CN1031945A - 从电解法制取氯酸盐体系中除掉并回收重铬酸盐 - Google Patents
从电解法制取氯酸盐体系中除掉并回收重铬酸盐 Download PDFInfo
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- 238000000034 method Methods 0.000 title claims abstract description 59
- SOCTUWSJJQCPFX-UHFFFAOYSA-N dichromate(2-) Chemical compound [O-][Cr](=O)(=O)O[Cr]([O-])(=O)=O SOCTUWSJJQCPFX-UHFFFAOYSA-N 0.000 title claims abstract description 18
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
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- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
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- C25B1/00—Electrolytic production of inorganic compounds or non-metals
- C25B1/01—Products
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- C25B1/26—Chlorine; Compounds thereof
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- C—CHEMISTRY; METALLURGY
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- C25B15/00—Operating or servicing cells
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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Abstract
从盐水电解所得富含氯酸盐并含有次氯酸钠和
重铬酸盐的溶液中除掉重铬酸盐的方法。采用两阶
段法,在受控的pH和温度条件下通过加入氨将该重
铬酸盐还原成为混合的二价和三价氢氧化铬,使之从
溶液中沉淀并将之除去,从而从电解法制取氯酸盐的
溶液中回收铬提供了经济的方法。
Description
本发明涉及从碱金属氯化物电解制成的碱金属氯酸盐溶液中除去重铬酸盐的方法。
在纸浆漂白工艺中广泛使用二氧化氯,此化合物一般是通过氯酸钠水溶液与一种酸,一般用硫酸反应而制成。而该氯酸钠溶液一般是由氯化钠电解制成。在该电解工艺中,氯化钠电解生成氯、氢氧化钠和氢。氯与氢氧化钠立即反应而成为次氯酸钠,然后在受控的pH和温度条件下进一步转化成为氯酸钠。
当此含有残余量次氯酸钠的溶液离开电解工序之后,通常要经过处理以除去这种使溶液具有腐蚀性的次氯酸盐。工业上一般应用的除去次氯酸盐的方法包括加拿大专利1,112,845号所述的与氨反应,以及与亚硫酸钠或过氧化氢反应。
在这种电解质溶液中要加入少量铬,通常是重铬酸盐,一般是重铬酸钠,以防止其阴极电流效率下降。在工艺过程中这些重铬酸盐并不消耗掉,而是留在氯酸钠/氯化钠溶液中。但是,重铬酸钠是昂贵的化工原料,把它留在产品溶液中就是一项经济损失。此外,这种铬化合物在其后的二氧化氯工艺中也未能消耗掉,而是通过制浆工艺而进行到环境中。
为从电镀浴和其他金属处理溶液中除掉重铬酸盐而研究了许多种方法。这些金属处理溶液中一般不存在氯离子,并且通过将铬从六价还原至三价态,随后以水合氧化铬形式沉淀,从而使溶解铬含量达到极低的程度。不利的是,在含氯化物溶液中存在的水合氧化铬化合物的溶度积要提高105倍,并且来自电解装置的准备处理的氯酸盐溶液中,氯化物含量约为100克NaCl/升。
为了使电解所得的氯酸盐溶液经还原处理后的铬含量远低于10ppm,发现有必要把至少一些铬还原到低于Cr3+价态。在Olin,Corporation的加拿大专利,1,187,036号中,描述了制成相信是Cr(OH)2沉淀物的方法(当还原到低于Cr(OH)3价态的化合物时,很容易看到沉淀物颜色从绿色转变为亮蓝-绿色),并且滤液中残余的铬含量低于0.01ppm。在Chemetics International的加拿大1,139,080号增补专利中,将该特征蓝-绿色沉淀物的组成描述为O/Cr比率一般在1.3-1.4之间。因此,该水合氧化物沉淀的近似化学式为Cr3O4·XH2O,即每摩尔该化合物含有2摩尔Cr3+加上1摩尔Cr2+。
一般认为理想的除铬工艺应具备以下条件:能将溶液中铬含量降低至1ppm以下,应使用廉价和无毒的反应药剂,并且所生成的铬化合物能直接循环回用于氯酸盐生产工艺中。
肼和羟胺都能从氯酸盐溶液中得到蓝-绿色的铬沉淀物,并作为除铬法而得到专利权(加拿大专利1,119,772号及1,139,080号及瑞典专利218,495号)。但是,这些化学品很昂贵,并且肼对于操作者有一定毒性。
有许多专利都涉及到从电镀溶液或类似溶液中除铬的方法,但都认为与本发明没有真正的密切关系。但也有一些专利涉及到从含有氯酸盐的溶液中除铬。
美国专利3,616,344号描述了一种方法,是将用于电化学加工的碱金属氯酸盐使用亚铁盐或碱金属亚硫酸盐或亚硫酸铵或亚锡盐进行处理,将六价铬还原为三价铬的氢氧化物而从溶液中沉淀出来,另外的方法是使用铅、锌、钴或铜的二价可溶性盐,作为不溶性铬酸盐来除掉铬酸盐离子。
美国专利4,086,150号描述了从碱金属氯酸盐溶液中除掉铬酸盐的方法,此法是加入一种水溶性硫化物,随后加入一种亚铁盐。分离出一种含不溶性的三价铬的物质,另外的方法是用一种“铁泥”来沉淀含有不溶性三价铬的物质。
如加拿大专利1,112,845号所述,可以在pH6.75左右使用氨来产生氯胺,从而将次氯酸盐破坏掉。在此种pH条件下,相信所生成的单一和二氯胺会迅速相互反应,从而互相破坏而生成氮。当pH高于8.5时,氨与次氯酸盐反应只生成单氯胺(参考:Corbett等,J.(1953)PP.1927-1929),并且多年来以已为公知,此化合物与过量氨反应生成肼。但是,已知该种肼生成反应对于痕量金属杂质的存在是十分敏感的,因此在其工业生产中必须使用极纯的溶液并加入大量明胶来制取此化合物(见E.Schmidt,Hydrazine & Its Derivatives,Preparation,properties &Applications,John wiley & Sons(1984))。
美国专利4,268,486描述了从碱金属氯酸盐溶液中除掉铬酸盐的方法,是通过与一种肼化合物反应并从该溶液中分离出三价铬化合物。
上述多种方法若应用于电解法生产碱金属氯酸盐时,将使产物溶液中加进不希望有的化学杂质,或者使该电解工艺中所分离出的铬不能回收。这些可直接应用于碱金属氯酸盐生产中的方法尚未证实是经济的。美国专利4,268,486号的方法使用昂贵并有毒的化学品肼,而美国专利4,335,000号的方法是使用离子交换树脂,要求严密控制溶液的pH值在酸性条件,以防释放出二氧化氯和氯。再者,那些只把铬还原到3价态的方法不足以使含氯化物溶液达到很低含铬量。
因此很需要这样一种方法,要能够从氯酸钠和氯化钠溶液中经济地回收铬,并能够任选循环回用到该氯酸钠工艺的电解工序中。
因此本发明的目的之一是提供改进的从电解生成的富含氯酸盐的碱金属氯酸盐-氯化物溶液中除掉重铬酸盐的方法,其中在不加入昂贵或有害化学品的情况下将该水溶液中的铬清除到极低含量。
本发明的另一目的是提供一种方法,此法不但能用不太昂贵的设备从富含氯酸盐的溶液中成功地除掉铬,并可任选将该“纯净的”氢氧化铬沉淀物循环回用到该氯酸盐生产工艺中。
本发明还有一个目的,就是不需要将不希望的杂质带入到该母液中,并且经处理的氯酸盐-氯化物溶液的主要组分组成无变化,即氯酸盐和氯化物浓度保持恒定。
在后文中描述如何达到这些目的和附加的目的。
本发明者意外地发现,当在来自生产过程的典型含残余次氯酸盐的重铬酸盐-氯酸盐电解液中加入氨和少量碱使其pH值提高到8.5以上,并将所得溶液保持在60℃以上温度,使该六价铬发生还原,生成含有淡绿色沉淀的绿色溶液。将过量氨除掉并使pH值降至8.5以下之后,使这里铬进一步还原,最终生成蓝-绿色沉淀物,并从溶液中实质上完全除掉铬。
因此按本发明是提供经过改进的从含氯酸盐、次氯酸盐以及重铬酸盐之类离子的溶液中除掉重铬酸盐的方法,该方法包括将所述重铬酸盐的六价铬还原成为氢氧化物沉淀形式的混合二价及三价铬,其改进之处包括按两阶段进行所述还原反应:
(a)在pH值高于8.5,温度高于60℃,用氨处理所述溶液以生成所述氢氧化物沉淀;所述铵及所述次氯酸盐有足够过量,以便生成所述氧化物沉淀;
(b)将所得溶液的pH值调节至低于8.5,温度高于40℃,使所述二价及三价氢氧化铬实质上完全沉淀。
任何含有可还原六价铬离子的碱金属氯酸盐水溶液均可用本发明的方法处理。典型的碱金属氯酸盐溶液包括氯酸钠、氯酸钾以及它们的混合物。
按本发明的一般性步骤,是把氨和碱直接加入到从电解槽送出的含次氯酸盐-氯酸盐的电解质中,同时保持该溶液迅速混合。可用的最低温度为60℃,也可高于90℃,但已发现在75-85℃之间可使次氯酸盐达到最高利用效率。在反应过程中,溶液的pH值最好应高于10.5左右。pH太低使次氯酸盐和氨的利用率下降,而pH过高使所需的氢氧化钠加入量加大而造成浪费。经过在80℃大约30分钟反应之后,从溶液中除掉过量的氨,并加入酸,最好是加入稀盐酸将pH值调节到低于8.5(最适宜pH值为6.5-7.5)。经过在80℃再搅拌30分钟后,形成具特征蓝-绿色的混合价态氢氧化铬沉淀物,最后用过滤法将之除掉。可以理解到,在步骤(a)和(b)中进行沉淀的时间将因所用pH和温度条件之不同而变化。但技术人员很容易确定出最适宜数值。上述提供的时间只是作为指南。
将本方法进行小的改动之后,可以使氨和次氯酸盐在一部分制成的电解质中反应,并将所得的溶液加入到另一部分电解质中。但已发现,采用这种方式时,次氯酸盐的利用效率要比前述的方法低得多,因此,最好用前述那个方法。
如果次氯酸盐在该电解质中的存在量不足以完全除掉重铬酸盐,可将氨和碱加入到该电解质中,随后再进一步加入次氯酸盐。全部操作都要良好搅拌。已发现这是非常高效的利用次氯酸盐的方法。
为从溶液中完全清除铬,所需次氯酸盐、氨和碱的用量取决于对该反应序列所选用的条件,并且本领域的技术人员很容易确定出这些用量。一般情况下,若反应温度为80℃,则次氯酸盐需用量是需要除掉的重铬酸钠重量的二倍,即对于2.5克/升的重铬酸钠需用5克/升次氯酸钠。氨的需用量大约是次氯酸盐量的二倍,即对于5克/升的次氯酸钠需用10克/升的氨。当对于六价铬的存在量具备了足够量的氨和次氯酸盐之后,按后文定义的本发明的方法即可作为改进的除掉重铬酸盐的方法。很明显,使氨和次氯酸盐稍有过量对于所述工艺是有利的。对于第一状态反应所需氨量有任何过量,可任选采用任何后续的真空处理加以回收。
在本发明方法的(a)阶段中,可以在该富含氯酸盐的溶液中加入足量的无机碱而将pH值调节到高于8.5。典型的无机碱包括氢氧化钠、氢氧化钾水溶液以及它们的混合物。所具体选用的无机碱应当相应于进行除铬酸盐的具体碱金属氯酸盐溶液。例如,当处理氯酸钠溶液时,最好使用氢氧化钠作为该种无机碱。所用无机碱一般是该种碱的水溶液,其浓度范围约为1-10克/升,最好为4克/升。
在(b)阶段中,可以在该富含氯酸盐的溶液中加入足量的无机酸而将pH值调节到低于8.5。在本发明的方法中,凡是能够将所得溶液的pH值控制到从低于8.5到6.0范围,并且对于该溶液中所存在的碱金属氯酸盐和六价铬不起到还原剂作用的任何无机酸,都可以使用。典型的无机酸包括盐酸、硫酸和硝酸。关于该种酸的浓度,一般为水溶液中的无机酸含量约5-75%(重量)。
在(b)阶段完成后,可将已沉淀的二价和三价氢氧化铬从溶液中分出,可采用任何适当的固体-液体分离技术,例如沉降、过滤、离心分离等等。
可任选使用次氯酸钠将该二价和三价氢氧化铬沉淀氧化,并将所得的重铬酸钠返回到电解法制造氯酸钠所用的进料盐水中。
以下举出的实例是用于更全面地阐明本发明,但并非对本发明的限定。
在这些实例中,采用两阶段工艺把六价铬从浓缩的氯酸钠水溶液中实质上除干净。
实例1
从电解槽出口直接取得为制取氯酸钠而产生的温度为80℃溶液。该溶液中含有氯酸钠400克/升,氯化钠100克/升,重铬酸钠2.5克/升,还有次氯酸钠5克/升。将此溶液快速搅拌并加入4g/升的氢氧化钠,20克/升的氨,使其pH达到10.5。在阶段(a)的实施中,将该溶液在80℃保持30分钟并持续搅拌。在这段时间终了时,将此溶液送入一个真空容器中,在此容器中保持30分钟。放掉真空之后,在阶段(b)的实施中,加入少量盐酸将其pH值调节至7.5。
将此溶液进一步在80℃保持30分钟之后,将此含有该蓝-绿色氢氧化铬沉淀物的溶液过滤,分析滤液的铬含量,得出其存在浓度低于0.2ppm。
实例2
按实例1的相似方式取得该溶液,不同之处是其中含有5克/升的重铬酸钠和2.5克/升的次氯酸钠,还有同前述含量的氯酸钠和氯化钠,将之用以下步骤处理以除掉铬。
作为阶段(a),在剧烈搅拌下加入氨和碱,加入量分别为20克/升和4克/升。
仍在剧烈搅拌下加入补充量的次氯酸钠,使其总含量达到8克/升。在阶段(a)的全部历程中,溶液温度保持在80℃。30分钟后,将该溶液真空处理,酸化至pH-7.0,然后作为阶段9b)在80℃搅拌30分钟。经过滤分出的该种蓝-绿色沉淀物中,O/Cr比率为1.36,残余溶液中的铬含量为0.2ppm。将该沉淀物再溶解于次氯酸钠溶液中,然后送回到该电解槽。
Claims (5)
1、一种经改进的从含氯酸盐、次氯酸盐以及重铬酸盐之类离子的溶液中除掉重铬酸盐的方法,该方法包括将所述重铬酸盐的六价铬还原成为氢氧化物沉淀形式的混合二价及三价铬,其特征在于改进之处包括按两阶段进行所述还原反应:
(a)在PH值高于8.5,温度高于60℃,用氨处理所述溶液以生成所述氢氧化物沉淀;所述铵及所述次氯酸盐有足够过量,以便生成所述氢氧化物沉淀;
(b)将所得溶液的PH值调节至低于8.5,温度高于40℃使所述二价及三价氢氧化铬实质上完全沉淀。
2、按权利要求1的方法,其中所述溶液在阶段(a)的pH值高于10.5,温度是选自75-85℃范围,并且在阶段(b)的pH值是选自6.5-7.5范围,温度是选自75-85℃范围。
3、按权利要求2的方法,其中在阶段(a)之后,将所述溶液中余留的氨在进行阶段(b)之前用真空处理而全部除去。
4、按权利要求3的方法,其中在阶段(a)该溶液的pH值是通过加入氢氧化钠来调节,在阶段(b)通过加入盐酸来调节。
5、按权利要求1-4中任一项的方法,其中所述包含氯酸盐、次氯酸盐和重铬酸盐离子的溶液,是在电解槽中通过盐水电解反应而产生的包含氯酸钠和氯化钠的一种溶液。
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CA000546835A CA1314688C (en) | 1987-09-14 | 1987-09-14 | Stripping and recovery of dichromate in electrolytic chlorate systems |
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CN102421941A (zh) * | 2009-05-15 | 2012-04-18 | 阿克佐诺贝尔化学国际公司 | 阴极的活化 |
CN102811952A (zh) * | 2010-03-23 | 2012-12-05 | 朗盛德国有限责任公司 | 用于制备氧化铬(iii)的方法 |
CN103249677A (zh) * | 2010-12-08 | 2013-08-14 | 朗盛德国有限责任公司 | 用于制备氧化铬(iii)的方法 |
CN113088981A (zh) * | 2021-04-10 | 2021-07-09 | 贵州丝域环能科技有限公司 | 一种不锈钢酸洗钝化液的制备、处理及再生方法 |
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US5000858A (en) * | 1989-07-17 | 1991-03-19 | Coltec Industries Inc. | Method for removing hexavalent chromium from water |
US5093089A (en) * | 1990-07-16 | 1992-03-03 | Chemetics International Company Ltd. | Process for the separation of sulphate |
US5294307A (en) * | 1992-07-31 | 1994-03-15 | Huron Tech Corp | Integrated process for the production of alkali and alkaline earth metal chlorates and chlorine dioxide |
US5211853A (en) * | 1992-07-31 | 1993-05-18 | Huron Tech Corp. | Method for the removal of chromium compounds from aqueous solutions |
WO1996032696A1 (fr) * | 1995-04-13 | 1996-10-17 | Dai Nippon Printing Co., Ltd. | Carte et module de circuit integre |
WO2010026886A1 (ja) * | 2008-09-05 | 2010-03-11 | 日本化学工業株式会社 | 水酸化クロムの製造方法 |
EP2565162A1 (de) * | 2011-09-05 | 2013-03-06 | LANXESS Deutschland GmbH | Verfahren zur Herstellung von Chrom(III)-oxid |
JP6331145B2 (ja) * | 2014-11-26 | 2018-05-30 | 三菱重工環境・化学エンジニアリング株式会社 | アンモニア処理システム |
CN116119620A (zh) * | 2023-03-03 | 2023-05-16 | 湖南恒光科技股份有限公司 | 一种氯酸钠芒硝脱铬工艺 |
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SE218495C1 (zh) * | 1964-03-10 | 1968-01-23 | ||
US3843769A (en) * | 1972-01-20 | 1974-10-22 | Hooker Chemical Corp | Process for removing hexavalent chromium from chlorate containing liquors |
JPS5521508A (en) * | 1978-07-31 | 1980-02-15 | Nippon Denko Kk | Recovering method for useful substance from aged solution of chromic acid |
US4268486A (en) * | 1979-07-02 | 1981-05-19 | Olin Corporation | Selective chromate removal from a chlorate solution |
CA1112845A (en) * | 1979-07-16 | 1981-11-24 | Ian H. Warren | Destruction of sodium hypochlorite in solutions from a chlorate electrolytic cell |
US4259297A (en) * | 1979-09-04 | 1981-03-31 | Olin Corporation | Chromate removal from concentrated chlorate solution by chemical precipitation |
IT1130595B (it) * | 1980-05-12 | 1986-06-18 | Stoppani Luigi Spa | Procedimento continuo per l'eleminazione di cromo da acque di rifiuto e la valrizzazione del cromo ricuperato |
US4477318A (en) * | 1980-11-10 | 1984-10-16 | Omi International Corporation | Trivalent chromium electrolyte and process employing metal ion reducing agents |
US4680126A (en) * | 1986-02-18 | 1987-07-14 | Frankard James M | Separation and recovery of reusable heavy metal hydroxides from metal finishing wastewaters |
CA1242307A (en) * | 1986-05-21 | 1988-09-27 | Superior Plus Inc. / Superieur Plus Inc. | Removal of chromium from cell liquor |
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1987
- 1987-09-14 CA CA000546835A patent/CA1314688C/en not_active Expired - Fee Related
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1988
- 1988-01-12 US US07/142,958 patent/US4804528A/en not_active Expired - Fee Related
- 1988-07-28 NZ NZ225601A patent/NZ225601A/xx unknown
- 1988-08-02 AU AU20341/88A patent/AU611465B2/en not_active Ceased
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- 1988-09-14 PT PT88498A patent/PT88498B/pt not_active IP Right Cessation
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Cited By (6)
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CN102421941A (zh) * | 2009-05-15 | 2012-04-18 | 阿克佐诺贝尔化学国际公司 | 阴极的活化 |
CN102811952A (zh) * | 2010-03-23 | 2012-12-05 | 朗盛德国有限责任公司 | 用于制备氧化铬(iii)的方法 |
CN102811952B (zh) * | 2010-03-23 | 2014-12-10 | 朗盛德国有限责任公司 | 用于制备氧化铬(iii)的方法 |
CN103249677A (zh) * | 2010-12-08 | 2013-08-14 | 朗盛德国有限责任公司 | 用于制备氧化铬(iii)的方法 |
CN103249677B (zh) * | 2010-12-08 | 2016-08-17 | 朗盛德国有限责任公司 | 用于制备氧化铬(iii)的方法 |
CN113088981A (zh) * | 2021-04-10 | 2021-07-09 | 贵州丝域环能科技有限公司 | 一种不锈钢酸洗钝化液的制备、处理及再生方法 |
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US4804528A (en) | 1989-02-14 |
ZA886083B (en) | 1989-04-26 |
EP0308175A1 (en) | 1989-03-22 |
NZ225601A (en) | 1989-09-27 |
EP0308175B1 (en) | 1992-01-29 |
SE461227B (sv) | 1990-01-22 |
FI884230A (fi) | 1989-03-15 |
ES2039633T3 (es) | 1993-10-01 |
SE8900332D0 (sv) | 1989-01-31 |
CN1015088B (zh) | 1991-12-18 |
FI90438C (fi) | 1994-02-10 |
FI90438B (fi) | 1993-10-29 |
PT88498A (pt) | 1988-10-01 |
PT88498B (pt) | 1992-11-30 |
BR8804713A (pt) | 1989-04-18 |
SE8900332A (zh) | 1990-01-22 |
AU611465B2 (en) | 1991-06-13 |
FI884230A0 (fi) | 1988-09-14 |
AU2034188A (en) | 1989-03-16 |
CA1314688C (en) | 1993-03-23 |
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