Recycled nanofiltration membrane as a low-cost alternative to remove uranium from drinking water in remote communities

This study investigated the use of recycled membranes for groundwater treatment contaminated with uranium aimed to provide safe drinking water for human consumption. Two modules of end-of-life reverse osmosis membranes (3.69 -4.53 L/m 2 h.bar) were recycled through an oxidative treatment with sodium hypochlorite (NaOCl), differing between them in terms of the exposure time to the oxidant. The first module (NF -1; NaOCl: 440,000 ppm.h) showed a stable permeate flux (21.4 +/- 0.3 L/m 2 h; transmembrane pressure: 0.5 bar); however, the uranium concentration in its permeate exceeded the maximum contaminant level (0.03 mg/L) after a 40 % recovery rate. In contrast, the second one (NF -2; NaOCl: 220,000 ppm.h) was effective to remove uranium, but was more prone to flux decay, corresponding to a 53 % decay compared to its initial value of 10.3 L/m 2 h (transmembrane pressure: 0.5 bar). Standard blocking and complete blocking were the prevailing fouling phenomena. Its morphology and composition were verified through scanning electron microscopy, energy dispersive X-ray, and excitation-emission matrix fluorescence spectroscopy. Despite the lower flux, NF -2 achieves high uranium rejection and represents an alternative for further implementation in isolated and remote regions.