Yongqiang Guo

Polyamide aromatic (PA) reverse osmosis (RO) membranes are currently the most important materials in the seawater desalination and wastewater treatment industry. This study used hydrophilic macromolecular polyvinylpyrrolidone (PVP) in a PA selective layer to develop a new polyamide thin-film composite (TFC), namely PA-g-PVP RO, which will be used for water treatment. The TFC is prepared via an interfacial polymerisation process, and TFC-based PVP can be transplanted on a PA surface by radiation. PA-g-PVP RO was characterised by ATR-FTIR, SEM, XPS, AFM and contact angle test and then evaluated by determining its permeability, salt retention and antifouling performance, among other properties. Results show that the chemical composition and surface morphology of the polyamide film significantly changed. A PVP brush grafted on an RO membrane surface significantly enhanced the hydrophilicity and antifouling performance of the membrane. When the PVP concentration was increased in an aqueous solution to 2%, the water contact angle of the sacrificial layer of the modified membrane decreased to 24.3°, the fouling recovery ratio to 93.4% and the salt retention increased to 99.5% at a small flux change. This combined technology can also be used for other macromolecules to modify the membrane and study the preparation and modification of ultra-filtration and nano-filtration membranes.

A novel aromatic polyamide (PA) reverse osmosis membrane with nanoscale water channels and hydrophilic molecular skin surface, similar to those of biomimetic neural networks, was realized for textile wastewater treatment via the facile strategy of interfacial polymerization with the addition of free radicals. The free-radical polymerization of diallyl dimethyl ammonium chloride, dispersed inside and on the surface of the PA functional layer, was initiated by irradiation to form a polyimide-hydrophilic polyolefin interpenetrating network structure as the functional layer and a molecular brush as the hydrophilic surface layer. Compared with the thin film composite (TFC) membrane, the water contact angle of the modified membrane was reduced drastically from 58.23° to 19.95°, and surface roughness and negative charge also decreased. Moreover, the water flux and salt rejection performances of the modified membrane improved simultaneously. The hydrophilic polyolefin network exhibited the same structure and function as those of neural networks, through which water molecules, but not salts, could pass through nanoscale water channels formed by polymerization. Then, contaminant rejection rates using TFC or modified membranes for textile wastewater treatment were investigated. The modified membrane yielded high rejection (>99%) of ion salts and high chemical oxygen demand removal (>99.3%) of organics with low molecular weights. Apart from its excellent anti-fouling property, the modified membrane was also satisfactorily stable for long-term separation. The integration of low-cost, high-performance, and facile strategy indicates the potential application of the proposed membrane for textile wastewater treatment.