JP2015533660A - Recycling method of waste abrasive containing ceria - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve efficiency of a regeneration process including a cleaning process while effectively removing impurities contained in a ceria-containing waste abrasive, and to recycle the ceria-containing abrasive during the cleaning process. The present invention relates to a method for regenerating a ceria-containing waste abrasive that can suppress aggregation. SOLUTION: The method for reclaiming the ceria-containing waste abrasive comprises mixing ceria (CeO2) -containing waste sludge and a solubilizer solution containing a fluorine-based compound, and silica (SiO2) contained in the waste sludge. A step of selectively dissolving the impurities containing impurities, and a step of selectively removing the impurities containing silica (SiO2) by passing the ceria-containing waste sludge through a cross-flow filtration system. And drying and firing the washed ceria-containing waste sludge. [Selection] Figure 2

Description

  The present invention relates to a method for recycling a ceria-containing waste abrasive. More specifically, the present invention can improve the efficiency of the regeneration process including the cleaning process while effectively removing impurities contained in the ceria-containing waste abrasive, and the ceria-containing polishing during the cleaning process. The present invention relates to a method for regenerating a ceria-containing waste abrasive that can suppress reaggregation of the material.

In general, TV cathode-ray tubes and glass substrates for TFT-LCDs used in liquid crystal panels are produced with poor surface flatness and roughness during the production process. Difficult to use for glass substrates. In particular, TFT-LCD glass panels used in liquid crystal panels have been studied for various methods to improve the brightness, viewing angle, contrast, etc. of the products, and such characteristics are for TFT-LCDs. It is known that the surface of the glass substrate is affected by many effects. For this reason, companies that produce glass substrates are making efforts to improve the surface of the glass substrate, and various glass substrate abrasives are used. Among them, as general abrasives, abrasives containing ceria (CeO ₂ ) are widely used.

  However, such a ceria-containing abrasive is discarded as waste sludge due to a reduction in polishing efficiency after a glass polishing step for a certain time. This is because the polishing efficiency of the abrasive decreases after the polishing process for a certain time, and agglomeration between the abrasive particles occurs, which increases the possibility of generating a large amount of scratches. In addition, impurities derived from the polishing pad generated during polishing flow into the abrasive slurry, which increases the possibility of occurrence of scratches.

  Accordingly, the abrasive needs to be discarded after being used in the polishing process for a certain period of time, which may reduce process efficiency and economy. As a result, several techniques for reusing the abrasive have been studied.

  In the case of a conventionally known method for reusing and recycling ceria-containing waste abrasives, a glass substrate such as silica contained in ceria-containing waste sludge is used by using a solution of a solution containing hydrofluoric acid or a hydrogen fluoride compound. A method of regenerating the waste sludge and waste abrasives after dissolving impurities derived from them and separating such impurities from the waste sludge by a washing process, followed by a drying and firing process has been mainly used. In particular, in such a conventional regeneration method, a natural sedimentation method, a filtration method, or a method using a decanter or a centrifugal separator is applied in the washing step while washing the waste sludge. Then, the impurities dissolved in the solubilizer solution were solid-liquid separated and removed from the waste sludge.

  In the case of such a solid-liquid separation and washing method, there is a drawback in that a continuous process is impossible, the washing efficiency is lowered, and the yield of the entire regeneration process is lowered. In addition, in the case of the method using the decanter or the centrifuge, agglomeration between abrasive particles contained in the waste sludge occurs in the process of solid-liquid separation by strong centrifugal force, and a redispersion step is separately performed. There was a risk that it would need to be allowed to proceed, or that large particles were generated and scratches were generated due to the use of recycled abrasives. Moreover, even if the redispersion step is performed separately, there are disadvantages such as it is difficult to sufficiently remove the large particles and it is difficult to obtain a desired particle size distribution.

  Even when a conventional filtration method or the like is applied, there is a drawback that powder derived from impurities or the like is easily accumulated in the filter, and it is difficult to remove the powder and the life of the filter is shortened.

  Therefore, the present invention can efficiently improve the regeneration process including the cleaning process in a continuous process while effectively removing impurities contained in the ceria-containing waste abrasive, and the ceria-containing abrasive during the cleaning process. A method for reclaiming a ceria-containing waste abrasive that can suppress reaggregation of the material is provided.

The present invention comprises a step of mixing ceria (CeO ₂ ) -containing waste sludge and a solubilizer solution containing a fluorine-based compound to selectively dissolve silica (SiO ₂ ) -containing impurities contained in the waste sludge. And cleaning the ceria-containing waste sludge through a cross-flow filtration system to selectively remove the silica (SiO ₂ ) -containing impurities; and A method for reclaiming a ceria-containing waste abrasive comprising the steps of drying and firing waste sludge.

  Hereinafter, the reproduction | regeneration method of the ceria containing waste abrasives concerning embodiment of invention, etc. are demonstrated in detail.

According to one embodiment of the present invention, a ceria (CeO ₂ ) -containing waste sludge and a solubilizer solution containing a fluorine compound are mixed to select silica (SiO ₂ ) -containing impurities contained in the waste sludge. Dissolving the ceria-containing waste sludge while passing it through a cross-flow filtration system to selectively remove the silica (SiO ₂ ) -containing impurities; There is provided a method for reclaiming ceria-containing waste abrasive comprising the steps of drying and firing the washed ceria-containing waste sludge.

  In one embodiment of the method for regenerating a ceria-containing waste abrasive, the ceria-containing waste sludge derived from the waste abrasive is dissolved in a predetermined solubilizer solution to dissolve impurities derived from the glass substrate and the like, and this is performed by washing. After removing the impurities, the ceria-containing waste abrasive can be regenerated into a recycled abrasive through drying and firing processes.

  In particular, in the regeneration method according to an embodiment, when the cleaning process proceeds, the waste sludge treated with the solubilizer solution is passed through a cross-flow filtration system (Cross-flow filtration system), and cleaning is performed. Waste sludge and impurities dissolved in the solubilizer solution are solid-liquid separated to remove such impurities. The cross-flow filtration system used at this time includes a predetermined filter in the system, and filters the target solution while the target solution continuously passes through the upper space of the filter in a direction perpendicular to the filter. Called. That is, in such a cross-flow filtration system, the target solution continuously contacts the lower filter while passing through the system, and impurities and the like in the target solution can be filtered and removed by the filter.

  In the regeneration method of one embodiment, the washing process is performed using such a cross-flow filtration system, and thus the waste sludge treated with the dissolving agent solution is continuously passed through the cross-flow filtration system. Can be advanced. Therefore, in the regeneration method of one embodiment, the washing and regeneration steps can be made continuous. In addition, waste sludge treated with the solubilizer solution is in contact with the lower filter while continuously passing through the crossflow filtration system, so that impurities dissolved in the solubilizer solution are filtered, solid-liquid separated and removed, Impurity removal and cleaning efficiency, and the overall regeneration process yield can be further improved.

  Moreover, as a result of our experiments, the agglomeration of the abrasive during the cleaning process can be suppressed by advancing the cleaning process using the cross flow filtration system. It was confirmed that the production of can be greatly reduced. Therefore, the recycled abrasive obtained by the method of one embodiment can exhibit a preferable polishing rate without fear of scratches caused by large particles, and an additional redispersion step, pulverization or classification step for removing large particles There is a significant reduction in need for

  In addition, in the case of the cross-flow filtration system, the powder on the filter surface can be easily removed and reused by back flow to the filter or the like. Therefore, the life of the filter can be increased, and the cleaning and the entire regeneration process including the cleaning can be made more efficient.

  As a result, the regeneration method of one embodiment can efficiently improve the regeneration process including the cleaning process in a continuous process while effectively removing impurities contained in the ceria-containing waste abrasive. Aggregation of the ceria-containing polishing material therein and generation of giant particles can be suppressed.

  Hereinafter, with reference to the drawings, a method for recycling a ceria-containing waste abrasive according to an embodiment will be described in detail according to each stage. As a reference, FIG. 1 is a diagram schematically illustrating an example of a method for regenerating a ceria-containing waste abrasive according to an embodiment, and FIG. 2 is a method for regenerating a ceria-containing waste abrasive according to an embodiment. It is a figure which shows typically the basic principle and structure of a cross-flow filtration system used by A.

First, the ceria-containing waste abrasives and the waste sludge derived therefrom that are subject to the regeneration method of one embodiment are derived from ceria-containing abrasives used for polishing glass substrates in TFT-LCD manufacturing processes and the like. It may be. Accordingly, the ceria-containing waste sludge and the like contain silica (SiO ₂ ) and alumina (Al ₂ O ₃ ) derived from a glass substrate as main impurities. The waste sludge and waste abrasive may contain impurities such as a polishing pad that has been polished and various organic substances derived from a back pad used to support a glass substrate to be polished. ), Chromium (Cr), or other metal component-containing impurities such as nickel (Ni).

  Therefore, in regenerating the ceria-containing waste sludge and the like, a step of removing such silica and alumina, a step of removing other impurities containing metal components derived from the polishing pad, the back pad, etc. Further, it is necessary to proceed with a process for adjusting the surface characteristics, particle size distribution, crystal size, and the like of the ceria-containing abrasive.

Referring to FIG. 1, in the regeneration method according to one embodiment, first, ceria (CeO ₂ ) -containing waste sludge and a solubilizer solution containing a fluorine-based compound are mixed, and silica contained in the waste sludge. The step of selectively dissolving the (SiO ₂ ) -containing impurities can be advanced. At this time, the dissolving agent solution does not substantially dissolve ceria regenerated as an abrasive from the waste sludge (for example, about 0.01 wt% or less of the ceria content contained in the waste sludge, Alternatively, only about 0.001% by weight or less is dissolved) and impurities derived from the glass substrate contained in the waste sludge and waste abrasive, such as silica (SiO ₂ ) and alumina (Al ₂ O ₃ ), are selected. The silica (SiO ₂ ) -containing impurities can be completely or almost completely removed by a subsequent washing step. Thereby, the removal rate of impurities can be increased, the loss of the ceria together with the silica-containing impurities can be suppressed, and the regeneration rate of ceria can be greatly increased.

For this purpose, the solubilizer solution contains hydrofluoric acid or a hydrogen fluoride compound and a strong base of sodium hydroxide or potassium hydroxide, or (a) NaHF ₂ , (NH ₄ ) HF ₂ , or KHF _2. Or (b) a mixture of a predetermined fluorine salt of NaF, (NH ₄ ) F, or KF and a non-hydrofluoric acid such as sulfuric acid, nitric acid, or hydrochloric acid. Can do. In this case, the “non-hydrofluoric acid” refers to hydrochloric acid, sulfuric acid, nitric acid, or the like that does not contain fluorine in its chemical structure. Excluded from the category of “acid acids”. Hereinafter, unless otherwise specified, “non-hydrofluoric acid” is used in the above-mentioned meaning.

  In such a solubilizer solution, the hydrofluoric acid or hydrogen fluoride compound is a component mainly used in a glass etching solution, which also selectively dissolves impurities such as silica and alumina derived from the glass substrate. Can be made. The strong base can also selectively dissolve impurities such as silica derived from the glass substrate.

In another example of the solubilizer solution, (a) a fluorine-based compound such as NaHF ₂ , (NH ₄ ) HF ₂ , or KHF ₂ , or (b) NaF, (NH ₄ ) F, or KF When a mixture of a fluorine salt and a non-hydrofluoric acid is dissolved in a solubilizer solution, the mixture can exhibit an ionization and dissociation state similar to the above-described hydrofluoric acid, and thereby the waste sludge and waste abrasive. The impurities derived from the glass substrate, such as silica (SiO ₂ ) and alumina (Al ₂ O ₃ ), contained in the glass substrate can be selectively dissolved to be completely or almost completely removed by nearly 100%.

  Further, the above-described solubilizer solution does not substantially dissolve ceria regenerated as an abrasive from the waste sludge, and suppresses loss of such ceria together with impurities such as silica, thereby regenerating ceria. The rate can be greatly increased.

  Therefore, when the ceria-containing waste sludge is dispersed and processed in, for example, a solution solution in an aqueous solution using the solubilizer solution, impurities derived from the glass substrate contained in the waste sludge, for example, silica and Alumina is selectively dissolved by the dissolving agent solution and can be separated from the waste sludge.

At this time, in consideration of the content of impurities such as silica or alumina contained in the waste sludge, etc., the fluorine-containing compound, fluorine salt, non-fluorine compound containing hydrofluoric acid or hydrogen fluoride compound in the solubilizer solution is used. The concentration of hydrofluoric acid or strong base can be adjusted appropriately. However, in order to effectively remove impurities such as silica and alumina from waste sludge used for polishing ordinary LCD glass substrates, the hydrofluoric acid, hydrogen fluoride compounds and other compounds such as NaHF ₂ , Fluorine-based compounds including fluorine salts such as NaF and the like are suitably contained in the dissolving agent solution at a concentration of about 0.01 to 20M, alternatively about 0.1 to 15M, alternatively about 1 to 10M. The non-hydrofluoric acid or strong base contained together with the hydrofluoric acid, hydrogen fluoride compound, or fluorine salt is about 0.01 to 20M, or about 0.1 to 15M, It may be included at a concentration of about 1-10M. If the concentration of each component in the solubilizer solution is too low, the removal efficiency of impurities may be reduced, and conversely if it is too high, the amount of raw material used may increase unnecessarily.

  On the other hand, after the ceria-containing waste sludge, particularly the silica-containing impurities contained therein, is dissolved in a predetermined solubilizer solution, such waste sludge is washed to remove the silica-containing impurities from the waste sludge. It can be selectively removed by liquid separation. At this time, since the solubilizer solution does not substantially dissolve ceria regenerated from waste sludge, only the silica-containing impurities selectively dissolved in the solubilizer solution by the washing are selected while reducing the loss rate. It can be removed by solid-liquid separation.

  In particular, in the regeneration method according to an embodiment, the cleaning process is performed while continuously passing the waste sludge treated with the dissolving agent solution through a cross-flow filtration system.

  Referring to FIG. 2, the cross-flow filtration system includes a predetermined filter in the system, and the waste sludge-containing solution continuously passes through the head space of the filter in a direction perpendicular to the filter. And a system in which solid-liquid separation proceeds. In such a system, the waste sludge-containing solution continuously contacts the lower filter while passing through the system, and liquid impurities (for example, silica and alumina) dissolved in the solubilizer solution enter the filter. It can be filtered, solid-liquid separated and removed, and the remaining highly concentrated solution containing waste sludge can be discharged from the system without passing through the filter. In addition, such a highly concentrated solution is circulated and the above-described process is repeated while passing through the cross-flow filtration system and the filter again a plurality of times, for example, about 2 to 10 times.

  By performing the cleaning process using the cross flow filtration system through such a process, the above-described cleaning process can be converted into a continuous process and can be performed more efficiently. In addition, as already described above, the waste sludge-containing solution contacts the lower filter with a large surface area while continuously passing through the system, so that impurities dissolved in the dissolving agent solution are filtered, solid-liquid separated and removed. Impurity removal and cleaning efficiency, and the overall regeneration process yield can be further improved. In addition, the agglomeration of abrasive particles and the generation of giant particles can be suppressed during such a cleaning process.

  On the other hand, in such a cleaning process, the cross-flow filtration system is used to filter particles having a particle size of about 5 μm or less, or about 0.002 to 5 μm. A ceramic material filter such as alumina or zirconia can be included. By using such a filter, it is possible to prevent the abrasive particles in the waste sludge from being filtered and lost by the filter and reduce the regeneration yield, and more effectively and completely eliminate the impurities dissolved in the solution of the solution. The life of the filter can be improved while being removed.

  In addition, the cross-flow filtration system can remove the powder on the filter surface by back flow with respect to the filter, thereby reducing the accumulation of powder on the filter and shortening of the filter life. The cleaning and regeneration process can be made more efficient overall.

  When the above-described cleaning process is performed, the waste sludge and glass substrate-containing impurities such as silica or alumina dissolved in the dissolving agent solution are solid-liquid separated, and impurities can be separated and removed from the waste sludge. it can. At this time, the cleaning process can be performed while adding another cleaning solution such as deionized water, water or other aqueous solvent to the filtration system, but more effective cleaning of impurities dissolved in the solubilizer solution and For removal, the cleaning solution may be an aqueous solvent adjusted to pH 1-4 or pH 10-14. In order to appropriately adjust the pH, an acid or a base can be appropriately dissolved in the water or deionized water and used as a cleaning solution. It can be completely removed.

  And in such a washing | cleaning process, the flux used at the baking process mentioned later may be thrown into the said waste sludge of the reproduction | regeneration object.

  On the other hand, as shown in FIG. 1, after the cleaning process is performed, the cleaned ceria-containing waste sludge can be dried. In such a drying process, the water used in the above-described dissolving agent solution treatment process and the washing process can be dried and removed from the waste sludge from which the impurities have been removed. The sludge may be dried to have a moisture content of about 1 wt% or less, or about 0-1 wt%.

  Such a drying process may be performed using an oven dryer or a CD dryer (Compact Disc dryer). Among them, the CD dryer is a type of a disk type dryer that dries the waste sludge on a rotating disk supplied with heat, and by using such a CD dryer, Aggregation between abrasive particles (for example, ceria particles) can be suppressed, thereby suppressing the formation of giant particles and suppressing the occurrence of scratches when the regenerated ceria-containing abrasive is used. it can. Therefore, the CD dryer can be used more appropriately in the drying process. This is presumed to be because heat can be efficiently and uniformly transferred to the waste sludge by allowing the CD dryer to proceed with drying.

  The drying step is performed in an oven dryer at a temperature of about 100 to 200 ° C. for about 1 to 30 seconds, or on a CD dryer rotating at about 1 to 10 rpm, alternatively about 5 to 10 rpm. The process can proceed at a temperature of 200 ° C. for about 1-30 seconds. If the rotational speed of the CD dryer is excessively low, or if the drying time is excessively long, there is an increased risk of scratches due to aggregation between particles, and conversely the rotational speed is excessively high. When the drying time becomes excessively short, the drying process may not be performed efficiently.

  In contrast, when the drying process proceeds under optimized conditions, the regenerated ceria-containing regenerated abrasive can have a suitable average particle size of about 0.5-3.0 μm, about 6. The generation of large particles of 0 μm or more is suppressed, and not only the risk of scratching is reduced, but also a recycled abrasive with a moisture content of about 1% by weight or less can be easily obtained through efficient drying. Can do.

  On the other hand, after the above-described drying process is performed, as shown in FIG. 1, the presence of a flux containing ammonium salt, alkali metal salt, metal oxide, metal oxyacid, or alkaline earth metal salt, etc. A process of firing the dried waste sludge at about 800 to 1200 ° C, alternatively about 800 to 1000 ° C, alternatively about 800 to 900 ° C may be performed. Through the progress of such a firing process, the surface characteristics and crystal characteristics of the ceria-containing abrasive contained in the waste sludge can be recovered to increase the polishing rate of the recycled abrasive, and various organic substances derived from the pad, etc. The impurities can be removed.

  At this time, the flux has a content of about 1 to 3.0% by weight, alternatively about 1 to 2.0% by weight, alternatively about 1 to 1.5% by weight, based on the weight of waste sludge to be recycled. Can be used in By appropriately adjusting the use content of the flux and the above-described firing temperature, the particle size distribution and the crystal size of the recycled abrasive are about 0.5 to 3.0 μm and about 60 to 90 nm, respectively. While the size is adjusted appropriately, the generation of large particles due to particle aggregation is suppressed, the polishing rate of the recycled abrasive is adjusted to be excellent, and the generation of scratches due to the generation of large particles is suppressed. Is possible.

  In the firing step described above, the flux is an ammonium salt such as ammonium fluoride, ammonium chloride, or ammonium sulfate; an alkali metal salt such as sodium chloride, sodium fluoride, sodium hydroxide, potassium chloride, sodium borate, or barium chloride or an alkali salt. An earth metal salt; a metal oxide such as boron oxide; a metal oxygen acid such as boric acid, or two or more selected from these may be used together. By using such a flux, the surface characteristics or crystal characteristics of the recycled abrasive can be adjusted to a preferred range after the firing step.

  And as already mentioned above, the flux may be introduced and wet-mixed at the previous cleaning stage, or may be dry-mixed immediately before the firing process, preferably wet-mixed at the cleaning stage. . Also, the firing step may proceed for about 1 to 4 hours at the temperature described above.

  By the progress of the above-mentioned optimized firing process, a ceria-containing recycled abrasive having a crystal size of about 60 to 90 nm and an average particle size of about 0.5 to 3.0 μm and with suppressed formation of giant particles is obtained. It is done. If the crystal size or the average grain size is excessively small, the polishing rate of the recycled abrasive material may not be sufficient. Conversely, if the crystal size or the average grain size is excessively large, a polishing process using the recycled abrasive material. In some cases, scratches may be generated, and the grinding and classification process that proceeds as necessary after the firing process may be unnecessarily inefficient. Moreover, when the grinding and classification process is excessively advanced in order to reduce the particle size and crystal size which are too large, not only the efficiency of the regeneration process is greatly reduced, but also the recycled abrasive during the progress of such a grinding process. Rather, the surface characteristics of the recycled abrasive may be deteriorated.

  On the other hand, after the above-described firing step is advanced, if necessary, the pulverization or classification step is additionally performed to reduce the particle size distribution or crystal size of the recycled abrasive or to remove the large particles. Such grinding and classification steps can proceed in a manner well known to those skilled in the art. For example, the pulverization process can be performed using a jet mill or the like, and the classification process uses an air classifier such as a cyclone, a dry classifier, a 2-pole or a 3-pole Tip. It can be carried out using an EJ-ELBO classifier or a sieve for classification.

  According to the above-described regeneration method, impurities derived from a glass substrate or the like are substantially completely effectively removed, the entire regeneration process including the cleaning process is made continuous and efficient, and ceria-containing polishing during the cleaning process. Aggregation of materials and generation of large particles can be suppressed. Therefore, the above-mentioned regeneration method provides a ceria-containing regenerated abrasive that exhibits excellent properties with excellent efficiency and yield and suppresses the formation of large particles. Such ceria-containing recycled abrasives can be used alone or in combination with new abrasives to be reused for polishing glass substrates for LCDs, etc., which can greatly contribute to the improvement of process economy and yield. it can.

  According to the present invention, the cleaning process and the regeneration process including the cleaning process can be made efficient in a continuous process while effectively removing impurities contained in the ceria-containing waste abrasive by the cleaning process and the like. Provided is a method for regenerating a ceria-containing waste abrasive that can suppress agglomeration of the ceria-containing abrasive and generation of giant particles.

It is a figure which shows roughly an example of the reproduction | regeneration method of the ceria containing waste abrasive | polishing material concerning one Embodiment according to each step. It is a figure which shows typically the basic principle and structure of a cross flow filtration system used with the reproduction | regeneration method of the ceria containing waste abrasives of one Embodiment. It is the graph which measured the particle size distribution of the obtained recycled abrasive | polishing material after progressing to the washing | cleaning process in Example 1. FIG. It is the graph which measured the particle size distribution of the obtained recycled abrasive | polishing material after progressing to the washing | cleaning process in Example 2. FIG. It is the graph which measured the particle size distribution of the obtained reproduction | regeneration abrasive | polishing material after progressing to the washing | cleaning process in Example 3. FIG. It is the graph which measured the particle size distribution of the obtained reproduction | regeneration abrasive | polishing material after progressing to the washing | cleaning process in the comparative example 1. It is the graph which measured the particle size distribution of the obtained reproduction | regeneration abrasive | polishing material after progressing to the washing | cleaning process in the comparative example 2. It is the graph which measured the particle size distribution of the obtained reproduction | regeneration abrasive | polishing material after progressing to the washing | cleaning process in the comparative example 3.

  Hereinafter, preferred embodiments will be presented for understanding of the invention. However, the following examples are merely for illustrating the invention, and the invention is not limited thereto.

Example 1 Regeneration of Ceria-Containing Waste Abrasive Material 4 kg of NaHF ₂ was added to a waste sludge aqueous solution containing ceria (CeO ₂ ) -containing waste sludge at a solid content concentration of 15% by weight and dissolved and reacted for 2 hours. Thereafter, the washing process proceeds while the waste sludge-containing solution is continuously passed 8 times through a cross-flow filtration system (product name: Membralox, Pall), and is concentrated to a solid content of 50 wt% each time, and additionally removed. Ion water was replenished. After the progress of such a cleaning step, it was confirmed that the ionic conductivity (IC) value was lowered from 23 mS / cm to 450 μS / cm, and the residual content of silica was confirmed to be 0.05% by weight or less.

Thereafter, using a CD dryer (product name: CD500, Kumsan Technology Industry), the drying process was allowed to proceed for 5 seconds at a temperature of 120 ° C. under rotation of 7 rpm. After the drying process, it was confirmed that the water content of the waste sludge was 1% by weight or less. Subsequently, the dried waste sludge was calcined at 850 ° C. for 2 hours in the presence of 1% by weight of ammonium fluoride added in the above-described washing step (compared to the weight of the waste sludge that was first regenerated). The recycled abrasive material of Example 1 was obtained. Yield: 99%; Total washing time: 3 hours
Example 2 Regeneration of Ceria-Containing Waste Abrasive Material ₂ kg of NaHF ₂ was added to a waste sludge aqueous solution containing ceria (CeO ₂ ) -containing waste sludge at a solid concentration of 15% by weight and dissolved and reacted for 2 hours. Thereafter, the cleaning process proceeds while the waste sludge-containing solution is passed through a cross flow filtration system (product name: Membralox, Pall) 5 times continuously, and is concentrated to a solid content of 50 wt% each time, and additionally removed. Ion water was replenished. After the progress of such a cleaning process, it was confirmed that the ionic conductivity (IC) value decreased from 11 mS / cm to 300 μS / cm, and the residual content of silica was confirmed to be 0.05% by weight or less.

Thereafter, using a CD dryer (product name: CD500, Kumsan Technology Industry), the drying process was allowed to proceed for 5 seconds at a temperature of 120 ° C. under a rotation of 7 rpm. After the drying process, it was confirmed that the water content of the waste sludge was 1% by weight or less. Subsequently, the dried waste sludge was calcined at 850 ° C. for 2 hours in the presence of 1% by weight of ammonium fluoride added in the above-described washing step (compared to the weight of the waste sludge that was first regenerated). The recycled abrasive material of Example 2 was obtained. Yield: 99%; Total washing time: 2 hours
Example 3 Regeneration of Ceria-Containing Waste Abrasive Material 8 kg of NaHF ₂ was added to a waste sludge aqueous solution containing ceria (CeO ₂ ) -containing waste sludge at a solid concentration of 15 wt% and dissolved and reacted for 2 hours. Thereafter, the cleaning process proceeds while the waste sludge-containing solution is continuously passed 10 times through a cross-flow filtration system (product name: Membralox, Pall), and is concentrated to a solid content of 50 wt% each time, and additionally removed. Ion water was replenished. After the progress of such a cleaning step, it was confirmed that the ionic conductivity (IC) value was lowered from 45 mS / cm to 400 μS / cm, and the residual content of silica was confirmed to be 0.05% by weight or less.

Thereafter, using a CD dryer (product name: CD500, Kumsan Technology Industry), the drying process was allowed to proceed for 5 seconds at a temperature of 120 ° C. under rotation of 7 rpm. After the drying process, it was confirmed that the water content of the waste sludge was 1% by weight or less. Subsequently, the dried waste sludge was calcined at 850 ° C. for 2 hours in the presence of 1% by weight of ammonium fluoride added in the above-described washing step (compared to the weight of the waste sludge that was first regenerated). The recycled abrasive material of Example 3 was obtained. Yield: 99%; Total washing time: 5 hours
Comparative Example 1 Regeneration of Ceria-Containing Waste Abrasive Material 4 kg of NaHF ₂ was added to a waste sludge aqueous solution containing ceria (CeO ₂ ) -containing waste sludge at a solid concentration of 15% by weight and dissolved and reacted for 2 hours. Thereafter, the waste sludge-containing solution was added to a decanter (product name: DSD25ML, Tozai Co., Ltd.) to proceed with the washing step, and such washing step was repeated 5 times. In addition, deionized water was additionally supplied to the concentrated solution every time the washing process was performed once. After the progress of such a cleaning step, it was confirmed that the ionic conductivity (IC) value was lowered from 23 mS / cm to 450 μS / cm, and the residual content of silica was confirmed to be 0.05% by weight or less.

Thereafter, the drying and firing steps were performed in the same manner as in Example 1 to obtain a recycled abrasive material of Comparative Example 1. Yield: 70%; Total washing time: 48 hours
Comparative Example 2: Regeneration of Ceria-Containing Waste Abrasive Material 4 kg of NaHF ₂ was added to a waste sludge aqueous solution containing ceria (CeO ₂ ) -containing waste sludge at a solid content concentration of 15 wt% and dissolved and reacted for 2 hours. Thereafter, after the waste sludge-containing solution was precipitated by a natural sedimentation method, the washing process was advanced by a method of separating the supernatant, and such a washing process was repeated five times. In addition, deionized water was additionally supplied to the concentrated solution every time the washing process was performed once. After the progress of such a cleaning process, it was confirmed that the ionic conductivity (IC) value decreased from 23 mS / cm to 1000 μS / cm, but the residual silica content was 0.1% by weight and a part of the silica remained. did.

Thereafter, the drying and firing steps were performed in the same manner as in Example 1 to obtain a recycled abrasive material of Comparative Example 2. Yield: 80%; Total washing time: 40 hours
Comparative Example 3 Regeneration of Ceria-Containing Waste Abrasive Regenerated abrasive of Comparative Example 3 in the same manner as Comparative Example 2 except that 4 kg each of NH ₄ F and hydrogen peroxide were used instead of NaHF ₂ Got. After the cleaning process, it was confirmed that the ionic conductivity (IC) value decreased from 30 mS / cm to 1500 μS / cm. However, the residual silica content was 0.2% by weight and part of the silica remained.

Thereafter, the drying and firing steps were performed in the same manner as in Comparative Example 2 to obtain a recycled abrasive of Comparative Example 3. Yield: 75%; Total washing time: 40 hours
Test example:
1. After proceeding to the cleaning steps of Examples 1 to 3 and Comparative Examples 1 to 3, the particle size distribution of the abrasive was measured with a particle size analyzer (product name: LA950, Horiba), and FIG. 3 to FIG. 5 and FIG. To FIG. Referring to FIGS. 3 to 5 and FIGS. 6 to 8, in Examples 1 to 3, the maximum particles are not so large, whereas in Comparative Examples 1 to 3, the particles are aggregated during the washing process. It was confirmed that large particles exceeding about 10 μm were generated.

  2. Using the regenerated abrasives of Examples 1 to 3 and Comparative Examples 1 to 3, a polished glass surface (250 mm * 220 mm) of glass with a top surface plate pressure of 100 psi and a bottom surface plate speed of 100 rpm for 5 minutes. The bottom surface) was polished, washed twice, and scratch evaluation was performed with a scratch analyzer (equipped with Dr. schenk). As a result of the evaluation, it was confirmed that no scratches identifiable with the naked eye were generated when the recycled abrasives of Examples 1 to 3 were used, and 10,000 scratches were observed when the recycled abrasives of Comparative Examples 1 to 3 were used. It was confirmed that this occurred.

Claims (18)

Mixing ceria (CeO ₂ ) -containing waste sludge with a solubilizer solution containing a fluorine-based compound to selectively dissolve silica (SiO ₂ ) -containing impurities contained in the waste sludge;
Cleaning the ceria-containing waste sludge while passing it through a cross-flow filtration system to selectively remove the silica (SiO ₂ ) -containing impurities;
Drying and firing the washed ceria-containing waste sludge. A method for reclaiming a ceria-containing waste abrasive. The method for regenerating a ceria-containing waste abrasive according to claim 1, wherein the ceria (CeO ₂ ) -containing waste sludge contains silica, alumina, and other metal components as impurities.   2. The method for regenerating a ceria-containing waste abrasive according to claim 1, wherein the solubilizer solution is an aqueous solution containing hydrofluoric acid or a hydrogen fluoride compound and a strong base of sodium hydroxide or potassium hydroxide. . Dissolution agent _{solution, (a) NaHF 2, (} NH 4) HF 2, or comprises a fluorine-based compound of _{KHF 2, (b) NaF,} (NH 4) F or a fluorine salt KF,, non-fluorinated acid The method for regenerating a ceria-containing waste abrasive according to claim 1, wherein the method is an aqueous solution containing a mixture with an acid.   The method for reclaiming a ceria-containing waste abrasive according to claim 1, wherein the solubilizer solution contains a fluorine-based compound at a concentration of 0.01 to 20M.   The method for regenerating a ceria-containing waste abrasive according to claim 3 or 4, wherein the solubilizer solution contains the strong base or the non-hydrofluoric acid at a concentration of 0.01 to 20M.   2. The ceria-containing waste abrasive according to claim 1, wherein the cross-flow filtration system includes an alumina or zirconia filter that filters particles having a particle size of 5 μm or less. Playback method.   The method of reclaiming a ceria-containing waste abrasive according to claim 7, wherein the cross-flow filtration system removes the powder on the filter surface by back flow with respect to the filter.   The method for reclaiming a ceria-containing waste abrasive according to claim 1, wherein the cleaning step proceeds with an aqueous solvent adjusted to pH 1 to 4 or pH 10 to 14.   The method for reclaiming a ceria-containing waste abrasive according to claim 1, wherein the drying step is performed using an oven dryer or a CD dryer (Compact Disc dryer).   2. The ceria-containing waste polishing according to claim 1, wherein the drying process is performed in an oven dryer at a temperature of 100 to 200 ° C. or in a CD dryer at 1 to 10 rpm for 1 to 30 seconds. How to recycle the material.   The firing step is performed by firing the waste sludge at 800 to 900 ° C. in the presence of a flux containing an ammonium salt, an alkali metal salt, a metal oxyacid, a metal oxide, or an alkaline earth metal salt. A method for reclaiming a ceria-containing waste abrasive according to claim 1.   The flux includes at least one selected from the group consisting of ammonium fluoride, ammonium chloride, sodium chloride, sodium fluoride, sodium hydroxide, potassium chloride, ammonium sulfate, boron oxide, barium chloride, boric acid, and sodium borate. The method for reclaiming a ceria-containing waste abrasive according to claim 12, wherein:   The method for reclaiming a ceria-containing waste abrasive according to claim 12, wherein the flux is introduced in a cleaning stage.   The method for reclaiming a ceria-containing waste abrasive according to claim 1, further comprising a step of pulverizing and classifying the ceria-containing regenerated abrasive obtained from the calcined waste sludge after the firing step. .   The grinding step proceeds using a jet-mill, and the classification step is an EJ-ELBO classifier or classifier using an air classifier, a dry classifier, a 2-pole or 3-pole Tip. The method for reclaiming a ceria-containing waste abrasive according to claim 15, wherein the method proceeds using a sieve.   The method for regenerating a ceria-containing waste abrasive according to claim 1, wherein a ceria-containing recycle abrasive having a crystal size of 60 to 90 nm and an average particle size of 0.5 to 3.0 µm is obtained.   2. The method for regenerating ceria-containing waste abrasive according to claim 1, wherein the ceria-containing waste sludge is derived from a ceria-containing abrasive used for polishing a glass substrate.