Removal of micropollutants from water by commercially available nanofiltration membranes

Abstract

The current work is focused on the use of nanofiltration in the removal of micropollutants, specially drugs (diclofenac and ibuprofen) and heavy metal (zinc sulphate and zinc nitrate) from wastewater. The commercially available nanofiltration (NF) membranes (AFC 80, AFC 40, AFC 30) were characterised by demineralised water and the ability of the membranes to reject drugs and zinc(II) was subsequently examined. The influence of the operating conditions on the rejection and the permeate flux was evaluated. The operating conditions tested included the transmembrane pressure (5-30 bar); the effect of the feed concentration on the heavy metals rejection (50-200 mg L^-1); the effect of ionic strength on the diclofenac and ibuprofen rejection (0-10 g L^-1 NaCl) and the volumetric flow rate (5-15 L min^-1). It has been shown that increasing the transmembrane pressure increases the intensity of the permeate flow and rejection. Drugs rejection also increases with increasing bulk feed flow rates; however, decreases with increasing ionic strength (NaCl concentration in feed). Experimental data indicated that concentration polarisation existed in the membrane separation process. The stable permeation flux and high rejection of drugs and heavy metals indicated the potential of NF for the recovery of drugs and zinc(II) from wastewater.

Keywords: Diclofenac; Flux; Ibuprofen; Nanofiltration; Rejection; Zinc(II).