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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]

In order to investigate the effect of visible light irradiation on oxidative desulfurization. Three kinds of coals (SM, YYH and GZ) and four sulfur model compounds were selected as research objects. The effects of different irradiation time (30, 60, 90 and 120 min) and light source power (150, 220 and 300 W) of coal desulfurization were investigated. The samples before and after desulfurization were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and electrochemical impedance spectroscopy (EIS). The results show that when coal:H2O2 = 1:5 (g:mL), light source power is 220 W and irradiation is 60 min, the desulfurization rate of SM, YYH and GZ can reach the maximum, which were 27.97%, 56.28% and 66.22%, respectively. According to the characterization of samples before and after desulfurization, it was found that the low-valence sulfur changes into the high-valence sulfur with a more stable structure through a certain transition state during the desulfurization process. Coal responds to visible light, which can promote the generation of electron–hole pairs in the system, so as to enhance the oxidative desulfurization ability of the system. Visible light irradiation can promote the production of strong oxidation active group HO·, thereby improving the desulfurization rate of coal. [ABSTRACT FROM AUTHOR]