Design fiber-based membrane with interfacial wettability rapidly regulated behavior by pH for oily wastewater high-efficient treatment

pH-responsive materials are an important choice for the preparation of smart membranes due to their simplicity of operation, but their substrate requirements are high and most of the existing materials are slow to respond. Cotton fabrics with three-dimensional structures have high strength and resistance to acid and alkali, enabling rapid penetration of acid and alkali solutions with fast response time. In this paper, hexadecyltrimethoxysilane (HDTMS) was used to hydrophobically modify the surface of polydopamine (PDA)-modified CF, and novel CF with pH-adjustable wetting properties were designed by the Michael addition reaction and the Schiff base reaction among 12-aminodododecanedioic acid (NH2(CH2)11COOH) and PDA. In neutral and acidic aqueous solutions (pH ≤ 7), the coated cotton fabric showed hydrophobicity and lipophilicity, with a separation efficiency of 97.3 % and a separation flux of 3.8 × 104 L·m−2·h−1. On the contrary, in alkaline aqueous solutions (pH > 7), the coated cotton fabric had a fast conversion time (within 20s), exhibited oleophobicity and hydrophilicity, with a separation efficiency of 99.9 % and a separation flux of 2.8 × 104 L·m−2·h−1. In addition, the cycling and durability tests showed that the cotton fabric had excellent cyclability and durability. This simple, green, intelligent wetting material can be ideal for controllable on-demand oil-water separation.