2023 Volume 79 Issue 25 Article ID: 23-25037
Insolubilization of arsenite (As(III)) in water sample was investigated through a combined treatment using ferrate (Fe(VI)) and water treatment sludge (WTS). Arsenate (As(V)) formed by As(III) oxidation with Fe(VI) was successfully insolubilized by coprecipitation with hydroxide of Al derived from WTS suspension, which was acidified with a dilute HCl solution. Whereas As(V) insolubilized with ferrate only or WTS suspension only was resolubilized under alkali or acidic condition, the combined treatment inhibited the resolubilization of As(V) under weakly acidic and alkali conditions. Furthermore, As(V) insolubilized with Fe(VI) only was resolubilized via Fe(III) reduction under the presence of dithionite as a reducing agent. However, the treatment using WTS suspension only or the combined treatment inhibited As resolubilization under the same reducing condition.
These results indicate that the combined treatment using Fe(VI) and WTS suspension could prevent the insolubilized As(V) from being resolubilized even though the environmental conditions such as pH or ORP are changed after application of the treated sample to lands.
