CAS OpenIR
碱性介质电化学高级氧化体系活性氧调控及催化氧化基础研究
薛玉冬
Subtype博士
Thesis Advisor张懿
2019-07-01
Degree Grantor中国科学院大学
Degree Discipline化学工艺
Keyword活性氧,电化学,高级氧化,碱性介质,两性金属
Abstract

难处理、低品位原生金属矿物资源以及二次资源高效清洁综合利用是湿法冶金领域的重大战略需求,以活性氧调控为核心的湿法冶金高级氧化技术成为研究的热点。中国科学院过程工程研究所研发了亚熔盐介质两性金属矿物高效清洁氧化技术,利用介质中赋存的具有强氧化能力的活性氧组分,取得很好的反应效果,但活性氧强化两性金属氧化过程机理、提升活性氧产量及氧化能力的调控手段仍需进一步深入研究。 电化学方法可以深入原子和分子水平层次,以电极-碱介质界面电子转移过程作为活性氧的调控手段,具有过程可控、清洁高效、精准灵敏的优点,本论文提出碱性介质活性氧的电化学调控方法,重点研究电化学体系活性氧的原位生成、量化测定、定向调控和催化氧化过程,在此基础上,提出异质原子掺杂和异质(复合)结构耦合策略提升电化学二电子氧气还原反应性能的主要思路,以定向调控活性氧的生成、大幅度提高活性氧的产量,进而建立以氢过氧根离子和羟基自由基为核心的碱性介质电化学高级氧化反应体系,并在铬、钒、砷的催化氧化反应过程中进行验证研究,为两性金属高效转化提供理论依据。 论文取得如下创新性成果:(1)构建了碱性介质电化学活性氧的原位生成体系,利用电化学二电子氧还原过程在阴极产生大量的氢过氧根离子,建立了氢过氧根离子的量化测试方法,系统研究了工作电位、工作电流、通氧速率和搅拌速率等条件对电化学活性氧原位生成的影响,发现在氧还原反应区域升高工作电位或工作电流,提高通氧速率和搅拌速率均能够促进活性氧的生成。研究了活性氧作用下三价铬的转化,电子自旋共振波谱和猝灭实验结果表明三价铬的氧化过程诱导产生了具有更高氧化能力的羟基自由基,拓展了对电化学活性氧物种的认识范围。(2)基于异质原子掺杂和异质(复合)结构耦合的思路,制备了氮掺杂碳毡和二硫化钼/碳毡复合电催化电极。电极材料表征结果显示,碳毡电极表面含氮基团的引入以及二硫化钼纳米片的自组装生长,分别形成了具有较高电催化活性的表面含氮基团和二硫化钼催化层,成为催化活性位点;循环伏安法、计时电流法和旋转圆盘/环盘电极等电化学测试结果表明,采用上述方法可以大幅提升电化学二电子氧还原活性,提高活性氧的生成能力。与碳毡电极相比,氮掺杂碳毡电极和二硫化钼/碳毡复合电极表面活性氧的产量能够分别提升48%、50%。(3)研究了活性氧催化氧化作用下铬、钒的高效转化过程,在活性氧催化氧化铬、钒转化过程中,三价铬和三价钒分别能够诱导氢过氧根离子发生电化学-类芬顿反应,激发产生具有更高氧化能力的羟基自由基,促进了氧化反应的继续进行,从而建立了碱性介质电化学高级氧化反应体系。相比于电化学直接氧化过程,活性氧催化氧化作用使三价铬和三价钒的转化率分别增加71%和63.7%。电子自旋共振波谱和猝灭实验结果发现氢过氧根离子和羟基自由基在催化氧化过程中具有协同作用,共同促进氧化的进行;在三价铬和三价钒的转化过程中,羟基自由基的贡献比例分别为30%和35%。(4)将碱性介质电化学高级氧化反应体系应用于砷中毒废SCR催化剂的再生以及三价砷废水的高效氧化过程。提出了电极表面吸附-原位氧化反应机制,钒基电化学-类芬顿反应产生的羟基自由基对电化学脱砷过程起到重要作用;在电化学活性氧催化氧化作用下,废SCR催化剂表面砷元素脱除率达到95.2%,再生催化剂的脱硝性能恢复到新鲜催化剂的水平。采用电化学活性氧协同氧化处理三价砷废水,加速了三价砷的转化过程,与电化学直接氧化和氧气氧化相比,电化学活性氧的协同作用将三价砷的转化率分别提升80%和65%;通过耦合后续沉淀脱砷工序,五价砷脱除率近100%,含砷废水可达标排放。;The high-efficiency, clean, and comprehensive utilization of the refractory, low grade primary metal ores and secondary resources is a major strategic demand in the hydrometallurgical field. The hydrometallurgical advanced oxidation process, focused on the tuning of reactive oxygen species (ROS), is growing to a hot topic. The cleaner oxidation technique for the amphoteric metal ores by the sub-molten salt (SMS) media was developed by Institute of Process Engineering, Chinese Academy of Sciences. The SMS technology has obtained favorable application effect, which utilizes ROS with high oxidizing capacity in the SMS media. However, the mechanism of ROS intensified amphoteric metal oxidation process and the tuning strategy for increasing the ROS production and oxidative capacity still need further investigations.As a controllable, efficient, accurate, and sensitive method, electrochemistry can control the interfacial electron transfer process for the ROS tuning at the atomic and molecular level. In this dissertation, the ROS electrochemical tuning strategy in alkaline media was proposed. The in-situ generation, quantitative determination, targeted tuning, and catalytic oxidation of ROS in the electrocatalytic process was mainly studied. On this basis, in order to achieve the targeted tuning of ROS and greatly enhance the ROS production, we proposed that the main strategies for improving electrochemical two-electron oxygen reduction reaction (ORR) performance is heteroatoms doping method and hetero (composite) structure design. The alkaline electrochemical advanced oxidation process (EAOPs) was further constructed based on the tuning of HO2- and ·OH species. The alkaline EAOPs have applied in the catalytic oxidation processes of chromium, vanadium, and arsenic, supporting the theoretical basis of amphoteric metal conversion. The main progresses are achieved as follows:(1) The electrochemical ROS in-situ generation system in alkaline media has been established based on the electrochemical two-electron ORR reaction. Large amount of HO2- can be produced in the cathodic region. The quantify determination method was built and the effect of work potential, current density, oxygen flow rate, and stirring speed on the electrochemical ROS in-situ generation process was discussed in order to obtain the optimization conditions. The Cr(III) oxidation by ROS was investigated by the electron spin resonance (ESR) spectroscopy and the quenching experiments. The results indicated that ·OH with higher oxidative capacity was induced by Cr(III), plays a vital role in the oxidative process, which expands the scope of knowledge of ROS in the electrochemical system. (2) Based on the heteroatoms doping and hetero (composite) structure design strategies, nitrogen-doped carbon felt (N-doped CF) and MoS2/CF composite electrodes are fabricated, respectively. The material characterization results demonstrated that the nitrogen groups are introduced onto the CF surface and the MoS2 nanosheets are self-assembly grown on the CF, which are considered as the main electrocatalytic active sites. The electrochemical experiments including cyclic voltammetry (CV), chronoamperometry, and rotating disk electrode/rotating ring disk electrode (RDE/RRDE), indicated that the improved two-electron ORR performance was obtained. In comparison to the CF, the ROS production on the N-doped CF and MoS2/CF increased by 48% and 50%, respectively.(3) High-efficiency Cr and V conversion processes by ROS catalytic oxidation effect were investigated. In the ROS catalytic oxidation process, the ·OH presents high oxidation capacity, which is generated from the chromium-based or vanadium-based electro-Fenton-like reaction. During the oxidation/dissolution process, ·OH is induced by Cr(III) and V(III), causing a much higher improvement for further catalytic oxidation. Therefore, we proposed a new concept of alkaline EAOPs, achieving effective conversion of chromium and vanadium under the effect of ROS catalytic oxidation processes. In comparison with direct electrochemical oxidation process, the conversion ratio of Cr and V by ROS catalytic process increased by 71% and 63.7%, respectively. The ESR and quenching experiment results showed that the synergy of HO2- and ·OH can promote the oxidation process. During the conversion of Cr(III) and V(III), the contribution of ·OH is 30% and 35%, respectively. (4) The proposed alkaline EAOPs have applied in the regeneration of arsenic-poisoning spent SCR catalyst and the treatment of As(III) wastewater. The surface adsorption and in-situ oxidation mechanism in the regeneration of spent SCR catalyst was proposed. The ·OH generated in the vanadium-based Fenton-like reactions plays a significant role in the arsenic removal. The arsenic remove ratio on the catalyst surface can be reached 95.2% by the presented method. The SCR performance of the regenerated catalyst is recovered to the commercial level. Highly efficient oxidation of As(III) in the arsenic-containing wastewater is achieved by the synergetic effect of electrochemical oxidation and ROS oxidation. In comparison with electrochemical direct oxidation and oxygen oxidation processes, the conversion ratio of As(III) by this method increased by 75% and 60%, respectively. Combing with the following precipitation step, the arsenic-containing wastewater, with almost 100% As(V) removal ratio, can reach the demand of discharge standards. 

Language中文
Document Type学位论文
Identifierhttp://ir.ipe.ac.cn/handle/122111/40682
Collection中国科学院过程工程研究所
Recommended Citation
GB/T 7714
薛玉冬. 碱性介质电化学高级氧化体系活性氧调控及催化氧化基础研究[D]. 中国科学院大学,2019.
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