Abstract:
Leather tanning industry is one of the high foreign exchange earning industries in Pakistan. A number of big cities in Punjab like Sialkot, Kasur, Gujranwala, and Sheikhupura are famous for this industry. No serious attention has been paid so far towards processing of tannery wastes before leaving them into some nearby water channel. The result is that the out-coming waste is polluting water channels, poisoning vast land areas and adversely affecting the health of local habitants. In tanning industry, sulphide salts are normally used for hair shaving of hides and skins. Sulphide is highly toxic material and has an obnoxious odor. When sulphide is released into some water channel or municipal sewer system, the accumulation of sulphide gases in the pipes causes corrosion and may also release a highly poisonous gas, hydrogen sulphide. Similarly, chromium salts, used as tanning reagents in leather industry, are also considered as water and land pollutants especially when chromium is present in hexavalent state. This work was started to develop a cheap and simple method to cure the sulphide and chromium content of the tannery waste. Model experiments were designed in the laboratory to oxidize sulphide by bubbling air though aquous solution of sulphide. Different catalysis were employed to accelerate the oxidation process and the effects of certain other parameters, like temperature, pressure and mode of air pumping have been checked to investigate the possible aerial oxidation of sulphide contents in tannery wastes. Chromium, usually present as Cr(III) in tannery wastes, was precipitated as chromium hydroxide by increasing pH of the waste using cheaper precipitants and then removed by sedimentation. The separated chromium (III) was precipitated as chromium (III) hydroxide by using cheaper precipitants. The chemical can be recycled in the tannery process.
Page(s):
87-91
DOI:
DOI not available
Published:
Journal: Pakistan Journal of Environmental Science, Volume: 1, Issue: 1, Year: 2001