JP5722601B2 - Silicon cutting waste treatment method - Google Patents

Description

  The present invention relates to a method for treating silicon cutting waste liquid, more specifically, silicon cutting waste liquid discharged by cutting of crystalline silicon in semiconductor element manufacturing or the like is well-liquid separated by simple and inexpensive means, and the silicon cutting waste liquid is The present invention relates to a method for treating silicon cutting waste liquid that enables or easily recovers, recycles, and reuses the contained silicon and other useful components.

  In the manufacturing process of semiconductor elements, solar cells, etc., single crystal or polycrystalline silicon serving as a base material is subjected to cutting, grinding, cutting, and polishing processes (hereinafter collectively referred to as “cutting process” as necessary). However, many of the large amounts of silicon chips generated by these cutting operations are discarded.

  For example, in the manufacture of semiconductor elements, a single crystal silicon ingot as a material is cut into a thin silicon wafer (slicing), the silicon wafer is chamfered and double-sided and polished to a mirror surface, and then silicon. The same circuit is formed in a number of rectangular areas partitioned by dividing lines on the wafer surface, the back surface of the silicon wafer is thinned to a predetermined thickness by grinding (back grinding), and then the semiconductor element is cut by dicing. It is divided and cut into individual pieces (chips), and fine chips of silicon chips generated by a series of cutting processes are processed water (grinding water, cutting water, etc.) The waste liquid contained in the cleaning water (hereinafter referred to in this specification as a result of all or part of the above-described series of cutting processes being discharged. Are discharged from the production process as a.) Called a silicon cutting waste any of waste liquid.

  A large amount of silicon cutting waste generated by these cutting processes and contained in the silicon cutting waste liquid is discharged and discarded. For example, Patent Document 1 states that “when the volume of the silicon ingot is 100%, the silicon ingot is sliced. The volume discarded when forming the base wafer is 20%, the volume discarded when mirror finishing is 20%, and the volume discarded when the wafer back surface is ground to reduce the thickness of the wafer. Is 55%, the volume discarded when the wafer is divided into individual devices is 1%, and 96% of the silicon ingot is discarded before the device is obtained. "

  Disposing a large amount of silicon in this way not only increases the manufacturing cost of semiconductor device products, but it is also a major problem in terms of effective use of valuable resources and the environmental impact of disposal. In addition, when silicon recovered from silicon cutting waste liquid is re-refined, melted and re-solidified into a silicon ingot, it must be reused in semiconductor element manufacturing in terms of purity. Although it is not realistic, there is still room for reuse in the manufacture of semiconductor substrate materials for solar cell substrate materials and TFTs for liquid crystal displays, as well as deoxidizers used in electric furnace insulation and smelting processes in steel production. Various uses for recycling, such as raw materials for silicon DPF used in automobile DPF and abrasive grains, and raw materials for iron silicide, which is attracting attention as an environmental semiconductor, are expected. Kill.

  For this reason, it is strongly required to collect, recycle, and reuse not only silicon cutting waste contained in silicon cutting waste liquid but also other useful components such as abrasive grains and coolant, and various proposals have been made for this purpose. However, the separation and recovery of the above-mentioned useful components, which are prerequisites for regeneration and reuse, involve a heavy burden on complicated processing steps, equipment, and facilities, but sufficient recovery efficiency is not secured to meet commercial profitability. Many of the useful components contained in silicon cutting waste fluid, including silicon cutting waste, are still being discarded, and it cannot be said that a practical way to practice recovery, recycling, and reuse has been opened.

  As described above, the present inventor has the following major factors that impede a large burden on the processing steps, equipment and facilities for the recovery of useful components contained in the silicon cutting waste liquid, and prevent the practical recovery, regeneration and reuse. Think like that.

  In other words, silicon cutting waste liquid contains useful solid components such as silicon cutting scraps and abrasive grains and solid components of impurities such as abrasive pieces of grinding wheels and wire saws and crushed abrasive grains as fine particles. Since solid component particles are colloidally dispersed to form silicon cutting waste liquid as a stable suspension, good solid-liquid separation can be achieved by ordinary means such as natural precipitation of solid components, filtration with a filter or separation membrane, and centrifugation. It is extremely difficult to separate and recover the solid phase, and because hydrogen gas is actively generated in the silicon cutting waste liquid due to the oxidation reaction of the fine particles of silicon cutting waste, separation by distillation is also extremely dangerous. .

  This point has already been pointed out in the prior art. For example, when Patent Document 4 is viewed, even if silicon cutting waste liquid is collected in a sedimentation tank and spontaneous precipitation is performed and pH adjustment is performed, the solid waste is at a level intended for disposal. Although only liquid separation is possible, even when solid-liquid separation is performed with a centrifuge, the liquid phase can be reused by filtration, but the solid phase treatment is extremely difficult and the processing speed is slow and the processing efficiency is poor. Further, even if filtration with a separation membrane is attempted, the fractionation performance has to be made fine for capturing the solid components, so the filtration rate is slow and the throughput cannot be kept up.

  As described above, since effective and good solid-liquid separation at a level that can withstand practical implementation is extremely difficult for silicon cutting waste liquid, this imposes a heavy burden on insufficient solid-liquid separation itself. The process of separating and recovering desired useful solid components such as silicon and abrasive grains from the solid phase recovered by insufficient solid-liquid separation as well as coolant from the liquid phase where the solid phase is not sufficiently separated and recovered The processing steps for separating and recovering useful components such as these have resulted in complicated and cumbersome processing, equipment, and a large burden on facilities, and costs that hinder practical implementation.

  One example of this is the “silicon recovery method” cited in Patent Document 5, and as shown in the flowchart of FIG. In addition to the need for processing steps and complicated and cumbersome processing of each step and a great burden on equipment and facilities, according to Patent Document 2, even if the solid content is washed with an organic solvent, a dispersant is used. It is difficult to remove impurities such as, preventing the improvement of the purity of the silicon that remains in the solid content and recovered, and even if the solid content is thrown into the airflow, the silicon oxide and abrasive grains are not necessarily removed sufficiently. It has been pointed out as a problem that it is difficult to obtain pure silicon. Further, the “method for producing silicon from waste sludge” according to Patent Document 2 also discloses waste sludge from which magnetic materials are separated. Although it is separated into a sedimentation layer of solid impurities mainly composed of silicon dispersion and abrasive grains by center separation, sufficient solid-liquid separation cannot be achieved by centrifugation, so the subsequent processing steps demand a great burden. It is difficult to say that it is simple and efficient before it can withstand actual implementation.

  Conversely, if good solid-liquid separation can be realized easily and inexpensively at the initial stage of processing of silicon cutting waste liquid, not only can the processing load and cost of the solid-liquid separation process itself be greatly reduced, but this In addition, the processing steps for separating and recovering useful components separately from the separated solid phase and liquid phase for recycling and recycling are simple, easy and inexpensive, and all of the silicon cutting waste liquid contains. Since it is also easier to separate and recover useful components than in the past, there is a realistic way to recover, recycle and reuse useful components such as silicon that have been disposed of while being contained in silicon cutting waste liquid. Although it will be greatly developed, as far as the conventional technology is concerned, no meaningful proposal or suggestion regarding such processing can be found.

JP 2010-46763 A JP 2007-33001 A JP 2006-315099 A JP 2005-334992 A JP 2001-278612 A

  The object of the present invention is to solid-liquid-separate the silicon cutting waste liquid in which fine particles of solid components, such as silicon cutting scraps, are dispersed and suspended in a colloidal form by a simple and inexpensive means, and to separate the solid phase It is an object of the present invention to provide a method for treating silicon cutting waste liquid that makes it possible or easy to recover a desired useful component from both the liquid phase and the liquid phase at a low burden and at a low cost and to recycle and reuse.

  As a result of continuous research and experiment, the present inventor has found that these fine particles in silicon cutting waste liquid discharged containing silicon cutting waste and other solid particles generated in the manufacturing process of semiconductor devices and the like. The reason why the refractory material is dispersed and suspended in a colloidal form and refuses easy solid-liquid separation is as follows.

  That is, for example, in slicing processing for cutting a silicon wafer from a silicon ingot in semiconductor element manufacturing, cutting is performed while circulating and supplying slurry consisting of abrasive grains and coolant (cutting oil) to the pressing portion of the wire saw for cutting and the silicon ingot. Therefore, the silicon cutting waste liquid contains waste slurry (abrasive grains and coolant), but the main components of this coolant are diol solvents, their partial ethers and their mixtures, surfactants and pH adjusters. , A diol solvent or surfactant is adsorbed on the surface of the solid component fine particles contained in the silicon cutting waste liquid to form micelles to form colloid micelles, and these colloid micelles repel each other electrically. A stable dispersion state is maintained, preventing solid-liquid separation by spontaneous precipitation of solid phase or filtration. It is believed that there.

  If this is the case, colloidal micelles may be destroyed by a method such as neutralizing the charge on the surface of the solid component fine particles contained in the silicon cutting waste liquid, resulting in the loss of stable dispersion, which is based on electrostatic interactions. Because it is considered that the solid component fine particles come into contact with each other due to intermolecular force and agglomerate to cause secondary agglomeration, so that the solid phase can be agglomerated and precipitated. , Colloidal micelle collapse and solid component fine particles can be agglomerated and the solid phase was agglomerated and precipitated.

As a result of the inventor's research and experiment based on the above knowledge, when the components classified into the following are added to the silicon cutting waste liquid, the good solid-liquid separation required by the inventor is easily secured. I was able to find out. (Hereinafter, these are referred to as “phase separation components” in this specification.)
(1) Polar aprotic solvent consisting of polar molecules having an electric dipole moment in the molecule and not dissociating protons under normal conditions (2) Polar protic solvent consisting of polar molecules but having proton donating properties (3 ) Nonionic flocculants that are nonionic (4) Organic chelating agents (aminocarboxylic acids, polycarboxylic acids, phosphonic acids, etc.), inorganic acids such as hydrochloric acid and sulfuric acid

The present invention relates to the results of the above-mentioned researches and experiments by the present inventors. The invention of claim 1 is based on dispersion of silicon cutting scraps and the like generated by cutting of crystalline silicon in semiconductor element manufacturing or the like. A phase separation component which is a polar aprotic solvent containing any of acetone, methyl ethyl ketone, methyl isobutyl ketone, acetonitrile, 1,4-dioxane, 1,3-dioxolane or tetrahydrofuran is added to the turbid silicon cutting waste liquid to form a solid liquid A method for treating silicon cutting waste liquid, characterized in that separation is performed.

The invention of claim 2 is to separate and recover the solid phase from the silicon cutting waste liquid solid-liquid separated by the phase separation component using a filter press, a belt press, a centrifuge, a pressurized or reduced pressure filter. It is the processing method of the silicon cutting waste liquid of Claim 1 characterized by the above-mentioned.

The invention of claim 3 is characterized in that the silicon cutting waste liquid after separating and recovering the solid phase is separated into a cutting oil raw material and a phase separation solvent and recovered by decompression or atmospheric distillation. It is a processing method of the silicon cutting waste liquid described in Claim 6.

  According to the present invention, it is extremely simple and inexpensive to add a phase separation component to silicon cutting waste liquid in which fine particles of solid component contained such as silicon cutting waste are dispersed and suspended in a colloidal form and solid-liquid separation is difficult. The solid phase can be easily coagulated and settled by simple means, ensuring good solid-liquid separation at the beginning of the treatment process, and reducing the useful components from both the separated solid phase and liquid phase. It is nothing but providing a method for treating silicon cutting waste liquid that makes it possible or easy to collect and recycle and reuse at a low cost.

It is a flowchart which shows an example of the process which isolate | separates and collects the useful component in waste liquid based on the processing method of the silicon cutting waste liquid which concerns on this invention. (Example 1) It is a flowchart which shows the process process which isolate | separates and collects the useful component in a waste liquid by a prior art. (Patent Document 5)

  An embodiment according to the present invention will be described below with reference to FIG.

  The silicon cutting waste liquid to be treated in this embodiment is a single crystal silicon cutting process in semiconductor element manufacturing (slicing from dicing to slicing a silicon wafer from a silicon ingot to dicing and cutting individual semiconductor element pieces forming a circuit. Waste water consisting of processing water (grinding water, cutting water, etc.) and cleaning water discharged including silicon cutting waste generated by grinding, cutting and polishing). The components shown in Table 1 below (As is clear from the table, it is considered that the liquid phase after the treatment according to the present invention in which the contained solid components are sufficiently separated and recovered can be used for reuse). As a phase separation component added to the waste liquid, methyl ethyl ketone, which is one of polar aprotic solvents, was selected.

  In the present embodiment, the silicon cutting waste liquid discharged from the semiconductor element manufacturing process is accommodated in a resin container (capacity 200 L) and transported to the processing site, and the lid of the resin container is opened at the processing site to show hydrogen gas. After a sufficient amount of is released, the desired amount (2000 g) of dark brown waste liquid in which solid component particles are dispersed and suspended in a colloidal form is transferred to a SUS304 processing container (capacity 5 L) to prepare for the addition of phase separation components. It was.

  Thereafter, 2000 g of liquid methyl ethyl ketone selected as a phase separation component was quickly added from the dropping tank to 2000 g of silicon cutting waste liquid prepared in the processing vessel, and the mixture was allowed to stand after rapid stirring using a propeller motor agitator. However, after 5 minutes, agglomeration of solid components in the silicon cutting waste liquid was observed, and after 20 minutes, the solid phase was condensed and precipitated at the bottom of the processing vessel and was well separated from the clear liquid phase.

As described above, the silicon cutting waste liquid in which the solid component is condensed and precipitated at the bottom of the processing vessel and the solid phase and the liquid phase are separated is introduced into the centrifuge, and the bottom discharge centrifuge TD- manufactured by Toko Machine Co., Ltd. is used for 15 minutes. 12 (filter cloth pyrene PS2111, aeration rate of 0.75 ml / cm ² / sec) was centrifuged at 500 G. As a result, 600 g of a clay-like separated cake phase was recovered, and the solid phase was separated. As a result of separately analyzing the liquid phase after the recovery, the total weight of the remaining solid containing silicon was 0.1 g.

  For comparison, 2000 g of silicon cutting waste fluid under the same conditions was introduced into the same centrifuge without adding any phase separation component and centrifuged at 500 G for 15 minutes. About 50 g of a solid phase in a sludge state containing a large amount and excessively wet was separated and recovered, and the total weight of the remaining solids containing silicon was also about 375 g in the analysis result of the liquid phase after the solid phase separation and recovery performed separately. .

  As described above, the results of the present example in which methyl ethyl ketone as a phase separation component was added to silicon cutting waste liquid to coagulate and precipitate the solid phase and the comparative example in which no phase separation component was added were summarized in Table 2 below. As is clear from the above, it is possible to ensure good and sufficient solid-liquid separation at the initial stage of waste liquid treatment only by adding a phase separation component to silicon cutting waste liquid.

  Thus, according to the silicon cutting waste liquid processing method according to the present embodiment, good solid-liquid separation is ensured at the initial stage of the waste liquid treatment without any particular burden on the processing and on the equipment and facilities. As a result, for each of the recovered solid phase and liquid phase, the burden on the subsequent processing steps for separating and recovering useful components separately for use in recycling and recycling is greatly reduced, making the system simple and inexpensive. Since this has been done, the following explains this point.

First, the solid phase treatment process will be described. The solid phase separated and recovered from the silicon cutting waste liquid by the above-described centrifugal separation is silicon, which is a useful component, and abrasive pieces and grinders such as abrasive grains and impurities, and worn pieces and crushing abrasives It is agglomerates of agglomerated particles, etc., and impurities must be removed and useful components separated and recovered separately. However, because it is wet and has a coolant attached, it is easy to handle afterwards. A dry solid phase was obtained using a fluid-type dryer (conical dryer) that indirectly heated the vacuum space where the outside air was shut off, but the recovered solid phase in this example was good. Since it has undergone solid-liquid separation and the adhesion rate of coolant and phase separation components is about 35% by weight, no special consideration or incidental treatment is required, and the coolant composition is diethylene glycol. And because it was easily composition resulting azeotropic such propylene glycol monomethyl ether and water can easily dry, it was possible to achieve a very simple efficient drying process.

  After crushing the massive dry solid phase obtained by the above drying treatment into a powder, according to a known method, for example, separation and removal of wire saw wear pieces (mainly iron) by hydrochloric acid and hydrofluoric acid treatment In addition, the abrasive grains and the crushed abrasive grains were separated by a 5000 G high-speed centrifuge to obtain a water slurry liquid consisting only of a silicon component, and the abrasive grains could be easily separated by a turbo classifier.

  Next, the recovered liquid phase obtained by centrifugation in the present example also has a solid component sufficiently separated, and as a result, an expensive ceramic having an opening of about 0.1 μm that has been conventionally used to remove the residual solid component The process of microfiltration using a filter, etc., does not require consideration of the process of ensuring safety against hydrogen gas caused by residual silicon, so separation and recovery of useful components is extremely simple and does not involve any particular burden. In this example, the recovered liquid phase to which methyl ethyl ketone was added could be easily separated and recovered into the coolant raw material and the phase separation solvent by atmospheric distillation.

  As described above, according to this embodiment, the solid phase is formed by a very simple and inexpensive means of adding methyl ethyl ketone as a phase separation component to silicon cutting waste liquid in which fine particles of a solid component are dispersed and suspended. As it is easy to agglomerate and ensure good solid-liquid separation at the first stage of the treatment process, as is clear from the comparison with the conventional example (Fig. 2), In addition, the process of separating and recovering a desired useful component from the separated solid phase and liquid phase can be easily carried out with low burden and low cost.

  In this example, methyl ethyl ketone was used as a phase separation component, but many polar aprotic solvents can be used, and as long as the present inventors have confirmed through experiments, acetone, methyl Isobutyl ketone, acetonitrile, 1,4-dioxane, 1,3-dioxolane, tetrahydrofuran, N, N-dimethylformamide, N, N-dimethylacetamide, 1,3-dimethyl-2-imidazolidinone, etc. are good solids. A liquid separation resulted.

Further, in the present embodiment and the following examples, all cutting steps in the semiconductor device manufacturing silicon discharged in (slicing, mirror polishing, back grinding, cutting across the dicing, grinding, cutting, a series of processing of grinding) Although the cutting waste liquid was treated, the waste liquid discharged in the silicon cutting process and containing silicon cutting waste is not limited to semiconductor element manufacturing, and is similarly discharged in some cutting processes. Only waste liquid can be treated.

Furthermore, solid-liquid separation means of the silicon cutting waste shown in the present embodiment, the processing of a useful component separation return on recovered solid phase and the liquid phase by solid-liquid separation shows an example, these separation and recovery process There is no place to limit the present invention in terms of means and apparatus for the purpose. For example, the separation means for the silicon cutting waste liquid in which the solid phase is condensed and precipitated by adding a phase separation component is not limited to the centrifuge described in this embodiment. In addition to ensuring easy separation and recovery of the solid and liquid phases using a press, belt press, pressurized or vacuum filter, etc., the use of dryers other than fluid-type dryers is eliminated. In addition, when separating the recovered liquid phase, vacuum distillation may be performed instead of atmospheric distillation in the present embodiment.

The following example shows another example in which the silicon cutting waste liquid treatment method is implemented. The treatment target is silicon cutting waste liquid under the same conditions as in Example 1, and methanol is a polar protic solvent as a phase separation component. When 2500 g of methanol was added to 2000 g of silicon cutting waste liquid and left to stir, the solid phase and the liquid phase were clearly separated after 40 minutes.

  Thereafter, centrifugal separation was performed under the same conditions as in Example 1, and 650 g of a clay-like separated cake phase was recovered. As a result of separately analyzing the liquid phase after separating and recovering the solid phase, residual solids containing silicon were obtained. The total weight of was 0.5 g.

  Methanol is the cheapest solvent and has a low boiling point and lower costs for solid-liquid separation, but the particle size of the aggregated precipitate is slightly finer than that of methyl ethyl ketone, and the amount of liquid required for separation increases. To do.

As mentioned above, the implementation results of the present example in which methanol was added as a phase separation component to silicon cutting waste liquid and the comparative example in which no phase separation component was added are summarized in Table 3 below. In this stage, good and sufficient solid-liquid separation could be secured.

Also in this example , each of the solid phase and liquid phase separated by solid-liquid separation by adding methanol was subjected to the same treatment as in Example 1 to separate and recover each useful component. As a result of ensuring good solid-liquid separation at each stage, as in Example 1, the burden and cost of each processing step could be greatly reduced.

In this example , methanol was used as the phase separation component, but other polar protic solvents such as water and alcohols having 1 to 4 carbon atoms can also be used, resulting in good solid-liquid separation.

The following example also shows another example in which the processing method of the silicon cutting waste liquid according to the present invention is carried out. The processing target is silicon cutting waste liquid under the same conditions as in Example 1, and the nonionic flocculant is used as the phase separation component. Using Diaflock NP800 (made by Diamond Nitrix Co., Ltd.)
60 g of 0.1 wt% aqueous solution of Diafloc NP800 was added to 2000 g of silicon cutting waste liquid, and the mixture was allowed to stand with stirring. After 120 minutes, the solid phase and the liquid phase were clearly separated.

  Thereafter, centrifugation was performed under the same conditions as in Example 1, and 800 g of a clay-like separated cake phase was recovered. As a result of separately analyzing the liquid phase after separating and recovering the solid phase, residual solids containing silicon were obtained. The total weight of was 0.05 g.

  Organic polymer flocculants are characterized by the fact that they have a large agglomeration effect even in a small amount, and the cost for solid-liquid separation can be reduced.This is a very effective means when focusing on the recovery on the liquid phase side The organic polymer flocculant remains on the solid phase side and the process for reuse becomes complicated, and metal contaminants are also drawn together, so it is difficult to obtain high-purity silicon and abrasive grains.

Regarding this example in which the nonionic flocculant was added as a phase separation component to the silicon cutting waste liquid, the results of the comparison with the comparative example in which no phase separation component was added are summarized in Table 4 below. In this stage, good and sufficient solid-liquid separation could be secured.

In this example , each of the solid phase and the liquid phase separated by adding a nonionic flocculant and subjected to solid-liquid separation was treated in the same manner as in Example 1 to separate and recover each useful component. Although it is difficult to obtain high purity for the silicon and abrasive grains recovered as described above , as in Example 1, the burden and cost of each processing step were greatly reduced.

The following example also shows another example in which the silicon cutting waste liquid treatment method according to the present invention is implemented. The processing object is silicon cutting waste liquid under the same conditions as in Example 1, and the phase separation component is ethylenediaminetetraacetic acid. When 20 g of ethylenediaminetetraacetic acid was added to 2000 g of silicon cutting waste liquid and allowed to stand with stirring, the solid phase and the liquid phase were clearly separated after 180 minutes.

  Thereafter, 750 g of a clay-like separated cake phase was recovered by centrifugation under the same conditions as in Example 1, and the liquid phase after separating and recovering the solid phase was analyzed separately. As a result, residual solids containing silicon The total weight of was 0.3 g.

  The effect is almost the same as in the case of the organic polymer-based flocculant. However, since the molecular weight of the phase separation component is small, it can be completely removed by a thermal decomposition method during purification on the solid phase side.

Phase regard to this embodiment with the addition of ethylenediaminetetraacetic acid as a separate component, but compares working results of the comparative example without the addition of phase-separated components in Table 5 below, satisfactory in the beginning stage of effluent treatment, even this example sufficient Solid-liquid separation could be secured.

Also in this example , each of the solid phase and the liquid phase separated by solid-liquid separation by adding methanol was subjected to the same treatment as in Example 1 to separate and recover each useful component. Although it is difficult to obtain high purity for the abrasive grains, the burden and cost of each processing step are greatly reduced as in the case of Example 1 to the previous example.

In this example , ethylenediaminetetraacetic acid was used as a phase separation component, but other organic chelating agents (aminocarboxylic acid type, polyvalent carboxylic acid type, phosphonic acid type, etc.), inorganic acids such as hydrochloric acid and sulfuric acid, etc. Good solid-liquid separation was confirmed.

Claims (3)

Silicon cutting waste generated by the cutting of crystalline silicon in semiconductor device manufacturing is dispersed and suspended in silicon cutting waste liquid containing acetone, methyl ethyl ketone, methyl isobutyl ketone, acetonitrile, 1,4-dioxane, 1,3-dioxolane, or tetrahydrofuran. Adding a phase separation component which is a polar aprotic solvent containing any one to perform solid-liquid separation,
A method for treating silicon cutting waste fluid. Separating and recovering the solid phase from the silicon cutting waste liquid separated into solid and liquid by the phase separation component using a filter press, a belt press, a centrifuge, a pressurized or reduced pressure filter,
The processing method of the silicon cutting waste liquid of Claim 1 characterized by these. Separating and recovering the silicon cutting waste liquid after separating and recovering the solid phase into a raw material of cutting oil and a phase separation solvent by distillation under reduced pressure or atmospheric pressure;
The processing method of the silicon cutting waste liquid of Claim 2 characterized by these.