Preparation And Application Of Chrome Tanning Agent From Chrome-Contained Waste

Chrome sludge has been used to prepare regenerated chrome tanning agents by hydrogen peroxide oxidation method, thermal decomposition method and dichromate oxidation method, respectively. The experimental conditions for three oxidation methods are optimized by orthogonal test and single factor test. The tanning properties of regenerated chrome tanning agents are compared with standard chrome tanning agent by tanning. Regenerated chrome tanning agents have been characterized with UV-Vis spectrum, infrared spectroscopy and pH potentiometric titration.The experimental results of orthogonal test and single factor test show that the optimal oxidation conditions of hydrogen peroxide oxidation method are as follows:H2O260%, NaOH10%, temperature90℃, time1h, H2SO420%and ratio of two steps chrome sludge1:7, and the optimal oxidation conditions of dichromate oxidation method are H2SO420%, Na2Cr2O71%.The experimental results of tanning show that the tanning properties of the regenerated chrome tanning agent A and B approach to the ones of standard chrome tanning agent at content of Cr2O3, tensile strength, breaking elongation and tensile strength. The Ts of wet blue can reach100℃.The Ts of the wet blue tanned by regenerated chrome tanning agent can only reach92℃, which has a gap to standard chrome tanning agent. The effect of the Ts of wet blue is the content of Cr(VI) in oxidation process. The more content of Cr(Ⅵ), the higher Ts of wet blue.The characterizations of regenerated chrome tanning agents by UV-Vis spectrum and infrared spectroscopy show that regenerated chrome tanning agent and standard chrome tanning agent have the same organic acid and sulfate ligands; but the concentration and coordination mode are different, and the concentration of organic acid ligands is higher. The analysis of pH potentiometric titration shows that the titration curves of regenerated chrome tanning agents are almost straight lines. So the hydrolysis process of regenerated chrome tanning agents is gentler than that of standard chrome tanning agents.