| The solid phase extraction technique got a rapid development because of its obvious advantages.The higher enrichment factors,absence of emulsion,low organic solvent consumption and environment friendly of solid phase extraction make this technique adapt to determination of noble metal ions in complex matrices,and determination of trace impurities in noble metal material.We find that the complex cation of gold can reacts with quaternary ammonium salt to form a hydrophobic ion association.The ion association can be preconcentrated by solid phase with high enrichment factor.This show the solid phase extraction has good application prospects in gold extraction.In this dissertation,the application of solid phase exaction in the fields of extraction of gold from cyanide solution, trace gold determination and trace impurities determination in gold products were studied. The main research works are listed as follow:(â… )Study on the extraction of gold from cyanide solution by solid phase exaction.(1)The extraction of gold from cyanide solution by solid phase exaction with cetyl trimethylammonium bromide(CTMAB)was studied.The condition for the formation of ion association(the pH of solvent,the amount CTMAB used,the accessory reagent used,et al)and the condition for solid phase extraction of the ion association(the extraction sorbents,the capacity of the cartridge,the enrichment factor,the recovery of gold,et al) were carefully studied.The results show that the reasonable conditions are the molar ratio of CTMAB:Au 1:1,pH 9.5-12,sample flow rate 20 mL/min.The capacity of the cartridge for gold extraction reaches 23.6 mg/g under this condition.The enriched gold was eluted from the cartridge with 5.0 mL of ethanol as eluent.The enrichment reaches 100-1000 times for 1.0×10-5～2.0×10-4mol/L of gold solutions.The effects of reversed phase sorbents(C2,C4,C8,C18)on gold extraction were studied.The results show that C18has the best effect.The effects of various quaternary ammonium salts on gold extraction were also studied.The alkyltrimethyl ammonium type quaternary ammonium salts has the best effect. The optimal reagents for gold extraction are tetradecyl trimethyl ammonium chloride,cetyl trimethyl ammonium chloride or dodecayl trimethyl amine chloride. The mechanisms of the gold extraction with quaternary ammonium salts by solid phase extraction were studied.The ion association of CTMAB with Au(CN)2- was synthesized,and it structure was verified by IR,1HNMR and MS.The high performance liquid chromatography analysis show that the hydrophobicity of the ion association is strong than that of CTMAB.The images of the sorbent and the sorbent which absorbed gold were obtained by scanning electron microscope,and the retention behaviors of ion association on octadecyl silane(C18)were studied.By the above experipents and the previous work reported,the mechanisms of the gold extraction were proposed.The CTMAB can reacts with Au(CN)2- to form a hydrophobie ion association.When the ion association solution passing the extraction cartridge,the solvents molecular(water)gives a repelling force to the ion association,and the non-polar stationary phase(C18)has an adsorption to the ion association.The ion association was reversibly absorbed onto the C18. When using organic solvent as eluant,the repelling force to ion association,and affability of C18to ion association decreased markedly,and the ion association which absorbed on C18 can be eluted from the cartridge.(â…¡)The scale-up experiment,selective experiment,and the elementary procedure for extraction.(1)The scale-up experiment was carried out.The results show that the amount of gold extraction increase with the increasing of sorbent amount.However,the capacity of the gold extraction decrease with the increasing of sorbent amount.The sample flow rate linearly increase with the increasing of cartridge cross sections.The sample flow rate linearly decrease with the increasing of cartridge length.The eluant needed linearly increase with the increase of the gold amount absorbed on the cartridge.For various different type cartridges,the diameter to length ranged to 1:1-1:2 have the largest extraction capacity to gold.The effect of interfering ions on gold extraction was studied. The results show that Ag(â… ),Fe(â…¡),Cu(â… ),Ni(â… ),Zn(â…¡),Co(â…¡)can interfere the gold extraction.The interfering orders are Ag(â… )＞Cu(â… )≈Ni(â… )≈Zn(â…¡)＞Co(â…¡)＞Fe(â…¡).The interference of these ions has a synergistic effect when they simultaneously existed.The extraction of gold from typical cyanide solution was also studied.The results show that the gold extraction capacity decreas ripadly because of interfering ions exised.The gold mud obtained contain 13.68%gold.This indicated that the selectivity of solid phase extraction method is not obviously improved compared to that of activated carbon adsorption method.(2)The precipitating of gold with CTMAB in cyanide solution was studied.The ion association of CTMAB with Au(CN)2- has low solubility in water solution,only 7.12μg/mL.The precipitation can formed when gold contraction above 7.12μg/mL at 25℃. we carefully studied the factors which affects the ion association solubility.The medium pH does not affects the solubility.However,the temperature and the organic solvent in medium greatly affect the solibility.The solibility was increased markedly with the increasing of temperature and increasing the organic solvent proportion in medium.The effect of various different quaternary ammonium salts to precipitate gold was studied.The solubility orders are D1622＜HDBAB＜CPB＜CTMAB and OTMAB＜CTMAB＜TTMAB＜DTMAB. Because the ion association has low solubility,the ion association solution should be filtrated when the gold concentration above 7.12μg/mL.The recovery of gold from eluant was also studied.The results show that the recovery of gold can be achieved by zinc dust precipitation method,direct electrodeposition method,and hydrometallurgy or thermometallurgy when ethanol evaporated.(3)By above experimients,the reasonable procedure for gold extraction was primary identified.The quaternary ammonium salts was added to the cyanide solution.This solution was applied to solid phase extraction(The solution was filtered when the gold concentration above 7.12μg/mL).After the extraction finished(The gold absorption attains saturation),the cartridge was eluted with ethanol.The ethanol in eluant was recoveried by distillation,and the gold mud was obtained.The gold mud was afforded to refining,and the residual cyanide solution can be afforded to cyanide leaching again.(â…¢)The applacition of solid phase extraction in gold determinationA new method for the determination of gold based on the color reaction of gold with 5-(2-hydroxy-4-nitrophenylazo)-thiorhodanine(HNATR)and the solid phase extraction of the colored chelate with a reversed phase polymer-based C18cartridge was developed.In the presence of 0.05-0.5 mol/L of phosphoric acid solution and emulsifier-OP medium,HNATR reacts with gold to form a red chelate of a molar ratio 1:3(gold to HNATR).This chelate was enriched by the solid phase extraction with a polymer-based C18cartridge and eluted the chelate from the cartridge with dimethyl formamide(DMF).The enrichment factor of 100 was achieved.In the DMF medium,the molar absorptivity of the chelate is 1.37×105 L.mol-1.cm-1at 520 nm.Beer's law is obeyed in the range of 0.01～3μg/mL in the measured solution.The detection limit,based on the three times of standard deviation is 0.02μg/L in the original sample.This method was applied to the determination of gold in water and ore with good results.The relative standard deviations are 2.8%-3.5%.The standard recoveries are 88%-96%.The determination results are agreed with that of reference method (ICP-MS method).The solid phase extraction and flame atomic absorption spectrometry method for the determination of gold using MCI GEL reversed phase resin loaded with TBP as sorbent was studied.The gold was quantitatively absorbed on the MCI GEL resin when the sample solution pass the cartridge as 1.0-6.0 mol/L hydrochloric acid medium.The absorbed goht was eluted from the cartridge with 0.06 mol/L sodium sulphite solution as eluant.The enrichment factor above 100 was achieved.The gold in eluant was determination by flame atomic absorption spectrometry method.Beer's law was obeyed in the range of 0.1～3.5μg/mL.The detection limit reaches 5.0 ng/L.This method was applied to the determination of gold in ore and water samples.The relative standard deviations are 2.4%-2.8%,and the recoveries are 88%-104%.The determination results are agreed with that of reference method(ICP-MS method).A new method for the simultaneous determination of palladium,platinum,rhodium and gold by solid phase extraction and high performance liquid chromatography using 2-carboxyl-1-naphylidene rhodanine(CNR)as pre-column derivatization reagents was studied.In the presence of pH 3.5 acetic acid-sodium acetate buffer solution and triton X-100 medium,the palladium,platinum,rhodium and gold ions were reacted with CNR to form colored chelates.The Pd-CNR,Pt-CNR,Rh-CNR and Au-CNR chelates were enriched by solid phase extraction with Waters Sep-Pak C18cartridge.The enrichment factor of 100 was achieved by eluting the retained chelates from the cartridge with DMF.These chelates were separated on a ZORBAX Stable Bound rapid analysis column(4.6×50 mm,1.8μm) with 54%methanol(containing 0.1%of acetic acid and 0.1%of Triton X-100)as mobile phase and detected with a photodiode array detector from 400～600 nm.The palladium, platinum,rhodium and gold chelates were separated completely within 2.5 min.The detection limits(S/N=3)of palladium,platinum,rhodium and gold reaches 1.2μg/L,0.8μg/L,1.4μg/L and 1.0μ/L,respectively.This method was applied to the determination of palladium,platinum,rhodium and gold in water and geological samples.The relative standard deviations were 2.4%-3.6%.The standard recoveries were 91%-95%.The determination results are agreed with that of reference method(ICP-MS method).(â…£)Simultaneous determination of trace impurities in gold potassium cyanide for electroplating by on-line solid phase extraction and high performance liquid chromatographyA new method for the simultaneous determination of trace impurities in gold potassium cyanide for electroplating was developed by high performance liquid chromatography equipped with on-line solid phase extraction technique.The samples were digested with aqua regia by microwave acid-digestion.The silver,copper,iron,lead,nickel and zinc ions in the digested samples were pre-column derivatized with 2-(2-quinolinylazo)-resorcin(QAR)to form colored chelates in pH 7.0-9.5 buffer solution and emulsifier-OP medium.The Ag-QAR,Cu-QAR,Fe-QAR,Pb-QAR,Ni-QAR and Zn-QAR chelates can be absorbed onto the front of the enrichment column when they were injected into the injector and sent to the enrichment column[Zorbax Stable Bound,10 mm×4.6 mm,1.8μm]with a buffer solution of pH 8.0 pyrrolidine-acetic as mobile phase. After the enrichment had finished,by switching the six ports switching valve,the retained chelates were back-flushed by mobile phase and traveling towards the analytical column. These chelates separation on the analytical column[Zorbax Stable Bound,10 mm×4.6 nun,1.8μm]was satisfactory with 65%methanol(containing 0.01 mol/L of pH 8.0 pyrrolidine-acetic buffer salt and 0.1%of emulsifier-OP)as mobile phase.The Ag-QAR, Cu-QAR,Fe-QAR,Pb-QAR,Ni-QAR and Zn-QAR chelates were separated completely within 2.5 min.The detection limits(S/N=3)of silver,copper,iron,lead nickel and zinc reaches 1.8 ng/L,1.8 ng/L,1.5 ng/L,2.0 ng/L,2.2 ng/L and 1.8 ng/L,respectively.The method was applied to the determination of silver,copper,iron,lead,nickel and zinc in gold potassium cyanide for electroplating.The relative standard deviations were 2.2%-3.6%,and the standard recoveries were 91%-104%.The determination results are agreed with that of reference method(ICP-MS method).(â…¤)Determination of trace impurities in gold by minitype extraction and inductively coupling plasma-mass spectrometryIn this work,a minitype extraction device was designed,and the determination of trace impurities(silver,copper,iron,lead,stibium and bismuth)in gold by minitype extraction and inductively coupling plasma-mass spectrometry(ICP-MS)was studied.The gold samples were digested in qua regia with a microwave oven,and the silver,copper,iron, lead,stibium and bismuth were separated from gold by minitype extraction using methyl isobutyl ketone as extraction reagent.The impurities in gold were determined by ICP-MS, and the Sc,Y,In were added as internal standards to eliminate the matrix interferences.The results show that the relative standard deviations for silver,copper,iron,lead,stibium and bismuth were below 3.0%,the standard recoveries of these elements were in the range of 91%-98%,and the detection limits were in the range of 0.006-0.01μg/L.By minitype extraction,only 0.1g of samples was needed for the determination of impurities.Compared to routine method,the samples consumption was markedly decreased,and the cost for analysis was markedly saved.
|
PDF Full Text Request