Semiequilibrium Dialysis versus Ultrafiltration for the Separation of Arsenic from Water Using Cationic Amphiphilic Aggregates

A process, which does not require the addition of large amounts of chemicals, for the removal of arsenic (V) utilizing amphiphilic aggregates (i.e. cetylpyridinium chloride (CPC) micelles) and ultrafiltration (UF) membranes has been studied. The suitability of UF process was evaluated with semi-equilibrium dialysis (SED) cell since the UF process incorporated with amphiphilic aggregates is an equilibrium process. The SED removes up to 100% arsenic (V) from simulated water with the presence of CPC micelles. Furthermore, UF experiments were carried out using regenerated cellulose (RC) membranes (10 kDa NMWCO) and polyethersulfone (PES) membranes (5 and 10 kDa NMWCO) with and without the addition of CPC. Without the addition of CPC, all UF membranes failed to reduce arsenic concentration below the revised maximum contaminant level (MCL) of 10 ppb. However, in the presence of CPC micelles arsenic concentration was reduced below the MCL. The membrane material, membrane nominal molecular weight cut-off (NMWCO) and water pH were found to play an important role on the arsenic removal efficiency.