1.APPLICATION OF ALGAL BIOMASS FOR THE REMOVAL OF SILVER FROM WASTE By M.F.MANSURI 1 AND K.C.PATEL2

Abstract

Silver, one of the heavy metals, is rare but naturally occurring, often found deposited as a mineral ore in association with other elements. Silver has been used for ornaments and utensils for almost 5000 years and as a precious metal, a monetary medium and a basis of wealth for more than 2000 years. Extensive use of silver has led to serious problems of contamination of terrestrial and aquatic ecosystems. Disposal of silver waste to surface and subsurface waters pose unacceptable health risks. The chief source of silver contamination of water is silver thiosulfate complexes in photographic developing solutions that photofinishers discard directly to sewers. Silver complexed with thiosulfate is difficult to remove from photographic waste. Thus a two stage removal approach was used. Thiosulfate oxidizing bacteria ware initially applied to breakdown the silver thiosulfate complex. The liberated silver is then removed using algal system. Algal Species of Mougeotia, Spirogyra and Chara were employed for this. As much as 70% removal of silver is reported here. These findings can help in the development of a green economic process.
KEY WORD: silver remediation, silver waste, thiosulfate oxidising
bacteria.