A critical review on the technique and mechanism of microwave-based denitrification in flue gas

Microwave radiation has received extensive attention due to its significant thermal and non-thermal effects, and the development of MW-based denitrification in flue gas has become one of the most promising methods to avoid the defects of ammonia escape, high temperature and cost in traditional SCR. This review introduces the thermal and non-thermal effects of microwaves and divides MW-based denitrification methods into MW reduction and oxidation denitrification, systematically summarizes these denitrification methods, including MW discharge reduction, MW-induced catalytic reduction using active carbon, molecular sieves, metal oxides (transition metals, perovskites, etc.), MW-induced oxidation denitrification with and without additional oxidant, and discusses their removal pathway and mechanism. Finally, several research prospects and directions regarding the development of microwave-based denitrification methods are provided.     

Remediation of arsenic-contaminated paddy field by a new iron oxidizing strain (Ochrobactrum sp.) and iron-modified biochar

Iron-oxidizing strain (FeOB) and iron modified biochars have been shown arsenic (As) remediation ability in the environment. However, due to the complicated soil environment, few field experiment has been conducted. The study was conducted to investigate the potential of iron modified biochar (BC-FeOS) and biomineralization by a new found FeOB to remediate As-contaminated paddy field. Compared with the control, the As contents of G_B (BC-FeOS), G_F (FeOB), G_FN (FeOB and nitrogen fertilizer), G_BF (BC-FeOS and FeOB) and G_BFN (BC-FeOS, FeOB and nitrogen fertilizer) treatments in pore water decreased by 36.53%–80.03% and the microbial richness of iron-oxidizing bacteria in these treatments increased in soils at the rice maturation stage. The concentrations of available As of G_B, G_F, G_FN, G_BF and G_BFN at the tillering stage were significantly decreased by 10.78%–55.48%. The concentrations of nonspecifically absorbed and specifically absorbed As fractions of G_B, G_F, G_FN, G_BF and G_BFN in soils were decreased and the amorphous and poorly crystalline hydrated Fe and Al oxide-bound fraction was increased. Moreover, the As contents of G_B, G_F, G_FN, G_BF and G_BFN in rice grains were significantly decreased (*P < 0.05) and the total As contents of G_FN, G_BF and G_BFN were lower than the standard limit of the National Standard for Food Safety (GB 2762-2017). Compared with the other treatments, G_BFN showed the greatest potential for the effective remediation of As-contaminated paddy fields.     

纳米TiO2/ZJ-01复合相促脱剂对高浓度氨氮吹脱效率的协同强化机制研究

为了强化煤化工废水中高浓度氨氮(500~7000mg/L)的吹脱去除效率,进一步减少投碱量,制备了一种纳米TiO₂/ZJ-01复合相促脱剂,并对其稳定性、促脱效率及强化机理进行了研究.结果表明,在有机组分质量分数6.0%,5nm TiO₂固含量0.4%,超声分散30min时,纳米TiO₂/ZJ-01复合相促脱剂性价比最好.在纳米TiO₂/ZJ-01复合相促脱剂投加量为7.5mL/L时,氨氮吹脱率便可以达到95.14%,且在任何pH值条件下投加纳米TiO₂/ZJ-01复合相促脱剂,氨氮吹脱率均能提高17.02%~32.46%.与直接吹脱法相比,投加纳米TiO₂/ZJ-01复合相促脱剂吹脱40min,原水pH=10时的氨氮吹脱率便已高于直接吹脱法pH=11.5时的氨氮吹脱率,极大降低了碱耗量.进一步对纳米TiO₂/ZJ-01复合相促脱剂作用机理研究发现,纳米TiO₂/ZJ-01复合相促脱剂能极大的降低气液相间表面张力,从而降低传质过程中的液膜阻力,减小气泡尺寸,增大传质接触面积,加快氨气的逸出;同时,在吹脱过程中纳米TiO₂/ZJ-01复合相促脱剂能够增强界面湍动及对流现象,加快气泡液膜表面部分更新,减少有效传质边界层厚度,从而降低氨氮传质阻力,强化了气液间传质的进行.     

A blessing for the Yangtze River: optimization of Chinese regional policy planning for water yield and purification in the Three Gorges Reservoir Area

Environmental Science and Pollution Research - Land use/land cover (LULC) changes impact the structure and functioning of ecosystems, which consequently influences the provisioning of a range of...     

A research on the relationship between resistivity index and relative permeability at different measurement conditions based on the pore structure

Environmental Fluid Mechanics - Relative permeability and resistivity index are important parameters in petrophysics experiments and reservoir evaluations. According to the results of previous...     

Emissions of ammonia and greenhouse gases during combined pre-composting and vermicomposting of duck manure

Combined pre-composting and vermicomposting has shown potential for reclamation of solid wastes, which is a significant source of ammonia (NH₃), and greenhouse gases (GHG), including nitrous oxide (N₂O), methane (CH₄), and carbon dioxide (CO₂). Earthworms and amendments may both affect physico-chemical characteristics that control gas-producing processes, and thus affect NH₃ and GHG emissions. Here, we used two-way ANOVA to test the effects of addition of reed straw and combined addition of reed straw and zeolite on NH₃ and GHG emissions during pre-composting of duck manure, either with or without a follow-up phase of vermicomposting. Results showed that cumulative N₂O, CH₄, and CO₂ emissions during pre-composting and vermicomposting ranged from 92.8, 5.8, and 260.6 mg kg^?1 DM to 274.2, 30.4, and 314.0 mg kg^?1 DM, respectively. Earthworms and amendments significantly decreased N₂O and CH₄ emissions. Emission of CO₂ was not affected by earthworms, but increased in responses to addition of reed straw. Cumulative NH₃ emission ranged from 3.0 to 8.1 g kg^?1 DM, and was significantly decreased by reed straw and zeolite addition. In conclusion, combined pre-composting and vermicomposting with reed straw and zeolite addition would be strongly recommended in mitigating emissions of N₂O, CH₄, and NH₃ from duck manure. Moreover, this method also provides nutrient-rich products that can be used as a fertilizer.     

A GIS-based decision support system for regional eco-security assessment and its application on the Tibetan Plateau

Regional eco-security assessment is an intricate, challenging task. In previous studies, the integration of eco-environmental models and geographical information systems (GIS) usually takes two approaches: loose coupling and tight coupling. However, the present study used a full coupling approach to develop a GIS-based regional eco-security assessment decision support system (ESDSS). This was achieved by merging the pressure-state-response (PSR) model and the analytic hierarchy process (AHP) into ArcGIS 9 as a dynamic link library (DLL) using ArcObjects in ArcGIS and Visual Basic for Applications. Such an approach makes it easy to capitalize on the GIS visualization and spatial analysis functions, thereby significantly supporting the dynamic estimation of regional eco-security. A case study is presented for the Tibetan Plateau, known as the world’s “third pole” after the Arctic and Antarctic. Results verified the usefulness and feasibility of the developed method. As a useful tool, the ESDSS can also help local managers to make scientifically-based and effective decisions about Tibetan eco-environmental protection and land use.     

分光光度法测定氯化氢的实验条件改进

硫氰酸汞分光光度法测定大气中的氯化氢,所使用的硫氰酸汞-乙醇溶液配置时间长,浓度低,曲线线性不好,不适用于环境现场监测。通过对氯化氢测定过程中遇到的问题进行分析,对硫氰酸汞-乙醇溶液的配置方法进行改进,提高该溶液的浓度。实验证明,使用定性滤纸过滤后的0.40%硫氰酸汞-乙醇溶液,曲线线性关系好,标样准确度高,适用于现场监测分析。