Preparation of Forward osmosis composite membrane with Chitosan/ Tannic acid co-deposition interlayer and its fluoride removal performance

The treatment of fluorine-containing wastewater has very important significance for environmental protection. Forward osmosis (FO), using osmotic pressure gradient as driving force, can remove ion from aqueous solutions effectively. The key to improve the separation efficiency of FO is to prepare the membrane of excellent performance. In this work, chitosan (CS)/tannic acid (TA) interlayer was constructed by the strategy of polyphenol/ polyamine liquid phase co-deposition, then three-layer FO membranes with more uniform surface and higher hydrophilicity were obtained by interfacial polymerization on the interlayer. And the effects of co-deposition time and mass ratio of CS/TA on the performance of FO treating simulated fluorine-containing wastewater were also investigated. Experimental results showed that the optimal co-deposition time was 60 min and the mass ratio of CS/TA was 0.5. The water flux of the TFC-CS/TA0.5-60 membrane (TFC means thin film composite, 0.5 is the mass ratio of CS/TA, 60 means the co-deposition time is 60 min) reached 22.3 LMH and the fluorine rejection was 99.93%, when it was applied to treat model waste water containing fluoride of 300 mg/L. In FO test on fluorine-containing wastewater from a semiconductor factory, compared with commercial Aquaporin InsideTM FO membrane, the water flux of TFC-CS/TA0.5-60 membrane was 49.3% higher than that of the commercial membrane. This study provides a new idea for the preparation of high-efficiency FO membranes and has a good prospect for the treatment of industrial fluorine-containing wastewater.