Method of separating and recycling SiO2 and ammonium fluorosilicate from fluorine-containing dust

Abstract

The invention provides a method of separating and recycling SiO2 and ammonium fluorosilicate from fluorine-containing dust, which includes: 1) independently adding two types of fluorine-containing dust, which are sorted according to whiteness of 80%, respectively to different leaching troughs, adding water, circulating washing liquid or crystallization mother liquid for dissolution, wherein the solution is heated during the process with complete stirring, thus leaching the substance; 2) filtering or press-filtering the leached slurry while hot, and separating a leachate and filter residue; 3)adding the leachate into a crystallization kettle for cooling crystallization, and after the substance is completely crystallized, separating the crystal and the crystallization mother liquid; 4) carrying out heat-leaching to the filter residue with the crystallization mother liquid again and performing secondary cooling crystallization; 5) performing multistage countercurrent washing to the filter residue, produced from the material with whiteness being higher than 80%, and drying and crushing the product to obtain SiO2; 6) mixing the crystallization mother liquid and primary concentrated washing liquid of the filter residue, and performing evaporative concentration-cooling crystallization to a part of the solution to obtain the ammonium fluorosilicate.

Description

technical field [0001] The invention relates to a fluorine-containing waste treatment technology in hazardous waste treatment, in particular to a method for separating and recovering silicon dioxide and ammonium fluorosilicate from fluorine-containing ammonium silicate dust after chemical vapor deposition tail gas treatment. Background technique [0002] Chemical vapor deposition technology (Chemical Vapor Deposition, referred to as CVD) is a new technology for the preparation of inorganic materials developed in recent decades. Chemical vapor deposition has been widely used to purify substances, develop new crystals, and deposit various single crystal, polycrystalline or glassy inorganic thin film materials. These materials can be oxides, sulfides, nitrides, carbides, or binary or multi-component interelement compounds, and their physical functions can be precisely controlled by the deposition process of vapor phase doping. At present, the materials prepared by CVD technolo...

AI Technical Summary

Problems solved by technology

[0004] The semiconductor industry produces a large amount of this kind of fluorine-containing ammonium silicate, ammonium fluoride and silica dust every year. The particles of this kind of dust are small, the specific surface area is large and fluffy, and it is easy to form a gel when it meets water, and it is difficult to separate and recover valuable components.

At present, the industry mainly adopts lime neutralization method to remove fluorine for this kind of fluorine-containing dust, but it will produce a large amount of calcium fluoride slag and silica slag, the amount of sludge is large, the treatment cost is high, and it is easy to cause secondary pollution