Determination Of Trace Toxic Elements Of F,Cl,P,As And Hg In Coal

China utilizes the largest quantity of output and consumption of coal in the world.The fraction of coal in the total energy is more than 70% for China.The control of the content of toxic elementals of coal is crucial for the environment protect due to the emission after the coal combustion.So the accurate determination of the content of toxic elementals is of importance.The certified reference materials(CRMs)for the trace toxic elementals are used for the validation of the analytical methods,which assures the accuracy and consistency of results.Up to now,the CRMs are still certified by the classic pre-treatment and analytical methods whose repeatability and accuracy needs improvement.In present paper,the analytical methods of 5 trace elementals,including fluorine,chlorine,phosphor,arsenic and mercury,in the coal were investigated systematically.The pre-treatment method of coal,including microwave induced combustion(MIC),microwave digestion(MD)and combustion at high temperature-hydrolysis-absorption by solution,were systematically investigated in order to make the elemental transmit from the solid matrix into solution with high recovery,convenience and speed.The comparison studies between MIC and combustion-hydrolysis-absorption by solution indicated that the MIC has a better repeatability.The MIC-MD with hydrofluoric acid(HF)method was proposed to pre-treat the coal and applied in the determination of the contents of phosphor and arsenic.By this pre-treatment,a small quantity of HF,no more than 1 mL,can dissolve the residue of coal after combustion completely,which avoid the interference of impurities from the large quantity of strong acid and achieve a high recovery of elementals.The MIC-MD pre-treatment method was proposed for the determination of the content of mercury,which possessed a high recovery.In the present study,the analytical method of 5 elementals were systematically investigated,including the ion chromatography(IC)and potentiometric titration for fluorine and chlorine,inductively coupled plasma mass spectrometry(ICP-MS),inductively coupled plasma atomic emission spectrometry(ICP-AES)and IC for phosphor,ICP-MS and ICP-AES for arsenic,and ICP-MS,ICP-AES and combustionconcentration by amalgam-atomic absorption spectrometry(AAS)for mercury.The IC method for the determination of phosphor in coal was firstly proposed,including the pre-treatment of MIC-MD with HF-acid evaporation and the analysis by IC.This method can reduce the interference of multi-elementals in coal matrix.A patent for invention based on this method has been applied.This method has a good potential for routine analysis due to the lower cost of instruments.Finally,the optimized methods were performed in the homogeneity test of 5 elementals of 3 CRMs.And then each elementals of CRM were determined by two analytical methods based on different principles.In summary,the present study founded the pre-treatment and analytical methods for 5 trace toxic elementals in coal,which had high recovery and accuracy.These methods had been successfully applied in the certification of CRMs.These achievement of methods have a good potential of application in analysis.