The inherent complexity of cellulose, hemicellulose, and lignin contributes to the recalcitrance of lignocellulosic biomass, resulting in a low conversion efficiency and high cost of bioethanol conversion. Pretreatment methods that disrupt the plant cell structure of lignocellulose, such as straw, can significantly enhance the conversion efficiency. In this study, we utilized an acid-assisted mechanocatalytic depolymerization technique to pretreat rice straw, and the results demonstrated a significant disruption of the cellulose structure of the straw. Compared to the untreated straw, the particle size of pretreated straw reduced from 279 μm to 11.8 μm, the crystallinity of cellulose decreased from 43.05% to 22.71%, the specific surface area increased by 177%, and the surface oxygen-to-carbon ratio (O/C) ratio was enhanced by 75%. The changes in microstructure enabled the pretreated straw to achieve a total sugar yield of over 95% within 12 h of enzymatic hydrolysis, significantly superior to the 36.24% yield from untreated straw, the 45.20% yield from acid impregnated straw, and the 73.25% yield from ball milled straw. Consequently, acid-assisted mechanocatalytic depolymerization emerges as a highly effective pretreatment strategy to enhance both the enzymatic hydrolysis and the overall conversion efficiency of rice straw.

Antibiotic contaminants such as tetracycline (TC) from agricultural production have become widely distributed and persistently accumulated in aquatic environments (rivers, lakes, and oceans), posing severe threats to ecological security and human health. This study developed a modified rice-straw-derived biochar through NaOH activation and ball-milling-assisted Fe₃O₄ loading, which simultaneously enhanced TC adsorption capacity and enabled magnetic recovery. The Box–Behnken design (BBD) response surface methodology was employed to optimize three key preparation parameters: ball-milling time (A, 39.95 min), frequency (B, 57.23 Hz), and Fe₃O₄/biochar mass ratio (C, 2.85:1), with TC adsorption capacity as the response value. The modified biochar was systematically characterized using SEM, BET, FTIR, XRD, and XPS, while adsorption mechanisms were elucidated through kinetic studies, isotherm analyses, and pH-dependent experiments. The results demonstrate that modification via ball-milling with Fe₃O₄ loading significantly enhanced the biochar’s tetracycline adsorption capacity. The maximum adsorption capacity of the modified biochar reached 102.875 mg/g, representing a 114.85% increase from the initial value of 47.882 mg/g observed for the pristine biochar. Furthermore, the modified biochar exhibited excellent stability, maintaining robust adsorption performance across a wide pH range. The primary adsorption mechanisms involved metal coordination complexation, supplemented by hydrogen bonding, π-π interactions, and pore filling.

Conversion of the lignocellulosic biomass to bioethanol contributes to the reduction of greenhouse gas emissions, enhancement of energy security, utilization of waste materials, and the promotion of sustainable agricultural practices. In this study, we report the effect of combining ball milling followed by liquid hot water (LHW) pretreatment of corn stover to lower the amount of enzyme required while also greatly increasing the recovery of xylose in fermentable form compared to either pretreatment alone. Short-duration ball milling for 60 min reduces the particle size of corn stover to 37.3 μm; however, the glucose only increased to 47% compared to 32% for unpretreated corn stover. In contrast, liquid hot water pretreatment alone can achieve increasing enzyme hydrolysis yields of cellulose from 49% to 93% as the pretreatment severity factor is increased from 3.24 to 4.41. However, the xylose yield decreased to 36% due to the fact that a considerable part of the xylose was degraded into furfural and humins. Surprisingly, the combination of mild ball milling (30 min) followed by mild liquid hot water pretreatment (190 °C, 15 min) could achieve both high glucose (83%) and xylose (72%) yields for a total sugar yield of 79%, theoretically. Thus, combining ball milling with liquid hot water pretreatment allows for milder conditions for both processes that lead to enhanced cellulose conversion without sacrificing xylose to degradation, which hinders enzymatic hydrolysis.