The Effect of Fe(II), Fe(III), Al(III), Ca(II) and Mg(II) on Electrocoagulation of As(V)

The interaction between metal chlorides and electrocoagulation was tested. Precipitation of As(V) was found to be optimal at pH 4.9 using FeCl2, 2.6 for FeCl3, 3.8 using AlCl3, 11.6 using CaCl2 and 8.6 using MgCl2. As(V) removal through electrocoagulation went down as initial pH (pH(i)) of the solution increased. Addition of FeCl2 increased removal of As(V) at all pH(i) but was not able to achieve full removal at pHi 7. FeCl3 had a similar effect but a lower Fe(III) concentration of 30 mg/L was not sufficient for full removal at pH(i) 5 either. AlCl3 addition reduced removal efficiency at pH(i) 3 but removed all or most As(V) through precipitation at pH(i) 5 and 7, with complete removal followed through electrocoagulation. The addition of CaCl2 and MgCl2 resulted in nearly identical behavior. Addition of either at pH(i) 3 had no influence, but at pH(i) 5 and 7 caused complete removal to take place.