硼掺杂金刚石薄膜电极的制备及其在密闭空间废水处理回用中的应用

发布时间：2018-03-25 01:31

本文选题：热丝化学气相沉积　切入点：硼掺杂金刚石薄膜电极　出处：《浙江大学》2016年博士论文

【摘要】：硼掺杂金刚石薄膜电极具有优异的电化学性能,它具有较宽的电化学窗口、极低的背景电流、很高的稳定性,是电化学氧化中阳极材料的最佳选择之一,在电化学氧化领域具有很好的应用前景。本文利用热丝化学气相沉积(HFCVD)的方法制备了不同尺度硼掺杂金刚石薄膜电极,并研究了其对密闭空间内冷凝水和尿液的降解规律。以甲烷和氢气为反应前驱气体,采用HFCVD法分别制备了微米级金刚石薄膜和纳米级金刚石薄膜。考察了甲烷浓度、反应压力、衬底温度等对薄膜质量以及金刚石薄膜生长速率的影响,建立了金刚石薄膜的生长动力学模型。结果表明甲烷浓度、反应压力、衬底温度是金刚石薄膜生长的主要影响因素。以乙硼烷作为硼源,分别制备了硼掺杂微米级金刚石薄膜(BDMCD)电极和硼掺杂纳米级金刚石薄膜(BDNCD)电极。并以此为阳极,不锈钢板为阴极,构建了电化学催化氧化体系,降解模拟冷凝水和模拟尿液。BDMCD电极和BDNCD电极对模拟冷凝水的矿化效率均超过95%,而对模拟尿液的矿化效率均可达99%。研究表明,纳米尺度的BDNCD电极相比微米尺度的BDMCD电极表现出了较慢的降解速率及氧化滞后性的微纳尺度效应,其原因是纳米尺度的BDNCD电极中含有大量的sp2碳,降低了其降解速率。模拟冷凝水电化学降解过程中,有机物首先被氧化成甲酸、乙酸、乙二酸等小分子酸,并且最终有机物只以乙二酸一种形式存在；模拟尿液电化学降解过程中,无机阴离子中的硫酸根不会被氧化,含氯化合物最终将被氧化成高氯酸盐,含氮化合物将以硝酸盐形态存在于最终溶液中。为深度处理电化学氧化后的溶液,耦合离子交换树脂,以200mL模拟尿液为例,经处理最终尾水TOC为7mg/L,电导率约为0.6μS/cm,整个反应电化学过程能耗为0.096kWh,阴阳离子交换树脂消耗量分别为26.9g。对于真实尿液,能耗及离子交换树脂消耗量均有所增加,同样以200mL真实尿液为例,经处理最终尾水TOC为30mg/L,电导率约为0.7μS/cm,整个反应电化学过程能耗为0.166kWh,阴阳离子交换树脂消耗量分别为67.4g,可满足密闭空间废水再生回用的要求。尽管BDNCD电极降解速率略慢,其对模拟冷凝水和尿液的拟一级动力学降解速率常数仅分别为BDMCD电极的76.7%和69.9%,但BDNCD电极的使用寿命显著提高。BDNCD电极加速寿命实验的使用寿命约为465h,比BDMCD电极高了32.6%,这是由于BDNCD电极的金刚石颗粒粒径小,且其表面粗糙度仅为BDMCD电极的1/20。而据此推算其在实际电催化氧化模拟冷凝水和模拟尿液中的稳定使用寿命分别可达约17年和1.6年,足以满足密闭空间对电极更换周期的要求。
[Abstract]:Boron doped diamond thin film electrode has excellent electrochemical performance, it has wide electrochemical window, very low background current, high stability, and is one of the best choice of anode material in electrochemical oxidation. In this paper, boron doped diamond thin film electrodes with different scales have been prepared by hot filament chemical vapor deposition (HFCVD). The degradation of condensate water and urine in confined space was studied. Micrometer diamond films and nanoscale diamond films were prepared by HFCVD method using methane and hydrogen as precursor gases. The concentration of methane and reaction pressure were investigated. The effect of substrate temperature on the quality of diamond film and the growth rate of diamond film are studied. The kinetic model of diamond film growth is established. The results show that methane concentration, reaction pressure, Using boron borane as boron source, boron doped micrometer diamond thin film (BDMCD) electrode and boron doped nanocrystalline diamond thin film (BDNCD) electrode were prepared. Electrochemical catalytic oxidation system was constructed by using stainless steel plate as cathode. The mineralization efficiency of simulated condensate water and simulated urine. BDMCD electrode and BDNCD electrode for simulated condensate water were higher than 95. 95% and 99% for simulated urine. Nano-scale BDNCD electrode shows a slow degradation rate and a micro-nano scale effect of oxidation lag compared with micron scale BDMCD electrode. The reason is that nanoscale BDNCD electrode contains a large amount of sp2 carbon. In the process of electrochemical degradation of simulated condensate water, organic compounds are first oxidized to small molecular acids such as formic acid, acetic acid and adipic acid, and the final organic compounds only exist in the form of adipic acid. In the process of simulating the electrochemical degradation of urine, the sulfate in inorganic anions will not be oxidized, and the chlorinated compounds will eventually be oxidized to perchlorates. The nitrogen-containing compounds will be present in the final solution in the form of nitrate. For advanced treatment solution after electrochemical oxidation, coupling ion exchange resin, taking 200mL simulated urine as an example, After treatment, the TOC of the tail water was 7 mg / L, the conductivity was about 0.6 渭 S / cm, the energy consumption of the whole reaction electrochemical process was 0.096 kWhand the consumption of anion and anion exchange resin was 26.9 g. For the real urine, the consumption of the ion exchange resin and the consumption of the ion exchange resin were increased. Also take 200mL's real urine as an example. After treatment, the TOC of tail water is 30 mg / L, the conductivity is about 0.7 渭 S / cm, the energy consumption of the whole reaction electrochemical process is 0.166 kWhand the consumption of anion and anion exchange resin is 67.4 g, which can meet the requirements of regeneration and reuse of sealed space wastewater, although the degradation rate of BDNCD electrode is a little slow. The pseudo-first-order kinetic degradation rate constants of simulated condensate water and urine were only 76.7% and 69.9% of that of BDMCD electrode, respectively, but the service life of BDNCD electrode was significantly increased by 465 h, which was higher than that of BDMCD electrode. This is due to the small diameter of diamond particles at the BDNCD electrode, The surface roughness of the electrode is only 1 / 20 of that of the BDMCD electrode. Based on this, the stable service life of the electrode in simulated condensate water and urine can be estimated to be about 17 years and 1.6 years, respectively, which is sufficient to meet the requirements of the electrode replacement period in the closed space.
【学位授予单位】：浙江大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：X703;TB383.2

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