有色冶炼废渣中有价金属回收的冶金方法应用之综述
|
摘要
随着经济和科技飞速发展,有色冶炼技术发展迅速,冶炼废渣也不断增加。冶炼废渣中含有大量的有价金属。从废渣中有效提取利用有价金属,能缓解资源短缺和环境污染的问题。论述了在冶炼废渣领域有价金属Cr、Cu、Zn等的回收方法:电化学法、沉淀法、吸附法、离子交换法和液膜分离法,及其在相关领域的研究现状。吸附法在纳米技术领域发展空间巨大;离子交换法在树脂材料领域具有多样性发展;液膜分离法近几年发展迅速,开发稳定高效的液膜是其主要研究方向。吸附法、离子交换法和液膜分离法三种方法的广泛应用将逐渐代替具有二次污染的沉淀法和成本高的电化学法。
With the rapid development of economy and technology, non-ferrous smelting technology has developed rapidly, and smelting waste residue has also increased. The waste residue contains a large amount of valuable metals.Extracting and utilizing these valuable metals can effectively alleviate the shortage of resources and environmental pollution. The paper discusses the recovery methods of valuable metals such as Cr, Cu and Zn in the field of smelting waste slag: electrochemical method, precipitation method, adsorption method, ion exchange method and liquid membrane separation method, and their research status in related fields. The adsorption method has a huge space in the field of nanotechnology; the ion exchange method has diverse development in the field of resin materials; the liquid membrane separation method has developed rapidly in recent years, and the development of stable and efficient liquid membrane is the main research direction. The wide application of the three methods will gradually replace the precipitation method with secondary pollution and the high cost electrochemical method.
With the rapid development of economy and technology, non-ferrous smelting technology has developed rapidly, and smelting waste residue has also increased. The waste residue contains a large amount of valuable metals.Extracting and utilizing these valuable metals can effectively alleviate the shortage of resources and environmental pollution. The paper discusses the recovery methods of valuable metals such as Cr, Cu and Zn in the field of smelting waste slag: electrochemical method, precipitation method, adsorption method, ion exchange method and liquid membrane separation method, and their research status in related fields. The adsorption method has a huge space in the field of nanotechnology; the ion exchange method has diverse development in the field of resin materials; the liquid membrane separation method has developed rapidly in recent years, and the development of stable and efficient liquid membrane is the main research direction. The wide application of the three methods will gradually replace the precipitation method with secondary pollution and the high cost electrochemical method.
引文
[1]丁忠浩,翁达.固体和气体废弃物再生与利用[M].北京:国防工业出版社,2006:24-33.
[2]王明燕,贾木欣,肖仪武,等.中国钨矿资源现状及可持续发展对策[J].有色金属工程,2014,4(2):76-80.WANG Mingyan,JIA Muxin,XIAO Yiwu,et al.Current status of China's tungsten resources and countermeasures for sustainable[J].Development Nonferrous Metals Engineering,2014,4(2):76-80.
[3]黄振德,王伏生.高密度钨合金在军工中的应用及展望[J].湖南有色金属,1997(3):44-46.HUANG Zhende,WANG Fusheng.Application and prospect of high density tungsten alloy in military industry[J].Hunan Nonferrous Metals,1997(3):44-46.
[4]赵慕岳,范景莲,王伏生.我国钨基高密度合金的发展现状与展望[J].中国钨业,1999,19(增刊1):38-43.ZHAO Muyue,FAN Jinglian,WANG Fusheng.Development status and prospect of tungsten-based high density alloys in China[J].China Tungsten Industry,1999,19(supply1):38-43.
[5]朱俊.我国白钨资源状况初析[J].中国钨业,1997,17(增刊1):29-33.ZHU Jun.Preliminary analysis on the status of white tungsten resources in China[J].China Tungsten Industry,1997,17(supply1):29-33.
[6]刘凯凯,周广柱,周静.铅锌冶炼渣性质及综合利用研究进展[J].山东化工,2013,42(7):58-60,64.LIU Kaikai,ZHOU Guangzhu,ZHOU Jing.Lead and zinc smelting slag properties and the progress of its comprehensive utilization[J].Shandong Chemical Industry,2013,42(7):58-60,64.
[7]刘玉星,朱明娟,龙燕.电化学法在工业含铬废水处理中的应用研究[J].当代化工研究,2016(8):68-69.LIU Yuxing,ZHU Mingjuan,LONG Yan.Application research of electrochemistry method in industial chromecontained wastewater treatment[J].Modern Chemical Research,2016(8):68-69.
[8]裴先茹,黄振旭,卫世乾.电化学氢化法处理废水回收锑的研究[J].湖北农业科学,2016,55(12):3157-3160.PEI Xianru,HUANG Zhenxu,WEI Shiqian.Study on wastewater treatment and the recovery of antimony by electrochemical hydrogenationt[J].Hubei Agricultural Sciences,2016,55(12):3157-3160.
[9]张家玮,王夏阳,何静.直流电协同锌板置换提镉的工艺实践[J].有色金属科学与工程,2015,6(5):22-26.ZHANG Jiawei,WANG Xiayang,HE Jing.Technology practice of cadmium extraction by replacement of zinc plate synergized with direct curren[J].Nonferrous Metals Science and Engineering,2015,6(5):22-26.
[10]梁琥琪,徐扣珍,陈世,等.电化学法从废料中回收金银和铅的工艺研究[J].环境科学,1996(6):53-56.LIANG Huqi,XU Kouzhen,CHEN Shi,et al.Electrochemical separation process of recovery of gold,silver and lead from scrap[J].Environmental Science,1996(6):53-56.
[11]金美珊,王三反,穆永信,等.膜电解法回收含钴废水中钴的研究[J].环境工程,2014,32(3):57-59.JIN Meishan,WANG Sanfan,MU Yongxin,et al.Study on recovering cobalt from cobalt-containing wastewater with membrane electrolysis Method[J].Environmental Engineering,2014,32(3):57-59.
[12]PAIDAR M,BOUZEK K,LAURICH M,et al.Application of a three-dimensional electrode to the electrochemical removal of copper and zinc ions from diluted solutions[J].Water Environment Research,2000,72(5):618-625.
[13]LANZA M R V,BERTAZZOLI R.Removal of Zn(Ⅱ)from chloride medium using a porous electrode:Current penetration within the cathode[J].Journal of Applied Electrochemistry,2000,30(1):61-70.
[14]FLEET B.Evolution of electrochemical reactor systems for metal recovery and pollution control[C].ACS Symposium Series,1989,390(1):554-577.
[15]赵金艳,王金生,郑骥.有色金属冶炼废渣有价金属湿法回收技术及现状[J].矿产综合利用,2012(4):7-12.ZHAO Jinyan,WANG Jinsheng,ZHENG Ji.Technology and current situation of hydrometallurgical recovery valuable metal from nonferrous metal[J].Multipurpose Utilization of Mineral Resources,2012(4):7-12.
[16]徐华蕊,李凤生.沉淀法制备纳米级粒子的研究--化学原理及影响因素[J].化工进展,1996(5):29-31,57.XU Huarui,LI Fengsheng.Precipitation process of nanometer particles chemical prineiples and effeets of operation parameters[J].Chemical Industry and Engineering Progress,1996(5):29-31,57.
[17]白圆,高凌超,刘寰.化学沉淀法去除工业废水中的六价铬[J].中国资源综合利用,2012,30(11):30-33.BAI Yuan,GAO Lingchao,LIU Huan.Removal of Cr(Ⅵ)by chemical precipitation from industrial wastewater[J].China Resources Comprehensive Utilization,2012,30(11):30-33.
[18]付忠田,黄戊生,郑琳子.化学沉淀法处理葫芦岛锌厂含镉废水的研究[J].环境保护与循环经济,2010,30(10):44-46.FU Zhongtian,HUANG Wusheng,ZHENG Linzi.Study on treatment of cadmium containing wastewater in Huludao zinc plant by chemical precipitation[J].Environmental Protection and Circular Economy,2010,30(10):44-46.
[19]熊英禹,付忠田,黄戊生.化学沉淀法处理模拟含铜废水的研究[J].环境保护科学,2014,40(2):35-38.XIONG Yingyun,FU Zhongtian,HUANG Wusheng.Research on treatment of simulated wastewater containing copper by chemical sedimentation method[J].Environmental Protection Science,2014,40(2):35-38.
[20]王吉华,阮琼.沉淀分离法回收真空炼锌渣中铟的研究[J].云南冶金,2016,45(1):34-37.WANG Jihua,RUAN Qiong.The Study on indium recovery from vacuum zinc metallurgical slag by precipitation separation[J].Yunnan Metallurgy,2016,45(1):34-37.
[21]杨巧,李媛媛,张广积,等.稀硫酸浸出结合生物氧化硫酸铁沉淀法处理铜砷滤饼废渣[J].计算机与应用化学,2013(6):587-590.YANG Qiao,LI Yuanyuan,ZHANG Guangji,et al.Dilute sulfuric acid leaching combined with bio-oxidation of ferric sulfate precipitation to handle Cu-As filter cake waste[J].Computers and Applied Chemistry,2013(6):587-590.
[22]张蕊.改性活性炭吸附染料及稻壳基活性炭吸附重金属研究[D].南京:南京农业大学,2011.ZHANG Rui.Adsortions of dye by modified activated carbon and heavy metals by rice husk-based activated carbon[D].Nanjing:Nanjing Agricultural University,2011.
[23]VOLESKY B,PRASETYO I.Cadmium removal in a biosorption column[J].Biotechnology and Bioengineering,1994,43(11):1010-1015.
[24]LIANG S,GUO X,TIAN Q.Adsorption of Pb2+and Zn2+from aqueous solutions by sulfured orange peel[J].Desalination,2011,275(1):212-216.
[25]孟桂花,吴建宁,魏忠,等.超声-微波法合成粉煤灰分子筛及吸附性能研究[J].合成材料老化与应用,2015(1):74-76.MENG Guihua,WU Jianning,WEI Zhong,et al.Synthesis of molecular sieve from fly ash with ultrasonic and microwave method and its study on abso[J].Synthetic Materials Aging and Application,2015(1):74-76.
[26]易飞鸿.从冶锌废渣中提取锗、铟的研究[D].广州:广东工业大学,2003.YI Feihong.Study on extraction of germanium and indium from annealed zinc sediment[D].Guangzhou:Guangdong University of Technology,2003.
[27]黎林根.湿锌法净化钴渣中金属回收[J].科技创新导报,2009(36):99-100.LI Lingen.Purification of metal recovery in cobalt slag by wet zinc method[J].Science and Technology Innovation Herald,2009(36):99-100.
[28]雷兆武,孙颖.离子交换技术在重金属废水处理中的应用[J].环境科学与管理,2008,33(10):30-31.LEI Zhaowu,SUN Yin.Application of lon exchange technology in heavy metals wastewater treatment[J].Environmental Science and Management,2008,33(10):30-31.
[29]陆继来,曹蕾,周海云,等.离子交换法处理含镍电镀废水工艺研究[J].工业安全与环保,2013,39(12):13-15.LU Jilai,CAO Lei,ZHOU Haiyun,et al.Nickel plating rinse wastewater treatment by ion exchange method[J].Industrial Safety and Environmental Protection,2013,39(12):13-15.
[30]邱伟明,奚长生,丘秀珍,等.从冶锌工业废渣中提取镓和铟[J].有色金属(冶炼部分),2017(5):28-32.QIU Weiming,XI Changshseng,QIU Xiuzhen,et al.Extraction of gallium and indium from zinc residues[J].Nonferrous Metals(Extractive Metallurgy),2017(5):28-32.
[31]陈文森,陈炳稔.两性离子交换树脂对含锌废水的处理[J].化工时刊,2004,18(1):47-48.CHEN Wensen,CHEN Bingnian.The treatment to zincic waste water by amphoteric ion exchange resin[J].Chemical Industry Times,2004,18(1):47-48.
[32]LEE S K,LEE U H.Adsorption and desorption property of iminodiacetate resin(Lewatit R:TP207)for indium recovery[J].Journal of Industrial&Engineering Chemistry,2016(40):23-25.
[33]白炳贤,白涛,靳建华,等.MHA型离子交换剂处理含Zn2+废水[J].化工环保,1997,17(5):281-283.BAI Bingxian,BAI Tao,JIN Jianhua,et al.Treatment of zinc-containing wastewater by MHA typeion exchanger[J].Environmental Protection of Chemical Industry,1997,17(5):281-283.
[34]郑磊,徐中慧,刘桂江,等.4A沸石对锰渣渗滤液中Mn2+吸附解吸研究[J].中国锰业,2014(4):27-31.ZHENG Lei,XU Zhonghui,LIU Guijiang,et al.Adsorption and desorption behavior of zeolite 4A on Mn2+from manganese residues leaching[J].China's Manganese Industry,2014(4):27-31.
[35]何燧源,金云云.用离子交换法回收废渣中锌的研究[J].上海环境科学,1991(2):11-13.HE Suiyuan,JIN Yunyun.Study on the ion-exchange method for recovering zinc from the residue of activited carbon production[J].Shanghai Environmental Sciences,1991(2):11-13.
[36]王向德,王军波.乳状液膜用于湿法冶锌中除铜的研究[J].水处理技术,1998,24(4):210-214.WANG Xiangde,WANG Junbo.The removal of copper(Ⅱ)by emulsion liquid membrane in zinc hydrometallurgy[J].Technology of Water Treatment,1998,24(4):210-214.
[37]刘宏江,张碧波.湿法冶锌中回收铟除铁液膜分离技术的研究[J].广东有色金属学报,2003,13(2):89-93.LIU Hongjiang,ZHANG Bibo.Liquid membarne separation technqiue for removal of iron during the successive recovery of indium in zinc hydormetallurgy[J].Journal of Guangdong Non-ferrous Metals,2003,13(2):89-93.
[2]王明燕,贾木欣,肖仪武,等.中国钨矿资源现状及可持续发展对策[J].有色金属工程,2014,4(2):76-80.WANG Mingyan,JIA Muxin,XIAO Yiwu,et al.Current status of China's tungsten resources and countermeasures for sustainable[J].Development Nonferrous Metals Engineering,2014,4(2):76-80.
[3]黄振德,王伏生.高密度钨合金在军工中的应用及展望[J].湖南有色金属,1997(3):44-46.HUANG Zhende,WANG Fusheng.Application and prospect of high density tungsten alloy in military industry[J].Hunan Nonferrous Metals,1997(3):44-46.
[4]赵慕岳,范景莲,王伏生.我国钨基高密度合金的发展现状与展望[J].中国钨业,1999,19(增刊1):38-43.ZHAO Muyue,FAN Jinglian,WANG Fusheng.Development status and prospect of tungsten-based high density alloys in China[J].China Tungsten Industry,1999,19(supply1):38-43.
[5]朱俊.我国白钨资源状况初析[J].中国钨业,1997,17(增刊1):29-33.ZHU Jun.Preliminary analysis on the status of white tungsten resources in China[J].China Tungsten Industry,1997,17(supply1):29-33.
[6]刘凯凯,周广柱,周静.铅锌冶炼渣性质及综合利用研究进展[J].山东化工,2013,42(7):58-60,64.LIU Kaikai,ZHOU Guangzhu,ZHOU Jing.Lead and zinc smelting slag properties and the progress of its comprehensive utilization[J].Shandong Chemical Industry,2013,42(7):58-60,64.
[7]刘玉星,朱明娟,龙燕.电化学法在工业含铬废水处理中的应用研究[J].当代化工研究,2016(8):68-69.LIU Yuxing,ZHU Mingjuan,LONG Yan.Application research of electrochemistry method in industial chromecontained wastewater treatment[J].Modern Chemical Research,2016(8):68-69.
[8]裴先茹,黄振旭,卫世乾.电化学氢化法处理废水回收锑的研究[J].湖北农业科学,2016,55(12):3157-3160.PEI Xianru,HUANG Zhenxu,WEI Shiqian.Study on wastewater treatment and the recovery of antimony by electrochemical hydrogenationt[J].Hubei Agricultural Sciences,2016,55(12):3157-3160.
[9]张家玮,王夏阳,何静.直流电协同锌板置换提镉的工艺实践[J].有色金属科学与工程,2015,6(5):22-26.ZHANG Jiawei,WANG Xiayang,HE Jing.Technology practice of cadmium extraction by replacement of zinc plate synergized with direct curren[J].Nonferrous Metals Science and Engineering,2015,6(5):22-26.
[10]梁琥琪,徐扣珍,陈世,等.电化学法从废料中回收金银和铅的工艺研究[J].环境科学,1996(6):53-56.LIANG Huqi,XU Kouzhen,CHEN Shi,et al.Electrochemical separation process of recovery of gold,silver and lead from scrap[J].Environmental Science,1996(6):53-56.
[11]金美珊,王三反,穆永信,等.膜电解法回收含钴废水中钴的研究[J].环境工程,2014,32(3):57-59.JIN Meishan,WANG Sanfan,MU Yongxin,et al.Study on recovering cobalt from cobalt-containing wastewater with membrane electrolysis Method[J].Environmental Engineering,2014,32(3):57-59.
[12]PAIDAR M,BOUZEK K,LAURICH M,et al.Application of a three-dimensional electrode to the electrochemical removal of copper and zinc ions from diluted solutions[J].Water Environment Research,2000,72(5):618-625.
[13]LANZA M R V,BERTAZZOLI R.Removal of Zn(Ⅱ)from chloride medium using a porous electrode:Current penetration within the cathode[J].Journal of Applied Electrochemistry,2000,30(1):61-70.
[14]FLEET B.Evolution of electrochemical reactor systems for metal recovery and pollution control[C].ACS Symposium Series,1989,390(1):554-577.
[15]赵金艳,王金生,郑骥.有色金属冶炼废渣有价金属湿法回收技术及现状[J].矿产综合利用,2012(4):7-12.ZHAO Jinyan,WANG Jinsheng,ZHENG Ji.Technology and current situation of hydrometallurgical recovery valuable metal from nonferrous metal[J].Multipurpose Utilization of Mineral Resources,2012(4):7-12.
[16]徐华蕊,李凤生.沉淀法制备纳米级粒子的研究--化学原理及影响因素[J].化工进展,1996(5):29-31,57.XU Huarui,LI Fengsheng.Precipitation process of nanometer particles chemical prineiples and effeets of operation parameters[J].Chemical Industry and Engineering Progress,1996(5):29-31,57.
[17]白圆,高凌超,刘寰.化学沉淀法去除工业废水中的六价铬[J].中国资源综合利用,2012,30(11):30-33.BAI Yuan,GAO Lingchao,LIU Huan.Removal of Cr(Ⅵ)by chemical precipitation from industrial wastewater[J].China Resources Comprehensive Utilization,2012,30(11):30-33.
[18]付忠田,黄戊生,郑琳子.化学沉淀法处理葫芦岛锌厂含镉废水的研究[J].环境保护与循环经济,2010,30(10):44-46.FU Zhongtian,HUANG Wusheng,ZHENG Linzi.Study on treatment of cadmium containing wastewater in Huludao zinc plant by chemical precipitation[J].Environmental Protection and Circular Economy,2010,30(10):44-46.
[19]熊英禹,付忠田,黄戊生.化学沉淀法处理模拟含铜废水的研究[J].环境保护科学,2014,40(2):35-38.XIONG Yingyun,FU Zhongtian,HUANG Wusheng.Research on treatment of simulated wastewater containing copper by chemical sedimentation method[J].Environmental Protection Science,2014,40(2):35-38.
[20]王吉华,阮琼.沉淀分离法回收真空炼锌渣中铟的研究[J].云南冶金,2016,45(1):34-37.WANG Jihua,RUAN Qiong.The Study on indium recovery from vacuum zinc metallurgical slag by precipitation separation[J].Yunnan Metallurgy,2016,45(1):34-37.
[21]杨巧,李媛媛,张广积,等.稀硫酸浸出结合生物氧化硫酸铁沉淀法处理铜砷滤饼废渣[J].计算机与应用化学,2013(6):587-590.YANG Qiao,LI Yuanyuan,ZHANG Guangji,et al.Dilute sulfuric acid leaching combined with bio-oxidation of ferric sulfate precipitation to handle Cu-As filter cake waste[J].Computers and Applied Chemistry,2013(6):587-590.
[22]张蕊.改性活性炭吸附染料及稻壳基活性炭吸附重金属研究[D].南京:南京农业大学,2011.ZHANG Rui.Adsortions of dye by modified activated carbon and heavy metals by rice husk-based activated carbon[D].Nanjing:Nanjing Agricultural University,2011.
[23]VOLESKY B,PRASETYO I.Cadmium removal in a biosorption column[J].Biotechnology and Bioengineering,1994,43(11):1010-1015.
[24]LIANG S,GUO X,TIAN Q.Adsorption of Pb2+and Zn2+from aqueous solutions by sulfured orange peel[J].Desalination,2011,275(1):212-216.
[25]孟桂花,吴建宁,魏忠,等.超声-微波法合成粉煤灰分子筛及吸附性能研究[J].合成材料老化与应用,2015(1):74-76.MENG Guihua,WU Jianning,WEI Zhong,et al.Synthesis of molecular sieve from fly ash with ultrasonic and microwave method and its study on abso[J].Synthetic Materials Aging and Application,2015(1):74-76.
[26]易飞鸿.从冶锌废渣中提取锗、铟的研究[D].广州:广东工业大学,2003.YI Feihong.Study on extraction of germanium and indium from annealed zinc sediment[D].Guangzhou:Guangdong University of Technology,2003.
[27]黎林根.湿锌法净化钴渣中金属回收[J].科技创新导报,2009(36):99-100.LI Lingen.Purification of metal recovery in cobalt slag by wet zinc method[J].Science and Technology Innovation Herald,2009(36):99-100.
[28]雷兆武,孙颖.离子交换技术在重金属废水处理中的应用[J].环境科学与管理,2008,33(10):30-31.LEI Zhaowu,SUN Yin.Application of lon exchange technology in heavy metals wastewater treatment[J].Environmental Science and Management,2008,33(10):30-31.
[29]陆继来,曹蕾,周海云,等.离子交换法处理含镍电镀废水工艺研究[J].工业安全与环保,2013,39(12):13-15.LU Jilai,CAO Lei,ZHOU Haiyun,et al.Nickel plating rinse wastewater treatment by ion exchange method[J].Industrial Safety and Environmental Protection,2013,39(12):13-15.
[30]邱伟明,奚长生,丘秀珍,等.从冶锌工业废渣中提取镓和铟[J].有色金属(冶炼部分),2017(5):28-32.QIU Weiming,XI Changshseng,QIU Xiuzhen,et al.Extraction of gallium and indium from zinc residues[J].Nonferrous Metals(Extractive Metallurgy),2017(5):28-32.
[31]陈文森,陈炳稔.两性离子交换树脂对含锌废水的处理[J].化工时刊,2004,18(1):47-48.CHEN Wensen,CHEN Bingnian.The treatment to zincic waste water by amphoteric ion exchange resin[J].Chemical Industry Times,2004,18(1):47-48.
[32]LEE S K,LEE U H.Adsorption and desorption property of iminodiacetate resin(Lewatit R:TP207)for indium recovery[J].Journal of Industrial&Engineering Chemistry,2016(40):23-25.
[33]白炳贤,白涛,靳建华,等.MHA型离子交换剂处理含Zn2+废水[J].化工环保,1997,17(5):281-283.BAI Bingxian,BAI Tao,JIN Jianhua,et al.Treatment of zinc-containing wastewater by MHA typeion exchanger[J].Environmental Protection of Chemical Industry,1997,17(5):281-283.
[34]郑磊,徐中慧,刘桂江,等.4A沸石对锰渣渗滤液中Mn2+吸附解吸研究[J].中国锰业,2014(4):27-31.ZHENG Lei,XU Zhonghui,LIU Guijiang,et al.Adsorption and desorption behavior of zeolite 4A on Mn2+from manganese residues leaching[J].China's Manganese Industry,2014(4):27-31.
[35]何燧源,金云云.用离子交换法回收废渣中锌的研究[J].上海环境科学,1991(2):11-13.HE Suiyuan,JIN Yunyun.Study on the ion-exchange method for recovering zinc from the residue of activited carbon production[J].Shanghai Environmental Sciences,1991(2):11-13.
[36]王向德,王军波.乳状液膜用于湿法冶锌中除铜的研究[J].水处理技术,1998,24(4):210-214.WANG Xiangde,WANG Junbo.The removal of copper(Ⅱ)by emulsion liquid membrane in zinc hydrometallurgy[J].Technology of Water Treatment,1998,24(4):210-214.
[37]刘宏江,张碧波.湿法冶锌中回收铟除铁液膜分离技术的研究[J].广东有色金属学报,2003,13(2):89-93.LIU Hongjiang,ZHANG Bibo.Liquid membarne separation technqiue for removal of iron during the successive recovery of indium in zinc hydormetallurgy[J].Journal of Guangdong Non-ferrous Metals,2003,13(2):89-93.