Lu Liu,Shuzhong Wang,Wei Liu,Jinlong Wang,Baoquan Zhang,Jianqiao Yang,Hui Liu,Yanhui Li
In this paper, ZnO particles with the particle size as low as 23 nm were successfully prepared by supercritical hydrothermal synthesis technique. The particle size of nano-ZnO decreased with the increase of temperature and pressure. Nano-ZnO particles in ZnSO 4 system were spherical with smaller particle size. The discrepancy in nano-ZnO produced by different precursor of Zn(NO 3 ) 2 , Zn(CH 3 COO) 2 or ZnSO 4 is attributed to the anion effects and supersaturation . The particles in the KOH system (29 nm) were smaller than those in the NaOH system (44 nm). For precursor concentration, intermediate Zn(OH) 2 was generated at lower concentration, while Zn 4 SO 4 (OH) 6 ·4H 2 O was produced at higher concentration. For alkali concentration, as the gradual increase of KOH concentration, Zn(OH) 2 began to decrease and gradually transformed into Zn(OH) 3 – and [Zn(OH) 4 ] 2− . When the KOH concentration reached a certain value, [Zn(OH) 4 ] 2− occupied the dominance in the mixed solution.
Bamboo is a fast-growing, high-biomass, and mechanically strong renewable resource. It shows great potential in cellulose-based materials and bio-based products. However, its complex tissue structure and unique lignin distribution limit the efficiency and applicability of conventional delignification processes. In this study, a synergistic lignin removal strategy combining high-proportion chlorine dioxide (ClO 2 ) pretreatment with oxygen delignification was developed. Two process sequences, O-D PI and D PI -O, were systematically compared in terms of reaction mechanisms during bamboo fiber lignin removal. Results showed that, in the D PI -O process, ClO 2 preferentially oxidized lignin to form quinone-type intermediates. These intermediates were then effectively degraded in the subsequent oxygen delignification stage. This led to a significantly higher lignin removal rate (84.90 %) and a notable reduction in kappa number (2.49) and AOX generation (0.267 kg/t pulp). Multidimensional characterization using 2D HSQC NMR and 31 P NMR confirmed more complete cleavage of S/G units and β-O-4 linkages in the D PI -O system. The carboxyl group content of residual lignin increased significantly to 1.194 mmol/g, revealing the critical role of quinone intermediates in deep oxidative degradation. Kinetic studies further showed that the lignin removal rate was highly sensitive to alkali concentration (a 1 = 0.6012), especially under low oxygen pressure. In low-alkali environments, oxygen pressure became more influential (b 1 = 0.1382). This study elucidates the reaction pathway and key controlling parameters of oxygen-assisted, high-proportion ClO 2 delignification. It provides both theoretical and practical support for efficient lignin degradation and high-purity cellulose fiber production.
危险品化学品经营许可证（带存储）