Hide unhairing: Achieving lower pollution loads, decreased wastewater toxicity and solid waste reduction

Abstract

This study aims to diminish the pollution being discharged into wastewaters through changes in the unhairing process. To this aim, we are replacing a reductive hair degrading process with a process which combines a reductive hair degrading process with an oxidative hair degrading process. Hydrogen peroxide is used to decrease the supply of sulfide as unhairing chemical. As a result, commercially acceptable leather regarding both costs and quality is obtained and significant reductions in the contaminant load of the wastewater being discharged are observed. Results indicate that wastewater conductivity is cut by 26%, suspended solids decrease by 75%, observable sulfide disappears, while the amount of chromium being absorbed by the hides is increased. This leads to considerable savings in the chromium salt offer in hide tanning and, consequently, a decrease in the amount chromium in the wastewater.