Factors influencing chromium recovery from chromium sulphate tanned leather scrap ashes

Abstract

Basic chromium salt is the main tanning reagent used all over the world and it represents one of the most important applications of chromium salts. When leather scrap tanned with chromium sulphate is burned, the respective ashes contain meaningful amounts of chromium, some of it in the hexavalent form. This paper presents some efforts aimed at using the ashes from a fixed grate incinerator (FGI) as a source of chromium for various applications. Two types of ashes were characterised. Several tests with mixtures of alkaline and alkaline earth fluxes followed by hot washing the product were carried out to recover chromium from the ashes. The factors influencing chromium recovery were screened through an experimental design approach and hypothesis testing. Using ashes as pigment for ceramic glazes was also evaluated.