MnOx–CNT nanocomposites are efficient towards ozone decomposition owing to the electron transfer from the CNTs to MnOx that facilitates the activation of ozone.
Gamma-valerolactone
(GVL) assisted NaOH/water pretreatment for
hybrid pennisetum delignification was first investigated.
Contrary to the hypothesized results, the addition of GVL significantly
suppressed the delignification and hemicellulose removal by mild alkaline
pretreatment (37 °C for 24 h). An addition of GVL to GVL/NaOH
molar ratio of 1/1 resulted in lignin removal at ∼23% compared
with that at ∼75% without GVL. This suppression effect was
further confirmed by scanning electron microscopy and Fourier-transform
infrared spectroscopy. The extracted lignin was further characterized
by two-dimensional heteronuclear single quantum coherence nuclear
magnetic resonance spectroscopy, suggesting that the addition of GVL
suppressed the decomposition of large lignin molecules by NaOH/water
and the release of hemicellulose, resulting in extracted lignin with
lower molecular weights and less hemicellulose. The decrease in the
partial alkalinity (PA) of alkaline solutions caused by GVL addition
was likely the main reason for the suppressed delignification, suggested
by the good correlation between PA and delignification in both GVL/NaOH/water
and NaOH/water (R
2 = 0.967). This study
suggested that solvent-assisted alkaline pretreatment can also result
in an unwanted suppression effect, and the changes in PA could be
referred to as an indicator while selecting organic solvents.
The conversion of lignocellulosic biomass into various high-value chemicals has been a rapid expanding research topic in industry and agriculture. Among them, alkaline removal and utilization of lignin are important for the accelerated degradation of biomass. Modern biorefinery has been focusing the vision on the advancement of economical, green, and environmentally friendly processes. Therefore, it is indispensable to develop cost-effective and simple biomass conversion technologies to obtain high-value products. In this study, the black liquor (BL) obtained from the alkaline pretreatment of biomass was added to polyvinyl alcohol (PVA) solution and used to prepare degradable ultraviolet (UV) shielding films, achieving direct and efficient utilization of the aqueous phase from alkaline pretreatment. This method avoids the extraction step of lignin fraction from black liquor, which can be directly utilized as the raw materials of films preparation. In addition, the direct use of alkaline BL results in films with similar UV-shielding properties, higher physical strength, and similar thermal stability compared with films made by commercial alkaline lignin. Therefore, this strategy is proposed for alkaline-pretreated biorefineries as a simple way to convert waste BL into valuable products and partially recover unconsumed sodium hydroxide to achieve as much integration of biomass and near zero-waste biorefineries as possible.
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