PREPARATION AND APPLICATION OF Cr-Fe TANNING AGENT MADE FROM REDUCTION OF DICHROMATE WITH SHAVINGS CONTAINING CHROME AND FERROUS SULPHATE

摘要

In order to minimize chromium consumption and chrome recycling in tanning industry, a Cr-Fe tanning agent was prepared using chrome shavings and Ferrous sulfate as a reducing agent. By carefully observing the effect of Cr/Fe ratios, basicity on the storage stability and tanning properties of preparation, synthesis methods can be selected and improved. It is possible to optimize both the reaction parameters and mixture ratio of the masking agent with Cr~(3+). A series of novel organic Cr-Fe tanning agents were prepared. Formulae were also developed to calculate: 1) the demand quantity of sulfuric acid. 2) the amount of Cr~(3+) and Fe~(3+) in the new Cr-Fe tanning agent and 3) the basicity based upon the determination method and theory of conventional chrome tanning agent. The stability, structure and composition of each prepared tanning agent was investigated by potentiometric titration and ultraviolet-visible spectroscopy. The aging stability, heat stability and physical-mechanical properties of the crust leather tanned by 1) new Cr-Fe tanning agent. 2) conventional chrome tanning agent arid 3) ferric sulfate were compared by subjecting them to various aging tests, for example, hot-air ageing, wet-heat ageing, hot-oxygen, DSC analysis and physico-mechanical. Chromium and nitrogen content of spent tan liquors were measured and compared between the developed Cr-Fe tanning agents and conventional chrome tanning agent by atomic absorption spectrometry and Kjeldahl nitrogen methodology.