Detanning of Chrome-ladden Collagenous Matrix for Protein Recovery from Tannery Solid Waste

Abstract

Aim: To optimize conditions for maximum recovery of protein from wet blue as large quantities of chromium containing biological solid wastes are generated in the tanning industry which poses environmental hazard. The chromium recovery from this acidic (pH ≃ 3.5) solid waste is necessary for environmental protection and economic reasons. This study therefore focuses on the conditions that facilitate the optimum recovery of protein from the chrome-tanned biological matrix of tannery with minimum protein loss using H2SO4. Methodology: The Chrome-tanned skin (wet blue) specimen before and after different concentrations of acid treatment were characterized for their mechanical property and thermal stability with a view to observe chemical and morphological characteristics changes by Fourier Transform Infra-Red spectroscopy and Scanning Electron Microscopy respectively. The modification in functional group and chemical composition of the samples is correlated with that of the tensile property and thermal decomposition pattern (by Thermo Gravimetric Analysis) and thermal energy (by Differential Scanning Colorimeter) as well. Results: A gradual change in the mechanical properties of the wet blue was observed with respect to increase in acid concentration. As the acid concentration is increased, the loss of Cr is also increased. The total Cr was estimated in the acid treated wet blue samples and a sudden fall in the Cr content of the specimen after 3% acid treatment was observed. 35% of protein loss was observed in 3% acid treated sample and the % of protein loss increased with acid concentration. FTIR results showed that the acid doesn’t aid the conversion of Cr (III) into Cr (VI). Conclusion: The removal of chromium from chrome-tanned skin could be achieved without transforming Cr (III) into highly toxic Cr (VI), by simple acid treatment.