纳米氧化铁的优化制备及其可见光芬顿降解水中的双酚S

发布时间：2017-12-28 02:06

本文关键词：纳米氧化铁的优化制备及其可见光芬顿降解水中的双酚S　出处：《哈尔滨工业大学》2017年博士论文　论文类型：学位论文

【摘要】：双酚S因其优良的物化稳定性,被视为双酚A的理想替代物,广泛应用于聚碳酸酯、环氧树脂、聚酯树脂、聚砜、聚醚砜等高分子材料的合成。同时,作为双酚A的代替品,它也被大量应用于热敏打印纸、食品包装等日常品的生产。然而,随着研究深入发现,双酚S也具有与双酚A类似的生理毒性。更令人堪忧的是,双酚S已在地表水体中被频频检出,这对人类健康构成了潜在的威胁。因此,实现水中双酚S的高效去除,对改善水生环境具有重要的现实意义。与传统芬顿技术相比,均相光芬顿技术在一定程度能弥补传统芬顿技术的不足,然而它依然存在反应条件苛刻(p H≤3)、污泥产量多等问题。针对这些问题,本研究通过设计、制备经济环保的纳米氧化铁固相催化剂,进而构建绿色、稳定的异相光芬顿体系,最终实现水中双酚S的高效去除。首先,针对氧化铁实心颗粒所存在的比表面积小、活性点位暴露少等问题,本研究提出了“二氧化硅软模板”合成策略,实现了氧化铁中空球的温和、可控制备。在此基础上,阐明了氧化铁中空球微观结构-物化特性-光芬顿活性三者间的内在关系。三次循环降解实验表明,优选出氧化铁异质中空球的耐用性和持久性较好。经典的捕获剂实验结果表明在该光芬顿体系中起主要氧化作用的活性氧物种分别为超氧自由基和羟基自由基。在可见光照射下,优选出的氧化铁异质中空球对双酚S的降解率为30%,高于实心氧化铁纳米颗粒(商业品)的3%。分析原因是异质氧化铁中空球具有较大的比表面积、发达的孔隙结构,因此有利于催化剂活性点位的充分暴露,进而产生活性物质,以实现双酚S的有效降解。虽然通过中空化处理(即微观结构的物理优化)可提高氧化铁的比表面积和材料表面的活性点位的数量,但仍不足以克服氧化铁作为光催化剂所固有的本征缺陷,如光生电子-空穴易复合等问题。针对这个问题,本研究在合成制备氧化铁时原位引入具有超高迁移率的石墨烯,进而获得了不同形貌氧化铁/石墨烯复合催化剂。氧化降解实验表明氧化铁量子点/石墨烯复合催化剂的光芬顿活性最高。自由基捕获实验和荧光光谱数据表明该体系里起主要降解作用的活性物质为羟基自由基。在可见光照射下,优选出的氧化铁量子点/石墨烯复合催化剂对双酚S的去除率可达83%,高于氧化铁异质中空球的30%。分析原因是石墨烯的引入一方面可有效阻碍光生电子空穴的复合,另一方面二维石墨烯纳米片会对双酚S产生较为强烈的吸附作用(40%)。为获得催化活性更高的氧化铁纳米材料,进一步提出了“二氧化硅水凝胶协助溶解重结晶”的合成策略,成功制备了(110)高能晶面暴露的氧化铁超薄纳米片。在可见光照射下,以氧化铁纳米片所构建的光芬顿体系对双酚S的去除率高达91%(注:吸附仅占3%),高于商业P25二氧化钛的56%,且远高于氧化铁纳米颗粒(合成品)的16.6%。分析原因是:1)由于光生电子在(110)晶面的迁移率非常高,导致光生载流子的分离效果好,使得参与后续反应的光生电子数量增多;2)氧化铁纳米片的厚度仅为3.2 nm,能有效克服光生空穴扩散路程短的缺陷(2 4 nm),使得参与后续反应的光生空穴数量增多;3)由于催化剂具有超薄二维片层结构,使得其比表面积较大,活性点位的暴露较为充分。最后,采用UPLC/MS对双酚S的降解产物进行了鉴定。结果表明双酚S的降解产物主要有二羟基苯磺酸、羟基苯磺酸、3-烯丙氧基-1-丙磺酸和苯酚钠。据此,可推断羟基化是驱动双酚S分解的主要机制。
[Abstract]:Bisphenol S is regarded as an ideal substitute for bisphenol A because of its excellent physical and chemical stability. It is widely used in the synthesis of polycarbonate, epoxy resin, polyester resin, polysulfone, polyethersulfone and other polymer materials. At the same time, as a substitute for bisphenol A, it has also been widely used in thermal printing paper, food packaging and other daily goods production. However, with the further study, bisphenol S also has a physiological toxicity similar to that of bisphenol A. What is more worrying is that bisphenol S has been detected frequently in the surface water, which poses a potential threat to human health. Therefore, the efficient removal of bisphenol S in water is of great practical significance for the improvement of aquatic environment. Compared with the conventional Fenton technique, homogeneous light Fenton technology in a certain extent can make up the insufficiency of traditional Fenton technology, but it still exists in harsh reaction conditions (P, H = 3), sludge production and other issues. In order to solve these problems, we design and prepare an economical and environmental protection nano iron oxide solid phase catalyst, and then construct a green and stable heterogeneous optical Fenton system. Finally, we can achieve efficient removal of bisphenol S in water. First of all, aiming at the problems of small specific surface area and little exposure of active sites for iron oxide solid particles, a silica soft template synthesis strategy is proposed to achieve the mild and controllable preparation of iron oxide hollow spheres. On this basis, the intrinsic relationship between the microstructure and physicochemical properties of the iron oxide hollow sphere, the three of the light Fenton activity, is clarified. The three cyclic degradation experiments showed that the optimization of the durability and durability of the iron oxide heterogeneous hollow sphere was better. The experimental results of the classic capture agent show that the active oxygen species, which have the main oxidation in the light Fenton system, are superoxide radicals and hydroxyl radicals, respectively. Under the light of visible light, the degradation rate of bisphenol S is 30%, which is higher than that of solid iron oxide nanoparticles (commercial products), which is higher than 3% of the solid iron oxide nanoparticles. The reason for the analysis is that the heterogeneous iron oxide hollow spheres have large specific surface area and well-developed pore structure. Therefore, it is beneficial to fully expose the active sites of catalysts and produce active substances, so as to achieve the effective degradation of bisphenol S. Though the medium cavitation treatment (i.e. physical optimization of microstructure) can improve the specific surface area of iron oxide and the number of active sites on the material surface, it is still not enough to overcome inherent defects of iron oxide as photocatalyst, such as photoelectron hole recombination. To solve this problem, we synthesized in situ the graphene with ultra-high mobility in the preparation of ferric oxide, and obtained different morphologies of iron oxide / graphene composite catalyst. The oxidation degradation test showed that the light Fenton activity of the iron oxide quantum dot / graphene composite catalyst was the highest. The free radical capture experiment and fluorescence spectrum data show that the main bioactive substance in the system is hydroxyl radical. Under the light of visible light, the optimal removal rate of the ferric oxide quantum dot / graphene composite catalyst for bisphenol S is up to 83%, which is higher than that of 30% of the iron oxide hollow sphere. The reason for the analysis is that the introduction of graphene can effectively obstruct the recombination of photoelectron holes. On the other hand, two-dimensional graphene nanosheets will strongly adsorb bisphenol S (40%). In order to obtain iron oxide nanomaterials with higher catalytic activity, we further put forward the synthetic strategy of "silica gel assisted dissolution and recrystallization", and successfully prepared (110) iron oxide ultra-thin nanosheets exposed to high energy crystal surface. Under visible light irradiation, the removal rate of bisphenol S by Fe Fenton nanosheets was as high as 91% (3%). The removal rate of bisphenol P25 was 56% higher than that of commercial TiO2, which was much higher than that of iron oxide nanoparticles (16.6%). The reasons are: 1) because of the photogenerated electrons in the crystal face (110) the migration rate is very high, resulting in separation of photogenerated carriers, which participate in the subsequent reaction of photogenerated electron number; 2) iron oxide nano film thickness is 3.2 nm, can effectively overcome the photohole diffusion in the short distance the defect (24 nm), which involved in the subsequent reaction of the photogenerated hole number; 3) because the catalyst has thin two-dimensional layer structure, the larger specific surface area, active sites exposed to more fully. Finally, UPLC/MS was used to identify the degradation products of bisphenol S. The results show that the degradation products of bisphenol S mainly include two hydroxy benzenes sulfonic acid, hydroxybenzenes sulfonic acid, 3- allyl -1- propane sulfonic acid and sodium phenol. Therefore, it is inferred that hydroxylation is the main mechanism to drive the decomposition of bisphenol S.
【学位授予单位】：哈尔滨工业大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：X703

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