Yanlong Li

Addressing the challenge of efficient lignin depolymerization, this study focuses on environmentally friendly choline amino acid ionic liquids ([Ch][AA] ILs) and systematically investigates the microscopic mechanism of β-O-4 bond cleavage in a lignin model compound (GG) using density functional theory (DFT). This study systematically compares three potential pathways: ionic liquid acid catalysis, base catalysis, and stepwise acid-base synergistic catalysis, proposing for the first time a highly advantageous "stepwise acid-base synergistic catalytic mechanism". The results demonstrate that compared to single base and acid catalysis, which exhibit excessively high energy barriers, the synergistic pathway effectively lowers the energy barrier of the rate-determining step through the tautomerism of key intermediates. The results indicate that the synergistic pathway exhibits a relative energetic advantage. Whereas, accounting for computational accuracy, the acid-catalyzed pathway may be considered as a competing reaction pathway under experimental conditions. Furthermore, the study reveals the impact of anion structure on catalytic activity: on the one hand, polar groups on the anion side chain can construct a strong hydrogen bond network and ion-dipole interactions, significantly reducing the rate-determining step energy barrier; on the other hand, long alkyl side chains effectively stabilize key transition states by enhancing noncovalent interaction. This study not only elucidates the key roles of multisite synergistic effects and van der Waals interactions in lignin depolymerization at the molecular level but also provides theoretical support for the design of efficient, low-toxicity catalytic systems for lignin valorization.

Sewage sludge is an important secondary phosphorus resource, but its thermochemical utilization is constrained by the presence of hazardous heavy metals (HMs). In this study, Fenton pretreatment was combined with pyrolysis-calcination to improve HM removal while maintaining phosphorus in the solid phase. Sludge samples were pretreated with different Fenton reagent concentrations, followed by pyrolysis at 500 °C and calcination at 900 °C. The pretreatment markedly enhanced the migration and volatilization of volatile HMs during calcination. At the optimal reagent concentration of 90 mM, the total HM content in the final biochar decreased to 1030.4 mg·kg-1, and the overall HM removal efficiency increased by 70.91%. In particular, Zn and Mn removal efficiencies increased from 70.37% and 73.06% to 99.68% and 93.38%, respectively. Sequential extraction showed that pretreatment shifted HMs from relatively stable fractions to more labile forms, facilitating their release during thermal treatment. In contrast, phosphorus remained largely stable, with only a slight change in total phosphorus and a retention rate close to 81%. FTIR, XRD, and XPS analyses indicated that hydroxyl radicals weakened HM interactions with organic ligands and mineral hosts, while the increased Fe content contributed to phosphorus preservation in the residue. Density functional theory calculations further supported the reduced stability of representative HM-ligand and HM-mineral interactions after hydroxyl radical attack. Overall, Fenton pretreatment improved the environmental safety of sludge-derived biochar and provided a practical option for safer sludge valorization.

Developing non-carbon-based adsorbents is essential for removing heavy metals from post-incineration flue gas. In this study, a new high-temperature-resistant adsorbent-activated boron nitride (BN) was prepared using precursors combined with a high-temperature activation method. The adsorption characteristics of BN for Zn, Cu, and Cd in simulated flue gas and sludge incineration flue gas were investigated using gas-phase heavy metal adsorption experiments. The results showed that BN prepared at 1350 °C for 4 h had defect structures, abundant pores, functional groups, and a high specific surface area of 658 m²/g. The adsorption capacity of BN in simulated flue gases decreases with increasing adsorption temperature, whereas it is always higher than that of activated carbon (AC). The total adsorption capacities for Zn, Cu, and Cd were the highest at 50 °C with 48.3 mg/g. BN had strong adsorption selectivity for Zn, with a maximum adsorption capacity of 54.45 mg/g, and its adsorption process occurred mainly on the surface. Cu and Cd inhibited Zn adsorption, leading to a decrease in the Zn adsorption capacity. In sludge incineration flue gas, BN can quickly reach adsorption equilibrium. The BN had a synergistic disposal capacity for heavy metals and fine particulate matter. The maximum adsorption capacity was reduced compared to the simulated flue gas adsorption capacity, which was 5.1 mg/g. However, BN still exhibited a strong adsorption selectivity for Zn, and its adsorption capacity was always greater than that of AC. The rich functional groups and high specific surface area enable BN to physically and chemically double-adsorb heavy metals.

With the rapid development of industry, the disposal of industrial solid waste needs to be solved urgently in China. Thus, an effective disposal method should be proposed to recycle these solid wastes in an environmentally friendly and sustainable manner. In this paper, ceramsite was prepared from sewage sludge (SS), magnesite tailings (MTs), and coal gangue (CG). The influence of the material ratio and sintering temperature on the properties of the ceramsite was investigated. The results show that the ceramsite had better properties when the following parameters were used: a ratio of SS: CG: MT of 4.5:4:1.5; a sintering temperature of 1250 °C; a compressive strength of 11.2 MPa (or it can be rounded to 11; our major remark relates to significant figures, and they should be up to 2–3 figures, according to measurement errors); a water absorption of 3.54%; and apparent and bulk densities of 1.19 and 0.81 g/cm³, respectively. The strength was superior to more than twice the 900-density grade prescribed by the Chinese national standard. After sintering, most of the heavy metals in the ceramsite mainly existed in the form of residue state (FD), meaning that they were highly stable. The leaching concentrations of Zn and Ni from the ceramsite were 0.72 and 0.25 mg/L lower than the prescribed regulatory limits (2.0 and 0.1 mg/L). The overall pollution toxicity index (OPTI) was only 240, less than that of raw pellets, indicating that the environmental risk is low. Not only did the ceramsite, prepared from SS, CG, and MT, exhibit excellent chemical properties, but it also proved to be an environmentally safe material. Therefore, it is an effective approach to realize the collaborative treatment of SS, CG, and MT by preparing ceramsite.

With the development of urbanization and industrialization, vast plenty of sewage sludge was produced. Incineration has been becoming the mainstream disposal method due to its many advantages. However, the problem of fine particulate matter produced from the incineration process made a restriction on the development of this method. In this study, the effects of temperature, particle size, and calcium-based additives (CaO) on the generation characteristics and micrographs of fine particulate matter were investigated via a lab-scale fluidized bed. The results revealed that the fine particulate matter showed a bimodal distribution and the two peaks was located at around 0.5 μm and 5 μm, respectively. With the increasing of temperature from 750°C to 950°C, the mass concentration of PM_0.5 increased by 12.88 mg/g, while PM₅ increased by 57.79 mg/g, which indicated as the temperature increases, the crushing degree of minerals and coke particles is more intense, which further leads to an increase in the amount of fine particles. The number of fine particles increased when the feed size getting smaller, which showed an intense link to the feed size. That was because the smaller the particle size, the more severe the degree of crushing, and the greater the number of fine particles formed after crushing. Furthermore, the results also found that CaO can be used as a good binder between particles to promote the growth and agglomeration of fine particles and inhibit the generation of fine particles. When the additive ratio was 3%, 6%, and 9%, the mass concentration of PM_0.3 decreased by 53.7%, 63.5%, and 86.1%, while the mass concentration of PM₃ decreased by 43.9%, 74.7%, and 91.7%. Therefore, CaO can be used to reduce the production of fine particles in practical engineering applications.

Boron nitride, also known as white graphene, has attracted extensive attention in the fields of adsorption, catalysis and hydrogen storage due to its excellent chemical properties. In this study, a phosphorus-doped boron nitride (P-BN) material was successfully prepared using red phosphorus as a dopant for the preparation of porous boron nitride precursors. The phosphorus content in the P-BN was adjusted based on the addition rate of phosphorus. The specific surface area of P-BN first increased and then decreased with increasing addition rate of phosphorus. The maximum specific surface area was 837.8 m ² g ⁻¹ when the phosphorus addition rate was 0.50. The P-BN prepared in the experiments was used as an adsorbent, and its adsorption capacity for heavy metals from flue gas was investigated. In particular, P-BN presented a stronger adsorption selectivity for zinc compared with other heavy metals, and its adsorption capacity for zinc was 5–38 times higher than for other heavy metals. The maximum adsorption capacity of P-BN for zinc and copper in a single heavy metal atmosphere was 69.45 and 53.80 mg g ⁻¹ , respectively.