Rejection Capacity of Nanofiltration Membranes for Nickel, Copper, Silver and Palladium at Various Oxidation States

Abstract

Electroplating and metalworking industries produce enormous amounts of waste containing heavy metals in their effluents, leading to potential threats to biotic and abiotic life. According to regulation, heavy metal contamination must be kept within the regulated standard of a few parts per million, which has led to a recent pique in interest in the utilization of nanofiltration technology for metal recovery. The effect of feed pH, pressure, metal concentration, and oxidation of metal on the rejection of heavy metal ions using three commercial nanofiltration membranes (NF, NF90, and NF270) were explored. To begin, studies of electrolyte salts, contact angle, and water permeability were employed to characterize the nanofiltration membranes. A dead-end module was used to test the permeation and retention capacities of the nanofiltration membranes. The results showed an increase in salt rejection for all metals examined irrespective of the membrane, at a pH below the isoelectric point. For divalent cations, the NF90 membrane achieved recovery capacities of 97% and 85% at 200 ppm and 20 ppm respectively, as compared to the recovery observed for Ni2+, Cu2+, and Pd2+ ions by NF and NF270. At a pH 2, 20 ppm and 5 bar, the NF90 membrane had the highest percent recovery, but at a pH 3, the recovery was at 95%. Mono and divalent stable Ag+ and Ni2+ ions showed a comparatively high percent recovery as compared to Pd2+ and Cu2+, which have high molecular weight and charge effect. In the presence of chelating agents, the membrane surface area is increased, resulting in high divalent ion recovery capacities due to favourable interaction with the polyamide functional group of the membranes. This study establishes the significance of oxidation in high removal efficiency cation in varying experimental conditions.

The Effect of Cu2+ and Pb2+ in the Feed Solution on the Water and Reverse Solute Fluxes in the Forward Osmosis (FO) Process Using Nanofiltration (NF) Membranes

“…Consequently, a better approach would be to select nanoparticles that specifically interact with heavy metal ions. The thiol (SH) functional groups enhance heavy metal adsorption through complexation [38]. They can be introduced into TFN membranes via, for example, L-cysteine functionalized cellulose nanocrystals [35].…”

Interaction between surfactants of different classes and nanofiltration membranes

“…This behavior could be explained the smallest pore size of SR90 and BW30 membranes, or to the higher electrostatic interaction between the NF90 and NFS membranes and the Mg 2+ , resulting in a reduction of the salt rejection for these membranes. Thabo et al (2021) [42] also observed higher rejections of Na + in NF270 and NF90 membranes and lower rejections of Mg 2+ , attributing this result to the charge effects of these membranes governed by Donnan exclusion.…”

Membrane Separation in the Nickel-Contaminated Wastewater Treatment

“…Brooms Thabo et al [12] compared three commercially available nanofiltration membranes. They chose two polyamide membranes: NF90 (MWCO = 150 Da), NF270 (MWCO = 200 Da), and one polypiperazine, PP-NF (MWCO = 150 Da).…”