Effect Of The Pretreatment Of Chromium-rich Sludge On The Quality Of Chrome Tanning Agent

The method of removing organic impurity from chrome tanning wastewater and chromium-enriched sludge and preparing high-quality chrome tanning agent by eliminating the combination of organic matter and chromium were studied in the paper.The efficiency of removing organic impurity from chrome tanning wastewater was researched by the way of acid enzyme,flocculent and Fenton oxidation.Similarly,the efficiency was researched by the way of separating organism and alkaline hydrolysis in chromium-enriched sludge.Then the chrome tanning agent recovery from chromium sludge would be used to tan suede.The experimental indicators were characterized by XRF,TG,TOC,ICP,SEM and FT-IR to study tanning properties.In this paper,the pretreatment of chrome tanning wastewater and chromium-enriched sludge were worked to get the best condition of removing organic matter.In the pretreatment of chrome tanning wastewater,the tannery waste chrome liquor was used as experimental material,and the results showed that the percentage reduction of TOC in the tannery waste chrome liquor by method of Fenton oxidation,acid enzyme and the flocculent were 68%,65.26% and 22.05% respectively.The method of alkali hydrolysis and extraction were used to remove the organic impurity from the chrome sludge.Firstly,the method of alkali hydrolysis is conducted according to the principle which saponification reaction between alkali and fat produce water soluble substances.The result showed the effect of degrading organic matter was so poor even in the best condition?pH of 11,5h,60? and concentration of 93g/L?that it isn't suitable for industrial production.Then,benzene and chloroform were selected as separating agent,and the organic components in tannery sludge decreased from 40.5% to 15.8% under the best extraction conditions?0.04 M H₂SO₄ ,2 h of stirring,60? in water bath,and 0.05 mL/g separating agent?.Then,the experiment recycling chrome was worked.And the chromium recovery rate reached up to 97.9% under the optimum recovery conditions?1.5 h of stirring,60? in water bath,0.8 M H₂SO₄ and 0.08g/g borax?.After experiment,the chrome tanning agents treated in the work and untreated were applied into the one-bath tanning process of laboratory which was comparable to commercial chromium powder.The crust leathers were assessed for color,grain tightness,fullness and so on by hand and visual examination of experienced tanners.And the application experiments showed that the properties of grain surface and fibers of the tanned leather with commercial chromium powder and chrome tanning agent prepared are nearly the same.