Method for preparing basic chromium sulfate tanning liquor by using tanning chromium sludge

Abstract

The invention discloses a method for preparing basic chromium sulfate tanning liquor by using tanning chromium sludge, and solves problems in existing method for preparing tanning liquor by using tanning chromium sludge, such as violent reaction, high operation risk coefficient, incomplete organic compound hydrolysis, poor infiltration of the obtained tanning liquor and complex preparation process and steps. The method comprises the following steps: (1) homogenization; (2) leaching; (3) filter pressing; (4) pressure reduction; and (5) cooling and depressurization. The invention has beneficial effects of mild chemical reaction, easily controlled reaction, capability of completely reducing hexavalent chromium to trivalent chromium, low production cost, no introduction of new impurity, simple processing steps, high purity of the finally obtained chrome tanning liquor, high reduction rate of hexavalent chromium, small consumption amount of ethanol or industrial alcohol, deep hydrolysis of organic small molecules, further enhancement of purity and tanning property of the finally obtained tanning liquor.

Description

technical field [0001] The invention relates to the technical field of leather chemical industry, in particular to a method for preparing basic chromium sulfate tanning liquor by utilizing tanning chrome mud. Background technique [0002] Chrome tanning is a key process in the leather manufacturing process. Since the chromium is not completely absorbed by the collagen fibers during the tanning process, the utilization rate of the chrome tanning solution is only about 70%, and the remaining 30% of the chrome tanning solution is not used. And into the waste water, on the one hand, it has caused serious pollution to the environment, and on the other hand, it has also caused a great waste of resources. [0003] At present, the most common method of treating chrome tanning wastewater is alkali precipitation method, that is, adding a certain amount of alkaline substances to the waste liquid to make chromium ions form chromium hydroxide precipitates, and then filter to obtain preci...

AI Technical Summary

Problems solved by technology

The disadvantage of this method is that (1), the chromium sludge is directly dissolved with sulfuric acid, the reaction is violent, the chromium sludge will sputter, and the operation risk factor is high; (2), the hexavalent chromium is not completely reduced to have tanning properties trivalent chromium; (3) adding sodium red alum, heated and oxidized under normal pressure to further remove organic matter in the chrome sludge, sodium red alum contains hexavalent chromium, which is a strong oxidizing chemical dangerous product, toxic, and poor in safety. Oxidation by heating, incomplete hydrolysis of organic matter, and poor penetration of chrome tanning solution; (4) Finally, it is necessary to use a reducing agent to remove residual red alum sodium, and then use alkaline materials to adjust the pH to obtain regenerated chrome tanning solution. The process steps are cumbersome and cannot be performed in one step The basic chrome sulfate tanning solution is obtained, which also increases the production cost

[0005] In addition, Chinese patent publication number: CN101041500A, publication date: September 26, 2007, discloses a kind of high-efficiency reuse method of chrome tanning waste liquor in tanning, in this method, after chromium mud is dissolved with acid, add chrome mud Medium Cr 2 o 3 A certain weight of oxidizing agent by weight uses the small organic molecules in the chrome sludge as a reducing agent to reduce the oxidizing agent to remove the small organic molecules. The mud will be sputtered, and the operation risk factor is high; (2) Oxidation of small organic molecules under normal pressure takes a long time, and the hydrolysis of small organic molecules is not complete; (3) Excessive oxidants need to be reduced with other reducing agents. The steps are more cumbersome and increase the production cost