Recovery of Chromium from Sludge Generated During The Production of Hydrolysate from Chrome Containing Leather Shaving Waste

Abstract

The leather industry generates hazardous chromium-laden sludge as waste during amino acid production from alkaline treated chrome shaving dust. This study presents an optimized sulfuric acid leaching method to recover chromium (Cr) from this sludge, promoting waste valorization and circular economy principles. Key parameters—pH, acid molarity, reaction time, and temperature—were systematically evaluated to maximize Cr recovery while minimizing residual toxicity. Under optimal conditions (pH 3, 0.3 M H₂SO₄, 2 hours, 25°C), 96.5% of total Cr was efficiently extracted, with speciation analysis confirming that recovered Cr existed predominantly as low-toxicity Cr(III) (99.9%), with negligible carcinogenic Cr(VI) (0.1%). The sludge’s initial Cr content was quantified at 5.55 %, and post-treatment residues contained only 0.21% Cr, demonstrating near-complete recovery. This process operates at ambient temperature, eliminating energy-intensive steps and reducing operational costs. By converting hazardous waste into reusable Cr(III), the method mitigates environmental risks associated with landfilling/incineration, reduces reliance on virgin chromium mining, and aligns with UN Sustainable Development Goals (SDGs 6, 12, 13). The study provides a scalable, economically viable solution for sustainable sludge management in the leather industry, with future research recommended for pilot-scale validation and residue upcycling.