Study On The Determination Of Microelements Bi,Cd,Cr,Cu,Fe,Pb And Major Elements Ca,P In Phosphate Ores And Phosphate Fertilizers

This article reviewed the determination of microelements and major elements in in phosphate ores and phosphate fertilizers,the methods to reduce the interference of matrix as well as advances in mass dilution both at home and abroad.On this basis,the paper has done the following researches:1,the paper researched the determination of microelements Bi,Cd,Cr,Cu,Fe and Pb in phosphate ores and phosphate fertilizers by inductively coupled plasma atomic emission spectrometry(ICP-AES),after separating and enriching by the ion exchange fibers.2,the paper researched the mechanisms of thermodynamics and kinetics for the solid-phase extraction systems in this article.3,Simultaneously determined the major elements Ca and P in phosphate ores and phosphate fertilizers by ICP-AES,after diluting the sample solutions by mass dilution.1,The research showed that when the mass concentration of calcium or phosphorus were greater than 10 times of cadmium and lead,the relative error of direct determination of cadmium and lead in phosphate ores and phosphate fertilizers by inductively coupled plasma optical emission spectrometry(ICP-AES)was equal or greater than 5%.However,the contents of calcium and phosphorus in phosphate ores and phosphate fertilizers are far more than it.The research showed that strong basic anion exchange fiber(SBAEF)can quantificational extract cadmium(?)and lead(?)from sample solution without extracting Ca2+,P043-or other cation,which sample solution was in condition of pH?2 and contained 0.01g/mL ascorbic acid and 0.20 mol/L KI.The extracted Cd(?)and Pb(?)can be quantificational eluted by 0.070 mol/L EDTA.Then it can be determined by ICP-AES without the interference of calcium and phosphorus.The lower limit of quantification for Cd and Pb is 1.00×10-2?g/g and 3.30×10-2?g/g.This method has been applied to determine the contents of cadmium and lead in actual phosphate ore and phosphate fertilizer samples,the relative standard deviation(RSD,n=5)was less than or equal to 4.4%,the recovery was in the range of 95.0%?107%.The method also can be used for FAAS to determine Cd and Pb in phosphate ores and phosphate fertilizers.2,The research showed that when the mass concentration of calcium were greater than 50 times of bismuth,chromium,copper and iron;when the mass concentration of phosphorus were greater than 1500 times of bismuth,chromium,copper and iron;when the mass concentration of iron were greater than 100 times of bismuth,chromium and copper the relative error of direct determination of bismuth,chromium,copper and iron in phosphate ores and phosphate fertilizers by ICP-AES was equal or greater than 5%.However,the contents of calcium and phosphorus relative to bismuth,chromium,copper and iron and the the contents of iron relative to bismuth,chromium and copper in phosphate ores and phosphate fertilizers are far more than it.The research showed that after adding 0.60g ascorbic acid for reducing Fe3+ to Fe2+,strong acid cation exchange fiber(SACEF)can quantificational extract the Ca2+ and Mg2+,Fe2+ without extracting BiY-?CrY-and CuY2-,which sample solution was in condition of pH?4,0.010mol/L EDTA.Then bismuth,chromium and copper can determined by ICP-AES with adding 1.00×102?g/mL P to standard solution to compensate the interference of P.As for the determination of iron,iron can be determined by ICP-AES,after adding 1.00×102?g/mL P to standard solution to compensate the interference of P which sample solution was in condition of pH?4,0.010mol/L EDTA without adding the ascorbic acid.This method has been applied to determine the contents of bismuth,chromium,copper and iron in actual phosphate ore and phosphate fertilizer samples,the relative standard deviation(RSD,n=5)was less than or equal to 3.4%,the recovery was in the range of 96.2%?107%.3,The research showed that when the sample solutions were determined after dissolving as national standard method,the concentration of calcium and phosphorus would be out of linear range and the relative error would be equal or greater than 5%.However,after diluting the concentration of calcium and phosphorus in the sample solutions into 1.00?10.0?g/mL,the concentration of calcium and phosphorus would be in the linear range and the relative error-would be less than 5%.In this paper,the concentration of calcium and phosphorus were determined by ICP-AES after diluting the concentration of calcium and phosphorus in the sample solutions into 1.00?10.0?g/mL and the analysis spectral lines were chosen as Ca 315.887nm and P 214.914nm.This method has been applied to determine the contents of calcium and phosphorus in actual phosphate ore and phosphate fertilizer samples,the relative standard deviation(RSD,n=5)was less than or equal to 1.8%,the recovery was in the range of 98.6%?108%.After comparing the results of mass dilution in this paper with volume dilution and national standard method,the results shows that the determination results of mass dilution were closer to the determination results of national standard method,and the relative error was less than 2.5%.4,This paper has researched the thermodynamics and kinetics of the solid-phase extraction system(SACEF extracting Ca2+ and Mg2+,SBAEF extracting CdI42-and PbI42-)in this article.The research showed that the extraction of SACEF extracting Ca2+ and Mg2+ fitted the equations of Freundlich and Langmuir.The empirical constant n of Freundlich equation are 1.87 and 4.46,it means the extraction processes would easily react.The hermodynamical parameters ?H>0,?S>0,?G<0 means the the extraction processes were endothermic,entropy increasing and spontaneous.The research of kinetics mechanism shows that the extraction fitted McKay pseudo-second-order kinetics process and the main rate-determining step is chemical reaction.The extraction of SBAEF extracting CdI42-and PbI42-fitted the equations of Freundlich and Langmuir.The empirical constant n of Freundlich equation are 3.08 and 3.09,it means the extraction processes would easily react.The hermodynamical parameters ?H>0,?S>0,?G<0 means the the extraction processes were endothermic,entropy increasing and spontaneous.The research of kinetics mechanism shows that the extraction fitted McKay pseudo-second-order kinetics process and the main rate-determining step is intra-fiber diffusion.