This paper presents the findings of a study on the efficiency of arsenic removal from source water and artificial freshwater during coagulation with ferric chloride and alum. They found that pH range for arsenic (V) removal with alum was more restricted than with ferric chloride and that arsenic (III) could not be removed from source water by coagulation with alum.
HERING, J.G. ; PEN-YUAN, C. ; WILKIE, J.A. ; ELIMELECH, M. (1997): Arsenic Removal from Drinking Water During Coagulation. In: Journal of Environmental Engineering: Volume 123 , 800-807. URL [Accessed: 14.05.2012]