ABSTRACT
This chapter aims to give a comprehensive overview on the use of nanofiltration membrane-based processes for arsenic removal. It provides a critical analysis of the treatment status using membrane based processes, and discusses new development directions that may help the advancement of arsenic removal in a more energy efficient manner. Compared to reverse osmosis, nanofiltration membranes show also relatively high removal rate for arsenic; however, at a relatively lower pressure, or lower energy demand. Nanofiltration membranes consist of an active layer and a support, which determine the separation properties and mechanical strength, respectively. There are several theories to explain the nanofiltration mechanism and the understanding of the transport mechanism reveals a contradictory picture of how the active layer behaves in nanofiltration. A dense skin layer was assumed by the Torell-Meyer-Sievers model and the hybrid model. The space-charge model and the Donnan-steric pore model described a porous skin layer.
