A comparative study of common metals scavenging efficiency for aqueous sulfide or sulfite pollutants in salt solution

Abstract

A comparative study was made in order to estimate the feasibility of using common metal alloy shavings for low level sulfide or sulfite removal from salt solution polluted with either pollutant under aerated and deaerated conditions. Unlike sulfide, sulfite is not considered as a pollutant that deteriorates the copper base alloys, however it is included in this study for comparative reasons. Six different metals and alloys were used in the form of shavings. A batch recycle reactor with a large recycle ratio was used for this purpose. It was found that in deaerated solution, mild steel has a superior scavenging efficiency for sulfide and sulfite removal with an estimated sulfide half-life of about sixty minutes. In aerated solution, copper and aluminum have the best efficiency for sulfide and sulfite removal, respectively, with estimated half-lives of 10 minutes. Generally all the heterogeneous systems performed better than the homogeneous reaction. The presence of oxygen can significantly improve the effectiveness of these metals and alloy shavings in removing pollutant. The sulfide and sulfite kinetic reaction was zero order with respect to pollutant concentration and the batch recycle reactor containing the shavings with large recycle ratio was shown to approximate ideal stirred tank reactor. A mechanism for protection of copper nickel alloys by the formation of an adherent protective layer of hermatite was postulated.