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. Accordi ngly, this study was conducted in order to identify the effect of solution pH on the removal efficiency of arsenic and antimony for drinking water usi ng recently developed RO membranes. In this study it was found that the rem ovals of As(V) and Sb(V) are much higher than those of As(III) and Sb(In) o ver all investigated pH levels (pH 3-10). The removal of arsenic compounds was strongly affected by the solution pH, especially As(III), whereas the r emoval of antimony compounds shows no dependence on the solution pH since t he oxidation state of antimony changes from Sb(III) to Sb(V) within very sh ort periods of time. It was demonstrated that pH control for the membrane f eed 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 efficien cy than that of arsenic compounds, regardless of pH changes.