Changes and removal of different sulfur forms after chemical desulfurization by peroxyacetic acid on microwave treated coals

High sulfur coal sample from C1 seam in Tabas mine (Iran) was studied. The effect of microwave pre-irradiation followed by a peroxyacetic acid (PAA) desulfurization on sulfur forms was investigated by atmospheric pressure-temperature-programmed reduction (AP-TPR) method. Implementing microwave irradiation at 300 W for 2 min resulted in a maximum total sulfur and organic sulfur reduction by PAA of about 63% and 49%, respectively. Pyrite reduction in the microwave treated - PAA desulfurized samples is more than 84% on all studied samples. Pre-irradiation improved pyrite removal by PAA around 21%. Organic sulfur alteration after PAA desulfurization was discussed based on recorded m/z 34 (H2S+) AP-TPR profile changes, qualitatively and partly quantitatively. Based on the m/z 48 and 64 (SO+, SO2+) AP-TPR profiles, organic sulfate and also minor amounts of sulfones and sulfoxides in the PAA treated samples have been noticed. AP-TPR off-line coupled with TD-GC/MS gives additional proves of the formation of oxidized sulfur compound present by PAA desulfurization and for a de-methylation reaction mechanism because of the pre-irradiation treatment.