Investigations of coal beneficiation by using choline chloride and urea-based deep eutectic solvent

Abstract

ABSTRACT The present study reports on the interaction, influence, and dissolution properties of coal samples (CS) by a green solvent, deep eutectic solvent (DES), prepared from choline chloride and urea. The bituminous coal has been collected from the Singrauli coalfield in India. DES was synthesized using urea as a hydrogen bond acceptor (HA) and choline chloride as a hydrogen bond donor (HD) in an equimolar amount. The synthesized DES has been used in the study for swelling behavior, proximate and ultimate analysis, and FTIR to understand the beneficiation of coal after DES treatment. The swelling index of DES-treated coal ranges from 1.12 to 1.43 when compared to raw CS. FTIR confirms the presence of different oxygen-containing phenolic, aromatic, and aliphatic hydrocarbon containing functional groups present in coal samples. Quantitative analysis of FTIR peaks was carried out through the Gaussian function peak processing method. Fourier transform infrared (FTIR) analysis of the raw coal and treated sample confirms the reduction of oxygen-carrying and phenolic vibrational groups by up to 86%. The ultimate and proximate analysis of raw coal and DES-treated CS shows the decrease in ash content (up to 26%) of DES-treated coal samples and confirms the FTIR results. Calorific value in the form of fixed carbon content was also increased by up to 4.7% after DES treatment. Hence, DES treatment efficiently benefits coal properties and makes them more useful for the industrial environment.