Improved thin-film-composite forward-osmosis membrane for coal mine water purification

During the emergency rescue, such as coal mining disasters, potable water was the primary factor to ensure the safety of people trapped underground, and it was easy to be obtained by the filtration of coal mine water. As a membrane separation technology, forward osmosis (FO) membranes were expected to be used in the emergency filtration of coal mine water with higher contents of SO42− and F−. In this paper, a thin film composite (TFC) FO membrane was prepared by phase conversion and interfacial bonding methods, and the influence of compound modification by TiO2, polyvinyl alcohol (PVA) and polydopamine (PDA) on the morphology and permeability of the TFC FO membrane was studied. The results show that the large size TiO2 (50 nm) was only physically deposited on the polysulfone (PSF) membrane, and PVA increased the binding strength of the PDA membrane to the polyamide (PA) membrane. As a result, 2 wt% TiO2 and 2 wt% PVA and PDA co-doping led to a low water contact angle of 27° and a high FO water flux performance of 12.9 LM−2H−1 using a 2 M NaCl draw solution. Furthermore, the composite membrane showed better hydrophilicity, and the rejection of SO42− and F− were 92.1% and 89.3%, respectively, indicating that TiO2 improved the internal channels of the TFC FO membrane and PVA and PDA increased the hydrophilicity of the PA layer. Therefore, the novel TFC FO membrane exhibited good rejection and reproducibility, and this study demonstrated that TFC FO membrane was a good candidate for the emergency filtration of coal mine water.