Lower adsorption of As(V) at acidic pH (pH < pHPZC) is probably due to the presence of excess H+ ions competing with As(V) for adsorption sites. As surface charge density decreases with an increase in the solution pH (pH > pHPZC), the electrostatic repulsion between the
positively charged As(V) and the surface of adsorbents is lowered,which may result in an increase in the removal % (V) [29].At higher pH (pH > 9.5) values a decrease in removal % were
observed and could be explained by the repulsion between negative charge of the predominant anionic species in solution (H2AsO4−1and HAsO42−) and the negative surface charge of the sorbents[30].