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The use of fertilizer is closely related to crop growth and environmental protection in agricultural production. It is of great significance to develop environmentally friendly and biodegradable bio-based slow-release fertilizers. In this work, porous hemicellulose-based hydrogels were created, which had excellent mechanical properties, water retention properties (the water retention ratio in soil was 93.8% after 5 d), antioxidant properties (76.76%), and UV resistance (92.2%). This improves the efficiency and potential of its application in soil. In addition, electrostatic interaction and coating with sodium alginate produced a stable core–shell structure. The slow release of urea was realized. The cumulative release ratio of urea after 12 h was 27.42% and 11.38%, and the release kinetic constants were 0.0973 and 0.0288, in aqueous solution and soil, respectively. The sustained release results demonstrated that urea diffusion in aqueous solution followed the Korsmeyer–Peppas model, indicating the Fick diffusion mechanism, whereas diffusion in soil adhered to the Higuchi model. The outcomes show that urea release ratio may be successfully slowed down by hemicellulose hydrogels with high water retention ability. This provides a new method for the application of lignocellulosic biomass in agricultural slow-release fertilizer.

The mercerization of fiber is an important method for the high-value utilization of cellulose. In this study, the bagasse fiber was mercerized by freeze–thaw-assisted alkali treatment (FT/AT). The effects of freezing temperature, freezing time, alkali concentration, and thawing temperature on cellulose and hemicellulose removal were studied. The optimal freezing temperature was −40°C, freezing time was 8.0 h, alkali concentration was 5.0%, and thawing temperature was 30°C. The highest removal rate of hemicellulose was 75.64%. It was 5.80% higher than that of alkali treatment (AT). The alkaline degradation of cellulose was inhibited. The penetration of alkaline solution to fiber was promoted by the assistance of freeze-thaw pretreatment. The effective alkali concentration (5.0%) of cellulose I completely transformed into cellulose II decreased by 66.67% compared with traditional alkaline mercerization (15.0%). The high-efficiency mercerization of fiber was achieved by FT/AT. It provides theoretical support for promoting the high-value utilization of lignocellulosic biomass.

As a green and efficient component separation technology, organic acid pretreatment has been widely studied in biomass refining. In particular, the efficient separation of lignin by p-toluenesulfonic acid (p-TsOH) pretreatment has been achieved. In this study, the mechanism of the atmospheric separation of bagasse lignin with p-TsOH was investigated. The separation kinetics of lignin was analyzed. A non-simple linear relationship was found between the separation yield of lignin and the concentration of p-TsOH, the temperature and the stirring speed. The shrinking nucleus model for the separation of lignin was established based on the introduction of mass transfer and diffusion factors. A general model of the total delignification rate was obtained. The results showed that the process of lignin separation occurred into two phases, i.e., a fast stage and a slow stage. The results provide a theoretical basis for the efficient separation of lignin by p-TsOH pretreatment.

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Alkali and alkali earth metals (AAEM) can be removed from lignocellulosic biomass via a new demineralization process constituting hydrothermal treatment. The dissolution mechanism of AAEM in different demineralization processes has not been extensively studied. This study employed calcium as a representative of the AAEM group, and changes in the concentration of calcium ions during the hydrothermal demineralization of eucalyptus wood were studied. The dissolution kinetics were modelled using Fick’s second law. The effects of the reaction temperature, hydrolysate pH, and holding time on the dissolution rate of calcium ions were investigated. The kinetic equation for calcium ion dissolution was expressed as ln(1.9532e0.0077T/1.9532e0.0077T-C) = (0.4257P-0.2142e-10622.1/8.314T)t + ln(1.9532e0.0077T/1.056×10-8T3.5263p0.4449). The activation energy of the reaction was 10.62 kJ/mol. The linear regression coefficient (R2) of the predicted and experimental values was 0.9879, which implied high precision of the kinetic model. The results showed that the calcium ions underwent rapid internal diffusion and dissolution during hydrothermal demineralization. The study provides theoretical support for the efficient removal of alkali earth metals via hydrothermal demineralization.