PVDF membrane was modified by hydroxymethylated lignin to improve its hydrophilicity in treating oily wastewater

Polyvinylidene fluoride membranes (PVDFMs) are frequently used in oil-water separation due to their stable properties, high porosity, and modification easily. However, the pollution, low separation efficiency, and low recovery rate of PVDFMs have limited the oil sewage treatment. This work is based on dopamine-modified PVDFMs, which prepared hydrophilic separation membranes by attaching hydroxymethylated lignin (HAL) to PVDFMs. Lignin was hydroxymethylated to improve its hydrophilicity. Additionally, HAL was assembled on the surface of PVDFMs with the effect of dopamine (DA) and 3-aminopropyltriethoxysilane (KH550). The effect of the ratio of DA and KH550 (D: K) and HAL concentration on the hydrophilic effect was explored. The modified membranes exhibited considerable separation efficiency (>99 %) for several kinds of oil-water emulsions and could be recycled multiple times. This green modification method using lignin provides an environmentally friendly solution for modifying PVDFMs.