TW200925112A - Method of recovering rare earth elements - Google Patents

Abstract

The invention provides a method of recovering rare earth elements that is a low-priced process of effectively recovering rare earth oxides from the waste grinding slurry containing rare earth elements. In a first process [I] including the following steps (1)-(5), rare earth oxides are recovered from the waste grinding slurry containing rare earth elements. In a second process [II] of a step (6), ammonium sulfate used in the first process [I] and water are reproduced upon demands and recycled in the process [I]. The process [I] comprises steps of: (1) mixing slurry containing rare earth oxides with a sulfuric acid compound to heat/roast the mixture so that it is dissolved in water to make rare earth element solution; (2) after adjusting a pH value of the rare earth element solution, dissociating insoluble components; (3) adding precipitant into the solution to separate out rare earth carbonate; (4) dissociating the rare earth carbonate from the slurry; and (5) calcining the rare earth carbonate to recover it as rare earth oxides. If the pH regulator of the step (2) and the precipitant of the step (3), which are in the first process [I], are aqueous ammonia and ammonium salt, the process [II] comprises the step of: (6) aqueous ammonium sulfate solution to which the rare earth carbonate has been separated is condensed to recover the aqueous ammonium sulfate solution with high concentration and the water.

Description

200925112 VI. Description of the Invention: [Technical Field] The present invention relates to a method for recovering rare earth oxides from a slurry containing rare earth elements, and more particularly relates to recycling of waste abrasive slurry for reuse as a high precision grinding process An inexpensive process for producing high quality rare earth oxides from raw materials. [Prior Art] A rare earth-based abrasive containing ruthenium and osmium as a main component (hereinafter sometimes referred to as "sludge abrasive") is widely used as a glass substrate for magnetic recording media such as a hard disk, an optical lens, and the like. An abrasive for polishing various glass materials such as a glass substrate of a liquid crystal display or a glass substrate for a photomask. When polishing various glass materials with the above-mentioned polishing agent, the polishing slurry is prepared by dispersing the atomized abrasive in the aqueous dispersion, and the slurry is applied to the glass material of the material to be polished and the polishing pad. Flow between them to perform the grinding operation. ❹ Generally, the abrasive slurry is recycled for use in the polishing process. Upon recovery, the polishing characteristics are gradually lowered due to the accumulation of the ground glass components, so that the polishing efficiency is maintained by intermittently replacing the fresh abrasive materials. The waste grinding of the wrecked iron and the polymer agglutination unit taken out from the grinding process to make it settled ^ ^ Hua Ming or chlorine and the disposal of industrial waste, such as the virtual / ιν " 77 after the wet cake was _ outside, still a large amount of nets, the waste, except

Earth Elements, rare earth elements), etc. Residual rare earths (Rare this does not simply give this to 097137448 200925112

Meaningful. Therefore, it is highly desirable to recover rare earth components from the used waste abrasive slurry and reuse it from the viewpoint of ensuring the recovery of rare earths - stable or efficient use of resources. Cost recovery _. For example, Japanese Patent No. 3,615,943 (Patent Document No. JP-A-2004-175652) (Patent Document 2), Japanese Patent Publication No. (Japanese Patent No. 2003-211356) (Patent Document 3), a method of performing an acid treatment to recover a rare earth element which is a raw material of an abrasive, or a method of Japanese Patent No. 3134189 (Patent Document 4), Japan In the patent publication (Japanese Laid-Open Patent Publication No. 2003-205460) (Patent Document 5), a method of performing alkali treatment to regenerate an abrasive is described. However, any of the conventional methods has problems. That is, (丨) can be recycled. A rare earth element, however, causes a large amount of wastewater containing ammonia or by-produced waste, and (ii) a problem that it is difficult to completely separate the iron component or the aluminum component dissolved in the recovered rare earth element. When the waste abrasive is dissolved in an acid and recovered, if hydrogen carbonate is used as a neutralizing agent, it can be recovered according to the type of rare earth carbonate having good filterability. However, in this method, there is a problem in that a high-priced ammonium hydrogencarbonate or a waste liquid containing a high concentration of ammonia is used to cause a wasteful treatment, which is costly, etc., and the like. Problems of the conventional method 097137448 4 200925112 Point 'Inexpensive process for efficiently recovering high-quality rare earth oxides from waste abrasive aggregates containing rare earth elements. The present inventors have diligently studied to achieve such a purpose. As a result, it was found that (1) in the method using ammonium hydrogencarbonate as a neutralizing agent, since the carbonic acid gas generated by the reaction is separated from (4) water, (10) and NH3, it is recycled and used as a hydrogen peroxide, and (ii) When separating and recovering rare earth carbonates (sometimes referred to as "rare earth carbonates"), the solid-liquid separation is carried out at a specific pH in advance, whereby the impurities such as iron ions dissolved in the coexistence can be selectively precipitated. The temple is removed, and high-purity rare earth carbonates can be easily produced, and the present invention is completed. In addition, 'it was found in the above method' by using waste grinding in the rare earth containing rare earth When sulfur sulphide is added to the slurry, the oxidized rare earth can be made into a soluble rare earth sulphate and the ammonium sulphate solution which is produced as a waste liquid can be recovered, and the above-mentioned reaction can be recovered to constitute a rare earth element recovery which hardly produces by-products. According to the present invention, the present invention has been completed. According to the present invention, the following method for recovering rare earth elements accompanied by reuse of ammonium sulfate (Ammonium Sulfate) is provided. [1] A rare earth A method for recovering a class of elements, characterized in that, in a first step [I] comprising the following step (1M5), the rare earth oxide is recovered from a waste abrasive slurry containing an oxide of a rare earth element, secondarily In the second step [II] including the following step (6), the sulfuric acid used in the first step [I] is recovered, and the recovered ammonium sulfate in 097137448 5 200925112 is reused in the first step [i]. Here, the first step [I] includes: (1) mixing a slurry containing a rare earth oxide (Rare Earth Oxide) with a sulfuric acid compound, heating and roasting to form a barium sulfate (Rare Earth Sulfate), and dissolving it. In water (step; (2) after adjusting the pH of the obtained rare earth sulfate solution to an appropriate condition, separating the insoluble component by solid-liquid separation means (step (2)); ❹ (3) adding a sink to the rare earth sulfate solution Rare earth carbonate (Rare

Earth Carbonate) is carried out (step (3)); (4) separating the rare earth carbonate from the obtained rare earth carbonate-containing slurry (step (4)); and (5) calcining it to form a rare earth oxide, Recovering the generated rare earth element (step (5)); in addition, the second step [II] includes: ❹ (6) the pH adjuster in the step (2) and the precipitating agent in the step (3) contain ammonia water or In the case of the ammonium salt, the ammonium sulfate aqueous solution in which the rare earth carbonate is separated is subjected to the end, the high-concentration ammonium sulfate aqueous solution is separated and recovered, and the recovered ammonium sulfate aqueous solution is reused as a reactant for forming the rare earth sulfate (step (6)). [2] The method described in [1] is carried out in the first step Π with ammonium sulfate and is reused in the first step [I], and the aqueous solution of the rare earth carbonate to ammonium acid is separated. The mixture is concentrated, and a high-concentration ammonium sulfate aqueous solution is recovered from water 097137448 6 200925112, and the water recovered by [3] is reused as a solvent for dissolving rare earth sulfate. If the method of [7].(8)^^^ described in [1] or [2] is further implemented, the second step (11) will be followed by [11] or [2]. In the step (3) of the first step [1] of the description, it is estimated that the ammonium hydrogencarbonate used as a precipitating agent for forming rare earth carbonate is recovered, and reused in the above step (3). Here, the third step [III] includes: ❹ ❹ (), recovering IlIL and ammonia generated by the heating and calcining step into an aqueous solution, and adding a precipitating agent to precipitate a fluorine component, and removing it by filtration, borrowing Recovering the aqueous ammonia solution (step (7)); and (8) subsequently contacting the recovered aqueous ammonia solution with the carbonic acid gas generated in the pH adjusting step, the rare earth carbonate crystallization step and the calcining step to form a solution of carbonic acid nitrogen Or a slurry, and the obtained solution or slurry of ammonium hydrogencarbonate is reused in the crystallization step as a precipitant for forming rare earth carbonate (step (8)). [4] As described in [丨] or [2] The method wherein the sulfuric acid compound of the step (1) is ammonium sulfate or hydrogen sulfate. [5] The method described in [丨] or [2] wherein the step ( The calcination temperature is 300 ° C or higher. [6] The method described in [丨] or [2], wherein the pH condition of the step (2) is 4-7, 097137448 7 200925112 pH adjuster is a soluble alkali metal [7] The method according to [1] or [2] wherein the solid-liquid separation means of the insoluble component in the step (2) is carried out by filtration. [8] - such as [ The method according to [1], wherein the precipitating agent of the step (3) is an ammonium salt, a metal carbonate, a carbonate of a soil-based metal, a metal hydrogencarbonate Q or an alkaline earth metal carbonate. [9] The method according to [1] or [2] wherein the precipitating agent of the step (3) is ammonium hydrogencarbonate. [10] such as [1], [2] or [ 8) The method of the method of the present invention, wherein the form of the precipitant added in the step [3] is a solid, a solution or a slurry. [11] The method according to [1] or [2], wherein, in the step (4) The produced rare earth carbonate is filtered, washed, separated, and purified. [12] The method according to [1] or [2] wherein the calcination in the step (5) is carried out in an air atmosphere at a temperature of 300-1200 ° C. [ [13] The method according to [1] or [2], wherein the concentration separation in the step (6) is a distillation or evaporation of the 097137448 200925112. [14] The method according to [1] or [2], wherein the step ( 7) The precipitating agent is a hydroxide I. [15] The method according to [1] or [2] wherein, in the step (8), the contact temperature is 10-40... 〇[16] as [ The method according to [1], wherein the concentration of the ammonium hydrogencarbonate in the step (8) is 5 to 25% by mass, and the form is a solution or a slurry. [17] A method for recovering a rare earth element, wherein the abrasive is used for polishing, and the rare earth element is recovered by the method described in any one of [1] to [16]. The rare earth element is reused as an abrasive raw material. [Embodiment] Hereinafter, the present invention will be described in detail with reference to the drawings. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a flow chart showing the steps of recovering rare earth elements including a recovery step of ammonium hydrogencarbonate and a recovery step of ammonium sulfate or the like which is characterized by the present invention. Here, the waste abrasive slurry 10 is a starting slurry for recycling treatment. (Waste Abrasive Slurry) In the waste abrasive slurry 10, in addition to the main component of the rare earth oxide (Rare Earth 097137448 9 200925112

Oxide), other than Rare Earth Fluoride, is a mixture of ground glass materials, ground glass, enamel fiber, and other foreign matter. The composition of the waste abrasive slurry 10 varies depending on the process conditions used, but is usually discharged from the grinding step 9 in a state of about 5 to 50% by weight of the solid content. The composition is the conversion amount of the rare earth oxide based on the dry product. TRE0 (= (total bauxite oxide mass / total oxide mass) χ 100)) is 82 mass% (in which about 25 is a gasified rare earth component) The crushed compound is about 5 ❹% by mass of the aluminum compound or the iron compound is about 1% by mass, and other foreign materials such as glass frit or mat fiber are mixed. The waste abrasive slurry 1 is in the polishing step 9, and the abrasive slurry which is recycled while being recycled is finally condensed by gravity sedimentation to prepare a gasified rare earth D conversion (T_(Total) Rare Earth Oxide)) is a slurry of about 3% by mass. When the concentrate is concentrated by the gravity sedimentation method, the waste slurry may be separately used, but the commercially available polymer flocculant may be used to carry out the sedimentation more effectively. This becomes the starting material for the spent abrasive slurry treated by step (1). (First Step [I]) The first step [I] includes the following steps (1) to (5). (Step (1)) (Transfer the rare earth element in the waste grinding (4) material to obtain a rare earth solution 097137448 200925112 First, a waste abrasive polymerization material is used in the reaction vessel, and a certain amount of sulfur is added thereto. The compound (4) (hereinafter sometimes referred to as "ammonium sulfate or the like") 20 is used as a reaction reagent, and is mixed under mixing. Thereafter, it is formed into a sheet (1) in a drying step 33 and a calcination step 35. Waste abrasives. ❹ • The shape should be qualified, and there is no limit. It is more suitable for the type of sulphuric acid compound which has at least the means of introduction of waste abrasives, ammonium sulfate, etc. The amount of addition is about 40 parts, 60 parts, preferably about 5 parts, relative to the waste abrasive material (P(4). If the amount is less than 40 parts, the insoluble content of the rare earth element is increased, and If more than 6 parts are added, the above effects cannot be exerted, and it is not preferable to increase the amount of the wasted drug. Further, as the sulfuric acid compound, hydrogen sulfate can be used in addition to sulfuric acid. The mixed slurry can be I [transfer to the domain step 35 However, if it is considered that the device brain or the like is heated at a temperature, it is preferable to perform drying in advance = water. The spear is not particularly limited as a drying device, and a box drier, a dryer, and a vacuum drying H can be applied. If any of the Hi degrees is preferably (9) _25 generations ^ particularly good is 90-20 (TC. If the drying temperature is lower than _, it is not good in terms of drying efficiency, and 'if it exceeds 25 (rc, it promotes sulfuric acid money) Decomposition, considering the rot of the device, the drying performed in advance becomes meaningless. Next, the mixed waste abrasive or sheet is heated and fired 097137448 200925112 35, whereby the rare earth can be used. > The apparatus for heating the L-fired 35 is not particularly limited, and a general-purpose calcining furnace such as a box furnace, a rotary furnace, or a tunnel furnace can be applied, and in the steps (7) and (8) described later, the lightening step is performed. Since ammonia gas reproduces hydrogencarbonate, it is preferable to provide an apparatus such as an exhaust gas absorption tank as a gas generated by absorption.

❹ If the temperature of the heated simmering 35 is such that the above reaction can form rare earth sulphate 4 〇, there is no special mosquito, preferably in the range of .1 ° ° C, especially preferably in the range of c less than 300 c, then the rare earth sulfate The formation reaction does not proceed smoothly: 3⁄4 over 1000 C' is the excess temperature required for the reaction, and is not good from the viewpoint of energy efficiency. Next, the rare earth sulfate 4(4) produced by heat-burning 35 is heated to a reaction barn (dissolving device), and water 43 is added to dissolve 45. The reaction container is not particularly limited, and is preferably a stirred tank type including at least a stirring means, a heating means, and a means for introducing rare earth sulfate. When the next step (2) (ph adjustment step) is carried out by the same apparatus, it is preferable to provide the introduction means of the pH adjuster and the carbonic acid gas recovery apparatus which will be described later in the step (2). The amount of water added is preferably from 2,000 to 10,000 parts, particularly preferably from 3,000 to 9000 parts, based on 1 part by weight of the rare earth sulfate. When the dissolution of the rare earth sulfate to water is poor, the solution can be promoted by adding a small amount of sulfuric acid or heating a solution containing the insoluble sulfuric acid rare earth. Further, sulfuric acid addition or solution heating may be combined. The amount of sulfuric acid added at this time is not particularly limited, but is preferably 1-2 parts by weight with respect to 100 parts of rare earth sulfate, and 5-10 parts by 097137448 12 200925112. The heating temperature is preferably 40-8 (TC, particularly preferably 5 〇 to 7 〇 ° C. When the dissolution of the rare earth sulfate 45 is completed, an acidic aqueous solution (hereinafter sometimes referred to as "acid solution") is obtained. 2)) (Step of separating Si, A, Fe, and insoluble from the acidic solution (slurry) of the rare earth element) 'In the above acidic solution (acidic slurry) of the end step (1), adding soluble cesium The alkali component is used as a pH adjuster 50' to adjust pH53 to increase the pH, thereby selectively analyzing only dissolved ceria (Si), aluminum (A1), and iron (Fe) into a residue ( Or the solid does not require a component. 63. As a pH condition for pH adjustment, it is preferably controlled to a pH of 4-7, more preferably a range of PH5-6. The pH is preferably 5. 5. If the pH is less than 4, the components of Si, Ai, and p are When the amount exceeds pH 7, the re-dissolution of the Al Si component or the precipitation of the rare earth element occurs, which is not preferable. The soluble alkali component of the pH adjuster 50 is not particularly limited. This can be applied to the detection of metal salts, alkaline earth metal salts, salt or ammonia (water), etc. From the viewpoint of the filterability of the precipitate, it is preferred to use a carbonated member such as NaHC〇3, NazCO3, NIhHCO3, etc. In the step (6) described later, when the waste liquid is recovered, it is particularly preferable to use ammonia water or Further, in the case where the carbonate solution is added to the acidic slurry as the > agent 50, 'the carbon dioxide gas body is formed by the reaction, and the solution is in a boiling state in appearance. Therefore, in the reactor, the milk is preferably 097137448 13 200925112, and the reflux condenser is set to cool the released carbonic acid gas (and the accompanying water vapor), and only the water vapor is condensed, and then introduced and recycled to the later step (8). In the acid gas absorption device. As described above, after the pH adjustment 53 was carried out, the slurry was cooled while stirring, at 3 〇 -5 Torr. A solid-liquid separation means for filtering, such as a solid residue component, which is precipitated by using cerium oxide (Slllca), alumina (Alumina), and iron (Iron) as a solid component, under a temperature condition of about 〇60 Separate and discard 65. Basically, the hydroxide which is made of cerium oxide or aluminum oxide is difficult to filter, but by precipitation as a carbonate, solid-liquid separation is possible by filtration or the like with good efficiency. The temperature such as filtration is not necessarily limited to the above range. However, if the temperature is too high, it is not preferable in the working environment, so it is preferable to operate at about 4 °C. As the solid-liquid separation means 6 〇, in the case of filtration, a filter press, a cartridge filter, a pump pressurized line filter or the like can be used as the filtration device. From the viewpoint of safety, it is preferable to carry out a pump cycle in a line filter provided in a piping line for processing. Further, an appropriate filter cloth such as a filter cloth, a ceramic filter or a filter paper can be used in combination with the filtration separation, the treatment amount, or the filterability of the solid. In the step (2), solid impurities (solid unnecessary components) are removed in a form of insoluble components (residues), and an acidic aqueous solution in which rare earth elements are dissolved is taken out. (Step (3)) 097137448 14 200925112 (Step of forming a rare earth solution or crystallization of rare earth carbonate) The acidic aqueous solution 70 of the rare earth element (rare earth sulfate) thus obtained is introduced into a suitable reactor, and a precipitant is added ( A crystallization agent, for example, ammonium hydrogencarbonate 73' is formed to crystallize 8 〇 to be a rare earth carbonate, and a rare earth carbonate-containing aggregate 83' is formed to simultaneously disperse the carbonic acid gas 85. As a sinking agent, at least one of a money salt, an alkali metal carbonate, a soil-based metal carbonate, an alkali metal hydrogencarbonate or an alkaline earth metal hydrogencarbonate® is basically used, but by using Ammonium hydrogencarbonate (NH4HC〇3) is used as a precipitation sword to obtain a rare earth carbonate crystal having good filterability and detergency. Therefore, the following description is directed to ammonium hydrogencarbonate, but other precipitants may be directly applied. The reaction vessel is not particularly limited, and is preferably a stirred tank type reactor including an introduction method of the acidic aqueous solution 70 and ammonium hydrogencarbonate 73, a stirring means, and a heating means. Further, since carbon dioxide gas (carbonic acid gas) is generated and released by the reaction, it is preferable to provide a reflux condenser to cool the carbon dioxide gas (and the accompanying water vapor), and only to condense the water vapor, and then introduce and recycle it. The carbon dioxide gas absorption device in the step (8) described later. The added hydrogen form or concentration of any mosquito can be added according to the water content or the state of the slurry. From the viewpoint of operability, it is particularly suitable for the aqueous solution of ammonium hydrogencarbonate having a concentration of 5-10%. use. ', the amount of ammonium bicarbonate 73 added' may be an amount sufficient to neutralize the acid of the acidic aqueous solution, the amount of the step (1) (four) grinding ride (or ^ 097137448 15 200925112 the amount of rare earth components in the grinding agent) It is preferable to add 20-50 parts, more preferably 30-40 parts per 100 parts of the dry product. The addition of the ammonium hydrogencarbonate 73 to the acidic aqueous solution 70 is preferably carried out at a high temperature as much as possible in order to allow the carbonic acid gas generated by the reaction to diffuse more smoothly from the system. Usually, for example, in a jacket of a reactor of a heating means, a hot water of about 80 C is circulated, and while stirring and heating, the division of ammonium hydrogencarbonate is carried out for 2-3 hours. ❹ (Step (4)) (Separation step of rare earth carbonate) The slurry containing the rare earth carbonate 83 is cooled to 6 Torr or less, preferably 3 〇 to 50 ° C, and then borrowed in the solid-liquid separation step 87. The rare earth carbonate 89 is separated from the ammonium salt (for example, aqueous ammonium sulfate solution) (filtrate) 90 by, for example, filtration. It is preferable that the separated rare earth carbonate is further washed with water of about 3 times by mass, thereby suppressing the impurity m in the waste abrasive slurry accompanying the adhesion of the mother liquid, in order to more fully The ground ride is washed, and the separated Wei rare earth slag can be further repulped in water to form a slurry, and the operation of the solid-liquid separation operation is repeated. Thus, in the step (4), the generated rare earth carbonate is separated and purified by filtration and washing. Further, the solid-liquid separation 87 referred to herein includes an operation of n washing. (Step (5)) (Step of calcining rare earth carbonate) The rare earth carbonate 89 which is subjected to the separation in the step (4) is dried in the 097137448 16 200925112 line and dried to 100% to form the rare earth oxide 105. The drying device is not particularly limited, and any one of a box dryer, a belt dryer, and a vacuum dryer is used. The drying temperature is preferably 6 〇 _25 〇 ° c, and particularly preferably 90 -20 (TC. The calcining equipment is not particularly limited, and any one of a box type furnace, a tunnel furnace, and the like is used. It is 3〇〇-1200 C, preferably 400-1100 ° C, more preferably 500-1 〇〇〇 in the atmosphere ring brother. 〇, the calcination time is about 1-24 hours, preferably about 3-20 hours. Further, although drying and calcination are described separately, drying and calcination may be simultaneously performed using a satin burning apparatus. Further, carbon dioxide gas (carbonic acid gas) 85 is released by the reaction during calcination. The exhaust gas absorbing device is combined in the calcining apparatus, and the released carbonic acid gas is cooled, and then introduced and recovered into the carbonic acid gas absorption device in the step (8) described later. The rare earth oxide (rare earth oxide) obtained by calcination is 1〇5. It is used to recover the oxidized rare earth, and after being pulverized, it is put into the micronization treatment step of the general abrasive production line, and then used as a raw material of the abrasive. The above is the first step [I]. That is, in the step Steps (1)-(5) are implemented in [I], self-contained The rare earth oxide is recovered from the waste abrasive slurry of the oxide of the earth element. (Second step [II]) Next, the second step [II] is described. In the step [II], the following steps are carried out (6) ), in the first step [I], the sulfuric acid compound, preferably sulfuric acid, which is the reaction required to form the rare earth carbonate 097137448 200925112, is recovered, and the recovered sulfuric acid clock is reused in the above-mentioned first step [1]. The water produced by the sulfuric acid (IV) is also used as a solvent for dissolving the rare earth sulfate in the first step (1) as the recovered water. (Step (6)) (Step of recovering ammonium sulfate and water) In the above-mentioned remarks (3), by the reaction of the following formula (1), the sulphuric acid money recorded by the carbon dioxide charged in the hydrazine is produced by the sub-type (1). This is done in the step (4) when the rare earth carbonate is contained. The mixed liquid of 2 to _ degrees is discharged into the filtrate, and the concentrated condensed scale is separated and separated into a high concentration aqueous solution of ammonium sulfate and water.

Ln2(S〇4)3+6HN4HC〇3^Ln2(C〇3)3| + 3(NH〇2S〇4 + 3C〇2 f + 3H2〇(1) (In the formula (1), Ln represents a rare earth Element (6) The above-mentioned 'polycarbonate containing rare earth 83 is separated into a rare earth carbonate 89 and an aqueous solution of ammonium sulfate (filtrate) by solid-liquid separation 87. The filtrate 90 containing sulfuric acid is subjected to concentration separation step 93, Separation and recovery of ammonium sulfate 20 and water 43 by separation of Hans. As a method of concentration separation 93, it is possible to use distillation, concentration, vacuum concentration, etc. by spray drying H, other drying equipment, It is completely dried and recovered. However, considering the use form of the recovered sulfuric acid, it is preferable to use ammonium sulfate as a solution in terms of energy efficiency. As a concentration of 097137448 200925112, the recovery of ammonium sulfate solution is not particularly high. Preferably, it is preferably 3 〇 to 7 〇 mass%, particularly preferably 40 to 60 mass%. As the actual concentration separation device, it is preferable to use an evaporation canister equipped with a condenser (condenser). It is supplied to the pot of the evaporation can, and the water 43c evaporated by heating is condensed and recovered. The water (or at least a part thereof) 43 for dissolving the rare earth sulfate 40 in the step (2) is used. On the other hand, the concentrated sulfuric acid solution 2 〇c is recovered from the steel, and can be used as the step ❹ (1) Ammonium sulfate 20 of the reaction reagent in the middle (third step [ΠΙ]) Next, the step [III] is described. In the step [UI], the following steps α) to (8) are carried out, and the first step [I] is performed. The ammonium hydrogencarbonate 73 which is a precipitant of rare earth carbonate is used for regeneration, and the regenerated ammonium hydrogencarbonate is reused in the above i-th step [I]. (Step (7)) ❹ (Ammonia recovery step) In the heating and calcining step 35 of the above step (1), the ammonia component of ammonium sulfate 20 added as a sulfuric acid compound as a reaction agent is produced in a gas (NH3) type. • Health. Further, at this time, the fluorine component contained in the polishing agent is simultaneously produced in the form of fluorine gas. The gas (F2/NH3)4 is taken up in water or an aqueous solution in the exhaust gas absorption step 112 to form an aqueous ammonium fluoride solution, and the gas component is removed from the sinking chamber to recover the ammonia water. Namely, a precipitant 097137448 19 200925112 110 was added to the aqueous ammonium fluoride solution recovered as described above to precipitate a fluorine component. The precipitant 11 () to be added is not particularly limited, but it is preferably a salt which can be used as a component of a calcium salt having a low solubility in a low solubility, such as a hydroxide, Barium carbonate and the like. Thus, the fluorine component precipitates as calcium fluoride, and is filtered 115, and 119 is discarded as residue 117. On the other hand, although the ammonia water κ is free, it is used in the next step (8) for the reaction absorption (carbonation reaction) of carbonic acid gas 13 〇. • (Step (8)) 〇 (recovery of carbonic acid gas and synthesis of ammonium bicarbonate) pH adjustment step 53 in step (2), rare earth carbonate formation in step (3), crystallization step 80 and step (5) In the calcination step 1 , the carbon dioxide gas discharged from the reactor or the like is absorbed by the ammonia aqueous solution recovered in the above step (7) (Gas Absorption Accompanied by Chemical Recation) (Carbonation) ) 130' is recovered in the form of ammonium hydrogencarbonate 73 by the following formula (2). ❹ HN3 + H2〇 + C〇2—HN4HC〇3 (2) The temperature of the liquid absorbed by the reaction is controlled in the range of 10 to 40 t, preferably 20 to 303⁄4. The apparatus for absorbing the carbonic acid gas to form ammonium hydrogencarbonate may be a general absorption tower type. However, since the locally concentrated ammonium hydrogencarbonate is also precipitated, it is preferably in the form of a stirring tank. That is, as the reaction container R for performing reaction absorption, as shown in FIG. 2, it is preferable to provide the carbonation gas introduction means 1, the stirring means 2, the temperature adjustment means 3, the condenser 4, and the counter current absorption tower (Counter Current) absorption tower. 5 097137448 20 200925112 drop absorption device. Further, the 6-series ammonia water was used for the reaction-adjusted ammonia aqueous solution. Moreover, it is preferred to combine the agitating absorption device of the preceding stage, the mate tower of the slab or the packed tower (Packed T〇we〇' Wet Wall Tower (Wetted Wali)) Further, 'the concentration of ammonium bicarbonate in the liquid is controlled to be 5 to 25% by mass, preferably 8 to 10% by mass or less, which is below the saturated solubility, if necessary, to supply fresh carbonic acid gas or dilution water. If the concentration is too low The equipment load of the absorption device is changed, and if the concentration is too high, since the ammonium hydrogencarbonate slurry is formed, it is preferably controlled within this range. As the stirring type absorption device, the stirring wing can be used. The tank type absorption device equipped with an anchor, a turbine, a paddle, a full-length Gullz〇ne wing, etc. can be appropriately selected from commercially available agitated gas absorption devices. The solution of ammonium hydrogencarbonate 73 is formed by absorption reaction with an aqueous ammonia solution (ammonia water for reaction absorption 6), and is temporarily stored in the intermediate tank and then supplied to the rare earth carbonate in the step (3). The crystallization step 8 is suitable for reuse as a crystallization agent for forming an acid-resistant rare earth. (Effect of the Invention) As described in detail above, according to the present invention, there is provided a method for recovering rare earth 70, which is a waste abrasive slurry containing a rare earth element such as cerium, which is usually discarded since the polishing rate is greatly reduced. In the waste abrasive slurry, a sulfuric acid compound such as sulfuric acid can be used as a reaction agent to selectively dissolve the rare earth oxide component 097137448 200925112 into rare earth sulfate. In addition, when the dissolved rare earth oxide component is separated and recovered in the form of rare earth carbonate, it is subjected to solid-liquid separation in advance, thereby selectively separating impurities such as dissolved iron ions into insoluble solids. The component 'by this' is obtained as a high-purity carbonic acid rare earth which can be reused as an abrasive raw material, and this can be satin-fired to easily recover the rare earth oxide. Further, according to the present invention, a rare earth oxide-containing slurry is mixed with a sulfuric acid compound such as ammonium sulfate of a reaction hydrazine, and calcined by heating to form a rare earth sulfate and dissolved in water. Then, the pH adjuster is adjusted to a specific pH, and impurities such as iron ions are subjected to solid-liquid separation in advance, and then ammonium hydrogencarbonate is added as a sinking agent to the acidic aqueous solution in which the rare earth oxide component is selectively dissolved. The reaction generates and crystallizes rare earth carbonate. When the pH adjuster and the precipitant used herein are ammonia or an ammonium salt, it is not necessary to discard ammonium sulfate and water which are produced by the reaction step, and it can be recovered and reused as the above-mentioned reaction agent and solvent. In addition, the ammonia gas generated in the above calcination step is recovered, and reacted with the carbonic acid gas generated in the pH adjustment step, the crystallization step, and the calcination step, as ammonium hydrogencarbonate, whereby high-priced ammonium bicarbonate can be recovered. And the harmless treatment of the step waste liquid becomes easy. [Examples] Hereinafter, the present invention will be described by way of examples. However, these are only the technical scope of the invention 097137448 22 200925112 (including the scope of the present invention), and are not limited or limited by the embodiments. Explanation. Also, under the unrestricted limit, % is the quality %. Further, the processing operation in the embodiment is carried out in accordance with the wire pattern of Fig. 1. [Example 1] (1) (The rare earth element of the waste abrasive slurry was dissolved to obtain a rare earth solution > Step (1)) The waste abrasive slurry 10 of the starting material was prepared as follows. By. In other words, the waste abrasive slurry generated by the grinding of the glass dish is subjected to gravity sedimentation treatment, and the slurry having a solid content concentration of about 3% by mass is adjusted to be a dry basis, and a part of the slurry is taken. The amount of the component elements obtained by the x-ray Fluorescence Analysis of the dried 1 day and night under the condition of death in the air is the result shown in Table i. ❹ Table 1 (Composition of waste abrasive slurry (dry product basis)) Component concentration (% by mass) TRE0 78.4 Si〇2 3. 6 AI2O3 1.0 Fe2〇3 6.9 097137448 23 200925112 F -—-一-- 5.2 Others 4.9 First, an operation of mixing the above-mentioned waste abrasive slurry with ammonium sulfate belonging to the reaction agent is carried out. The slurry lkg was taken up to a 3 L beaker, and 426 g of ammonium sulfate was added. Next, the mixture was mixed at a rate of about i5 rpm, i·J, and the slurry was dried in a box dryer at 90 ° C for 24 hours in the air to obtain 760 g of a dried product. Ο The dried product is heated in a small electric furnace at 50 (TC, 6 hours, and heated to obtain 520 g of rare earth sulfate.) The fluorine gas and ammonia gas generated at this time are absorbed into the aqueous solution to form ammonium fluoride. In the aqueous solution, ammonia is recovered in the step (7) described later, and the fluorine component is recovered and discarded in the form of calcium fluoride. The rare earth sulfate is dissolved in 20 L of water to obtain a rare earth elemental solution. (Separating from the acidic solution (slurry) of the rare earth element, the undissolved residue containing Si, A, Fe, the step (2)), and the acidic solution (slurry) in the mixture, at 120 rpm Under the conditions, an ammonium hydrogencarbonate solution having a concentration of 1% by weight as a pH adjuster is added, and the mixture is adjusted to pH 5.5 and stirred for an hour. At this time, the carbonation gas system formed by the neutralization reaction is dispersed with water vapor. / The liquid mixture is in a boiling state in appearance. Therefore, the liquid is cooled by a reflux condenser to condense water. After the gas is condensed, the carbon dioxide gas absorption device of the step (8) described later is introduced to carry out the reaction absorption by 097137448 24 200925112 ammonia. money Next, a Nutsche-type suction vessel having an inner diameter of 300 mm φ is used, and a filter paper (AdvanteCh manufactured by Toyo Co., Ltd.) is used to separate solid and liquid undissolved components into solids without the need to reduce the amount of miscellaneously solved the recovery of the rare earth element-based mechanically mixed aqueous solution. The quality of the dry product based on the solid content (rejection required) is 75g. 'Analysis by the fluorescent X-ray method confirms that the composition is ❹ dioxide, dream, iron. (3) (from rare earths The solution causes rare earth carbonate to be formed and crystallized: step (3)) The acidic aqueous solution in which the filtered rare earth element is dissolved is heated to about 6 (rc) under stirring conditions of 12 (four) m. Secondly, about 2 逐 is added successively. The mass % concentration of the acid-destroying hydrogen recorded solution is 2 〇〇〇g, and the reaction of the following formula (1) is successively performed to generate crystals of the rare earth carbonate and crystallize.

Ln2(S〇4)3 + 6HN4HC〇3-^Ln2(C〇3)3 | + 3(NH4)2S〇4+3C〇2 f + φ 3H2〇(1) (in the formula (1), 'Ln The rare earth element.) The ammonium hydrogencarbonate added is reversed with a rare earth sulfate as shown in the above formula to form a rare earth carbonate and release a carbonic acid gas. About 30 minutes after the addition of ammonium hydrogencarbonate, the generation of carbonic acid gas was stopped, and the end of the reaction was confirmed, so that the mixture was cooled to 40 C and stirring was stopped. Further, the carbon dioxide gas system which is produced by the reaction in the reaction is cooled by a reflux condenser in the upper portion of the reactor, and then introduced into the carbonic acid gas absorption device of the step (8), and reacted with ammonia (carbonation reaction), and 097137448 25 200925112 Recovered as ammonium bicarbonate. (4) (Separation of rare earth carbonate, step (4)) The above-mentioned slurry containing rare earth carbonate is filtered by a Nutseh-type suction filter having an inner diameter of 300 mmφ, and filtered using No. 5A filter paper (manufactured by Advantech Toyo Co., Ltd.). After that, it was washed and recovered three times with 500 g of pure water, and dried in a *-type dryer at 90 ° C in the air overnight to obtain a dry filter cake of 320 g of rare earth carbonate. (5) (Calculation of rare earth carbonate, step (5)) The obtained rare earth carbonate was calcined at 500 ° C for 5 hours in a small electric furnace to recover 235 g of a rare earth oxide. The recovery rate of the waste abrasive slurry in terms of oxidized rare earth component was about 95%. Further, the carbon dioxide gas system produced at this time is introduced into the carbon dioxide gas absorption apparatus in the step (8), and reacted with ammonia (carbonation reaction) to recover ammonium hydrogencarbonate. © (6) (Recovery of Sulfuric Acid Recording Water, Step (6)) In the step (4), the filtrate (ammonium sulfate aqueous solution) obtained by separating the rare earth carbonate slurry from the rare earth carbonate slurry is about 25 〇〇〇. g is subjected to distillation concentration (concentration separation) to separate and recover 2 g of aqueous ammonium sulfate solution and 23 g of water. 5质量质量。 The solid part of the aqueous solution was determined to be 1. 5 mass%. (7) (Ammonia recovery, step (7)) In the step (1), in the ammonium fluoride aqueous solution recovered from the calcination step, about 097137448 26 200925112 600g 'add 25% calcium hydroxide dissolved in a strong alkali agent To make the fluorination move, remove it by shouting; ^ pediatric agent 'liquid about 80 〇 ff. The type of η liquid recovers ammonia water _g. The ammonia concentration in the recovered liquid was about 6.0% by mass. In addition, calcium sulphate is added to the fluorine component contained in the solution, and calcium sulphate is added to the insoluble calcium fluoride to be harmlessly treated and recovered. I wish I would rather share it. , knowing to discard, but can also be added as a gas in the abrasive 〇 (8) (recovery of carbonic acid gas and synthesis of carbonic acid, step (8)) = (8) Weihua reaction 'as read in Figure 2, to have carbonic acid The gas is introduced into the Hungarian guide, the age, the temperature, the temperature, the third, the condenser 4, the countercurrent contact absorption tower 5 _ the mixing absorption device (with the condenser agitation tank) R (inner diameter φ12 〇 χ 高 high hl5Q_ It is carried out with a purple-type scrambled wing (10) x60W)). That is, the total amount of the 6.0% by mass of the ammonia reading liquid recovered and the reaction absorption © ammonia water 6 were filled in the fresh tank r with the condenser. This was mixed at a rate of 150 liters, and the outer jacket 3 was allowed to flow cold water to cool the inner temperature to 20 C, and the upper condenser 4 was cooled to 1 Torr. Hey. Then, the carbon dioxide gas is introduced into the tube by the agitation tank, and the carbon dioxide gas (the reaction gas generated when the rare earth carbonate is formed by adding hydrogen carbonate to the acidic rare earth solution) is stripped in the ammonia water for absorption 6 . The carbonic acid gas is absorbed by the reaction to form a carbonic acid nitrogen coin. Taking a part of the recovered ammonium bicarbonate slurry generated by the reaction absorption, the solid content obtained by the evaporation dry solid method by 097137448 27 200925112 is 28% by mass, and the calculated amount of the carbonium hydrogen ammonium hydroxide calculated is 224 g. . It means that about 87% of the ammonia in the ammonium sulfate is recovered in the form of ammonium hydrogencarbonate, and if necessary, fresh hydrogen carbonate or water jet can be added to the aqueous solution to directly recover the rare earth carbonate formation and crystallization step. It is reused as a raw material for the synthesis of rare earth carbonate (step (3)). - icp luminescence analysis method of rare earth oxides obtained by the step (5) and rare earth oxides of the new product (Shimadzu, Shimadzu Corporation)

The analytical values obtained by Corporation) are shown in Table 2. It is apparent from the table that the cerium oxide, aluminum oxide and iron components of the trace impurity component (Trace Contaminant) mixed in the polishing and polishing slurry concentration step are removed by 99% or more, and the purity is not Inferior to industrial gainers. (Table 2) (Composition of rare earth oxides) Component TRE0~~1 Si〇2~ AI2O3 Fe2〇3—Content (皙晋幻一_____ Waste abrasive slurry new product recovery – 78.4 91.2 90.4 3. 6 ] <0. 03 <0. 03 — 1.0 6.9 —' <0. 03 Γ <0.03 <0. 03 <〇. 〇3 F ---—J — 5.2 <0. 01 <0. 01 ❹ Oxide as a supplement, pulverized under the established conditions, and the fluorinated rare earth adjusted by the pulverization treatment is blended, mixed, satin-fired, pulverized, 097137448 28 200925112, and the enthalpy is formed according to the predetermined conditions. ), using _AI to carry out (four) treatment (about 10% by mass of concentrated fruit is shown in Table 3). The grinding characteristics of the 研磨 type grinder are evaluated by the industrial company, and the knot (Table 3) (recovering the oxidized rare earth μ-one-grinding property) is used. New product original - Relative grinding speed (damage, flatness) - 1.0 〇Γ~7~^一-Materials from 矣3 B Japanese ship, 1.0 〇一〇^ n 灾 Disaster used for the recovery of raw materials, β a The polishing rate and surface state are the same as those of the abrasive using the new material. [Example 2] Except for the following, 1) The oxide of the rare earth element is recovered by the same method: (1) the ammonium sulfate used in the step (1) is 2 〇〇〇g of the ammonium sulfate aqueous solution recovered in the first embodiment, and 150 g of the ammonium sulfate to which the reagent is added; (U) water for dissolving rare earth sulfate, 20 L of water recovered in Example 1, and (iii) ammonium hydrogencarbonate used in the step (4), which is an aqueous solution of ammonium hydrogencarbonate recovered in Example 1. In the 〇g, the amount of the ammonium hydrogencarbonate to be added was 180 g. The analysis values obtained by the ICP emission spectrometry (manufactured by Shimadzu Corporation) of the rare earth oxides and the rare earth oxides of the new products are shown in Table 4. It is apparent from the table that the cerium oxide, aluminum oxide and iron components of the impurity component of the micro-097137448 29 200925112 mixed in the polishing and polishing slurry concentration step are removed by 99% or more in terms of purity. (Table 4) (Composition of rare earth oxides) Component content (% by mass) __ Waste abrasive slurry new product recovery ______—1 TRE0 ------- 78.4 91. 2 Si〇2 3.6 <0.03 Al2〇3 1.0 <0· 03 Fe2〇a - 6. 9 Γ <〇.〇3 F 5.2 <0.01 <AJi- _ II _ — The oxide of the rare earth element recovered and the rare earth element of the new product are used as raw materials, and are pulverized under the predetermined conditions. At the same time, the fluorinated rare earth adjusted by the pulverization treatment is blended, mixed, calcined, pulverized, and classified according to the predetermined conditions to form an abrasive. The slurrying property (about 10% by mass) was evaluated by using a grinder (10) manufactured by HAMAI Industries Co., Ltd., and the results are shown in Table 5. (Table 5) Grinding characteristics of soil) ----- Relative polishing speed appearance (damage 1.0 _- Raw material To Ο__ = The same grinding speed as that of the abrasive using new raw materials, and the surface is apparent from Table 5. 097137448 30 200925112 (Industrial Applicability) According to the present invention, there is provided an inexpensive process which is a rare earth element-containing waste abrasive slurry which is generally discarded since the polishing rate is greatly reduced. An oxide-like oxide can be reused as an abrasive having a polishing rate. Further, according to the present invention, since ammonia gas, carbonic acid gas, ammonium sulfate, and water discharged from the self-made process can be completely recovered and reused, It is not only a rare earth element, but also a semi-permanent recycling process for the use of chemicals in the process, especially for the formation and crystallization of rare earth carbonates, due to the self-made process. The carbonation reaction of the discharged ammonia gas and the carbonic acid gas recovers and reuses ammonium hydrogencarbonate, so that high-priced ammonium argon carbonate can be recovered and used. The ammonium sulfate of rare earth sulfate is recovered from the filtrate containing the rare earth carbonate slurry during the formation and crystallization of rare earth carbonate, and can be reused as a reaction agent for generating rare earth sulfate, so that the waste liquid of the step is harmless. Further, according to the present invention, the rare earth sulfate aqueous solution is previously adjusted to a specific 'PH' and subjected to solid-liquid separation, whereby impurities such as dissolved iron ions can be selectively precipitated and removed, and can be easily produced. The high-purity rare earth carbonate is recovered. As described above, the present invention has great industrial applicability. [Simplified Schematic] FIG. 1 is a diagram showing the recovery step of the present invention including hydrogen carbonate money, sulfuric acid money and 097137448 31 200925112 Flow-sheet of the step of recovering the rare earth element in the water recovery step. Fig. 2 is an explanatory view showing a reaction vessel for reacting carbonic acid gas with ammonia water to form ammonium hydrogencarbonate. Description]

1 Nozzle (carbonic acid gas introduction means) 2 Stirring means 3 Cooling jacket (temperature adjustment means) 4 Condenser 5 Countercurrent contact absorption tower 6 Reaction absorption ammonia water 9 Grinding step 10 Waste abrasive slurry 20 Sulfuric acid money 20c Separated and separated Recovery of ammonium sulfate 30 Mixing step 33 Drying step 35 Calcination step 40 Rare earth sulfate 43 Dissolved water 43c Concentrated separated recovered water 45 Dissolving step 50 pH adjusting agent 097137448 32 200925112

53 60 63 65 70 73 80 83 85 87 89 90 93 100 105 110 112 115 117 119 120 130 pH adjustment step Solid-liquid separation step residue (solids do not require components) The waste step dissolves the acidic aqueous solution of rare earth elements (rare earth oxide) Ammonium bicarbonate carbonate rare earth formation • Crystallization step containing rare earth carbonates, carbonic acid gas, solid-liquid separation step, carbonated olefin filtrate, separation and separation step, calcination step, oxidation of rare earth sinking agent (calcium hydroxide, etc.), exhaust gas absorption step, filtration step, residue disposal step Ammonia water carbonation reaction step 097137448 33

Claims (1)

200925112 VII. Scope of application for patents··································································································· In the first step (II) including the following step (6), 'recovering the sulfuric acid money used in the first step (1), and recycling the recovered sulfuric acid in the above-mentioned step (1) for reuse; wherein, the first step [ The system includes ··· 0 (1) mixing the rare earth-containing filament with the touch compound, heating and calcining it into rare earth sulfate, dissolving it in water (step (1)); (2) adjusting the pH of the obtained rare earth sulfate solution to an appropriate condition Separating the insoluble components by means of solid-liquid separation means (step (2)); (3) adding rare earth sulphate to the rare earth sulphate to crystallization (step (3)); θ θ (4) from the obtained (10) containing carbonaceous soil for separation of carbonaceous soil (step © (4)); and evening (5) for satin burning into rare earth oxides, recovering the raw elements (step (5)); Step [II] includes: (6) pH adjusting agent in step (2) and When the precipitant of the step (3) contains & 7 or an ammonium salt, the aqueous solution of the ammonium sulfate separated by the rare earth carbonate is separated and recovered into a high-concentration ammonium sulfate aqueous solution, and the recovered ammonium sulfate water is condensed and used. A reactant formed by strontium aluminate (step (6)). Liquid re-097137448 34 200925112 · 2. As in the method of claim 1, the ammonium sulfate is used to recover water together, and in the first step of the first step [in the crucible and the ammonium sulfate aqueous solution of the separated rare earth carbonate, In the case of re-use, the acid aqueous solution is separated and recovered from the water, and is returned to the solvent which dissolves the positive concentration of the rare earth sulfate. Recycling to make sulfur 3·such as the rare earth system of claim 1 or 2 further implement the 7°_recycling method containing the next steps (7) to (8) , In step (111) of the first or second step, the carbon (step) (3) is used in the step (3) to re-use the carbon as the sinking of the rare earth carbonate; the gas recording is recovered therein, and the third step [III] The system comprises: (7) recovering the gas generated by the heating and calcining step and recovering the ammonia gas into the aqueous solution: 'precipitating a precipitating agent to precipitate the fluorine component, and removing it by filtration, thereby recovering the aqueous ammonia solution (step (7)); And (8) next to the recovered aqueous ammonia solution, the carbonation gas generated in the pH adjustment step, the carbonic acid digesting step and the sacrificial step is contacted (four) into a carbonated wind, and the solution or slurry 'records the obtained hydrogen carbonate The solution or the bulk material is reused in the crystallization step towel to form a carbon-soil formation rail (step (8)). 4. The method of claim 1 or 2, wherein the sulfuric acid compound of step (1) is ammonium sulfate or ammonium hydrogen sulfate. 5. The method of claim 1 or 2, wherein the stepping spine (1) has a calcination temperature of 300. 6. The method of claim 1 or 2, wherein the pH condition of the step (2) is 4-7, and the pH adjuster is a soluble alkali metal salt, ammonium salt or ammonia water. 7. The method of claim 1 or 2, wherein the solid-liquid separation means of the insoluble component in the step (2) is carried out by filtration. 8. The method of claim 1 or 2, Wherein the precipitating agent in the step (3) is at least one of an ammonium salt, an alkali metal carbonate, an alkaline earth metal carbonate, an alkali metal hydrogenate or an alkaline earth metal hydrogencarbonate. The method of claim 1 or 2, wherein the precipitating agent of the step (3) is ammonium hydrogencarbonate. 10. The method of claim 1, 2 or 8, wherein the step (3) is added The form of the precipitant is solid, solution or slurry. 11. The method of claim 1 or 2, wherein in the step (4) Q, the generated rare earth carbonate is filtered and washed. Separation and refining. 12If the method of claim 1 or 2 is applied The calcination in the step (5) is carried out in an air atmosphere at a temperature of 300 to 1200 ° C. The method of claim 1 or 2, wherein the concentration separation in the step (6) is distillation or evaporation. 14. The method of claim 1 or 2, wherein the precipitating agent of step (7) is barium hydroxide. 15. The method of claim 1 or 2, wherein step (8) 097137448 36 200925112, the contact temperature is 10-40 ° C. 16. The method of claim 1 or 2, wherein the concentration of ammonium bicarbonate in step (8) is 5-25% by mass, the form is A solution or a slurry. 17. A method for recovering a rare earth element, which is used for grinding, and the method of any one of claims 1 to 16 is used to produce a waste abrasive slurry. The rare earth element is recovered from the material, and the obtained rare earth element is reused as a raw material of the abrasive. 097137448 37