摘要
离子液体是一种绿色溶剂,它作为萃取介质可避免传统湿法冶金因有机溶剂挥发而产生环境污染。采用改进后的无溶剂法和程序升温法合成5种1-烷基-3-甲基咪唑六氟磷酸盐([CxMIm][PF6],其中X=4、6、8、10、12)离子液体。离子液体粗品用丙酮稀释后,活性炭脱色制得无色离子液体,产品在400~800 nm范围内无明显吸收。
离子液体理化性质被详细研究。紫外吸收光谱法测定离子液体在水中的溶解度。芘荧光探针测得离子液体极性和短醇类相当,并显示出随着烷基链的增加,极性逐渐降低的规律性。热稳定性、密度、粘度和表面张力等物理化学性质结果表明:离子液体的性能是由阴、阳离子的结构和性质共同决定的。热稳定性、密度、粘度和溶解性主要受阴离子种类影响;随着咪唑阳离子取代基链长的规律性增加,离子液体的热稳定性、密度、极性、水含量和表面张力逐渐降低;热分解温度均高于260 oC;密度介于1.1~1.4g.cm-3之间;表面张力高于传统有机溶剂正己烷,低于水的表面张力。因此离子液体的高稳定性、强憎水性、低表面张力的性质应用于萃取方面有着独特的优势。
以制备合成的离子液体(IL)、磷酸三丁酯(TBP)和三氯化铁(FeCl3)分别为萃取介质、萃取剂和协萃剂建立盐湖卤水锂萃取研究模型,考察离子液体性质和不同萃取条件对锂萃取率的影响。结果表明离子液体的粘度、极性和憎水性是影响锂萃取率的主要因素。锂的萃取率随离子液体中烷基碳原子数的增加而增加。然而,当碳原子数超过8时,离子液体室温下呈固态,在萃取过程中出现第三相,不利于萃取分离,因此,1-辛基-3-甲基咪唑六氟磷酸盐被确定为最终萃取介质。该体系的最佳萃取条件是:TBP/IL:9/1(v/v),水相酸度:0.03 mol/L HCl,相比(O/A):1.5:1和Fe/Li:1.3:1。在优化条件下,锂的单次萃取率和反萃率分别是87%和90%。卤水中的钾、钙、镁、钠等主要离子不干扰萃取。卤水中锂的串级萃取实验表明经过三级萃取和二级反萃后,锂的总提取率大于97%,有机相中Mg/Li比降至2.2左右。离子液体-TBP有机相可重复使用10次以上。机理研究表明,Li+与TBP和FeCl3形成极性较小的LiFeCI4·2TBP络合物而被萃取进入有机相,在有机相中加入盐酸因H+极化强于Li+而将Li+置换重新进入水相。因LiFeCl4·2TBP在弱极性的离子液体中溶解度优于非极性的溶剂煤油,离子液体萃取体系具有更高的锂萃取效率和容量。
此外,上述体系用于头发中痕量锂的富集测定,线性范围为0.00~2.50μg·L-1,检出限在2.5 ng·L-1,富集倍数在100倍以上,加标回收率在89%~92%之间,实现了简单设备对超复杂体系中超痕量组分的准确测定,结果满意。
Ionic liquid is green solvent and as extraction medium can avoid environmental pollution of conventional hydrometallurgy due to volatilization of organic solvent. The modified two-steps method using non-solvent and temperature programmed technologies was developed for synthesis of five ionic liquids 1-alkyl-3-methylimidazolium hexafluorophosphate abbreviated as [CxMIm][PF6], where X=4, 6, 8, 10 and 12. After the crude products were diluted by acetone, it was decolored with activated carbon and almost colorless ionic liquids were obtained. There was no obvious absorption peak in the wavelength range of 400~800 nm.
The physical and chemical properties of the ionic liquid such as thermal stability and solubility were investigated in detail. We determined the solubility of ionic liquids in water by ultraviolet absorption spectrum method. Polarity of ionic liquid was determined by pyrene fluorescence probe, and found polarity decreasing with the increasing of alkyl chain length. Besides, the physical properties containing thermal stability, density, viscosity and surface tension were determined. The results showed the properties were decided by both cations and anions of ionic liquids and exhibited how melting point, viscosity, density and surface tension were affected by changes in alkyl chain length. In the series of ionic liquids studied here, the thermal stability, polarity, water content and surface tension of ionic liquids were decreased with the increasing in alkyl chain length. All these ionic liquids exhibited excellent thermal stability of 260 oC; density was of 1.1~1.4g.cm-3; surface tension lower than water and higher than hexane. Therefore, the excellent properties containing high stability, strong hydrophobicity and low surface tension of ionic liquids proved its advantage in extraction.
A model for study on extraction lithium from salt lake brine was designed, in which the assayed ionic liquid (IL), tributyl phosphate (TBP) and FeCl3were used as extraction medium, extracting agent and synergic reagent, respectively. The effects of ionic liquid propertied and extraction conditions on the lithium extraction were investigated. The results indicated that the viscosity, polarity and hydrophobicity were the main factors which influenced the extraction efficiency. With increasing number of carbon atom of alkyl group in the ionic liquid the extraction efficiency of lithium will obviously increase. However, the ionic liquid was solid and resulted in appearing a third phase when number of alkyl group exceeded eight. Thus, 1-octyl-3-methylimidazolium hexafluorophosphate ionic liquid was finally selected as extraction medium. Optimal extraction conditions of the system included TBP/IL of 9/1(v/v), 0.03 mol/L HCl, O/A of 1.5:1 and Fe/Li of 1.3:1. Under optimal conditions, single extraction and back-extraction efficiencies are 87% and 90%, respectively. The interference study indicated the determination of lithium was free from the interference of almost all positive and negative ions such as K+, Ca2+, Mg2+ and Na+ found in brine water. Daisy extraction of salt lake brine indicated that total recovery of 97% was obtained by combination of three step extractions with two step back-extraction, and Mg/Li ratio was lower to about 2.2. The reuse of ionic liquid-TPB organic phase was up to 10 times. Study on the mechanism revealed Li+ combines with TBP and FeCl3 to form a low polar LiFeCI4·2TBP and was extracted into organic phase because, and addition of HCl in the organic phase will result that Li+ was again back-extracted into aqueous phase due to strong polarization force of H+. As LiFeCl4·2TBP is more easy to small polar ionic liquid than non-polar solvent paraffin, the system with ionic liquid is of higher extraction efficiency and the capacity of lithium.
Moreover, the above system was applied to the preconcentration of ultra trace lithium in hair. Proposed procedure allowed the rapid lithium determination at 2.5μg.L-1 level in hair samples with satisfactory results. The detection limit, calculated using three times the standard error of estimate of the calibration graph, was 2.5 ng of lithium per liter hair sample. The enrichment factor of lithium was more than 100 times. Lithium recoveries between 89 and 92% for samples proof the accuracy of the proposed method.
引文
[1]徐月和.我国锂的产品品种[J].第十届全国锂铷铯学术会议论文,2001,33.
[2]蒋明.锂及锂化合物的应用[J].无机盐工业,1983,9:32-36.
[3] Andrew N,William D.Implementing and Managing E-Security. New York:McGraw-Hill Education,2001,57-121.
[4]张明杰,郭清富.21世纪的能源金属—锂的冶金现状及发展[J].盐湖研究,2001(3):52-60.
[5]曹兆汉.国外锂资源的开发利用(上)[J].盐湖研究,1989,1:38-39.
[6]曹兆汉.国外锂资源的开发利用(下)[J].盐湖研究,1989,2:33-35.
[7] Johonson F N.The early history of lithium therapy Lithium.Current Appliaction in scince, medicine and Technology,1985,(1):337-338.
[8] Rodney N H.Lithium and its Compounds.I.E.C., 1951,30(12):2637-2641.
[9]林大泽,锂的用途及其资源开发[J],中国安全科学学报, 2004,14(9):72-76.
[10] Rodney N. hander et al, Lithium and its Compounds[J], I.E.C.,1951,30(12): 2637-2641.
[11]王安建.矿产资源与国家经济发展[M].地震出版社,2002,10:64-129.
[12]刘建军.我国锂工业的生产现状和发展对策[M].新材料产业,2004,5:32-37.
[13]汪镜亮.锂矿物的综合利用[J].矿产综合利用,1992,5:19-26.
[14] Lindsey T.Industry Minerals.Geological Survey,2005,29(17):217-246.
[15]秦俊法.锂的生物必需性及人体健康效应[J].广东微量元素科学,2000,7(3):1-16.
[16]张红.氯化锂对Ⅱ型糖尿病患者离体红细胞胰岛素受体磷酸化的作用[J].中国现代医学杂志, 2001,6:33-34.
[17] Birch N J,Sadler P J.Specialist Periodical Reports.Inorganic Biochemistry,1979,1:407-412.
[18] Birch N J,Sadler P J.Specialist Periodical Reports.Inorganic Biochemistry,1982,3:372-379.
[19] Moses J W,Leon M B,Popma J J,et a1.Sirolimus-eluting stents versus standard stents in patients with stenosis in anative coronary artery.N Engl J Med,2003,349(14):1315-1323.
[20] Moreno R,Fernandez C,Hernandez R,et a1.Drug-eluting stent thromhosis:results from a pooled analysis including andomized studies.J Am Coil Cardiol,2005,45 (6):954-959.
[21] Ge L,Airoldi F,Iakovou I,et a1.Clinical and angiographic outcome after implantation of drug- eluting stents in bifur-cation lesionswith the crush stent technique:importance of final kissing balloon postdilation.J Am Coll Cardiol,2005,46(4):613-620.
[22]冯安生.锂矿物的资源、加工和应用[J].矿产保护和应用,1993,1:39-46.
[23]游清治.对中国锂工业发展的思考[J].世界有色金属,1997,10:14-15.
[24]张兴儒.关于柴达木盆地盐湖锂资源开发的探讨[J].海湖盐与化工,1996,25(3):44-46.
[25]宋彭生.盐湖及相关资源开发利用进展[J].盐湖研究,2000,8(4):12-13.
[26]戴自希,李树枝.不可抗拒的趋势-从盐湖中提取锂资源[J].中国地质,2002,260:45-47.
[27]杨天风,袁建军.盐湖晶间卤水提锂工艺研究[J].海湖盐与化工,2002, 31(1): 21-23.
[28] Huang Z F,Zhang H Z,Wang C Z.First-principles investigation on extraction of lithium ion from monoclinic LiMnO2.Solid State Sciences,2009,11(1):271-274.
[29]潘立玲,朱建华,李渝渝.锂资源及其开发技术进展[J].矿产综合利用,2002,2: 28-32.
[30] Rodney N H.Lithium and its Compounds.I.E.C.,1951,30(12):2637-2641.
[31]王宝才.我国卤水锂资源及开发技术进展[J].化工矿物与加工,2000,10:13-15.
[32]戴自希.世界锂资源现状及开发利用趋势[J].中国有色冶金,2008,4(17):17-20.
[33]于明臻.我国锂盐工业的现状及技术进展[J].无机盐工业,1999,31(1):17-19.
[34] Samoilov V I,Kulenova N A.Extracting lithium from waste solutions of chemico-meta llurgical lithium carbonate production.TheoretiFoun Chem Eng,2008,4(5):714-717.
[35] Huang Z F,Zhang H Z,Wang C Z.First-principles investigation on extraction of lithium ion from monoclinic LiMnO2.Solid State Sciences,2009,11(1):271-274.
[36]杨天风,袁建军.盐湖晶间卤水提锂工艺研究[J].海湖盐与化工,2002, 31(1): 21-23.
[37]陈正炎,古伟良,陈富珍.国内外盐湖卤水提锂方法及其发展[J].新疆有色金属,1996,2: 21-25.
[38]赵武壮.我国锂资源的开发与应用.世界有色金属,2008,(4):38-40.
[39]张金才,王敏,戴静.卤水提锂的萃取体系概述[J].盐湖研究,2005,13(1):42-47.
[40]李丹,邓天龙,孙柏.无机离子交换法从卤水中提锂的研究进展[J].广东微量元素科学,2007, 14(1):6-8.
[41]汪镜亮.卤水锂资源提锂现状[J].化工矿物与加工,1999,28(12):1-5.
[42]肖小玲,戴志峰,祝增虎等.吸附法从盐湖卤水提锂的研究进展[J].盐湖研究,2005,13 (2): 66-69.
[43]钟辉,殷辉安.偏钛酸型锂离子交换剂表面性质与选择吸附性研究[J].离子交换与吸附,2003, 19 (1):55-60.
[44] Shiu J Y,Lin J R,Lee D C,et al.Method for adsorbing lithium ions from a lithium -containing aqueous solution by a granular adsorbent:US,2003:12-18.
[45]徐徽,许良,陈自珍等.高镁锂比盐湖卤水镁锂分离工艺[J].中南大学学报,2009,40(1): 36-40.
[46]邓友全.离子液体介质与材料研究进展[J].中国科学院院刊,2005,4:297-300.
[47]何桂英.离子液体及其研究进展[J].宁波职业技术学院学报,2004,5:85-86.
[48]张景涛,朴香兰,朱慎林.离子液体及其在萃取中的应用研究进展[J].化工进展,2001,12: 17-19.
[49]顾彦龙,石峰,邓友全.离子液体在催化反应和萃取分离中的研究和应用进展[J].化工学报, 2004,12:1957-1963.
[50]程玉良,韩燕.室温离子液体理化性能的探讨[J].平原大学学报,2004,21(6):124-125.
[51] Rogers R D,Jonathan G,Huddleston A E,et al.Green Chem,2001, 3:156–164.
[52] Moshe D,Solutskin E,Benjamin M,et al.J Am Chem Soc,2005,127:7796 -7804.
[53] Marco P,Angelini G,Chiappe C,et al.J Org Chem,2005,70:8193-8196.
[54] Yoshikata K,Kumiko M,Peter W,et al.J Phys Chem B,2005,109:9014-9019.
[55] Laszlo B,Zsombor M,Krisztina S N,et al.Chem Phys Lett,2004,400:296-300.
[56] Patrascu C,Sugisaki C,Mingotaud C,et al.New pyridinium chiral ionic liquids.Liquids Heterocycles,2004,63:2033-2041.
[57] Sheldon R.Catalytic reactions in ionic liquids.Chem Commum,2001,23:2399-2407.
[58] Maggel D,Seddon K R.Improved preparation of Ionic liquids using microwave irradiation.Green chem,2003,3:181-186.
[59]李长多,张学俊.1,3-二烷基咪唑类离子液体的合成研究[J].化工中间体,2008,11:62-66.
[60] Paul A,Mandal P K,Samanta A.How transparent are the imidazolium ionic liquids? A case study with 1-methyl-3-butylimidazolium hexafluorophosphate.Chem Phys Let,2005,402:375-379.
[61]王仲妮,王洁莹,司友华等.咪唑类离子液体的研究进展[J].化学进展,2008,20(7-8):1057-1063.
[62] Ngo H L,LeCompte K,Hargens L,et al.Thermal properties of imidazolium ionic liquids.Thermochim Acta,2000,357:97-102.
[63] Nishida T,Tashiro Y,Yamamoto M.Physical and electrochemical properties of 1-aklyl-3-methyl -limidazolium tetrafluoroborate for electrolyte.J fluorine Chem,2003,120(2) 135-141:.
[64] Suarez P A Z, Einloft S, Dullius J E L,et al.Synthesis and physical-chemical properties of ionic liquids based on 1-n-butyl-3-methylimidazolium cation.J Chim Phys,1998,95:1626-1628.
[65] Law G,Watson P R.Surface tension measurement of N-alkylimidazolium ionic liquids.Langmuir, 2001,17(20):6138-6141.
[66] Dzyuba S,Bartsch R A.Influence of structural variations in 1-alkyl(aralkyl)-3-methylimidazolium hexafluorophosphates and bis(trifluoromethyl-sulfonyl)imi des on physical properties of ionic liquids.Chem Phys Chem,2002,3:161-170.
[67] Fletcher K A,Storey I A,Hendricks A E,et al.Behavior of the solvatochromic probes Reichardt’s dye, pyrene, dansylamide, Nile Red and 1-pyrenecarbaldehyde within the room temperature ionic liquid bmimPF6.Green Chem,2001,3:210.
[68] Seddon K R.Ionic liquid for clean technology.J Chem Technol Biotech,1997,68(4):351-356.
[69] Wasserscheid P,Keim W.Ionic liquids-New“solutionin”for transition metal catalysis.Angew Chem Int Ed,2000,39(21):3772-3789.
[70] Wakai C,Oleinkova A,Ott M,et al.How polar are ionic liquids? Determination od the static dielectric constant of an imidazolium-based ionic liquid by microwave dielectric spectroscopy Chem.J Phys B.2005,109:17028-17030.
[71] Fletcher K A,Storey I A,Hendricks A E,et al.Behavior of the solvatochromic probes Reichardt’s dye, pyrene, dansylamide, Nile Red and 1-pyrenecarbaldehyde within the room-temperature ionic liquid bmimPF6.Green Chem,2001,3:210-211.
[72] Perry R L,Jones K M,Scott W D,et al.Densities,viscosity and conductivities of mixtures of selected organic cosolvents with the Lewis basic aluminum chloride+ 1-methyl-3-ethylimidazolium chloride molten salt.J Chem Eng Data,1995,40 (3):615-619.
[73] Schmid A,Dordick J S,Hauer B,et al.Industrial biocatalysis today and tomorrow.Nature, 2001,409(6818):58-268.
[74] Klibanov A M.Improving enzymes by using them in organic solvents.Nature,2001,409(6818): 241-246.
[75] Rumbau V,Marcilla R,Pomposo J A,et al.Ionic liquid Immobilized enzyme for biocatalytic synthesis of conducting polyaniline.Macromolecules,2006,39(25):8547-8549.
[76] Lu X,Hu J,Yao X,Wang Z,et al.Electrocatalytic oxidation of dopamine at an ionic liquid modified carbon paste electrode and its analytical application.Biomacromolecules,2006,7(3):975-980.
[77] Zhao H,Luo R G,Malhotra S V.oward green processes for fine chemicals synthesis biocatalysis: in ionic liquid-supercritical carbon dioxide biphasic systems.Biotechnol Prog,2003,19(3):1016- 1018.
[78] Kaar J L,Jesionowski A M,Berberich J A,et al.Impact of ionic liquid physical properties on lipase activity and stability.J Am Chem Soc,2003,125(14):4125-4131.
[79] Wang Y Z,Mei L H,Zhong Ch L,et al.A novel temperature-controlled ionic liquid as the medium for phenylethyl acetate synthesis catalyzed by lipase.Chin J Catal,2006,27(9):799-804.
[80] Chen P Y.The assessment of removing strontium and cesium cations from aqueous solutions based on the combined methods of ionic liquid extraction and electrodeposition.Electrochimica Acta,2007,52(17):5484-5492.
[81] Wang J L,Zhao D S,Zhou E P,et al.Desulfurization of gasoline by extraction with N-alkyl -pyridinium-based ionic liquids.Journal of Fuel Chemistry and Technology,2007,35(3):293-296.
[82]沈兴海,徐超,刘新起等.离子液体在金属离子萃取分离中的应用[J].核化学与放射化学, 2006,28(3):129-138.
[83]吕江平,王九思,来风习等.离子液体的特点及在液-液萃取中的应用研究[J].甘肃联夸大学学报(自然科学版),2007,21(1):70-75.
[84]于澄洁,王大伟.室温离子液体及其在绿色化学中的应用[J].西安石油学院学报:自然科学版,2002,17(5):59-65.
[85]丁琪,乐长高.室温离子液体在萃取中的应用[J].化工时刊,2006,20(7):64-67.
[86]邵媛,邓宇.离子液体的合成及其在萃取分离中的应用[J].精细石油化工进展,2005,6(11): 48-52.
[87]刘晓庚,陈梅梅,刘长鹏等.室温离子液体在化学合成和萃取分离中的应用[J].化学世界,2006, (10):629-635.
[88] Petrov P K,wibetoe G,Tsalev D L.Comparison between hydride generation and nebulization for sample introduction in the determination of lead in plants and water samples by inductively coupled plasma mass spectrometry, using external calibration and isotope dilution. Spectrochimica Acta Part B:Atomic Spectroscopy,2006,61(1):50-70.
[89] Dias L F,Miranda G R,Saint’Pierre T D,et al.Method development for the determination of cadmium, copper, lead, selenium and thallium in sediments by slurry sampling electrothermal vaporization inductively coupled plasma mass spectrometry and isotopic dilution calibration.Spectro chimica Acta Part B:Atomic Spectroscopy,2005,60(1):117-124.
[90] Ndung’u K,Hibdon S,Flegai A R.Determination of lead in vinegar by ICP-MS and GFAAS: evaluation of different sample preparation procedures.Talanta,2004,64(1):258-263.
