Abstract
This work focused on the removal of lignin from pine needles, leaving oriented porous cellulose. Deep eutectic solvent (DES) pretreatment of loblolly pine needles allowed for the removal of lignin from the biomass, leading to the exposure of the desired cellulose structure. Heating under reflux and microwave heating methods were used to pretreat loblolly pine needles with 12:1 lactic acid:choline chloride DES, 2:1 formic acid:choline chloride DES, and 1:2 oxalic acid:choline chloride DES. Characterization of the untreated and pretreated pine needles was done by Brunauer–Emmett–Teller analysis, Fourier-transform infrared spectroscopy, scanning electron microscopy, and ultraviolet–visible spectroscopy. Fiber analysis was also performed on the untreated and pretreated pine needles. The DES pretreated pine needles showed significant enhancements in both specific surface area and pore volume, with microwave pretreatment giving the best results. The oxalic acid:choline chloride DES was the most efficient at eliminating acid-soluble lignin. The optimal duration for conductive heat pretreatment to enhance specific surface area and pore volume was found to be 80 min. For microwave treatment, the formic acid:choline chloride DES was found to be most effective to increase the overall cellulose to lignin ratio.
Published Version
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