Arsenic sorption to nanoparticulate mackinawite (FeS): An examination of phosphate competition

• A competitive effect of PO43− was examined on sorption of As(V) and As(III) to nanoparticulate FeS.
• PO43− did not affect sorption of either As(V) or As(III) to nanoparticulate FeS at pH 6, 7 and 9.
• XANES spectroscopy indicated the involvement of several As redox transformations and formation of sorbed species.
• Nanoparticulate FeS immobilized 99% As in sulfidic reduced environments, in the presence of PO43−.