A salt-free pickling chrome tanning technology: Pretreatment with the collective polyoxyethylene diepoxy ether and urotropine

Abstract

Abstract Chromium and chloride are the staple pollutants in chrome tanning process due to the inclusion of common salt and chrome tanning agent. To reduce the environmental impacts of chrome tanning, a salt-free chromium tanning technology has been developed and optimized based on the collective treatment of polyoxyethylene diepoxy ether and urotropine on laboratory as well as on pilot scale. The results indicated that, without the application of sodium chloride, the pelts could be protected from acidic swelling in pickling and chrome tanning by the treatment of polyoxyethylene diepoxy ether, catalyzed by urotropine. Being superior to conventional processes, chrome tanning process could be conducted in the novel pickling conditions and during the course of experimentation the chromium uptake rate was increased to 96.0% from 74.3%, the Cr offering was decreased to 0.53% from 1.16% whereas, the residual Cr concentration in the spent chrome tanning liquors was cut down to 77.1 mg/L from 1083.3 mg/L around. The emissions of chemical oxygen demand and total dissolved solid were also lessened by 15% and 42%. In the course of pilot scale experiments, the organoleptic and mechanical properties were found to be similar with the ones from conventional ones. This investigation provides an improved assimilated method of leather making with the complete elimination of sodium chloride in pickling and proposes a green pollution free alleyway to the leather industry.