A COMPARATIVE-STUDY OF COMMON METALS SCAVENGING EFFICIENCY FOR AQUEOUS SULFIDE OR SULFITE POLLUTANTS IN SALT SOLUTION

A comparative study was made in order to estimate the feasibility of u sing common metal alloy shavings for low level sulfide or sulfite remo val from salt solution polluted with either pollutant under aerated an d deaerated conditions. Unlike sulfide, sulfite is not considered as a pollutant that deteriorates the copper base alloys, however it is inc luded 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 f or 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 e stimated half-lives of 10 minutes. Generally all the heterogeneous sys tems performed better than the homogeneous reaction. The presence of o xygen 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 th e batch recycle reactor containing the shavings with large recycle rat io was shown to approximate ideal stirred tank reactor. A mechanism fo r protection of copper nickel alloys by the formation of an adherent p rotective layer of hermatite was postulated.