Articles - Leather Technology Magazine Nº74

Formation of hexavalent chromium in leather associated to chromium supply and fat liquoring

Formation of hexavalent chromium in leather associated to chromium supply and fat liquoring

Key words: hexavalent chromium, chrome tanning, fat liquoring, rechroming

ABSTRACT

The growing importance of environmental concepts and consumers’ awareness of the products being used are requiring industries and service companies to adopt a new posture. Given the hazardous or toxic content of the substances that may be used in manufacturing processes, it has become necessary to deepen research on the subject and achieve their technical enhancement. In this context, discussions have emerged regarding the use of chromium as a basic constituent in leather, since it can be oxidized from the trivalent to the hexavalent state with carcinogenic potential and accumulate in the human body. This paper contains a study of the influence of the amount of chrome supplied in leather and the type of fat liquors - both under normal conditions and after accelerated aging - over chrome oxidation. In fat-liquored leathers, which have not undergone an aging process, the presence of hexavalent chromium was found to be below the detection limit in all cases. Aging caused the formation of hexavalent chromium. Sulfited and fish fat liquors showed higher levels of hexavalent chromium formation in aged leather samples, but not in synthetic fat liquor. The concentration of hexavalent chromium did not show significant variations on account of higher chrome supply in tanning, but it increased in chrome retanning.