WASTE MANAGEMENT IN LEATHER INDUSTRY

14 27CHAPTER FOURCHEMICALS USED IN TANNING PROCESSES4.1 Processing ChemicalsA variety of chemicals, from common salts (sodium chloride) to the finefinishing chemicals, are used in Leather sector. About 130 different types ofchemicals are applied in leather manufacturing, depending on the type of rawmaterial and the end product of the industry. These chemicals are divided intofour major classes, described below, as per their use.4.1.1 Pre- Tanning ChemicalsThese chemicals are used to clean and to prepare the skins for the tanningprocesses. These chemicals do not react with the skins’ fiber, therefore are notretained by the skins. These chemicals after performing their respective functionsare discharged with the wastewater.4.1.2 Tanning ChemicalsThese tanning chemicals react with the collagen fibers of the skin and convertthem into leather. As these chemicals react with the fiber, therefore, aconsiderable quantity is retained by the fiber. A Nevertheless, a significantamount remains unused and is discharged with the wastewater. Basic chromesulphate is the tanning chemical, which most widely used in local tanneries. Thisis an expensive chemical and also poses a serious environmental threat. Besidesenvironmental problems, its discharge into wastewater is also a financial loss.Vegetable tanning materials are also used in local tanneries but their use is notcommon as compare to chromium.14