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To research the efficient and economical desulfurization of Lingshi high sulfur coal (LS), the influence of acid and alkaline additives on an ultraviolet (UV) light oxidation desulfurization system was assessed. Sodium hydroxide (NaOH) and oxalic acid (OA) were selected as the alkaline and acid additives, respectively, to investigate whether acid and alkaline additives could promote oxidative desulfurization in the UV–H2O2 system. The coal samples were investigated via scanning electron microscopy (SEM), Brannuer–Emmett–Teller analysis (BET), contact angle analysis (CA), Fourier transform infrared spectroscopy (FTIR), X-ray diffractometry (XRD), and X-ray photoelectron spectroscopy (XPS). In addition, the desulfurization mechanism, including sulfur removal, sulfur conversion, and change of coal surface morphology on the reaction, was investigated. The results demonstrated that the surface morphology and the pore structure in coal improved; the wettability and oxygen-containing functional groups increased after the action of NaOH and OA, which indicated that the oxidation was enhanced during the reaction. This study proved that strong oxidation promoted the efficient removal of sulfur from coal samples, where NaOH reacted strongly with pyrite, and OA influenced the removal of organic sulfur, which played a directional desulfurization effect. [ABSTRACT FROM AUTHOR]

The desulfurization effect of Ningxia Shuangma coal (SM) with an acetic acid-hydrogen peroxide system assisted by microwave, ultrasonic and ultraviolet light was compared. The results show that microwave-assisted desulfurization has the best effect. When the microwave power is 900W, the irradiation time is 5 min, and the volume ratio of acetic acid to hydrogen peroxide is 1:10, the desulfurization rate can reach 55.82%. Moreover, microwave-assisted desulfurization can effectively improve the removal effect of organic sulfur. XRD, XPS, SEM and other characterization showed that microwave assisted can effectively reduce the mineral content, expose more sulfur-containing groups, and improve the desulfurization effect. The desulfurization rate of three sulfur-containing compounds is: dibenzyl sulfide > diphenyl sulfoxide > benzothiophene. With the increase of intensity of the applied electric field, the C–S bond gets easier to fracture, the applied electric field can reduce the reaction energy barrier, is a benefit to the reaction. [ABSTRACT FROM AUTHOR]