Research On The Origin Traceability Of Iron Ore Based On The Characteristics Of Trace Elements

With the rapid rise of China’ s economics and the development of steel industry,iron ore has gradually become an important strategic resource affecting the sustainable development of national economy.Although China has large iron ore reserves,there are few rich ore and too much poor ores and refractory ores.Under the influence of domestic iron ore shortage and international iron ore supply controlled by four mining companies,China’ s iron ore import has ushered in a period of rapid growth and its dependence on foreign countries continued to rise.In 2003,China became the world’ s largest importer of iron ore.In order to meet the rigid demand for imported iron ore in China,the situation of “global ore prospecting” by importers is becoming more and more common,which leads to the complicated source of imported iron ore,uneven quality and even the occurrence of fraud such as shoddy quality.To ensure the quality and safety of imported bulk resources,to maintain market order and to accelerate the rapid customs clearance of bulk resources products,it is necessary to build a short-cut method of origin traceability analysis for iron ore.The paper mainly adopted combustion-ion chromatography(C-IC)and high resolution inductively coupled plasma mass spectrometry(HR-ICP-MS)to carry out the development of quantitative analysis method for trace elements in iron ore.The characteristics of trace elements and chemometrics were combined to trace the origin of iron ore.The main research content is as follows:1.A method for simultaneous determination of fluorine and chlorine in iron ore by combustion-ion chromatography was proposed.This method is a kind of environment-friendly analytical method with high automation,convenient operation,good accuracy and high sensitivity,which greatly improves the efficiency of sample analysis.The limits of detection of fluorine and chlorine were 0.03 milligrams per gram and 0.04 milligrams per gram,respectively,which were similar to the Chinese national standard method(GB/T 6730.69-2010).Eight certified reference materials and four iron ore samples were used to evaluate the accuracy and precision of the C-IC method.The content of fluorine and chlorine in the iron ore samples ranged from 0.086 milligrams per gram to 1.773 milligrams per gram and 0.050 milligrams per gram to 3.10 milligrams per gram,respectively.The relative standard deviations of fluorine and chlorine were in the range of 0.77% to 4.27% and 1.36% to 3.74%,respectively,and the recoveries were in the ranges of 95.3%-104.6% and91.9%-104.3%,respectively.The accuracy of the method was further verified by comparing the determination results of four iron ore samples with those determined by steam distillation-ion chromatography.2.A method for the determination of 33 trace and trace elements in iron ore by high-pressure closed digestion and high-resolution inductively coupled plasma mass spectrometry was proposed.The accuracy and precision of the method were evaluated by using certified iron ore reference materials.The linear relation of 33 trace elements is good,the detection limits of most elements ranged from 0.002 milligrams per gram to 0.586 milligrams per gram.Compared with the certified values of each element in the certified reference materials,the precision of most elements was less than 5%,and the recovery was in the range of 80% to 115%.HR-ICP-MS had higher resolution and lower detection limits,which solved most problems of spectral interferences and realized the simultaneous determination of micro elements and trace elements in complex matrix samples.3.The two quantitative analysis methods are applied in practice,and the classification model of iron ore was established by principal component analysis and discriminant analysis.The content of F and Cl in iron ore imported from seven different countries was analyzed by single factor analysis of variance,to find out if there was any difference.The result showed that there are significant differences in chlorine content in iron ores from Kazakhstan,Brazil and Iran,but they are not intuitive enough.In order to understand the characteristic elements in different brands of iron ores,principal component analysis was carried out on 33 trace elements in 9brands of iron ore.The cumulative variable of the first three principal components reached 94.7%,which covered most of the original 33 elements.The characteristic elements,including Sr,Ce,V,Zr,Zn and Cr,were selected by PCA loading plot.However,it is still difficult to distinguish brand iron ore from the same mining area completely.After that,33 variables were selected by discriminant analysis,and finally 14 variables and 8 discriminant functions were adopted to build the iron ore brand discrimination model.The accuracy rate of modeling sample verification was 100% and the cross-accuracy rate was 98.7%.