Simultaneous removal of arsenate and fluoride by iron and aluminum binary oxide: Competitive adsorption effects

This study proposes the use of iron and aluminum binary oxide (FeAlOxHy) to achieve the simultaneous removal of arsenate [As(V)] and F, and the competitive adsorption between As(V) and F are investigated. Iron oxyhydroxide (FeOxHy) shows a high removal capability towards As(V) but exhibits little efficacy to remove F in systems where both As(V) and F co-exist or for solutions of fluoride alone. The introduction of aluminum oxyhydroxide (AlOxHy) to FeOxHy within FeAlOxHy enables the removal of F as well as As(V). AlOxHy may simultaneously remove As(V) and F over a wide pH range from 4 to 11; however, the removal of As(V) and F is highly pH dependent and the maximum removal is observed at the weakly acidic pH of 6. The electrostatic force at different pH plays a role, but the dissolution of AlOxHy dominates in the lower removal of As(V) and F by AlOxHy especially at low pH. Furthermore, the removal of As(V) and F by AlOxHy in the co-existing system is lower than that in single pollutant systems due to competitive adsorption effects. The introduction of FeOxHy to AlOxHy significantly alleviates the effect of pH on the removal of As(V) and F by AlOxHy; moreover, the adverse effects of competitive adsorption between As(V) and F are inhibited to a large extent. In comparison to FeOxHy and AlOxHy, FeAlOxHy shows superior performance in achieving the simultaneous removal of As(V) and F and may be used to treat water containing both As and F.

The introduction of iron oxide within FeAlOxHy remarkably alleviated the adverse effects of competitive adsorption between As and fluoride, and this was valuable to remove both As(V) and F in co-existing system.Figure optionsDownload as PowerPoint slideHighlights
► The introduction of AlOxHy to FeOxHy enables the removal of F besides As(V).
► Removal of As(V) and F by AlOxHy occurs, but is pH dependent.
► F removal is inhibited by competitive adsorption, As(V) removal is slightly affected.
► FeAlOxHy may simultaneously remove As(V) and F in a wide pH ranges.
► Competitive adsorption between As(V) and F is alleviated for FeAlOxHy versus AlOxHy.