Method for recycling silicon carbide and co-producing white carbon black from waste mortar for wire cutting

Abstract

The invention discloses a method for recycling silicon carbide and co-producing white carbon black from waste mortar produced by cutting and machining monocrystalline silicon or polysilicon into silicon wafers, which comprises the following steps: utilizing organic and inorganic solvents to dissolve cutting solution molecules in the mortar; removing iron from solid-state sand through mixed acid for acid cleaning and a chelating agent; adding the high-concentration aqueous solution of sodium hydroxide in the solid-state sand so that the aqueous solution of the sodium hydroxide is reacted with silicon in the mortar to produce sodium silicate, and performing filtering to obtain the pure silicon carbide; adding a little amount of high modulus water glass into the aqueous solution of the sodium silicate; and finally performing acid precipitation to separate flocculent sediment out, and drying the flocculent sediment to obtain the white carbon black product, wherein dilute sodium chloride solution can be recycled as a diluent. The method in the invention is simple in process and moderate in reaction conditions, can effectively recycle the silicon carbide, effectively reduce the cost on recycling the waste mortar and preparing the white carbon black by utilizing wastewater, is the practicable technology which can make waste profitable, greatly reduce the discharge of the wastewater and create remarkable economic and social benefits.

Description

technical field [0001] The invention relates to a method for preparing white carbon black and recovering silicon carbide from waste mortar generated during cutting or grinding silicon wafers of monocrystalline silicon or polycrystalline silicon rods. Specifically, the silicon in the waste wire-cut mortar produced in the silicon wafer processing process is used to prepare white carbon black, and the silicon carbide solid micropowder in it is recovered to achieve the purpose of reusing the silicon rod slicing process. Background technique [0002] The scientific name of silica is hydrated silica (mSiO 2 ·nH 2 O), because its microstructure and aggregate morphology are similar to carbon black, and its reinforcing performance is comparable to that of carbon black, it is called white carbon black. Silica has the characteristics of small particle size, large specific surface area, high chemical purity, and good dispersion performance. It is widely used in rubber, coatings, medic...

AI Technical Summary

Problems solved by technology

[0006] (1) During the airflow separation process, the very fine silicon powder will be lost, or efficient separation equipment is required, and the equipment investment is relatively high;

[0007] (2) In the airflow separation process, because the particle size of the silicon powder is relatively small, the specific surface area is relatively large, and the activity is high, so the silicon powder is easy to oxidize in the airflow separation process, and it is difficult to obtain high-purity silicon powder;

[0008](3) When heavy liquid is used for sorting, the viscosity of heavy liquid is relatively high, and the particles of silicon powder are relatively small, so it is easy to form a suspension and it is difficult to achieve stratification; Coupled with the fact that most of them are expensive and toxic, it is difficult to realize industrialization

But there is no effective reasonable recycling of silicon (mass 10%) in the wire cutting waste mortar