Leather waste--potential threat to human health, and a new technology of its treatment

In this paper, the authors deal with the problem of processing various types of waste generated by leather industry, with special emphasis to chrome-tanned waste. The agent that makes this waste potentially hazardous is hexavalent chromium. Its compounds can have negative effects on human health and some CrVI salts are considered carcinogens. The authors present the risks of spontaneous oxidization of CrIII to CrVI in the open-air dumps as well as the possible risks of wearing bad quality shoes, in which the chromium content is not controlled. There are several ways of handling primary leather waste, but no satisfactory technology has been developed for the secondary waste (manipulation waste, e.g. leather scraps and used leather products). In this contribution, a new three-step hybrid technology of processing manipulation waste is presented and tested under laboratory, pilot-scale and industrial conditions. The filtrate can be used as a good quality NPK fertilizer. The solid product, titanium–chromium sludge, can serve as an inorganic pigment in glass and ceramic industry. Further, the authors propose selective collection of used leather products (e.g. old shoes), the hydrolysable parts of which can be also processed by the new hybrid technology.