Determination of Halogens in Coal by Ion Chromatography Coupled with High Temperature Pyrolysis Pretreatment

A method was proposed for determination of the halogens in coal using high temperature pyrolysis pretreatment and ion chromatography. The coal sample (30.0-40.0 mg) was treated by pyrolysis at 1 100 ℃ in the oxygen of 350 mL·min^-1, and then the gas products of pyrolysis were absorbed in 5mL of 20 mmol·L^-1 NaOH solution. F^-, Cl^- and Br^- in the absorption solution were determined by ion chromatography with suppressed conductivity detector and IonPac AS18 column, and I^- in the absorption solution was determined by ion chromatography with integrated amperometric detector and Ionpac AS11-HC column. As shown by the results, linear relationships between values of peak area and mass concentration of F^-, Cl^-, Br^- and I^- were found in definite ranges, with detection limts (3s) of 3.03 mg·kg^-1 for F^-, 2.47 mg·kg^-1 for Cl^-, 0.80 mg·kg^-1 for Br^- and 8.85 mg·kg^-1 for I^-. Values of RSD (n=9) for precision test were all less than 5.0%. Test for recovery was made by standard addition method for the coal sample, giving results in the range of 83.6%-105%.