Zijun Tang

In this study, Mn-Ce/Al₂O₃/TiO₂ catalyst prepared by impregnation method was used for synergistic O₃ oxidation NO. The catalyst prepared by impregnating Al₂O₃/TiO₂ at a Mn:Ce molar ratio of 4:1 showed the best catalytic activity. The catalyst performance showed that when the molar ratio of Mn:Ce was 4:1 and the volume ratio of O₃:NO was 1:4, the removal rate of NO could reach 63%, which could increase the removal rate by 40% compared with that of NO oxidized by O₃ alone. BET, XRD, and TEM characterization results showed that when the molar ratio of Mn:Ce was 4:1, the catalyst specific surface area, and pore capacity were the largest. A large amount of MnOx and CeOx were distributed on the catalyst surface. The XPS analysis showed that the oxidation-reduction and oxygen vacancy of Mn (IV)/Mn (III)/Mn (II) and Ce (IV)/Ce (III), had a synergistic effect on the decomposition of O₃ into reactive oxygen species(O*), thus improving the catalytic capacity of Mn-Ce/Al₂O₃/TiO₂ catalyst for O₃. The O₂-TPD analysis showed that the oxygen vacancies and oxygen species in the catalyst could be used as the active point of decomposition of O₃ into O*. The experimental results show that the prepared catalyst can significantly improve the efficiency of ozone oxidation of NO and reduce the amount of ozone. The catalyst can be applied to ozone oxidation denitrification technology.

In this work, a two-stage activation method was used to prepare adsorbents from scrap tire rubber. Firstly, KOH was mixed with rubber using different impregnation ratios (12) for primary activation; a second activation was performed after pyrolysis at 650°C and 750°C; and finally, the samples were acid-washed using HNO₃. The prepared materials were characterized by elemental analysis, nitrogen adsorption isotherms, SEM, FTIR, and XPS. The adsorption capacity and mechanism of these materials on p-nitrophenol in wastewater were also investigated. It was found that after two-stage activation, the specific surface area of the materials can be effectively increased, and the surface of the materials can be enriched with oxygen-containing functional groups. The maximum adsorption capacity of PNP could reach 143.9mgg⁻¹, which is slightly higher than the literature data under the same conditions. The adsorption process is in the form of chemisorption and is dominated by hydrogen bonding and π-πEDA formation, but the adsorption tends to be monolayer, and the adsorption behavior can be described by a proposed secondary model. In addition, the adsorbent has a stronger adsorption capacity under acidic conditions.

The influences of four heating rates on the combustion and pyrolysis behavior in the N₂ and air atmosphere were investigated by the Fourier transform infrared spectrometry (FTIR) and thermogravimetric (TG) analysis. the distributed activation energy model (DEAM) and Flynn-Wall-Ozawa (FWO) were used to estimate Ea and A, ΔH, ΔG and ΔS. Experimental results showed that the similar thermal behavior emerged, but the temperatures in the air and N₂ atmospheres representing the end of the reaction were about 500 °C and 550 °C, respectively. The results of FTIR showed the peak positions were basically the same, but the concentrations of aromatics, aldehydes and ketones produced by pyrolysis in the N₂ atmosphere were higher. When the heating rate was 20 K/min, the comprehensive combustion parameters were 56.442 and 6.871 × 10⁻⁷%²/(min²• K³) in the air and N₂ atmospheres, respectively, indicating that the peanut shells had great potential to become bioenergy.

MOF-5 crystals were prepared by solvothermal synthesis, and characterized by electron microscopy (SEM), X-ray powder diffraction (XRD), and specific surface area (BET). The adsorption of formaldehyde, acetone, glycerol and toluene were studied. The effects of reaction solvent ratio, adsorption time and synthesis temperature on adsorption were investigated. The results show that the reaction solvent ratio is 2.6, the crystal particles have good integrity, the cracking phenomenon and aggregation phenomenon are less, the size is more uniform, highly crystalline, the specific surface area and pore volume are larger, and the pore size distribution is more concentrated. The adsorption time is 48 h, the synthesis temperature is 95°C. Under high temperature conditions, MOF-5 has a high-dimensional skeleton crystal structure with higher specific surface area and pore volume. MOF-5 has the best adsorption effect on toluene.

In this work, the feasibility of the simultaneous removal of NO_x and SO₂ through a simple process using a composite absorbent (NaClO₂/Na₂S₂O₈) was evaluated. Factors affecting the removal of NO_x and SO₂, such as NaClO₂ and Na₂S₂O₈ concentrations, solution temperature, the initial pH of solution, gas flow rate, and SO₂, NO, and O₂ concentrations were studied, with a special attention to NO_x removal. Results indicate that a synergistic effect on NO_x removal has been obtained through combination of NaClO₂ and Na₂S₂O₈. NaClO₂ in the solution played a more important role than did Na₂S₂O₈ for the removal of NO_x. The above factors had an important impact on the removal of NO_x, especially the solution temperature, the initial pH of the solution, and the oxidant concentrations. The optimum experimental conditions were established, and a highest efficiency of NO_x removal of more than 80% was obtained. Meanwhile, tandem double column absorption experiments were conducted, and a NO_x removal efficiency of more than 90% was reached, using NaOH solution as an absorbant in the second reactor. A preliminary reaction mechanism for NO_x and SO₂ removal was deduced, based on experimental results. The composite absorbent has the potential to be used in the wet desulfurization and denitration process, to realize the synergistic removal of multi-pollutants.