Enhancement of Water Permeability by Functionalized Halloysite Nanotubes Blended Ultrafiltration Membrane for Water Treatment

Abstract

Due to the world population growth, the fresh water consumption and demand are steadily increasing. There have been many approaches to purify water, and among these, membrane technology is gaining so much attention due to its high water quality, relatively simple concept and small equipment size requirement. However, there are some disadvantages such as low water flux and membrane fouling which may lead to short membrane life. In an attempt to achieve good antifouling properties, blending nano-materials to the polymer matrix for the membrane fabrication is widely used. Among various nano-materials, halloysite nanotubes(HNTs) are considered as promising nanofiller candidates. In this study, HNTs were successfully functionalized with 3-aminopropyltriethoxysilane(APTES) to improve hydrophilicity of the membranes and interfacial adhesion between HNTs and polyethersulfone(PES). The content of HNTs and functionalized HNTs(f-HNTs) are controlled from 0.5wt% to 2.0wt% of PES. The fabricated membranes were characterized and the performance were measured by lab-scale ultrafiltration system. Results showed that the mechanical strength of membranes with HNTs and f-HNTs were 20% higher than PES membrane. Increasing the f-HNTs content of the membranes enhances their tensile strength whereas the membranes with HNTs showed the decrease in tensile strength. This observation can be attributed to the improved interfacial adhesion between f-HNTs and polymer matrix The pure water flux of the fabricated membranes has dramatically improved with increase in of HNTs and f-HNTs contents, without a noticeable trade-off relation between water flux and rejection. This is due to the improved hydrophilicity and increased mean pore size of the membranes. The membranes with f-HNT showed better antifouling properties than the membranes with HNTs because of the increased hydrophilicity which results to formation of a thick hydration layer on the membrane surface, consequently preventing the adsorption and deposition of humic acid. In addition, the low roughness of the membrane surface prevents the accumulation of humic acid.