Effects of acetate and nitrate ions on radical and intercalation reactions initiated by CuZn hydroxy double salts

Abstract

The role of hydroxy double salts (HDS) in the effective removal of organic contaminants from water is still controversial among researchers. In this work HDS materials, copper-zinc hydroxy acetate (CuZn-HA), and copper-zinc hydroxy nitrate (CuZn-HN) were produced and treated with aqueous methyl orange (MO), acid red 44 (AR44), or congo red (CR) under ambient conditions. Evidence from dye removal testing, materials analyses, and spin trapping measurements suggested possible three removal processes, dye sorption, intercalation reactions, and ·OH radicals assisted oxidation for suitable matching between dye and HDS material. Such three processes are responsible for the complete color (from the aqueous 500 ppm MO and AR44) and TOC removal achieved by using the CuZn-HN. The structural stability of the dye and HDS chemical composition play a key role on the oxidative reactivity and the intercalation ability of the dye in HDS structure.