Effect of pH on the removal of arsenic and antimony using reverse osmosis membranes

Increasing attention has been focused on the health effects associated with ingestion of low levels of arsenic and antimony in drinking water. Accordingly, this study was conducted in order to identify the effect of solution pH on the removal efficiency of arsenic and antimony for drinking water using recently developed RO membranes. In this study it was found that the removals of As(V) and Sb(V) are much higher than those of As(III) and Sb(In) over all investigated pH levels (pH 3-10). The removal of arsenic compounds was strongly affected by the solution pH, especially As(III), whereas the removal of antimony compounds shows no dependence on the solution pH since the oxidation state of antimony changes from Sb(III) to Sb(V) within very short periods of time. It was demonstrated that pH control for the membrane feed water is more essential for the successful removal of arsenic compounds than the case of antimony compounds. Consequently, it is assumed that the removal of antimony in drinking water by RO membranes has a higher efficiency than that of arsenic compounds, regardless of pH changes.