硫掺杂二氧化钛的光催化活性及其对微囊藻毒素的降解

发布时间：2018-02-22 20:13

本文关键词： 微囊藻毒素可见光掺硫改性二氧化钛溶胶—凝胶法薄膜光降解　出处：《上海海洋大学》2017年硕士论文　论文类型：学位论文

【摘要】：微囊藻毒素(nsMicrocystiMCs,)是由7个氨基酸残基组成的环状多肽,它是由蓝藻细胞破裂产生,由于7个氨基酸残基中有两个可变残基,导致其具多变的排列方式,因此MCs具有很多同分异构体,目前已经发现90多种同分异构体。其中最为普遍、含量最多、毒性最强的是MC-LR。MC-LR对于生物体有许多毒性,例如神经毒性、遗传毒性和多器官毒性等,甚至长期接触MC-LR,会存在促癌的风险,它对人类的身体健康有着严重的影响,也是饮用水的一大隐患。MC-LR具有良好的稳定性、耐热性和耐水解特性,很难被常规水处理方式去除,因此给人们如何高效环保的去除它带来了难题。而属于高级氧化技术的可见光催化去除具有绿色环保,成本低,安全无污染的特点,能够较好地克服一般常规的水处理的缺点,将会成为去除环境中MCs的主要方式。本实验利用溶胶-凝胶法制备了不同添加硫脲顺序、不同煅烧温度,不同[S]/[Ti]配比的硫掺杂二氧化钛(-iOS T2)粉体,并使用相应的仪器对部分2S-OiT进行了表征。以MC-LR的去除率为考察指标验证S-TiO_2催化剂的活性,设计了S-TiO_2可见光下去除MC-LR的实验。而且研究了在经过过滤,清洗,干燥一系列回收过程后S-TiO_2的光稳定性和回收重复利用率。结果显示,非金属S的掺杂会导致TiO_2晶体粒径变小,并且影响其结晶程度。S以6S(10)取代了晶格中的4iT(10),形成S-O-Ti结构,提高了-iOS T2对可见光的响应。通过对比不同S-TiO_2对MC-LR的去除率,得到了制作S-TiO_2的最优条件:在水解部分将掺硫量的配比(]Ti/[]S[)为0.25的硫脲与钛酸丁酯充分混合后再进行缩合和陈化,然后在在温度为500℃下煅烧3h。通过对清洗液的筛选可知,25%乙醇水清洗2-iOS T后,-iOS T2的回收率最高且对催化剂光活性的影响最小。因此,25%乙醇水为最佳的清洗液。同时,本实验制备的2-iOS T在5次重复利用实验中对MC-LR的去除率无明显变化,证明其具有良好的稳定性和可重复利用性。但是在多次回收利用的过程中,2-iOS T粉末的损失严重,每次重复利用催化剂的损失率高达±%07.641,因此必须研究新形态的催化剂,使其更加完善。使用[S]/[Ti]配比为0.25,在马弗炉中选择500℃煅烧3h下制作的S-TiO_2对初始浓度为1.0mL1 g-×m的MC-LR进行光去除,以探讨MC-LR的最优可见光去除条件。实验的结果表明,2-iOS T在可见光下去除MC-LR的效果与光强和溶液中pH值大小有很大关系。当光强增大时,MC-LR的去除率也会跟着增大,并且在去除实验的后期去除率逐渐趋于稳定状态。最佳去除所需的pH由-iOS T2在水中的PZC和此时的MC-LR所带电荷决定。实验证明,pH在2.1-6.8之间时去除率最佳。最佳2-iOS T的投加量为0.1g·L-1。单因素对可见光催化去除MC-LR的影响程度由大到小分别为反应时间、投加量和光强。在本文设计的正交条件下,2-iOS T可见光下去除MC-LR的最优去除工艺为:光强3000lux,催化剂用量0.1g·L-1,反应时间16h。此时初始浓度为1.0mL1 g-×m的MC-LR去除率达到100%。通过探讨研究2-iOS T光催化去除机理,发现光催化去除的主要氧化基团是h+,限速步骤是电子与空穴的结合。为了改良2-iOS T粉状光催化剂损失率高、回收过程复杂的问题,制作了]Ti/[]S[配比为0.25的2-iOS T溶胶,利用涂覆法和浸渍提拉法在基板(盖玻片)上制作了两种掺硫改性二氧化钛催化剂的薄膜,并以其在可见光下去除MC-LR的去除率为指标,验证其可见光下的催化效率。结果显示,掺杂硫使二氧化钛催化剂薄膜的活性得到提高。同时,在制作的薄膜催化剂中,用浸渍提拉法制作的薄膜活性更佳,在可见光下对MC-LR连续处理18h,其去除率达到93.71%,但是微囊藻毒素的残留浓度并没有达到WHO规定的藻毒素含量标准。因此,在今后的研究中,应该从如何提高薄膜的光催化活性入手,分析煅烧温度、马弗炉升温速度、煅烧时间以及涂覆溶胶层数对薄膜光催化活性的影响,以寻找制作薄膜更好的方法。
[Abstract]:Microcystins (nsMicrocystiMCs) is a cyclic polypeptide composed of 7 amino acid residues, which is produced by cyanobacteria cell rupture, since there are two variable residues of 7 amino acid residues, which has changeable arrangement, so MCs has many isomers, has now found more than 90 isomers. One of the most common, the most content is the most toxic, MC-LR.MC-LR has a lot of toxicity to living organisms, such as neurotoxicity, genotoxicity and multiple organ toxicity, and long-term exposure to MC-LR, there will be the risk of cancer, it to human health have a serious impact,.MC-LR is also a great hidden danger drinking water has good stability, heat resistance and hydrolysis resistance, it is difficult to be removed by conventional water treatment, so how to give people efficient removal it brings a problem. But to the advanced oxidation technology of visible light. With the removal of the green environmental protection, low cost, safety and no pollution, can effectively overcome the shortcomings of conventional water treatment, will become the main way to remove MCs in the environment. The different order of thiourea was prepared by sol-gel method, different calcination temperature, sulfur doped TiO2 [S]/[Ti] with different ratio (-iOS T2) powder, and a part of 2S-OiT were characterized by using the corresponding instruments. With the removal rate of MC-LR as index to verify the activity of S-TiO_2 catalyst, designed the experimental removal of MC-LR S-TiO_2 under visible light. And studied after filtering, washing, drying after a series of recycling process of S-TiO_2 light stability and recycling rate. The results show that doping nonmetal S will lead to TiO_2 crystal particle size becomes smaller, and the effect of the crystallization of.S in 6S (10) to replace the lattice 4iT (10), the formation of S-O-Ti structure. The -iOS T2 on the visible light response. Through the comparison of different S-TiO_2, the removal rate of MC-LR, the optimal conditions of making S-TiO_2 in part of the sulfur doped hydrolysis ratio (]Ti/[]S[) and thiourea butyl titanate 0.25 mixing after condensation and aging, and then through the screening of the cleaning liquid for the annealed at 500 3h. in temperature, 25% ethanol water cleaning 2-iOS T after -iOS recovery rate of T2 influence on the catalyst activity and the highest light minimum. Therefore, 25% ethanol water as the best cleaning liquid. At the same time, this experiment prepared 2-iOS T 5 times in the repeated use of the MC-LR the removal rate of no significant change, indicating that it has good stability and can be reused many times. But in the recycling process of 2-iOS powder T serious loss, each repeated use of catalyst loss rate as high as%07.641 +, so we must study the new form of The catalyst to make it more perfect. The use of the ratio of [S]/[Ti] was 0.25, in a muffle furnace 500 calcined under 3H production of S-TiO_2 light on the removal of the initial concentration of 1.0mL1 g- * m MC-LR, to the best of MC-LR visible light removal conditions. The experimental results show that 2-iOS T can see the light in the removal of MC-LR the effect of light intensity and pH value of solution have great size. When the light intensity increases, the removal rate of MC-LR will follow the increase, and in a later removal experiment removal rate becomes stable. The best removal required by the pH -iOS T2 PZC in water and the MC-LR charge. Experiments show that the pH between 2.1-6.8 removal rate of the best. The best 2-iOS T dosage for MC-LR removal of the visible light photocatalytic single factor 0.1g and L-1. influence degree from large to small respectively, reaction time, dosage and intensity. In this paper a orthogonal design Under the 2-iOS T under visible light the best removal MC-LR removal process is: the intensity of 3000lux, 0.1g catalyst L-1, reaction time 16h. when the initial concentration of 1.0mL1 g- * m MC-LR removal rate reached 100%. by study on the removal mechanism of 2-iOS photocatalytic oxidation of T, found that the main groups of photocatalytic removal of h+ is the rate limiting step is a combination of electron and hole. In order to improve the 2-iOS T powder photocatalyst loss rate is high, the recovery process of complex problems, making the ratio of]Ti/[]S[0.25 2-iOS in T sol, coating and substrate by dip coating method (on coverslips) making two kinds of sulfur doped modified titanium dioxide thin film, and its the removal of MC-LR under visible light removal rate as the index, to verify its catalytic efficiency under visible light. The results showed that the sulfur doped TiO2 catalyst film activity improved. At the same time, the film made in catalysis Agent, film production activity is better by the dipping method, under visible light on MC-LR continuous treatment of 18h, the removal rate reached 93.71%, but the residual concentration of microcystins and the toxin content did not reach the standard stipulated by WHO. Therefore, in the future, should from how to improve the photocatalytic activity of thin films starting with the analysis of the calcination temperature, heating speed of muffle furnace, influence of calcination time and coating sol layers on the photocatalytic activity of the film, in order to find a better method of making films.

【学位授予单位】：上海海洋大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O643.36;O644.1;X52

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