Ultrasound-assisted oxidative desulphurization of coal using choline chloride-based deep eutectic solvents

Abstract

The emission of sulfur compounds during the combustion of coal is the main cause of atmospheric pollution and poses a threat to human health and the ecosystem. Thus, elimination of sulfur compounds from coal before its use is compulsory, and hence, coal desulfurization has become the key solution. In the present study, ultrasonic-assisted oxidative desulfurization of coal was conducted utilizing H2O2 in the presence of choline chloride/Acetic acid (ChCl/AcA) deep eutectic solvents (DESs). Three coal samples from different areas of Punjab were received for the investigation. The DES ChCl/AcA possesses sulfur removal efficiency of up to 58-64% pyritic sulfur, 54-63% sulfate sulfur, and 48-54% total sulfur from different coal samples. In addition to inorganic sulfur removal, a considerable decrease in organic sulfur 38-41% has been obtained using ultrasound-assisted oxidative desulfurization. FTIR study has shown that the treated coal samples have decreased sulfur contents as compared to untreated coal samples along with no significant change in the calorific values. These outcomes open new paths headed for more energy-effective and cleaner coal, utilizing cost-effective DESs. Graphical abstract: (Figure presented.)