Dimethyl phthalate, a common ingredient in the manufacture of plastics, is a typical persistent substance in the organic wastewater environment owing to its lipophilic and refractory properties. To achieve higher degradation of dimethyl phthalate, this study uses an experimentally constructed high-pressure resistant microwave-catalyzed experimental system, which can establish a coupling between the microwave and pressure fields in the wet oxidation process. Three types of catalysts are investigated for catalytic degradation, along with the effects of variables, such as reaction temperature, system pressure, and catalyst concentration, on the removal of dimethyl phthalate. Increasing the reaction temperature effectively increases the reaction rate constant. In addition, the COD content reduces from 4161.8 to 1710.5 mg/L within 5 min. Further, the energy flow and economy indices of the entire process are comprehensively analyzed. Finally, the analysis of the degradation intermediate and other characterization techniques reveals that the pollutant is degraded by center dot OH.

Interactions between microwaves and certain catalysts can lead to efficient, energy-directed convergence of a relatively dispersed microwave field onto the reactive sites of the catalyst, which produces thermal or discharge effects around the catalyst. These interactions form "high-energy sites" (HeS) that promote energy efficient utilization and enhanced in situ degradation of organic pollutants. This article focuses on the processes occurring between microwaves and absorbing catalysts, and presents a critical review of microwave-absorbing mechanisms. This article also discusses aqueous phase applications of relevant catalysts (iron-based, carbon-based, soft magnetic, rare earth, and other types) and microwaves, special effects caused by the dimensions and structures of catalytic materials, and the optimization and design of relevant reactors for microwave-assisted catalysis of wastewater. The results of this study demonstrate that microwave-assisted catalysis can effectively enhance the degradation rate of organic compounds in an aqueous phase and has potential applications to a variety of engineering fields such as microwave-assisted pyrolysis, pollutant removal, material synthesis, and water treatment.

针对高压微波催化湿式氧化技术(MW-CWPO)降解苯酚类废水进行了研究,实验设计了一种耐高压微波催化实验系统,选择对硝基苯酚(100 mg/L)为目标污染物,使用多壁碳纳米管和过氧化氢分别作为催化剂和氧化剂,研究发现高功率、高压、高浓度的催化剂和氧化剂均能有效促进对硝基苯酚的降解,并且在某些特定条件下(800 W,0.3 MPa)反应5 min后其降解率可以达到100％.此外,实验发现在优化条件下该技术对实际印染废水也有着很好的处理效果,上述研究结论可应用于实际工业生产中,通过人为控制压力、微波功率等因素以加速化学反应从而提高实际化工废水的降解率,实现污染物的降解和资源的可持续化利用.

This study demonstrated rapid degradation of malachite green (MG) by a microwave (MW)-induced enhanced catalytic process with CoFe2O4-SiC foam. The catalyst was synthesized from CoFe2O4 particles and SiC foam by the hydrothermal method. X-ray diffraction and scanning electron microscopy techniques were used to confirm that CoFe2O4 particles were settled on the surface of SiC foam. In this experiment, a novel fixed-bed reactor was set up with this catalyst for a continuous flow process in a MW oven. The different parameters that affect the MW-induced degradation rate of MG were explored. The MW irradiation leads to the effective catalytic degradation of MG, achieving 95.01% degradation within 5 min at pH 8.5. At the same time, the good stability and applicability of CoFe2O4-SiC foam for the degradation process were also discussed, as well as the underlying mechanism. In brief, these findings make the CoFe2O4-SiC foam an excellent catalyst that could be used in practical rapid degradation of MG.

Discharge phenomena can occur when metals are exposed to microwave radiation. The mechanism of the discharge can be effectively studied by using spectral analysis. In this study, a reactor that can withstand long-term high pressure was used in combination with a spectrometer to investigate the effects of pressure and other parameters on the microwave metal discharge plasma. It was observed that the increase of radiation power, pressure, and metal wire diameter can have positive effects on the intensity of spectral lines. If other experimental conditions remain unchanged, the spectral lines and discharge intensity exhibit dynamic changes because the wire melts and changes its shape under the high local temperature associated with discharge. Because factors like radiation power and pressure can enhance the intensity of the plasma significantly, they can be reasonably utilized to accelerate the chemical reactions or improve the degradation rate of pollutants, e.g. in microwave wet oxidation applications.

In this study, the removal efficiencies of phosphorus from synthetic wastewater using laboratory-scale membrane bioreactors (MBRs) with the addition of different iron salts were investigated. The distributions of phosphorus in the effluent, suspension, and sludge of the MBR systems after the addition of iron salts were analyzed. The removal efficiency of phosphorus in actual domestic sewage via the combination of MBR and Fe(II) was also investigated. The results indicated that after the MBR system effluent stabilized, the added Fe(II) was more efficient than Fe(III) was in removing phosphorus. Among the suspensions present in different zones of the MBR systems, the phosphorus concentrations varied significantly. Namely, the concentration of phosphorus in the first anoxic zone was the highest, for which the concentration of phosphorus in the MBR with added Fe(II) was higher than that in the MBR with added Fe(III). In addition, the percentage of the dissociable phosphorus in the sludge was relatively low. For the treatment of actual domestic sewage using the combination of MBR and Fe(II), a specific concentration of Fe(II) resulted in greater than 99% phosphorus removal efficiency as well as a stable effluent concentration. Furthermore, microbes present in the sludge exhibited better tolerance to Fe(II).