Ceramic hollow fibre membranes derived from natural resources for treatment of arsenic-contaminated water via membrane distillation

Abstract

Arsenic is regarded as one of the most toxic heavy metals and the largest mass poisoning material in the world. Recently, membrane distillation (MD) using hydrophobic membranes has been a promising technology for arsenic removal in water. While polymeric membranes are known to show drawbacks such as low thermal and chemical resistivity, similarly, commercial ceramic membrane from alumina that is extremely expensive. Therefore, the development of cost effective ceramic membranes from natural materials have grown inexorably to solve some of the underlying issues. In this work, hydrophobic ceramic hollow fibre membranes (CHFM) derived from natural resources (kaolin, rice husk waste and cow bone waste) were developed via phase inversion and sintering technique and modified through fluoroalkylsilane grafting. At the beginning of the study, characterization on chosen natural resources (kaolin, silica based rice husk ash and hydroxyapatite based cow bone) were performed. The prepared membranes were characterized and modified with 1H, 1H, 2H, 2H-perfluorodecyltriethoxysilane and ethanol solution for 24 hours with respect to their morphological structure, surface roughness, wettability behaviour, pore size distribution and porosity. The results revealed that the modification process successfully turned the CHFM from hydrophilic to hydrophobic with contact angle value of 145°, 157°, 161° and 170° for membranes prepared from kaolin, amorphous silica, crystalline silica and hydroxyapatite, respectively. Afterwards, the prepared CHFM were tested towards synthetic arsenic wastewater by varying direct contact membrane distillation (DCMD) parameters such as arsenic pH, arsenic concentration, and arsenic-feed temperature. It was found that CHFM prepared from kaolin (KHFM) prepared at kaolin content of 37.5 wt.% and sintered at 1300°C showed the best performance with 100% rejection of arsenite [As(III)] and arsenate [As(V)]) towards arsenic removal via DCMD system. Nevertheless, the last part of the study is treating the arsenic-contaminated water collected from Sungai Pengorak, Malaysia using the best membrane that induced 100% arsenic removal via DCMD system. When comparing the performance of the prepared membrane in this study with nanofiltration and reverse osmosis membranes, it was found that the newly-developed KHFM showed excellence performance in treating arsenic-contaminated water with 100% arsenic rejection and stable flux of 23kg/m2h. It is worth mentioning that no membrane fouling was observed in the prepared KHFM for 72 hours of operation in this study compared to polymeric membranes