 L m−2 h−1·bar−1), separation efficiencies (99.5%), and separation stability to separate oil/water mixtures during the gravity-driven filtration process. To achieve the ideal performance to separate oil-in-water emulsion, a coupled electrocoagulation-membrane separation system was constructed with Ni@PVA membrane and Al mesh as the cathode and anode, respectively. It was shown that the coupled electrocoagulation-membrane separation system could achieve 99.4% rejection with high flux of 12.0 × 103 L m−2 h−1·bar−1 for oil/water emulsion separation, under the current density of 8 mA cm−2 and 20 min electrolysis time. This study revealed that the proposed electrocoagulation-membrane separation system based on Ni@PVA membrane is a promising technique in oil/water separation.