A method for preparing chrome tanning agent from chrome tanning waste liquor

Abstract

The invention discloses a method for preparing a chrome tanning agent from a waste chrome tanning liquid. The method is characterized by comprising the following steps: collecting the waste chrome tanning liquid after tanning is completed, precipitating chrome by using alkali, and performing plate-frame pressure filtration to obtain chrome cakes; performing acidolysis on the chrome cakes by using sulfuric acid, cooling, filtering to obtain filtrate, adjusting the pH value to 2.0-2.5, separating by using a cation-exchange chromatography, measuring the content of the component chrome, adding corresponding parts of sodium formate and sodium acetate according to the contents of negative and neutral components, dissolving, boiling to concentrate until the final solid content is up to 50%, cooling for one hour, separating by using the cation-exchange chromatography, measuring the content of the component chrome, performing aging reaction for 4-7 days according to the contents of the negative and neutral components until the contents of the negative and neutral components are up to 75-84%, diluting for 6 times with water, adjusting the pH value to be 3.8-4.0, placing to stand for 6 hours until the contents of the negative and neutral components are 40-50%, and the content of a high electric charge component with the valence greater than +4 is 17-22%. The method for preparing the chrome tanning agent from the waste chrome tanning liquid is simple and flexible to operate, high in yield, excellent in property of the tanning agent, and applicable to tanning of first-layer high-class leather and second-layer leather of cattle, sheep, pigs and the like.

Description

technical field [0001] The invention relates to a method for preparing a chrome tanning agent from chrome tanning waste liquor, and belongs to the technical field of heavy metal recycling in the tanning industry. technical background [0002] Chrome tanning is one of the most common tanning processes in the current leather industry. If the conventional chrome tanning process is used, the utilization rate of chromium is only 65-80%, that is, 20-35% of the chromium is not absorbed and fixed by the rawhide and remains in the waste. In the tanning liquid, the concentration of chromium trioxide in the general waste tanning liquid is as high as 2-8g / L. In addition, chromium is also toxic. The toxicity of chromium is mainly reflected by hexavalent chromium. Chromium pollution can cause teratogenicity, gene mutation and carcinogenicity. From the perspective of environmental protection and sustainable development, the harmless, reduction and resource treatment of chrome tanning wast...

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Problems solved by technology

Such as my country's Sichuan University uses small molecule organic ligands and chromium to scientifically prepare, and has developed the KMC series self-alkaliizing masked chrome tanning agent (Li Guoying, Zhang Mingrang. Molecular design and development of KMC series chrome tanning powder [J], Leather Science and Engineering, 1992,2 (1): 13-21); but there are few application studies on the preparation of chrome tanning agent in reclaiming chrome tanning waste liquid alkali precipitation chrome cake, especially the combination of cation exchange chromatography and chrome tanning agent No patent studies have been reported on the combination of capping agents to control the performance of recovered chrome tanning agents