Iron and manganese removal by nanofiltration and ultrafiltration membranes: influence of pH adjustment

Iron and manganese present naturally in groundwater. Both metallic ions at excessive amounts normally contribute to rusty taste and reddish color to the water. Membrane technology may improve the conventional groundwater treatment method which commonly requires a large area and a lot of manpower. The present experimental work focused on membrane filtration of iron and manganese in order to study the influence of pH adjustment to the prepared artificial groundwater based on the permeate quality and membrane performances. In this study, two commercially available polyamide nanofiltration and ultrafiltration membranes (PA-NF, PA-UF) were tested to examine their capabilities in treating groundwater for drinking water resources. In order to achieve WHO drinking water standard, permeate quality of the artificial groundwater is considered satisfy if concentration of iron and manganese has reached 0.3 and 0.1 mg/L, respectively. Experimental results showed that pH at a range of 3-11 have significantly improved membrane performance in terms of their rejection. Rejection of iron at a feed concentration of 100 mg/L increased as pH of the feed solution increased for all tested membranes. However, the manganese rejection with a feed concentration at 50 mg/L showed various pattern of performance for each membrane. The pH of feed solution played an important role in changing the membrane surface properties and also, the characteristic of solute. This concludes that solute-membrane interaction mechanism has improved the performance of the tested membranes