Controlling Cr(VI) in Leather: A Review from Passive Prevention to Stabilization of Chromium Complexes

Abstract

The Cr(VI) content in leather has garnered much attention intoday’s world of increasingly stringent environmental and safetyregulations. In addition, the European Union (EU) countrieshave zero tolerance policies. For chromium-tanned leather, thereis a risk of converting trivalent chromium into the hexavalentform in the processes of production, storage, transportation andusage. In this article, the routes for the occurrence of Cr(VI) arebriefly analyzed, and the various types of Cr(VI) controltechnologies in leather manufacturing processes are reviewed.One control technology is passive PREVENTION, which couldinhibit the hexavalent chromium to some extent through theaddition of antioxidants and reducing agents, but it might notfundamentally solve the hexavalent problem.In contrast, CONSOLIDATION technologies to improve thestabilization of chromium complexes could play critical andresponsible roles to effectively prevent the emergence ofhexavalent chromium in leather. Several proposals are addressedfor the control of Cr(VI) in leather, and CONSOLIDATIONtechnology is determined to be more important thanPREVENTION technology.In addition, a new viewpoint is presented to completely solve theproblem based on the stability of Cr3+ complexes. Taking theamount of Cr(VI) as a quantitative indicator, the mechanismsand key technologies for the effect of specific coordinatingcompounds (ligands) on the stability of Cr3+ to prevent Cr(VI)formation would be recommended for further study toward.