Arsenic removal from drinking water using clay membranes

While many treatment technologies are available for arsenic removal from drinking water including coagulation/filtration, lime softening, activated alumina adsorption, ion exchange, and membrane processes, most of these approaches are expensive and more suitable for large water systems. In this study, membranes made of low-cost clay minerals were explored for arsenate removal. Montmorillonite, kaolinite, and illite were selected for membrane preparation. Feed water spiked with arsenate was pumped through the compacted clay membranes and the effluent was collected at the lower pressure side for arsenic analysis. The ability of clay membranes to retain arsenic was investigated at different initial arsenic concentrations and ionic strengths controlled by sodium chloride. The influence of applied pressure and the permeate flux on arsenic removal efficiency was also examined. The results indicated that a greater than 90% of arsenic rejection could be achieved for water with 50-100 mu g/l of arsenate using the clay membranes. The required pressure for clay membrane filtration was, however, significantly higher than that of synthetic organic membranes.