Po放射性废水净化及检测模拟实验研究
发布时间：2018-08-17 10:38
【摘要】：Po是乏燃料处理、铀矿开采及铅铋冷却反应堆核事故产生的放射性废水中的重要核素之一,其同时具有极毒性和放射性,净化与检测这种放射性核素是核能可持续发展必须考虑的问题之一。本文采用化学性质相似的非放射性碲代替放射性及高毒性钋,选择载银不锈钢编织网和氧化石墨烯两种吸附载体,开展了水中Te(Ⅳ)的吸附行为及机理研究;在此基础上,以氧化石墨烯为前驱体,以抗坏血酸、亚硫酸氢钠及乙二胺为还原剂,构建纳米银/石墨烯水凝胶,并确定碲信号最强的乙二胺还原诱导自组合纳米银/石墨烯水凝胶为基底材料,开展了表面增强拉曼散射技术对水中微量碲元素检测的探索研究,主要研究结果如下:通过开展镀铜电流、吸附时间及共存碘离子浓度对载银不锈钢编织网吸附Te(Ⅳ)行为影响的研究,结果表明:镀铜电流对载银不锈钢编织网吸附Te(Ⅳ)具有显著的正向性影响,这是不锈钢编织网表面银负载量随镀铜电流增加而增大的结果;镀银时间0.5 h和镀银时间2.5 h的不锈钢编织对Te(Ⅳ)的吸附随吸附时间的变化具有明显地前期快速上升阶段和后期平缓阶段,而镀银时间1.5 h的不锈钢编织网对Te(Ⅳ)的吸附率随吸附时间增加以恒定速率上升,在吸附64 h时,吸附率达到63±0.1%,载银不锈钢表面银膜表面积随镀银时间延长而变化是产生该现象的主要原因;载银不锈钢编织网对水中Te(Ⅳ)的吸附随共存碘离子浓度向增加呈现先下降后上升趋势,该现象是碘离子、Te(Ⅳ)种态竞争吸附和银、Te(Ⅳ)接触面积变化共同作用的结果。微观结构与物相分析表明:银膜表面吸附形成的化合物呈现明显的正四价氧化物形式和Ag2Te化合物形式,确定Te(Ⅳ)自发沉积和酸性条件下银、Te(Ⅳ)反应生成Ag2Te是载银不锈钢编织网吸附Te(Ⅳ)的主要机制。通过开展吸附时间、水溶液pH及氧化石墨烯浓度等因素影响氧化石墨烯吸附Te(Ⅳ)的研究,结果表明:氧化石墨烯表面吸附位点随吸附时间增加而逐渐减少,这是导致Te(Ⅳ)吸附率随吸附时间增加先上升后不变的主要原因;pH对氧化石墨烯表面官能团与Te(Ⅳ)间亲合力和水中Te(Ⅳ)溶解性及种态影响的综合作用,导致Te(Ⅳ)吸附率随pH增加呈现先上升后下降的趋势,并在pH值4.7左右,吸附率达到最大;氧化石墨烯对Te(Ⅳ)的吸附率随其浓度的增加先上升后不变,这是吸附位点和氧化石墨烯片团聚程度随氧化石墨烯浓度增加而增大的结果。基于上述实验,对氧化石墨烯吸附Te(Ⅳ)的动力学和等温线进行了研究,结果显示:氧化石墨烯吸附Te(Ⅳ)动力学数据符合伪二阶动力学方程,吸附平衡数据符合Sips方程及Freunlich方程,表明氧化石墨烯表面各吸附位点不均匀,对Te(Ⅳ)的吸附为非单层吸附,且随着吸附的进行,吸附限速步骤由内扩散逐渐转变为膜扩散,据此可得氧化石墨烯吸附Te(Ⅳ)离子是一个包含多种作用的复杂过程。微观结构及价态分析表明氧化石墨烯吸附Te(Ⅳ)并不会导致其化学价的改变,吸附机制涉及环氧基、羧基等含氧官能团和石墨烯苯环结构对碲离子的相互作用。利用表面增强拉曼光谱,开展了水中微量Te(Ⅳ)检测实验研究。通过对抗坏血酸、亚硫酸氢钠和乙二胺还原诱导自组合纳米银/石墨烯水凝胶吸附Te(Ⅳ)后的拉曼信号进行对比,发现乙二胺还原诱导自组合纳米银/石墨烯在584.9 cm-1的Te-O峰和642.9 cm-1的Te=O=Te振动峰显著增强,而抗坏血酸和亚硫酸氢钠还原诱导自组合纳米银/石墨烯水凝胶基底对碲的拉曼信号并无明显增强,确定乙二胺还原自组合纳米银/石墨烯水凝胶为基底材料,进一步开展水溶液pH值和Te(Ⅳ)浓度对基底材料吸附后拉曼信号影响的实验研究,结果表明:pH=5.5和584.9 cm-1峰分别为水中微量Te(Ⅳ)的检测条件和标志信号;在Te(Ⅳ)浓度7.84×10-9-7.84×10-5M范围内,该信号峰强度随Te(Ⅳ)浓度下降而降低,检出限约 100nM。基于上述研究结果可得,Ag是潜在的净化水中Po(Ⅳ)的强吸附载体,氧化石墨烯则是对微量Po(Ⅳ)吸附性能良好的优选基底材料,本项工作有望为放射性废水中的钋提供一种新的有效、快捷的净化及检测方法。
[Abstract]:Po is one of the most important nuclides in radioactive wastewater from spent fuel treatment, uranium mining and lead-bismuth cooled reactor accidents. It is extremely toxic and radioactive at the same time. Purification and detection of this kind of radionuclide is one of the problems that must be considered in the sustainable development of nuclear energy. The adsorption behavior and mechanism of Te(IV) in water were studied by choosing silver-loaded stainless steel braided mesh and graphene oxide as adsorbent carriers. On this basis, nano-silver/graphene hydrogel was constructed with graphene oxide as precursor, ascorbic acid, sodium bisulfite and ethylenediamine as reductant, and tellurium signal was determined. The strongest ethylenediamine reduction-induced self-assembled nano-silver/graphene hydrogel was used as the substrate material to study the surface-enhanced Raman scattering (SERS) technique for the determination of Trace Tellurium in water. The main results are as follows: Adsorption of Te (IV) onto silver-loaded stainless steel braided mesh by copper plating current, adsorption time and coexisting iodine concentration were studied. The results show that the copper plating current has a significant positive effect on the adsorption of Te (IV) on the silver-loaded stainless steel braided mesh, which is the result of the increase of silver load on the surface of the stainless steel braided mesh with the increase of copper plating current. The adsorption rate of Te(IV) on stainless steel braided mesh with silver plating time of 1.5 h increased at a constant rate with the increase of adsorption time. The adsorption rate reached 63.0.1% at 64 H. The change of surface area of silver film on silver-loaded stainless steel with the extension of silver plating time was the main reason for this phenomenon. The adsorption of Te (IV) on the silver-loaded stainless steel braided mesh firstly decreased and then increased with the increase of the concentration of coexisting iodine ions. This phenomenon was the result of the joint action of iodine ions, competitive adsorption of Te (IV) species and the change of contact area of silver and Te (IV). The main mechanism of adsorption of Te(IV) on silver-loaded stainless steel braided mesh was the formation of Ag(IV) by the spontaneous deposition of Te(IV) and the reaction of Ag(IV) with Ag(IV) under acidic conditions. The results show that the adsorption sites on the surface of graphene oxide decrease with the increase of adsorption time, which is the main reason that the adsorption rate of Te (IV) increases first and then remains unchanged with the increase of adsorption time. The adsorption rate of Te(IV) on graphene oxide increased first and then remained unchanged with the increase of pH, which was the result of the increase of adsorption sites and agglomeration degree of graphene oxide sheets with the increase of graphene oxide concentration. The kinetics and isotherms of adsorption of Te(IV) on graphene oxide were studied. The results showed that the kinetic data of adsorption of Te(IV) on graphene oxide conformed to pseudo-second-order kinetic equation. The adsorption equilibrium data conformed to Sips equation and Freunlich equation. The adsorption sites on graphene oxide surface were inhomogeneous and the adsorption of Te(IV) on graphene oxide was non-monolayer adsorption. Adsorption of Te (IV) ion by graphene oxide is a complex process involving many functions. Microstructure and valence analysis show that the adsorption of Te (IV) by graphene oxide does not change its chemical valence. The adsorption mechanism involves epoxy and carboxyl groups. The interaction between oxygen functional groups and graphene benzene ring structure on tellurium ion was studied by surface-enhanced Raman spectroscopy (SERS). The Raman signals of trace Te(IV) in water were compared with those of ascorbic acid, sodium bisulfite and ethylenediamine-induced self-assembled silver/graphene hydrogels. The Te-O peak and Te=O=Te vibration peak of 584.9 cm-1 and 642.9 cm-1 were significantly enhanced by reduction-induced self-assembly of nano-silver/graphene, while the Raman signal of Tellurium on the substrate of self-assembly nano-silver/graphene hydrogel induced by ascorbic acid and sodium bisulfite reduction was not significantly enhanced. It was confirmed that the self-assembly of nano-silver/graphene hydrogel by ethylenediamine reduction was formed. The influence of pH value and Te(IV) concentration on Raman signal after adsorption was studied. The results showed that the peak values of pH=5.5 and 584.9 cm-1 were the detection conditions and marker signals of trace Te(IV) in water, respectively. In the range of Te(IV) concentration 7.84 *10-9-7.84 *10-5 M, the peak intensity decreased with Te(IV) concentration. Based on the above results, Ag is a potential strong adsorption carrier for Po (IV) in purified water, and graphene oxide is a preferred substrate material with good adsorption performance for trace Po (IV). This work is expected to provide a new and effective method for the purification and detection of polonium in radioactive wastewater.
【学位授予单位】：中国科学技术大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TL941
[Abstract]:Po is one of the most important nuclides in radioactive wastewater from spent fuel treatment, uranium mining and lead-bismuth cooled reactor accidents. It is extremely toxic and radioactive at the same time. Purification and detection of this kind of radionuclide is one of the problems that must be considered in the sustainable development of nuclear energy. The adsorption behavior and mechanism of Te(IV) in water were studied by choosing silver-loaded stainless steel braided mesh and graphene oxide as adsorbent carriers. On this basis, nano-silver/graphene hydrogel was constructed with graphene oxide as precursor, ascorbic acid, sodium bisulfite and ethylenediamine as reductant, and tellurium signal was determined. The strongest ethylenediamine reduction-induced self-assembled nano-silver/graphene hydrogel was used as the substrate material to study the surface-enhanced Raman scattering (SERS) technique for the determination of Trace Tellurium in water. The main results are as follows: Adsorption of Te (IV) onto silver-loaded stainless steel braided mesh by copper plating current, adsorption time and coexisting iodine concentration were studied. The results show that the copper plating current has a significant positive effect on the adsorption of Te (IV) on the silver-loaded stainless steel braided mesh, which is the result of the increase of silver load on the surface of the stainless steel braided mesh with the increase of copper plating current. The adsorption rate of Te(IV) on stainless steel braided mesh with silver plating time of 1.5 h increased at a constant rate with the increase of adsorption time. The adsorption rate reached 63.0.1% at 64 H. The change of surface area of silver film on silver-loaded stainless steel with the extension of silver plating time was the main reason for this phenomenon. The adsorption of Te (IV) on the silver-loaded stainless steel braided mesh firstly decreased and then increased with the increase of the concentration of coexisting iodine ions. This phenomenon was the result of the joint action of iodine ions, competitive adsorption of Te (IV) species and the change of contact area of silver and Te (IV). The main mechanism of adsorption of Te(IV) on silver-loaded stainless steel braided mesh was the formation of Ag(IV) by the spontaneous deposition of Te(IV) and the reaction of Ag(IV) with Ag(IV) under acidic conditions. The results show that the adsorption sites on the surface of graphene oxide decrease with the increase of adsorption time, which is the main reason that the adsorption rate of Te (IV) increases first and then remains unchanged with the increase of adsorption time. The adsorption rate of Te(IV) on graphene oxide increased first and then remained unchanged with the increase of pH, which was the result of the increase of adsorption sites and agglomeration degree of graphene oxide sheets with the increase of graphene oxide concentration. The kinetics and isotherms of adsorption of Te(IV) on graphene oxide were studied. The results showed that the kinetic data of adsorption of Te(IV) on graphene oxide conformed to pseudo-second-order kinetic equation. The adsorption equilibrium data conformed to Sips equation and Freunlich equation. The adsorption sites on graphene oxide surface were inhomogeneous and the adsorption of Te(IV) on graphene oxide was non-monolayer adsorption. Adsorption of Te (IV) ion by graphene oxide is a complex process involving many functions. Microstructure and valence analysis show that the adsorption of Te (IV) by graphene oxide does not change its chemical valence. The adsorption mechanism involves epoxy and carboxyl groups. The interaction between oxygen functional groups and graphene benzene ring structure on tellurium ion was studied by surface-enhanced Raman spectroscopy (SERS). The Raman signals of trace Te(IV) in water were compared with those of ascorbic acid, sodium bisulfite and ethylenediamine-induced self-assembled silver/graphene hydrogels. The Te-O peak and Te=O=Te vibration peak of 584.9 cm-1 and 642.9 cm-1 were significantly enhanced by reduction-induced self-assembly of nano-silver/graphene, while the Raman signal of Tellurium on the substrate of self-assembly nano-silver/graphene hydrogel induced by ascorbic acid and sodium bisulfite reduction was not significantly enhanced. It was confirmed that the self-assembly of nano-silver/graphene hydrogel by ethylenediamine reduction was formed. The influence of pH value and Te(IV) concentration on Raman signal after adsorption was studied. The results showed that the peak values of pH=5.5 and 584.9 cm-1 were the detection conditions and marker signals of trace Te(IV) in water, respectively. In the range of Te(IV) concentration 7.84 *10-9-7.84 *10-5 M, the peak intensity decreased with Te(IV) concentration. Based on the above results, Ag is a potential strong adsorption carrier for Po (IV) in purified water, and graphene oxide is a preferred substrate material with good adsorption performance for trace Po (IV). This work is expected to provide a new and effective method for the purification and detection of polonium in radioactive wastewater.
【学位授予单位】：中国科学技术大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TL941
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