【摘要】：鈾是重要的核燃料資源,同時也是放射性廢液中主要的污染元素之一。無論是從能源安全還是從環(huán)境保護(hù)的角度,對水體中的鈾進(jìn)行有效分離富集都有著很重要的現(xiàn)實(shí)意義。在鈾的眾多分離富集方法中,吸附法因具有成本低廉、工藝簡單及適用范圍廣等優(yōu)點(diǎn)而被廣泛采用。高效吸附劑的開發(fā)無疑是吸附法在實(shí)際應(yīng)用中的關(guān)鍵。復(fù)合材料由于可根據(jù)不同用途選擇相應(yīng)基體與功能基團(tuán)進(jìn)行復(fù)合,已成為近年來對溶液中的鈾進(jìn)行分離富集的研究熱點(diǎn)。在眾多功能基團(tuán)中,偕胺肟官能團(tuán)由于對鈾的特殊絡(luò)合能力,被廣泛用于修飾多種多樣的基體材料。基體材料方面,近年來人們的注意力逐漸轉(zhuǎn)向新興的納米材料。本論文利用偕胺肟官能團(tuán)對這些年研究得較多的常見納米材料進(jìn)行功能化,合成了如下幾種復(fù)合材料,考察了所合成材料對鈾的吸附性能,并對吸附機(jī)理進(jìn)行了分析： 1,偕胺肟修飾磁性石墨烯 合成了偕胺肟修飾磁性石墨烯(AOMGO)復(fù)合材料,并應(yīng)用于水溶液中鈾的吸附。吸附鈾之后的材料可以在外加磁場下很方便地實(shí)現(xiàn)與液相分離。吸附動力學(xué)實(shí)驗(yàn)表明吸附過程可以在2h內(nèi)達(dá)到吸附平衡�？疾炝藀H值、離子強(qiáng)度、共存離子對鈾吸附的影響。結(jié)果表明,鈾在AOMGO材料表面的吸附受pH值影響顯著,而與離子強(qiáng)度關(guān)系不大。吸附等溫線符合Langmuir模型,在pH=5.0±0.1,T=298K時,理論最大吸附量達(dá)到1.197mmol/g。根據(jù)不同溫度下的吸附等溫線可計算出吸附過程的熱力學(xué)參數(shù),結(jié)果表明鈾在AOMGO材料表面的吸附是自發(fā)的吸熱過程�？焖俑咝У奈奖憩F(xiàn)表明所合成的AOMGO復(fù)合材料在廢水中鈾的去除以及海水中鈾的提取方面有著很好的應(yīng)用前景。 2,偕胺肟修飾二氧化硅包覆的四氧化三鐵 合成了偕胺肟修飾二氧化硅包覆的四氧化三鐵微球(Fe3O4@SiO2-AO)復(fù)合材料并進(jìn)行了詳細(xì)表征。合成的Fe3O4@SiO2-AO材料被用于吸附溶液中的鈾,得益于材料中偕胺肟官能團(tuán)對鈾的絡(luò)合能力,該材料的吸附容量相比于裸的二氧化硅包覆四氧化三鐵微球(Fe3O4@SiO2)得到了很大提高�？疾炝私佑|時間、pH值、離子強(qiáng)度、干擾離子、鈾起始濃度、溫度對鈾在Fe3O4@SiO2-AO材料上吸附的影響。pH值對吸附過程影響強(qiáng)烈而離子強(qiáng)度則幾乎沒有影響,表明吸附過程主要是內(nèi)層絡(luò)合。吸附等溫線與Langmuir模型相吻合,在pH=5.0±0.1,T=298K時,理論最大吸附量達(dá)到0.441mmol/g。負(fù)載鈾之后的材料可以通過外磁場加以分離,并可通過1mol/L的鹽酸處理使吸附劑再生,實(shí)現(xiàn)循環(huán)利用。 3,偕胺肟功能化的磁性介孔二氧化硅 在二氧化硅包覆的四氧化三鐵微球表面,利用十六烷基三甲基溴化銨做結(jié)構(gòu)導(dǎo)向劑,通過正硅酸乙酯與2-氰乙基三乙氧基硅烷的共縮聚反應(yīng)包覆介孔二氧化硅層,經(jīng)鹽酸羥胺還原后得到偕胺肟功能化的磁性介孔二氧化硅(MMS-AO)。該材料呈現(xiàn)三明治結(jié)構(gòu),內(nèi)核為四氧化三鐵,中間層為致密的二氧化硅,最外層為偕胺肟功能化的介孔二氧化硅。得益于介孔結(jié)構(gòu)和偕胺肟功能化,在pH=5.0±0.1,T=298K時,MMS-AO材料對鈾的最大吸附量達(dá)1.165mmol/G,優(yōu)于迄今為止見諸報道的諸多含磁性粒子材料。相比于未經(jīng)偕胺肟功能化的材料,MMS-AO材料對鈾的吸附選擇性得到了很大改善。由于二氧化硅層對四氧化三鐵內(nèi)核的保護(hù),吸附鈾之后的MMS-AO材料可經(jīng)1mol/L的鹽酸處理得以再生。結(jié)果表明MMS-AO材料不僅比表面積大,能夠?qū)崿F(xiàn)磁分離,而且磁性核在酸性環(huán)境中有很好的穩(wěn)定性。該材料在實(shí)際水體中鈾的分離富集方面有非常好的應(yīng)用前景。 4,偕胺肟功能化的SBA-15型介孔二氧化硅 利用Pluronic P123作為結(jié)構(gòu)導(dǎo)向劑,通過正硅酸乙酯與2-氰乙基三乙氧基硅烷共縮聚,改變其中2-氰乙基三乙氧基硅烷的摩爾比,合成了一系列SBA-15型介孔材料,并用于溶液中鈾的吸附。通過吸附等溫線和吸附動力學(xué)的研究分析了有機(jī)官能團(tuán)引入量對吸附性能的影響。結(jié)果表明,有機(jī)功能化對吸附容量與吸附速率的影響都是雙方面的。剛開始增加有機(jī)官能團(tuán)含量會提高吸附性能直至達(dá)到最大值,繼續(xù)增加有機(jī)官能團(tuán)含量則會引起吸附性能下降。最優(yōu)值對應(yīng)于材料介孔有序性與有機(jī)官能團(tuán)密度之間的平衡。通過材料吸附前后的X-射線光電子能譜與紅外光譜分析了吸附機(jī)理,結(jié)果表明吸附主要?dú)w功于鈾與偕胺肟官能團(tuán)之間的絡(luò)合作用。 綜合以上幾方面的內(nèi)容,本文對比了不同材料對鈾吸附行為的特點(diǎn),優(yōu)化了材料合成條件,分析了吸附機(jī)理。本文研究內(nèi)容能夠?yàn)楣δ芑榭撞牧显阝櫸廴局卫砗外櫟倪x擇性富集等實(shí)際應(yīng)用方面提供實(shí)驗(yàn)依據(jù)和理論基礎(chǔ)。
[Abstract]:Uranium is an important nuclear fuel resource and one of the major contaminating elements in radioactive waste liquid. It is of great practical significance to separate and enrich uranium in water from the point of view of energy security and environmental protection. The development of highly efficient adsorbents is undoubtedly the key to the practical application of adsorption methods. Composite materials have become a research hotspot for the separation and enrichment of uranium in solution in recent years because of their ability to choose the appropriate matrix and functional groups for different purposes. Aminoxime functional groups have been widely used to modify a variety of matrix materials due to their special complexation ability to uranium. In recent years, attention has been gradually turned to new nano-materials. In this paper, amidoxime functional groups have been used to functionalize common nano-materials which have been studied extensively in recent years. The adsorption properties of the synthesized materials on uranium were investigated, and the adsorption mechanism was analyzed.
1, modified magnetic graphene with amine.
The amidoxime modified magnetic graphene (AOMGO) composite was synthesized and applied to the adsorption of uranium in aqueous solution. The material adsorbed uranium can be easily separated from liquid phase in an external magnetic field. The adsorption kinetics experiment shows that the adsorption process can reach adsorption equilibrium within 2 hours. The adsorption of uranium by pH, ionic strength and coexisting ions was investigated. The results show that the adsorption of uranium on the surface of AOMGO material is significantly affected by pH value, but not by ionic strength. The adsorption isotherm is in accordance with Langmuir model. The theoretical maximum adsorption capacity reaches 1.197mmol/g at pH=5.0+0.1 and T=298K. The thermodynamic parameters of the adsorption process can be calculated according to the adsorption isotherm at different temperatures. The results show that the adsorption of uranium on the surface of AOMGO is a spontaneous endothermic process. The rapid and efficient adsorption performance shows that the AOMGO composite has a good application prospect in the removal of uranium from wastewater and the extraction of uranium from seawater.
2, silicon oxide coated iron oxide coated with amine.
Fe_3O_4@SiO_2-AO composite coated with amidoxime modified silica was synthesized and characterized in detail. The synthesized Fe_3O_4@SiO_2-AO material was used to adsorb uranium in solution, which was attributed to the complexation ability of Amidoxime functional groups to uranium, and its adsorption capacity was comparable to that of naked silica coated with tetroxide. The effect of contact time, pH value, ionic strength, interfering ions, initial uranium concentration and temperature on the adsorption of uranium on Fe3O4 @SiO2-AO was investigated. The effect of pH value on the adsorption process was strong, but the ionic strength was almost unchanged. The Langmuir model is consistent with each other. At pH=5.0 +0.1 and T=298K, the theoretical maximum adsorption capacity of uranium can reach 0.441mmol/g.
3, functionalized mesoporous silica with amine functionalized
Mesoporous silica was coated with hexadecyltrimethylammonium bromide (CTAB) on the surface of silica-coated ferric oxide microspheres by the co-condensation of tetraethyl orthosilicate with 2-cyanoethyltriethoxysilane. The magnetic mesoporous silica (MMS-AO) functionalized by amidoxime was prepared by the reduction of hydroxylamine hydrochloride. The core is ferric oxide, the middle layer is dense silica, and the outer layer is amidoxime functionalized mesoporous silica. Benefiting from the mesoporous structure and amidoxime functionalization, the maximum adsorption capacity of MMS-AO material for uranium is 1.165mmol/G at pH=5.0+0.1 and T=298K, which is superior to that of many reported magnetic-containing materials so far. The selectivity of MMS-AO material for uranium adsorption has been greatly improved compared with the material without amidoxime functionalization. Due to the protection of iron oxide core by silica layer, the MMS-AO material adsorbed uranium can be regenerated by 1 mol/L hydrochloric acid treatment. This material has a very good application prospect in the separation and enrichment of uranium in actual water.
4, SBA-15 type mesoporous silica functionalized with amine.
A series of SBA-15 mesoporous materials were synthesized by copolycondensation of tetraethyl orthosilicate with 2-Cyanoethyl triethoxysilane using Pluronic P123 as structure-directing agent and changing the molar ratio of 2-Cyanoethyl triethoxysilane. The adsorption isotherms and adsorption kinetics of uranium in solution were studied. The results show that the effects of organic functionalization on adsorption capacity and adsorption rate are both two-sided. Increasing the content of organic functional groups at the beginning will improve the adsorption performance until the maximum value is reached, while increasing the content of organic functional groups will decrease the adsorption performance. The adsorption mechanism was analyzed by X-ray photoelectron spectroscopy and infrared spectroscopy before and after adsorption. The results showed that the adsorption was mainly attributed to the complexation between uranium and amidoxime functional groups.
In this paper, the characteristics of uranium adsorption behavior of different materials are compared, the synthetic conditions of materials are optimized, and the adsorption mechanism is analyzed.
【學(xué)位授予單位】：中國科學(xué)技術(shù)大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2015
【分類號】：TQ136.2;TB383.1

【參考文獻(xiàn)】

相關(guān)期刊論文 前10條

1 馬玉琴;陳玉敏;于明珠;王錦蘭;;天然鈾的水平和危害[J];環(huán)境科學(xué);1982年02期

2 ;A brief review of graphene-based material synthesis and its application in environmental pollution management[J];Chinese Science Bulletin;2012年11期

3 ;Mesoporous silica SBA-15 functionalized with phosphonate and amino groups for uranium uptake[J];Science China(Chemistry);2012年09期

4 張文;葉鋼;陳靖;;鈾的復(fù)合吸附材料[J];化學(xué)進(jìn)展;2012年12期

5 CHI FangTing;HU Sheng;XIONG Jie;WANG XiaoLin;;Adsorption behavior of uranium on polyvinyl alcohol-g-amidoxime:Physicochemical properties, kinetic and thermodynamic aspects[J];Science China(Chemistry);2013年11期

6 XING Zhe;HU JiangTao;WANG MouHua;ZHANG WenLi;LI ShiNeng;GAO QianHong;WU GuoZhong;;Properties and evaluation of amidoxime-based UHMWPE fibrous adsorbent for extraction of uranium from seawater[J];Science China(Chemistry);2013年11期

7 SHAO DaDong;LI JiaXing;WANG XiangKe;;Poly(amidoxime)-reduced graphene oxide composites as adsorbents for the enrichment of uranium from seawater[J];Science China(Chemistry);2014年11期

8 劉梅;朱桂茹;蘇燕;王鐸;高從X&;;偕胺肟基纖維的合成及對鈾的吸附性能研究[J];水處理技術(shù);2009年07期

9 林瑩;高柏;李元鋒;;核工業(yè)低濃度含鈾廢水處理技術(shù)進(jìn)展[J];山東化工;2009年03期

10 魏廣芝;徐樂昌;;低濃度含鈾廢水的處理技術(shù)及其研究進(jìn)展[J];鈾礦冶;2007年02期

，

本文編號：2189033