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Process for recovering rare earth oxide from waste liquid containing rare earth element, and process for producing rare earth oxide using same

A technology of rare earth oxides and rare earth hydroxides, which is applied in the fields of rare earth metal compounds, chemical instruments and methods, and solid waste removal, and can solve problems such as removal of impurities

Inactive Publication Date: 2005-09-28
SHOWA DENKO KK
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0025] However, it should be noted that the impurities contained in the abrasive waste liquid cannot be removed to a desired degree by the methods and processes proposed so far, so that from the abrasive waste liquid Recovered rare earth oxides can be reused as abrasives for high-precision polishing

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0136] Embodiment 1 (recover rare earth oxide from abrasive waste liquid)

[0137] Rare earth oxides were recovered from abrasive waste liquids having solid components shown in Table 1, which were generated when glass dishes were polished, by the following procedure.

[0138] In 1 liter of abrasive waste liquid, adding 38 g concentration is 20 mass % aluminum sulfate aqueous solution and 0.2 g polymeric flocculant (KuriflocTM ; available from Kurita Water Industries Ltd.) and mixed to aggregate and deposit the solid ingredients. Separate and recover the sediment.

[0139] Then, 100 g of the recovered solid was put into a beaker containing 262 g of concentrated sulfuric acid having a concentration of 95% by mass, and the mixture was stirred for 5 minutes. The beaker was heated to 100°C, and the organic material was decomposed by the dehydration action of hot sulfuric acid, producing a black liquid. 20 g of aqueous hydrogen peroxide was added dropwise thereto, thereby removing...

Embodiment 2

[0144] Example 2 (Recovery of Rare Earth Oxide from Abrasive Waste Liquid)

[0145] Powdery rare earth oxides were recovered from abrasive waste liquids having solid components shown in Table 1, which were generated when optical filters were polished, by the following steps.

[0146] 100 g of the recovered powder was added to a SUS beaker containing 245 g of aqueous sulfuric acid having a concentration of 98% by mass, and the mixture was stirred with a SUS spatula. The beaker was then covered with a watch glass, placed on a heater, heated at 600W for 30 minutes, and allowed to cool.

[0147] The obtained yellow solid (rare earth sulfate) was placed in a mortar and crushed with a pestle. Another 1 liter of cold water was placed in a beaker surrounded by ice water and stirred. To this ice water was gradually added the crushed material obtained above and mixed to prepare an acidic sulfate solution containing rare earth sulfate (brown transparent solution). The rare earth sul...

Embodiment 3

[0153] Example 3 (Recovery of Rare Earth Oxide from Abrasive Waste Liquid)

[0154] Rare earth oxides were recovered from abrasive waste liquids having solid components shown in Table 1, which were generated when polishing glass substrates for hard disks, by the following steps.

[0155] 0.5 liter of abrasive waste liquid containing 100 g of solid content and 250 g of hydrochloric acid with a concentration of 35% by mass were put into a flask equipped with a water-cooled tube. This content was heated and maintained at a temperature of 103°C. The vapors emitted by heating are cooled by water-cooled tubes and sent back to the flask so that the liquid surface does not lower. When the contents were heated for 48 hours, the abrasive waste liquid became a mixed liquid consisting of a green acidic aqueous solution containing rare earth chlorides, white silica gel and insoluble materials such as polishing pad fragments.

[0156] The water-cooled tube was removed from the flask, an...

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Abstract

ABSTRACT Rare earth oxides capable of being re-used as an abrasive are recovered from an abrasive waste liquid by a process comprising the steps of (1) mixing and heating a rare earth element-containing waste liquid with an acid, to dissolve rare earth elements contained in the liquid; (2) removing insoluble matter from the rare earth element solution; (3) incorporating a soluble carbonate salt or a soluble hydrogencarbonate salt, or an oxalic acid in the rare earth element solution, to convert the rare earth elements to rare earth carbonates or rare earth oxalates; (4) separating the rare earth carbonates or rare earth oxalates from a slurry of the rare earth carbonates or rare earth oxalates; (5) baking the separated rare earth carbonate or rare earth oxalate to produce rare earth oxides; and (6) recovering the rare earth oxides.

Description

[0001] Cross-references to related applications [0002] This application is an application filed under 35 U.S.C § 111(a) claiming pursuant to 35 U.S.C § 119(e)(1) of provisional application 60 / 410,285 filed September 13, 2002 under 35 U.S.C § 111(b) and benefit from the filing date of provisional application 60 / 416,577, filed October 8, 2002. technical field [0003] The invention relates to a method for recovering rare earth oxides from waste liquid containing rare earth elements. More particularly, the present invention relates to a method for recovering rare earth oxides from a rare earth element-containing abrasive waste liquid, wherein the recovered rare earth oxides are of high quality so that they can be used as abrasives for high-precision polishing. Background technique [0004] In recent years, abrasives containing rare earth elements have been used in different fields. In particular, cerium-based abrasives are commonly used for polishing glass materials or crys...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): B09B3/00C01F17/00C22B59/00
Inventor 今井文男伊藤桂三枝浩
Owner SHOWA DENKO KK
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