Deep eutectic solvent-based green absorbents for the effective removal of volatile organochlorine compounds from biogas

Volatile organochlorine compounds (VOXs) present in biogas can cause many technological and environmental problems. During the combustion of biogas containing VOXs, corrosion, as well as the formation of toxic by-products (polyhalogenated dioxins and furans) and further emission to the atmosphere, may occur. Therefore, in this study, a new procedure based on physical absorption was developed. In order to meet the requirements of green chemistry and green engineering, new deep eutectic solvents (DESs) composed of natural components were used in the absorption studies. Several physical properties of new DESs were determined, along with the absorbent formation mechanisms, by means of spectroscopic analysis and density functional theory. The most important absorption parameters, i.e., the type of DES, gas flow rate,the type of matrix gas, temperature, and initial concentrations of VOXs were optimized. The obtained results indicate that DES composed of syringol and levulinic acid in a 1 : 1 molar ratio could efficiently absorb VOXs. The DES regeneration studies demonstrated that the absorption capacities of DES did not change after ten absorption-desorption cycles. Studies on the absorption mechanisms indicated that H-bonding and van der Waals interactions were the main driving forces for the removal of VOXs from biogas.