Treatment process of waste mortar in the processing course of silicon crystal

Abstract

The invention discloses a treatment process of waste mortar in the processing course of a silicon crystal. Monocrystalline silicon Si is separated from silicon carbide SiC by an electrophoretic separation technology to recycle the monocrystalline silicon Si and the silicon carbide SiC, wherein the monocrystalline silicon Si and the silicon carbide SiC are contained in the waste mortar. The treatment process comprises the following steps of: firstly adding 2-5 vol.% of diluted hydrochloric acid solution to the waste mortar, wherein the volume ratio of the diluted hydrochloric acid solution to the waste mortar is 1.5 to 3; subsiding for 24-48 hours, and then discharging supernatant liquid; adding distilled water, and repeatedly subsiding to discharge the supernatant liquid 2-4 times; adding 60-80 vol.% of the distilled water and 0.1-1 wt.% of dispersing agent acacia, ball-milling for 12-24 hours, and then regulating the pH value of a suspension to 3-3.5; carrying out electrophoretic separation to obtain an anode sediment; adding the distilled water and the acacia to the obtained anode sediment to regulate the pH value of the suspension to 3-3.5, and carrying out the electrophoretic separation to obtain a secondary anode sediment; and repeating the steps three times to obtain the anode sediment by five times.

Description

technical field [0001] The invention relates to a process for treating waste mortar in the process of silicon crystal processing, in particular to a process for separating monocrystalline silicon (Si) and silicon carbide (SiC) in the waste mortar. Background technique [0002] The production of thin-sheet products such as substrates for integrated circuits and solar cell substrates generally adopts multi-wire cutting technology, that is, steel wires are used to drive a mortar composed of silicon carbide abrasives to cut high-purity monocrystalline silicon or polycrystalline silicon rods. Although this kind of mortar can be recycled, as the cutting process progresses, silicon chips and steel chips are continuously mixed into the mortar, which reduces the cutting performance of the mortar and leads to a decrease in the precision of the obtained silicon wafer. Therefore, it is necessary to continuously discharge old waste during the cutting process. Mortar, and add new mortar. ...

AI Technical Summary

Problems solved by technology

However, as a strategic resource, in my country, 95% of the demand for high-purity silicon depends on imports. The main reason is that my country is still unable to process industrial silicon into high-purity polysilicon on a large scale.

The waste cutting mortar is mixed with 6-7wt% high-purity silicon powder, and the cutting loss rate of high-purity silicon rods is as high as 40wt% during the silicon rod cutting process.

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