Effect of oxalic acid and sodium hydroxide on the desulfurization of coal using UV–H₂O₂ oxidation system

Abstract

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.

GRAPHICAL ABSTRACT

KEYWORDS:

• UV radiation
• high sulfur coal
• oxalic acid
• sodium hydroxide
• directional desulfurization

Acknowledgements

We also gratefully acknowledge all reviewers and editors for their professional and constructive comments.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by the National Natural Science Foundation of China: [Grant Number 21666001]; Ningxia Provincial Natural Science Foundation: [Grant Number 2019AAC03112, 2020AAC03208]; the Graduate Innovation Program of North Minzu University: [Grant Number YCX20134]; Ningxia low-grade resource high value utilization and environmental chemical integration technology innovation team project, China.