Search

[Display omitted] • A novel eco-friendly and energy-saving additive, dicyandiamide, was presented. • The action mechanism of dicyandiamide was illustrated. • Dicyandiamide dissolving lignin was discovered for the first time. • Dicyandiamide can better reduce KOH diffusion resistance in lignin than urea. • Dicyandiamide blocked "pseudo-lignin" generation. Alkali pretreatment is one of the most commonly used pretreatment methods in lignocellulose bioprocessing. However, there are still some "pseudo-lignin" that hinder enzymatic hydrolysis and seriously affect the industrialization process of biorefining. Excellent pretreatment additives can effectively cover these shortages. However, most additives have disadvantages like high operating temperature, low effective utilization efficiency, or poor performance. To address this issue, we proposed a novel additive, dicyandiamide (DICY), by means of quantum chemical prediction, and verified its ability on assisting alkali to remove lignin by experiments. The results indicate that the lignin removal by KOH-DICY pretreatment is about 15% higher than KOH pretreatment, thereby increasing the enzymatic efficiency to 97%, while the reaction temperature was lower 20 ℃ than common alkali pretreatment. These are due to the "two birds with one stone" role of DICY on lignocellulose alkali-DICY pretreatment. DICY not only dissolves small amounts of lignin, but also assists alkali to remove lignin by reducing the diffusion resistance of KOH in lignin and blocking the generation of "pseudo-lignin". Thus, DICY effectively improved the lignin removal and enzymatic hydrolysis efficiency of alkali pretreated lignocellulose, and performed better than urea. Moreover, the waste liquid pretreated by DICY combined with KOH has the potential on preparation of agricultural fertilizers. In summary, DICY is a new, environmentally friendly, and energy conservation additive for lign ocellulose alkali pretreatment [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel KOH-UHP-Si pretreatment strategy of Lignocellulose was proposed. • The mechanism of KOH-UHP-Si pretreatment was illustrated. • The mechanism of urea promoting KOH pretreatment effectiveness was illustrated. • The removal rate of lignin and cellulose content were over 97% and 81%. • Glucose yield was 0.77 g/g, which was 9 times of untreated corn stover. Alkali pretreatments are considered as one of the most popular strategies to pretreat lignocellulose due to its high-efficiency, low-cost, high lignine removing and cellulose content. Nevertheless, glucose concentration obtained from lignocellulose by alkali pretrements still can't meet biorefinery requirements. Thus, a novel strategy to pretreat lignocellulose by combining KOH, UHP (urea peroxide) and organosilane (KOH-UHP-Si pretreatment) was proposed. This novel strategy solved two difficult problems that seriously affected the combined pretreatment of alkali and advanced oxidant, and then the cellulose relative content and glucose yield were increased by about 2.4 times and 9 times compared with the original straw, about 19% and 20% compared with the alkali (KOH) pretreatment, and about 2.2 times and 3.3 times compared with the advanced oxidation (UHP) pretreatment. After optimizing the pretreatment process, cellulose relative content in corn straw reached 81.4%, and the removal rates of lignin and hemicellulose were increased to 97.3% and 88.13%, respectively. In addition, we illustrated the mechanism of KOH-UHP-Si pretreatment, in which KOH plays the major role, the organosilane suspension and UHP play the auxiliary role. When the organosilane reduced mass transfer resistance in the reaction system, KOH and UHP assisted and promote each other mutually. Besides, we also illustrated the mechanism of urea assisting KOH removal of lignin through quantum chemical calculations. Moreover, the substances contained in wastewater produced by the novel technique could be turned into agricultural fertilizers after being processed simply, and there will be zero emission in the whole process. Our results indicate that KOH-UHP-Si pretreatment was a high efficiency low cost and eco-friendly strategy for lignocellulose pretreatment. [ABSTRACT FROM AUTHOR]