Treatment method for multi-crystalline silicon texturization etching waste liquid

Abstract

The invention relates to a treatment method for multi-crystalline silicon texturization etching waste liquid. The treatment method comprises the following steps: (a) under the stirring condition, adding an alkali metal compound in the waste liquid for reaction till precipitates are not generated any more, and filtering to obtain a first precipitate and first filtrate; (b) under the stirring condition, adding an alkaline earth metal compound in the first filtrate for reaction till precipitates are not generated, and filtering to obtain a second precipitate and second filtrate; (c) conducting condensation crystallization on the second filtrate to obtain a nitrate solid. The treatment method has the advantages that the alkali metal compound is added in the waste liquid for reaction till the precipitates are not generated any more, filtering is conducted, the alkaline earth metal compound is added in the another filtrate, filtering is conducted again, and finally, concentration is conducted, so that fluosilicic acid radical ions and fluorinions in the waste liquid can be removed, a fluosilicate solid, a fluoride salt solid and the nitrate solid can be obtained, and not only can the environment be protected, but also new economic benefits can be generated.

Description

technical field [0001] The invention belongs to the field of sewage treatment and relates to a treatment method for waste liquid, in particular to a treatment method for polysilicon texturing and etching waste liquid. Background technique [0002] Since photovoltaic power generation has no pollution to the environment and is an inexhaustible source of clean energy, the photovoltaic industry is an emerging industry strongly supported by the state and is developing rapidly. However, a large amount of harmful gas, liquid and solid emissions are produced during the manufacturing process of photovoltaic cells, which makes photovoltaics a highly polluting industry. Among the pollution sources of photovoltaic cell production enterprises, the acid waste liquid produced by polysilicon texture etching is a very important part. The waste liquid mainly contains hydrofluoric acid, nitric acid, fluosilicic acid and other components, which cannot be discharged directly. Harmless treatme...

AI Technical Summary

Problems solved by technology

However, during the manufacturing process of photovoltaic cells, a large amount of harmful gas, liquid and solid emissions are produced, which has led to photovoltaics becoming a highly polluting industry

Among the pollution sources of photovoltaic cell production enterprises, the acid waste liquid produced by polysilicon texture etching is a very important part. The waste liquid mainly contains hydrofluoric acid, nitric acid, fluosilicic acid and other components, which cannot be discharged directly. Harmless treatment is a huge expense, which is why many photovoltaic companies discharge waste directly without permission, causing environmental pollution

[0003] At present, there is a recycling method for the polysilicon texturing waste etching solution in the industry. For example, the Chinese invention patent with the publication number CN102534621A has announced the use of titration analysis and nitrate electrode analysis to determine the hydrogen in the etching waste solution. The concentration of hydrofluoric acid and nitric acid can be recycled by adding hydrofluoric acid and nitric acid; The concentration gradually increases, which affects the etching effect. When it increases to a certain extent, the etching solution cannot be recycled and can only be treated as waste liquid. Therefore, this method does not fundamentally solve the problem of etching solution treatment. question

[0004] Another example is the Chinese invention patent whose application number is 200610039980.1, which announces that sodium carbonate or sodium hydroxide is added to the waste liquid for neutralization until the pH reaches 3~3.5, and then calcium carbonate is added to make hydrofluoric acid precipitate in the form of calcium fluoride Precipitate, fluosilicic acid is precipitated in the form of calcium fluosilicate precipitation, filtered, and the filtrate sodium nitrate is concentrated and crystallized; the disadvantage of this method is that calcium fluoride and calcium fluosilicate are precipitated in the form of a mixture, It has no economic value and needs to be disposed of in the form of solid waste, which will generate additional costs