Formation of Arsenic Minerals in Aqueous Media During Electrocoagulation using Iron Electrodes

Abstract

Complex solid residuals can form during the electrocoagulation of arsenic from aqueous media based on the characteristics of the electrochemical system and cooccurring processes, such as adsorption, hydrolysis, chemical precipitation, and flotation. Herein, we study the composition and behaviors of solid residuals produced after electrocoagulation with iron electrodes in various solution media at pH 3, 7 and 10. The instrumental analysis including FTIR, XRD and SEM show that different minerals were formed by electrocoagulation depending on the pH of the solution, and they included scorodite (FeAsO 4 ⋅2H 2 O), symplesite (Fe 3 (AsO 4 ) 2 ⋅8H 2 O), and parasymplesite (Fe 3 (AsO 4 ) 2 ⋅8H 2 O) under acidic conditions; scorodite and kaatialaite (Fe(H 2 AsO 4 ) 3 ⋅5H 2 O) under neutral conditions; and scorodite, symplesite, parasymplesite, and schneiderhoehnite (FeFe 3 As 5 O 13 ) under alkaline conditions. The behaviors of solid residues on distilled water and acidic and alkaline solutions show that adsorption and chemical precipitation occurred simultaneously during the electrocoagulation of arsenic in aqueous media in the different reaction media.