TW201313295A - Method for recycling silicon carbide from waste liquid - Google Patents

Abstract

A method for recycling silicon carbide from a waste liquid, comprising steps of: separating a solid content containing silicon powder and silicon carbide powder and a liquid from a waste liquid by filtration; mixing the solid content with water to form a first mixed liquid; centrifugally removing the silicon powder and water from the first mixed liquid to mainly reserve the silicon carbide to obtain a first-stage product; performing at least one sediment separation process on the first-stage product to obtain a second-stage product; adding a sodium hydroxide solution in the second-stage product to react with silicon to obtain sodium metasilicate; removing the sodium metasilicate to obtain a third-stage product; removing sodium hydroxide and water remained in the third-stage product to obtain a purified silicon carbide. Accordingly, it is economic that the method of the invention is capable of effectively recycling and reusing silicon carbide from the waste liquid.

Description

Method for recovering niobium carbide in waste liquid

The present invention relates to waste liquid treatment, and more particularly to a method for recovering tantalum carbide in waste liquid.

In the process of general industrial processes, waste liquids containing solids are often produced. For example, the procedure for cutting bismuth in the photovoltaic industry semiconductor process uses a linear blade and is mixed with diamond or tantalum carbide (commonly known as emery). The cutting fluid cuts the germanium into a germanium wafer at a high speed rotation of the blade, and the fragments and debris generated during the cutting of the germanium block are mixed in the cutting fluid and gradually accumulate (in a twin About 40% of the cutting waste liquid is lost due to the width of the linear blade. As a result, the solid content of the cutting fluid is too high to be used as a waste liquid, and finally it can only be discarded, which is not environmentally friendly and does not conform to the economy. benefit.

Although some practitioners try to remove the solid content in the waste liquid by simply passing the waste liquid through the filter cloth, it is not known that the filter cloth filtration method can separate the more economical value of the carbonized niobium in the solid waste from the waste liquid, and Because the solid content will block the filter cloth, the filtration effect is not good.

It is an object of the present invention to provide a method for recovering niobium carbide in a waste liquid, which can effectively recycle the niobium carbide in the waste liquid.

In order to achieve the above object, the method for recovering niobium carbide in waste liquid provided by the present invention comprises the following steps: (a) separating solid content and liquid in a waste liquid by filtration, the solid content comprising niobium powder and niobium carbide (b) mixing the solid matter with water as a first mixed liquid; (c) removing the tantalum powder and water in the first mixed liquid by centrifugation, and retaining the first of the tantalum carbide powder a stage product; (d) performing at least one sedimentation separation procedure on the first stage product to obtain a second stage product, wherein the sedimentation separation program sequentially comprises the steps of adding water, stirring, standing, and removing the suspension; Adding sodium hydroxide solution to the second stage product, sodium hydroxide reacts with hydrazine to form sodium metadylate and removes it to obtain a third stage product; and (f) residual sodium hydroxide in the third stage product And water is removed to obtain purified niobium carbide.

In order to better understand the features of the present invention, the preferred embodiments are described below and described in conjunction with the drawings.

The first figure is a flow chart of a method for recovering ruthenium carbide in waste liquid according to a preferred embodiment of the present invention. First, in step S11, the solid content and the liquid in the waste liquid are separated by filtration, wherein the solid content comprises tantalum powder and tantalum carbide powder.

In the method of the present embodiment, the waste liquid 53 can be filtered using the apparatus 10 as shown in the second figure. The apparatus 10 mainly includes a filter aid accommodating barrel 20 containing a liquid 23 containing a filter medium 21 such as ruthenium. The agglomerate cutting fluid is connected to the inlet of a plate and frame filter press 40 provided with the filter cloth 41 via a filter medium injection pipe 30, and further, a waste liquid storage tank 50 is passed through a waste. The liquid line 31 is connected to the inlet of the plate and frame filter press 40 provided with the filter cloth 41, and the waste liquid containing tank 50 contains the waste liquid 53 containing the solid matter 51, and the plate and frame type filter press The outlet of the machine 40 is connected to a recovery liquid line 33 and a return line 35 respectively. The recovery liquid line 33 is connected to a recovery liquid storage tank 60, and the return line 35 is connected to the filter medium. Bucket 20. In the following embodiments, the germanium block cutting liquid used in the photovoltaic industry semiconductor process is exemplified, but it is not limited thereto.

With reference to the second and third figures, in the present embodiment, the filtration of the waste liquid 53 mainly passes the liquid 23 containing the filter medium 21 through a filter cloth 41, so that the filter medium 21 is stacked on the surface of the filter cloth 41. A filter layer 43 is formed, and the filter cloth 41 and the filter layer 43 covering the filter cloth 41 form a filter structure 45, and then the waste liquid 53 to be filtered is passed through a stack of filter cloth covered with the filter layer 43. 41, blocking the solid matter 51 in the waste liquid 53 through the filter aid layer 43 and the filter cloth 41 to obtain a relatively clear recovery liquid 61, that is, passing through the filter structure 45 to separate the solid content in the waste liquid 53 Matter 51 and liquid.

The filter aid 21 used in the filtration mode of the present invention may be diatomaceous earth, activated carbon, serpentine powder, ion exchange resin, quartz sand, manganese sand or a mixture thereof. If the waste liquid 53 to be filtered is a crystallization block cutting liquid, the filter medium 21 is preferably activated carbon.

Referring to the second and third figures, before the filtration is started, the clean cutting fluid 23 to which the auxiliary filter material 21 is added is injected into the plate and frame filter press 40 provided with the filter cloth 41 via the filter medium injection line 30. The cutting fluid 23 is passed through the filter cloth 41 and flows back to the filter medium receiving barrel 20 via the return line 35. After a plurality of cycles, the filter material 21 in the cutting fluid 23 is gradually stacked and covered on the filter cloth. The surface of the 41 is formed with the filter layer 43 (preferably having a thickness of not less than 0.8 mm). When the liquid refluxed by the return line 35 gradually becomes a clear liquid, the aforementioned cycle can be stopped and the filtration step of the waste liquid can be started.

When filtering, the waste liquid 53 containing the solid matter 51 is injected into the plate and frame filter press 40 via the waste liquid line 31, and is blocked by the filter cloth 41 covered with the filter layer 43 and blocked by the filter layer 43. The solid matter 51 is effective to filter the solid matter 51 in the waste liquid 53. In particular, in one embodiment of the present invention, the activated carbon powder as the filter aid 21 itself has a plurality of pores, so that not only the gap between the activated carbon powders can intercept the larger particle size of the waste liquid 53. The solid content 51 (mainly bismuth powder and strontium carbide powder), the pores of each activated carbon powder itself can also intercept the solid content 51 having a smaller particle size, and finally, the recovered liquid 61 obtained through the recovery liquid tube The road 33 flows to the recovery liquid storage tank 60.

It will be understood that the filtration method of the method of the present invention is not limited to the filtration of the waste liquid 53 using the apparatus 10 as shown in the second figure, and any filtration apparatus capable of solid/liquid separation is applicable.

Next, in step S12, the solid matter 51 is mixed with water to form a first mixed liquid. Preferably, the volume ratio of water to the solids 51 is at least 1.5:1, and more preferably, the volume ratio of water to the solids 51 is 2:1. After the solid matter 51 is mixed with water, the solid matter 51 is uniformly dispersed in the first mixed liquid to facilitate the separation of the components of the subsequent solid matter 51.

It is to be noted that when the filter medium 21 of the waste liquid 53 is activated carbon, the solid matter 51 after the filtration is doped with activated carbon particles. The activated carbon particles have a particle diameter of about 50 to 200 μm, the crucible has a particle diameter of about 0.6 to 0.8 μm, and the niobium carbide has a particle diameter of about 15 μm. Therefore, in another embodiment of the present invention, before step S12, The method comprises the steps of sieving activated carbon with tantalum powder and tantalum carbide powder. For example, the solid matter 51 is mixed with water and sieved by using a mesh sieve having 300 to 350 mesh, wherein the particle size is small. The tantalum powder and the tantalum carbide powder can pass through the sieve, and the activated carbon having a larger particle size cannot pass through the sieve, thereby separating the activated carbon from the tantalum powder and the tantalum carbide powder.

Next, in step S13, the tantalum powder and water in the first mixed liquid are removed by centrifugation, and the first stage product mainly composed of tantalum carbide powder is retained. The centrifugation step can be carried out in a horizontal centrifuge. Among them, the specific gravity of tantalum powder is about 2.33, and the specific gravity of tantalum carbide powder is about 3.23. When centrifuged, the carbonized tantalum powder with larger specific gravity and larger particle size will be separated into the outer layer and separated by specific gravity and particle size. The small tantalum powder and water remain in the inner layer, so that the first stage product mainly composed of tantalum carbide powder can be separated from the first mixed liquid by centrifugation.

Next, in step S14, the first stage product is subjected to at least one sedimentation separation process to obtain a second stage product, wherein the sedimentation separation process sequentially comprises the steps of adding water, stirring, standing, and removing the suspension. Preferably, the volume ratio of water to the first stage product is at least 1.5:1, preferably 2:1, and the standing time is at least 15 minutes, preferably 20 minutes.

In addition, in the cutting fluid used in the process of cutting the germanium in the photoelectric semiconductor manufacturing process, the solvent usually contains the solvent, and the first stage product obtained by the above filtration and centrifugation steps is carbonized. A trace amount of tantalum powder and solvent remain in addition to the powder. Among them, bismuth powder has a smaller specific gravity and particle size than strontium carbide powder. It is less likely to be precipitated and suspended in the liquid during the static sedimentation process. After the suspension is removed, the second purity of strontium carbide is higher. Stage product.

It can be understood that the purity of the tantalum carbide can be improved by the more sedimentation separation process. In the present embodiment, after the sedimentation separation process of the method of the present invention, the purity of the niobium carbide can reach 96 wt%; after the two-stage sedimentation separation procedure, the purity of the niobium carbide can reach 98 wt%. It should be emphasized that after two or more sedimentation separation procedures, the purity of niobium carbide becomes less obvious. Therefore, it is preferable to carry out only two sedimentation separation procedures to reduce the time and cost of recovering niobium carbide.

Then, in step S15, the sodium hydroxide solution is added to the second stage product, and sodium hydroxide reacts with hydrazine to form sodium bismuth metaphosphate. Because of its small specific gravity, it floats on the liquid surface and can be easily removed. Emulsification reaction with a solvent to generate a gas such as carbon dioxide to the atmosphere, thereby obtaining a third-stage product having a higher purity of niobium carbide.

Further, in step S16, the residual sodium hydroxide and water in the third stage product are removed to obtain purified carbonized ruthenium. In the embodiment, in step S16, dilute hydrochloric acid can be used to neutralize the residual sodium hydroxide acid base, thereby removing the residual sodium hydroxide in the third stage product and adjusting the pH value (preferably pH 6.8). . Alternatively, the third stage product may be rinsed with a large amount of fresh water in step S16 to remove residual sodium hydroxide in the third stage product. After removing the residual sodium hydroxide in the third stage product, the tantalum carbide and water (water produced by acid-base neutralization or water remaining after washing with water) are separated by centrifugation, and then a drying step is performed to leave the tantalum carbide powder. The surface water is removed, that is, the purified niobium carbide is obtained. The centrifugation step can be carried out in a horizontal centrifuge, but is not limited thereto.

Since the partially dried niobium carbide powder will be agglomerated, it is preferable to perform a dispersing step S17 after the drying step, and the agglomerated carbonized niobium can be broken into individual independent niobium carbide crucibles by using the rotating blades. .

After the pulverizing step, a non-sieve grading step S18 may be further performed, and the cerium carbide powder is blown by the air stream, and the cerium carbide powder of different particle sizes is divided into different positions according to the weight thereof, and the cerium carbide powder having a larger particle diameter has The larger the weight will fall at a closer distance, and the smaller particle size of the niobium carbide powder will fall farther away due to the smaller weight.

In this embodiment, three collectors (less or more collectors may be provided) at different distances to collect three sizes of carbonized tantalum, from three collectors in the near distance The particle size of the collected tantalum carbide is greater than 12.4 μm (1200 mesh below), 9.3-12.4 μm (1200 mesh to 1600 mesh), and less than 9.3 μm (1600 mesh or more). The purity of the niobium carbide powder after the dispersion step and the non-sieve classification step can reach 99 wt%, which makes the product more in line with market demand and the product value is also improved.

The method for recovering tantalum carbide in waste liquid is simple and low in cost, and the recovered tantalum carbide has high purity, and can be added again in the cutting liquid of the germanium crystal block as an abrasive material, in addition to avoiding the environment caused by waste liquid. Pollution, combined with the effect of resource recovery, is extremely economical.

The above embodiments are merely exemplary embodiments of the present invention, and are not intended to limit the present invention, and the scope of the present invention is defined by the claims. A person skilled in the art can make various modifications or equivalents to the invention within the spirit and scope of the invention, and such modifications or equivalents are also considered to fall within the scope of the invention.

10. . . Device

20. . . Filter media storage bucket

twenty one. . . Filter media

twenty three. . . liquid

30. . . Filter medium injection line

31. . . Waste pipe

33. . . Recovery line

35. . . Return line

40. . . Plate and frame filter press

41. . . Filter cloth

43. . . Filter layer

45. . . Filter structure

50. . . Waste storage tank

51. . . Solid content

53. . . Waste liquid

60. . . Recycling tank

61. . . Recyclate

S11~S18. . . Steps of the method of the invention

The first figure is a flow chart of a method for recovering bismuth carbide in waste liquid according to a preferred embodiment of the present invention;

Figure 2 is a schematic view of the apparatus used in the filtration mode of the preferred embodiment of the present invention;

The third figure is a schematic view of the filtration mode of the preferred embodiment of the present invention.

S11~S18. . . Steps of the method of the invention

Claims (10)

A method for recovering cerium carbide in waste liquid, comprising the steps of: (a) separating solid content and liquid in a waste liquid by filtration, the solid content comprising strontium powder and strontium carbide powder; (b) The solid content is mixed with water as a first mixed liquid; (c) the tantalum powder and water in the first mixed liquid are removed by centrifugation, and the first stage product mainly composed of tantalum carbide powder is retained; (d) The first stage product is subjected to at least one sedimentation separation process to obtain a second stage product, wherein the sedimentation separation process comprises the steps of adding water, stirring, standing, and removing the suspension; (e) adding a sodium hydroxide solution to In the second stage product, sodium hydroxide reacts with hydrazine to form sodium metadylate and is removed to obtain a third stage product; and (f) the sodium hydroxide and water remaining in the third stage product are removed, and purified. Carbonized bismuth. The method for recovering ruthenium carbide in the waste liquid according to claim 1, wherein in step (a), the solid matter and the liquid in the waste liquid are separated by filtration using a filtration structure. The method for recovering ruthenium carbide in a waste liquid according to claim 2, wherein the filter structure comprises a filter cloth and a filter aid layer. The method for recovering cerium carbide in a waste liquid according to claim 3, wherein the material of the filter layer is diatomaceous earth, activated carbon, serpentine powder, ion exchange resin, quartz sand, manganese sand or a mixture thereof. The method for recovering niobium carbide in the waste liquid according to claim 1, wherein the ratio of the volume of water to the solid content in the step (b) is at least 1.5:1. A method of recovering ruthenium carbide in a waste liquid according to claim 5, wherein a volume ratio of water to the solid content is 2:1. The method of recovering ruthenium carbide in the waste liquid as described in claim 1 is carried out in step (c) by centrifugation in a horizontal centrifuge. The method for recovering ruthenium carbide in the waste liquid according to claim 1, wherein in step (d), the volume ratio of water to the first stage product is at least 1.5:1, and the standing time is at least 15 minutes. The method for recovering niobium carbide in the waste liquid according to claim 1, further comprising a dispersing step after the step (f), dispersing the partially agglomerated tantalum carbide powder. The method for recovering niobium carbide in the waste liquid according to claim 9, further comprising a non-sieve classification step after the dispersing step, blowing the niobium carbide powder by the air current, and collecting the niobium carbide powder of different particle diameters at different positions.