Using ashes from incineration of chromium sulphate tanned leather scrap - Part 1: Characterization of ashes and chromium extraction

Abstract

Chromium is the basis of leather manufacture and its extractable reserves are limited in distribution, mainly in South Africa, Zimbabwe and ex-USSR countries. Almost 20% of the metal is used by the chemical industry where one third of it goes into leather production as chromium sulphate tanning agent.(1) The European Union depends on chromium imports. After burning leather scrap-tanned with chromium sulphate-the resulting very rich chromium ashes may present chromium(VI) in such a concentration that it becomes a hazardous waste and needs careful handling.(2,3) Thus, both economic and environmental reasons suggest the use of these ashes. This paper mainly summarizes some of the conclusions of the research carried out during the execution of CRAFT project BRST-CT96-5085, where leather incineration ashes generated by two different pilot combustion systems, respectively a fixed grill incinerator (FGI) and a fluidized bed incinerator (FBI) were characterized and chromium was leached using a mixed pyrometallurgical and hydrometallurgical route as well as a full hydrometallurgical route.