Steam explosion-ionic liquid pretreatments on wetland lignocellulosic biomasses of Phragmites (sp.) and Thalia dealbata for Bio H2 conversion

Abstract

Bio H₂ conversion from wetland lignocellulosic biomass is one of the promising alternatives to fossil fuels. Both Phragmites (sp.) and Thalia dealbata are holocellulose-rich and lignin-rich wetland plant biomasses. Scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) demonstrated alteration of lignocellulosic structures due to hemicelluloses removal by steam explosion (SE) pretreatment, and further disruption of cellulose crystallinity after treatment with SE followed by [Bmim]Cl (SE-[Bmim]Cl). Thermogravimetry/differential thermogravimetry (TG/DTG) revealed an increase in amorphous cellulose and partial delignification in lignocellulosic structures as a consequence of SE-[Bmim]Cl. The pretreatment of both SE and SE-[Bmim]Cl yielded lignocellulosic substrates with improved properties in terms of their conversion into glucose and bio H₂. Five-to-ten folds (by SE) and ten-to-twenty folds (by SE-[Bmim]Cl) more glucose was released from the lignocellulosic substrates of both plants than those of contrast samples. Compared to Phragmites (sp.), the greater destruction in lignocellulosic structure of Thalia dealbata as a result of SE and SE-[Bmim]Cl, increased the accessible surface area and disrupted the cellulose crystallinity much more, thus making it more efficient for bio H₂ conversion. The bio H₂ of 1.97 ± 0.14 mmol H₂ g⁻¹ dry weight (DW) was yielded after sludge anaerobic fermentation of Thalia dealbata treated with SE, and it increased to 4.79 ± 0.86 mmol H₂ g⁻¹ DW after SE-[Bmim]Cl treatment. For Phragmites (sp.) it was 1.45 ± 0.42 and 2.75 ± 0.76 mmol H₂ g⁻¹ DW after SE and SE-[Bmim]Cl pretreatment, respectively. Therefore, SE-[Bmim]Cl pretreatment can be developed for efficiently enhancing bio H₂ conversion from wetland plant Thalia dealbata.