Management of total dissolved solids in tanning process through improved techniques

Pickling, one of the pre-tanning operations in leather processing, carried out for conditioning skins prior to tanning contributes to about 35% total dissolved solids (TDS) in the effluents. Treatment of TDS is a technological challenge. Treatment methodologies to combat TDS such as membrane separation have disadvantages of generating large quantities of solid sludge containing concentrated salts and they also suffer from operational difficulties. In-plant process control is necessary for combating TDS issues. In this paper, two approaches viz., recycle/reuse of pickle liquor for the subsequent batches as well as resorting to pickle free alum-chrome combination tanning systems have been studied. Pickle liquor from the first batch has been successfully recycled for subsequent batches with appropriate replenishments. The use of potash alum for the pfl reduction process has been successfully employed in place of the conventional process. Significant levels of TDS reduction were observed through using both approaches. The strength property and organoleptic property assessments indicate that experimental leathers were comparable with those of leathers processed by the conventional process. It is believed that pickle liquor recycling and pickle free alum chrome combination tanning systems could be gainfully employed to overcome the environmental problems of TDS and chromium problems in the effluent and at the same time effectively obtain economic benefits. (C) 2004 Elsevier Ltd. All rights reserved.