Removing heavy metals from landfill leachate using electrospun polyelectrolyte fiber mat-laminated ultrafiltration membrane

Abstract

This study investigated the removal of selected heavy metals from landfill leachate by electrospun polyacrylic acid (PAA)/polyallylamine hydrochloride (PAH)-laminated ultrafiltration (UF) membranes (PAA/PAH-UF). The effect of leachate matrix on metal removal by the PAA/PAH-UF membrane was also examined. In synthetic metal solutions, the PAA/PAH-UF membrane exhibited 38–85% higher removal efficiency when compared to the unmodified membrane. This could be attributed to complexation of the metal ions with the carboxylate ions (–COO-) from the PAA/PAH fiber mats. Heavy metal removal was generally higher (up to approximately 18%) in landfill leachates than the laboratory-prepared solutions, likely resulting from the fouling of PAA/PAH fiber mat and the UF membrane substrate and the metal-organic complexation. The higher metal ion removal efficiencies (up to 20%) by the PAA/PAH-UF membranes in the presence of Suwannee River natural organic matter (SRNOM) were associated with the higher concentrations (50 and 100 mg/L) of SRNOM. When compared to the lower concentration (10 mg/L), metal removal increased (up to 30%) at higher concentrations (50 and 100 mg/L), with the influence of SRNOM being the most pronounced for Cu, followed by Cd and Pb. The enhanced metal removal, in the presence of SRNOM, can be attributed to metal complexation with SRNOM functional groups in addition to the rich functional groups from the PAA/PAH fiber mats. The trivial difference in flux decline of the PAA/PAH-UF membrane compared to the unmodified membrane may be outweighed by the marked enhancement in heavy metal removal when functionalizing the membrane with PAA/PAH fiber mats.