Harmless treatment method of red sludge in after-treatment liquid of cold galvanizing

Abstract

The invention discloses a harmless treatment method of red sludge in an after-treatment liquid of cold galvanizing, which includes following steps: (a) air-drying and demoisturizing the red sludge to obtain dry red sludge or slight-wet red sludge; (b) filling a container with the dried red sludge, compacting the dried red sludge and sealing the container; (c) heating the container in a high-temperature kiln, increasing the temperature to about 950 DEG C, maintaining the temperature for 8-10 h, and naturally decreasing the temperature for 15-17 h after the fire is extinguished; (d) taking out the container from the kiln and naturally cooling the container to obtain a solid substance formed after heating; (e) performing identification to the solid substance formed after heating the dried red sludge, wherein the solid substance is sheet-like (or piece-like) in appearance, is grey-black in color, is about 0.07 times by the volume of the non-heated dried red sludge and is about 0.22 times by the volume of the the non-heated dried red sludge. The main component of the solid substance is useful ferric oxide [Fe2O3] with a less amount of other harmless substances. The harmless treatment method is simple in processes, can effectively solve a problem of secondary pollution to environment due to the red sludge in the after-treatment liquid of cold galvanizing, is beneficial to environment protection, can increase economic benefit of the cold galvanizing industry and can reduce production cost.

Description

technical field [0001] The invention relates to a method for harmless treatment of industrial waste, in particular to a method for harmless treatment of red mud in post-treatment liquid of cold galvanizing. Background technique [0002] In the production of cold galvanizing, castings cleaned by shot blasting need to be pickled and washed for rust removal, and the waste liquid produced is mainly ferrous chloride [FeCl 2 ] and ferric chloride [FeCI 3 ] and the remaining hydrochloric acid [HCl]. For the needs of environmental protection, these waste liquids need to be post-treated according to the current industry standards, that is, adding sodium hydroxide [NaOH] and a small amount of polyaluminum chloride [PAC], ferrous sulfate [FeSO 4 ], polyacrylamide [PAM], defoamer. Sodium hydroxide is neutralized with waste liquid to form iron trihydroxide [Fe(OH) 3 ] and sodium chloride [NaCl] precipitates, polyaluminum chloride and polyacrylamide adsorb ferric hydroxide, making it ...

AI Technical Summary

Problems solved by technology

The red mud discarded without harmless treatment not only pollutes the environment twice, but also the valuable iron trihydroxide cannot be effectively utilized, resulting in a waste of resources

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