ABSTRACT
The need to treat large volumes of concentrated arsenic (As) industrial effluents is challenging. The increasing costs of effluent treatment and disposal, and the risks of contamination related to the long-term stability of the residues are some of the challenges worth to be mentioned. The use of secondary sources of reagents becomes attractive, in particular when there are restrictions in the application, as in the case of As-bearing residues. The present study reports the results of As removal from an industrial solution using and As-bearing hematite as the iron source. Arsenic concentration dropped from 1500 to 5 mg/L by the addition of ferric sulfate and lime in two stages (at pH 4.5 and 8.5-9) in a pilot plant. Ferric sulfate was produced in situ by sulfation of As-bearing hematite, followed by dissolution in water. In the final sludge, As(V) is mainly associated (77-88%) with amorphous and nano crystalline Fe(Al) (hydr)oxides, as as Fe (Al)-As coprecipitates, Ca and Al arsenates or strongly adsorbed (17%) onto these (hydro)oxides.
