Layered double hydroxides (LDHs) with hydrotalcite-like structures containing Co(II) and Fe(III) were prepared and used for the removal of direct red 23 (DR23) from water solution. These CoFe–LDHs were characterized before and after reaction by XRD, FTIR, BET, and XPS. The factors affecting the adsorption and catalytic performance of the CoFe–LDHs were systematically investigated. The adsorption process followed pseudo-first-order kinetics, while equilibrium adsorption isotherm data were well fitted by the Freundlich model. Moreover, CoFe–LDHs exhibited high catalytic activity in the degradation of direct red 23 in the pH range 4–10. Under a catalyst dosage of 0.5 g L⁻¹ and H₂O₂ concentration of 6.5 mmol L⁻¹, the degradation ratio of direct red 23 was 95.6% after 30 min. The adsorption–degradation relationship in the presence of CoFe–LDHs was investigated. Intermediates were detected by GC/MS and a possible pathway for DR23 degradation was proposed. The reaction mechanism showed that cobalt ions play a critical role in the catalytic performance of CoFe–LDHs. Furthermore, the catalytic activity of CoFe–LDHs was maintained after three reaction cycles, demonstrating the recyclability and stability of this catalyst.

The pyrolysis process is a thermochemical conversion reaction that encompasses an intricate array of simultaneous and competitive reactions occurring in oxygen-depleted conditions. The final products of biomass pyrolysis are bio-oil, biochar, and some gases, with their proportions determined by the pyrolysis reaction conditions and technological pathways. Typically, low-temperature slow pyrolysis (reaction temperature below 500 °C) primarily yields biochar, while high-temperature fast pyrolysis (reaction temperature 700–1100 °C) mainly produces combustible gases. In the case of medium-temperature rapid pyrolysis (reaction temperature around 500–650 °C), conducted at very high heating rates and short vapor residence times (usually less than 1 s), the maximum liquid yield can reach up to 85 wt% (on a wet basis) or achieve 70 wt% (on a dry basis), with bio-oil being the predominant product. By employing the pyrolysis technique, valuable utilization of tobacco stem waste enriched with lignin can be achieved, resulting in the production of desired pyrolysis products such as transportation fuels, bio-oil, and ethanol. The present review focuses on catalytic pyrolysis, encompassing catalytic hydropyrolysis and catalytic co-pyrolysis, and meticulously compares the impact of catalyst structure on product distribution. Initially, we provide a comprehensive overview of the recent pyrolysis mechanism of lignin and tobacco waste. Subsequently, an in-depth analysis is presented, elucidating how to effectively design the catalyst structure to facilitate the efficient conversion of lignin through pyrolysis. Lastly, we delve into other innovative pyrolysis methods, including microwave-assisted and solar-assisted pyrolysis.

One-step removal of hexavalent chromium in a wide pH range is of great significance. In this paper, a single thiourea dioxide (TD) and two-components thiourea dioxide/ethanolamine (MEA) were used as a green reducing agent for the efficient removal of Cr(VI), respectively. The reduction of Cr(VI) and the precipitation of Cr(III) were carried out simultaneously under this reaction system. The experimental results proved that TD was activated by amine exchange reaction with MEA. In other words, MEA promoted the generation of an active isomeride of TD by changing the equilibrium position of the reversible reaction. After adding MEA, the removal rate of Cr(VI) and total Cr could reach industrial water discharge standards in a wide pH range of 8–12. The change of pH, reduction potential and the decomposition rate of TD were investigated in the reaction processes. Meanwhile, reductive and oxidative reactive species were produced simultaneously during this reaction process. Further, oxidative reactive species (O₂˙⁻ and ¹O₂) were beneficial for the decomplexation of Cr(III) complexes and the formation of Cr(III) precipitation. The experimental results also demonstrated that TD/MEA was effective in practical industrial wastewater. Hence this reaction system has a significant industrial application prospect.