Functional group characteristics of coal treated with clean biomass surfactant via FTIR spectroscopy

This study investigates the impact of a novel compound biomass surfactant on the molecular structure and functional group characteristics of Huainan Liuzhuang coal via Fourier Transform Infrared (FTIR) spectroscopy. The experimental results reveal marked differences between raw, distilled water-treated, and surfactant-modified samples, particularly in the transformation of hydroxyl, aliphatic, and oxygen-containing functional groups: (1) The coal's IR spectra are categorized into four key absorption bands, representing hydroxyl groups, aliphatic hydrocarbons, oxygen-containing functional groups, and aromatic hydrocarbons. (2) Surfactant treatment reduces the total hydroxyl group content but increases hydroxyl-hydrogen bonding, enhancing coal's structural stability. (3) The aliphatic side chains in modified coal become shorter, with the 3:7 compound ratio yielding the highest aliphatic group content. (4) C-O-C stretching vibrations condense into aryl ethers, increasing aromatic ring condensation, particularly at the 3:7 ratio. (5) Aromatic hydrocarbon diversity decreases as side chains detach from benzene rings, with ortho-trisubstituted structures (3 H) becoming more prominent. The outcomes demonstrate that compound biomass surfactant treatment induces significant functional group restructuring in coal, notably enhancing its wettability and gas desorption capacity, and providing promising avenues for application in coalbed methane recovery and spontaneous combustion prevention.