| Summary: | The interaction between metal chlorides and electrocoagulation was tested. Precipitation of As(V) was found to be optimal at pH 4.9 using FeCl<sub>2</sub>, 2.6 for FeCl<sub>3</sub>, 3.8 using AlCl<sub>3</sub>, 11.6 using CaCl<sub>2</sub> and 8.6 using MgCl<sub>2</sub>. As(V) removal through electrocoagulation went down as initial pH (pH<sub>i</sub>) of the solution increased. Addition of FeCl<sub>2</sub> increased removal of As(V) at all pH<sub>i</sub> but was not able to achieve full removal at pHi 7. FeCl<sub>3</sub> had a similar effect but a lower Fe(III) concentration of 30 mg/L was not sufficient for full removal at pH<sub>i</sub> 5 either. AlCl<sub>3</sub> addition reduced removal efficiency at pH<sub>i</sub> 3 but removed all or most As(V) through precipitation at pH<sub>i</sub> 5 and 7, with complete removal followed through electrocoagulation. The addition of CaCl<sub>2</sub> and MgCl<sub>2</sub> resulted in nearly identical behavior. Addition of either at pH<sub>i</sub> 3 had no influence, but at pH<sub>i</sub> 5 and 7 caused complete removal to take place.
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