Development of coating materials from chrome tanned leather waste for sustainable packaging applications

An enhanced dechroming method was used to extract chromium-free nanoscale gelatin from chrome shaving dust, a hazardous byproduct of leather tanning. The extracted gelatin was subsequently utilized to develop biodegradable coatings for food packaging applications. To ensure compliance with EU/FDA standards for food contact materials, a dechroming process using 10% NaOH was employed, effectively reducing the chromium concentration from 222.8 to 0.04 ppm, with a removal efficiency of 99.98%. Fourier Transform Infrared spectroscopy validated the chemical composition of the gelatin by identifying characteristic functional groups and confirming the absence of chromium. The 75 nm diameter gelatin nanoparticles were incorporated into a biopolymer coating matrix composed of glycerol and chitosan. Spray methods were used to apply these coatings on paper substrates. The Coated with 20%C + CH+Gly (20% gelatin (C), 2% chitosan (CH), and glycerol (Gly) at 9:1:0.1 ratio) sample exhibited significantly enhanced properties. Compared to uncoated paper, tensile strength and burst strength increased by around 250 and 100%, respectively. Water vapor transmission rate and air permeability reduced by 82.51% and 73.15%, respectively. Contact angle measurements indicated a 51.61% increase against organic solvents and a 57.81% enhancement in water repellency. Antimicrobial tests against Escherichia coli and Bacillus subtilis revealed pronounced bacterial inhibition, with zones measuring up to 12.5 mm and 17 mm after 24 h. Cytotoxicity tests on Vero cells confirmed 95% viability, demonstrating the coatings’ biocompatibility and suitability for food-contact use. The biodegradability test showed that by day 25, the Coated with 20%C + CH+Gly sample remained largely intact, but by day 29, 7% weight loss was observed. It lost around 50% of its mass by day 32 and reached complete decomposition by day 40, confirming its environmentally sustainable nature as an alternative to conventional plastics. Dechromed gelatin meets EU/FDA safety limits with chromium level reduced to 0.04 ppm. FTIR and SEM confirmed strong molecular bonding and smooth surface in coated samples. Coated with 20%C + CH+Gly sample showed improved strength, flexibility, and barriers. Coated samples showed strong antimicrobial activity against E. coli and B. subtilis. Coated sample fully biodegraded within 40 days under natural soil conditions.