超重力强化废水中硝基苯类化合物的降解机制与效能

Ozone-based advanced oxidation processes have been used in wastewater treatment field due to the high oxidizability and no secondary pollution. However, the low solubility and utilization rate of ozone limit its application .In a primary electrochemical cell using inexpensive industrial coal iron as the anode, the degradation process involves the reduction of the nitro group to an easily degradable amine group at the cathode. While at the anode, Fe is oxidized to Fe2+ which can catalyze the conversion of ozone to hydroxyl radical, a more powerful oxidant, thus enhancing the degradation efficiency. Due to its low solubility in water and poor mass transport across different phases, however, the utilization efficiency of ozone in the traditional ozonation/electrolysis process is very low. To address these issues, a high gravity technique is proposed to enhance the mass transport of O3 so that ozone can be more effectively utilized, leading to lower cost and shorter degradation time. This project aims at designing and setting up a state-of-the-art high gravity apparatus for enhanced degradation of nitro-aromatics in wastewater and elucidating the roles played by Fe/C, RPB/O3、and Fe-C/RPB/O3 in the relevant degradation processes. The project also seeks to establish the degradation pathways through intermediate analysis and to gain insight into the electrochemistry, catalysis, redox, and adsorption processes. The successful completion of the project will open a new concept towards the ultimate treatment of wastewater containing hard-to-degradate organic pollutants and greatly expand the applications of the high gravity technique; The project has both significant scientific importance and great application potential.

臭氧高级氧化技术因其氧化能力强、无二次污染等特点，成为废水处理领域的研究热点，但存在臭氧水溶性差、利用率低等缺点。本项目提出超重力强化微电解催化臭氧降解有机废水的思路。以硝基苯为对象，采用廉价铁碳形成原电池，阴极的活性[H]将苯环上的-NO2还原为易降解的-NH2，阳极Fe氧化为Fe2+，Fe2+催化O3产生氧化能力更强的•OH，利用超重力提高液相湍动程度和气液接触面积，促进O3溶解，解决O3传质受限的关键问题，提高O3利用率，提升降解效能，达到可生化要求，实现“以废治废”的目的。本项目创建超重力强化O3传质新方法，旨在阐明Fe-C、Fe-C/O3、RPB/O3、Fe-C/RPB/O3等内在反应机制，通过分析中间产物，确定降解途径，揭示电化学、催化、还原、氧化等作用机理。项目的完成，为深度处理难降解废水提供新思路，对拓展超重力技术领域、催生新技术发展具有重要的科学意义和应用价值。

铁碳微电解还原法是一种处理硝基苯废水的有效方法，该法采用工业废铁屑与碳形成原电池，利用阴极产生的活性[H]将苯环上的-NO2还原为易降解的-NH2，阳极Fe氧化为Fe2+能催化O3产生氧化能力更强的·OH，进一步将苯胺去除。但臭氧存在水溶性差、利用率低等缺点。而超重力技术能够改善气液两相的湍动程度和增加气液接触面积，从而提高臭氧的传质效果。因此，本项目提出超重力强化微电解催化臭氧降解硝基苯废水，从而大幅度提升硝基苯的降解效能，实现“以废治废”的目的。在铁碳微电解体系中，在适宜操作条件下，硝基苯去除率达到90%，且拟合微电解反应为准一级动力学方程：Y=0.01052X+0.23373。同时，在相近实验条件下，超重力场中水中臭氧平衡浓度可达11.54 mg/L，远高于传统曝气装置的4.44 mg/L，证明了超重力技术可强化臭氧传质过程。采用半连续化方法研究了超重力场下臭氧降解硝基苯过程中的直接和间接反应动力学与降解机理。结果表明：超重力场中臭氧氧化硝基苯的直接和间接反应动力学基本符合准一级反应，其中直接反应速率常数为1.020 L/(mol s)；且速率常数随温度、初始pH、超重力因子和气相臭氧浓度的增大而增大，随初始硝基苯浓度的增大而降低。而间接反应速率常数为1.898(±0.145)×109 L/(mol·s)，且随温度、初始pH、超重力因子和初始硝基苯浓度的增大而增大。通过液相色谱和气相-质谱联用技术分析超重力强化微电解催化臭氧降解有机废水的降解机理，硝基苯先加氢还原为亚硝基苯，继而被还原为苯胲，最终转化为苯胺。再通过超重力强化Fe2+/O3，加快臭氧分解，利用体系中存在·OH或溶解氧攻击苯胺，12 min苯胺完全去除，60 min时TOC去除率可达73%，通过分析测试其降解过程为：将苯胺氧化生成对氨基苯酚、苯二酚、对苯醌，然后开环生成马来酸、乙酸、等小分子酸，最终矿化为CO2和H2O，这对于超重力技术领域具有重要的科学意义和应用价值。