Resource recovery from photographic waste by electro-winning

Abstract

Industries such as mining and industrial minerals, metallurgical, photographic, textile, leather and chemical produce wastewater containing heavy metals that are hazardous to man and the environment. Indiscriminate discharge of these effluents pollutes natural resources and disturbs vital eco systems. On the other hand most heavy metals in these effluents are rare in nature and hence are expensive industrial raw materials. Therefore a sustainable pollution control option for these industries should aim at resource recovery. Successful isolation of heavy metals from wastewaters will not only render such effluents non hazardous but also make waste management an attractive proposition, thus leading to multiple benefits in terms of resource conservation, pollution control and treatment cost savings. Photographic waste effluents arise from X-ray, lithographic and photographic operations. The photosensitive medium used in these operations is an emulsion of fine Ag halide matrix in gelatin. During fixing, the Ag+ is removed by the fixer solution. The developer and bleach solutions also contain the Ag heavy metal. The recovery of Ag" from such wastewater may be done by electro-winning, metallic replacement, evaporation, ion exchange, reverse osmosis and electro-dialysis. However many process parameters of these methods are not readily available and opportunities exist for optimization of methods to improve removal efficiencies. The aim of this research was to investigate the application of electro-winning technique for selective removal of Ag metals from photographic wastewater. The advantages of the application of electro-winning technique are no hazardous sludge generation, isolation of pure elements, no pretreatment requirement and l