凝固，花了TBP的稳定/ OK有机液体在磷酸 - 基矿物聚合物

抽象

一种用于固化花费磷酸三丁酯和煤油（TBP / OK）有机液体在基于酸式磷酸酯地质聚合物（PAG）方法进行了研究。含有吐温80（T80），TBP / OK有机液体的TBP / OK乳液，和H_3.PO₄制备。的TBP / OK乳液用偏高岭土混合，以获得固化的TBP / OK形式（SPT）。The compressive strength of the SPT was up to 59.19 MPa when the content of TBP/OK was 18%. The loss of compressive strength of SPT was less than 10% after immersion and less than 25% after freeze-thaw treatment. The final setting time was 40.0 h, and the shrinkage of SPT was nearly 3%. The leaching test indicated that the release of TBP/OK from hardened SPT was limited. Characterization of SPT suggested that solidification of TBP/OK using PAG occurred by physical encapsulation.

1.简介

放射性磷酸三丁酯（TBP）是一种含有多种放射性核素（如U和Pu）通过萃取（PUREX）工艺乏燃料再处理铀钚恢复期间产生的废有机溶剂。该液体的主要成分是TBP，其可以被用作萃取剂，和煤油（OK），其可以被用作稀释剂，并且这些组件是通过化学和放射性因素的影响。治疗和可燃有机溶剂的处置已经成为一个亟待解决的问题。

大体积硅酸盐水泥[1]制备固化TBP / OK有机液体，以及乳化凝固和吸附乳化凝固方法进行了比较。The TBP/OK contents in the solidified materials prepared by the two methods were 15% and 18%, and the compressive strengths of the solidified forms were 11.4 MPa and 9.3 MPa, respectively. The results of the adsorption-solidification method [2]表明，矿渣水泥用活性炭吸附剂混合的封装容量比波特兰水泥的更好。TBP的比例/由矿渣水泥包封行液体为14％，其力学性能和样品的浸泡电阻固化由矿渣水泥符合GB14569.1-2011的要求[3.]。张某等人。[4]由硫铝酸盐水泥研究TBP / OK有机液体的凝固。沸石，氢氧化钙，和MR-1型乳化剂混合到水泥掺混物，以提高固化的废物的性能。When the specification requirements were met, the compressive strength of the solidified samples reached 14.23 MPa, and the other material properties conformed to GB14569.1-2011. The TBP/OK organic solution was hydrolyzed and then solidified by alkali slag cementitious materials [5]。The compressive strength of the solidified forms was 18.9 MPa, and the TBP/OK content was 14.49%. The nuclide leaching rate and immersion resistance conformed to the Chinese specifications. This method requires the addition of NaOH to the TBP/OK organic solution, followed by heating. A high degree of corrosivity is required for the equipment, and it is thus not easy to apply this method on a large scale.

最近，许多国家都在开发新的材料来固化放射性废物。俄罗斯国家原子能公司[6]开发了可用于固化TBP并混合（水 - 有机双相）污泥新的聚合物材料。甲凝固试验在含有碱活化的偏高岭土基的聚合物[A模拟放射性有机液体进行7]，和有机液体的量凝固达到20％。

It can be noticed that the strength of TBP/OK solidified forms by cement was not more than 20 MPa. The productions of Portland cement, slag cement, and sulfur aluminate cement are characterized by high energy consumption and serious pollution, while geopolymers are environmentally friendly and green materials [8]。硅酸钠 - 偏高岭土地聚合物已应用于巩固重金属，核废料，和石油[9,10]。PAG是在酸性环境中合成的并具有较高的强度，耐久性和热稳定性比硅酸钠 - 偏高岭土地质聚合物[11]。研究了PAG固化放射性TBP/OK有机液体的工艺和机理。

本文以磷酸和偏高岭土为原料，采用T80作为乳化剂，制备了PAG。研究了膏体的流动性、凝固时间、力学性能、TBP/OK的浸出率和SPT的孔隙结构，并对TBP/OK的凝固机理进行了探讨。

2.材料和实验方法

在这项工作中所使用的高岭土主要由二氧化硅的₂（45.35重量％），铝₂O_3.（39.22重量％），和Fe₂O_3.(0.31 wt. %)。高岭土在800℃的选定温度下在马弗炉中处理4小时。获得的样品(偏高岭土)在空气中冷却到环境温度，然后在干燥的环境中保存。

凝固SPT样品的制备显示于图1。H的摩尔浓度_3.PO₄was 11 mol/L. The proportion of TBP/OK was defined as the weight of TBP/OK relative to the weight of all reactants. SPT containing 6% TBP/OK (CST), SPT containing 12% TBP/OK (DST), and SPT containing 18% TBP/OK (EST) were prepared. The dose of the emulsifier T80 was 4 vol% relative to the TBP/OK organic liquid content. The TBP/OK organic liquid was prepared by mixing OK and TBP at a volume ratio of 7 : 3. T80 was added to the TBP/OK organic liquid, and then phosphoric acid solution was added. The liquid mixture was treated with an ultrasonic disperser to prepare the emulsion (Figure2)。所述乳液和偏高岭土加入到搅拌罐中，搅拌15分钟，以获得新鲜的SPT（混合罐和混合桨叶是由304不锈钢）。甲维卡仪被用于测量的初始和最终凝固时间。固化温度为70℃，湿度为98％以上;而室温为36.4℃，湿度为65％。每个设定时间试验重复4次，并且选择的算术平均值。新鲜SPT倒入聚丙烯（PP）塑料模具，并且将样品振动的振动台上进行3分钟，然后固化在70℃和大于98％的湿度下7天。将样品从模具中7天后取出，并在40℃的烘箱中28天，然后固化。Shrinkage of the 25 mm × 25 mm × 250 mm hardened PAG and SPT was measured with a shrinkage-compensating concrete expansion rate tester, and Ø50 mm × 50 mm samples were used to measure the strength (Figure3.)。

After 28 days, the CST, DST, and EST samples were dipped in deionized water at 25 ± 1°C for 42 days (Figure4），强度为再次测试。Hardened PAG, CST, DST, and EST samples sealed in packets were put in a freezer at a temperature of −20°C for 3 h. The samples were removed from the freezer and immediately thawed in a water tank at 18°C. The thawing time was 4 h. The samples were subjected to five freeze-thaw cycles, and then their appearance was observed, and their compressive strength was tested. The amount of leached TBP/OK in the soaking solution was measured by gas chromatography.

的PAG，CST，DST，和EST样品的片段收集并在乙醇中浸渍。The fragments were dried in an oven at 105°C for 12 h before testing. The porosity was tested by Mercury intrusion porosimetry (MIP) experiments. An MIP instrument (Autopore IV 9500, Micromeritics) was used to measure the pore size distributions. Other dried fragments of samples were milled into powders and used for XRD measurements, FTIR, and MAS NMR experiments. XRD was conducted by using a Bruker D8 ADVANCE instrument under the following conditions: 40 kV, 40 mA, and CuKα radiation. The range of the 2θ扫描角为5°和80°之间。FTIR实验用VECTOR33红外光谱仪上进行。The samples were mixed with KBr, and the wavelength was varied from 400 cm⁻¹到4000厘米⁻¹。

3。结果与讨论

3.1。新鲜SPT的可加工性

Fresh PAG has a fluidity of 9.8 cm, as shown in Figure5。The fluidity of fresh CST, DST, and EST is proportional to the TBP/OK content, and the fluidity increased from 13.0 cm to 15.5 cm (Figure5)。偏高岭土具有层状结构，与水和H_3.PO₄履行空隙，降低浆料的润滑性。此外，H_3.PO₄具有一定的粘度，会降低新鲜PAG的流动性。T80作为表面活性剂加入，可以降低TBP/OK与水相之间的界面张力。将TBP/OK加入磷酸溶液中，超声分散后形成TBP/OK滴。

数字6显示了CST、SDT和EST样品中液滴的分布。当将凝固的样品打碎后，液滴被去除，留下球形孔。随着TBP/OK含量的增加，凝固试样中出现的孔洞增多。乳化后，有机液滴被外亲水性层包裹，形成球形液滴。分布在磷酸溶液中的球形液滴在润滑中起主导作用。因此，随着包封量的增加，固化形态的流动性增大。偏高岭土与乳液混合时，液滴数量越多，液体的表面张力降低，流动性越好。液滴的增加也使得凝固膏体中出现了更多的空气，气孔率随着TBP/OK含量的增加而增加。

当TBP / OK乳剂用偏高岭土混合，偏高岭土粉末颗粒和磷酸之间的接触减少。在液滴的外层水分子慢慢蒸发，地质聚合物的二羟基化减慢。这些过程延长了CST，DST，和EST样品的凝结时间。如图7,the initial setting time increased from 29.4 h to 30.6 h, and the final setting time increased from 35.7 h to 40.0 h. These long setting times limit the application of PAG in solidification.

3.2。硬化SPT力学性能

PAG样本线性收缩明显(3.2%)，CST、DST和EST收缩近2.9%(图)8)。正如预期的那样，抗压强度时，TBP / OK含量的增加而降低。PAGhas a high compressive strength of 79.07 MPa, and the strength of SPT is up to 59.19 MPa. The compressive strength did not decrease drastically with increasing TBP/OK content (Figure9)。当TBP/OK含量为18%时，复合材料的抗压强度降低了25%。结果表明，PAG是一种具有良好力学性能的刚性材料。经过浸泡试验和冻融试验，PAG、CST、DST、EST样品表面无明显裂纹。浸泡后抗压强度损失小于10%，冻融处理后抗压强度损失小于25%(图)10)。这些结果表明，SPT满足的力学性能的中国法规的要求“低中放射性废物固化形式，水泥固化体形式的性能要求。”

3.3条。硬化SPT成分

所研究的高岭土（KA）和煅烧高岭土（MK）示出了对应于所有高岭土衍射峰热处理后消失的X射线衍射图案的比较。在煅烧高岭土衍射图案中观察到对应于石英的衍射峰，而对应于石英和ALPO峰₄的晶体中，在和PAG SPT衍射图案（图观察11和12)。磷酸铝₄距离Al形成³⁺偏高岭土和从H_3.PO₄解。这表明在石英中的地质聚合过程中不受影响。PAG和SPT的X射线衍射图案在2显示出无定形特性θ15 - 20°。这表明PAG和SPT的结构是典型的玻璃样结构。

在与X射线衍射结果一致，红外光谱显示偏高岭土带的消失和相关的新物种（图新带的出现13和14). 煅烧高岭土在907 cm处的条带⁻¹冲高的Al（VI）-OH消失-OH在加热过程中解吸。Bands at 805 cm⁻¹, 688厘米⁻¹,和568 cm⁻¹冲高-Si-O-Al系（IV），-Si-O-Al系（V），和-Si-O-Al系（VI）分别出现在煅烧高岭土的光谱。These bands disappeared after geopolymerization, and new bands at 726 cm⁻¹，指示-P-O-AL-的形成的，在PAG [的光谱中观察到12]。The bands at 926 cm⁻¹归因于- p - o - p -振动[12,13]。

The Si-O symmetrical vibration of metakaolin at 1090 cm⁻¹shifted by approximately 13 cm⁻¹to 1103 cm⁻¹地质聚合后。In the spectra of PAG, new bands at 796 cm⁻¹可以归因于-Si-O-P- [14]。The bands at 455 cm⁻¹in the metakaolin spectrum, which could be ascribed to -Si-O-Si-, shifted to a higher wavenumber of 468 cm⁻¹在硬化PAG光谱。这种转变表示的Si-O转化成-Si-O-P- [9]。这可能归因于由[PO]四面体部分置换的〔固定相SiO〕四面体，因此导致局部化学环境的改变。这意味着，-Si-O-P-O-SI-的形成发生地质聚合物网络中的[15]。

在图14,in the spectra of the CST, DST, and EST samples, the bands at 924 cm⁻¹归因于-P-O-P-振动[12,13]。New bands at 732 cm⁻¹在与-P-O-AL-形成协议。The metakaolin bands at 455 cm⁻¹ascribed to -Si-O-Si- shift to a higher wavenumber of 475 cm⁻¹在硬化样品的光谱。Furthermore, new bands at 796 cm⁻¹有关-Si-O-P-观察。The Si-O symmetrical vibration of metakaolin at 1090 cm⁻¹shifted to 1128 cm⁻¹凝固后。这表明，SPT的网络结构包括-Si-O-P-O-Si和P-O型AL-以及[12]。该产品几乎为PAG和SPT相同。TBP / OK凝固可以通过物理封装发生。

3.4。TBP的浸出测试/ OK

The cumulative amounts of TBP/OK released into the leachates from SPT composite samples containing 6–18% TBP/OK at 25 ± 1°C are reported in Table1。前两周的实验期间TBP / OK中的渗滤液公布的累计数量缓慢上升后趋于保持稳定，其余42天。The cumulative leaching rates of the CST, DST, and EST samples for 42 days were 3.42 × 10⁻² cm, 4.13 × 10⁻² cm, and 4.32 × 10⁻² cm, respectively.

PAG和SPT的孔径分布示于表2。Most pore size diameters were smaller than 100 nm in PAG, CST, DST, and EST. The number of pores smaller than 10 nm decreased, while the number of pores between 10 nm and 100 nm increased. The number of pores larger than 1000 nm also increased in the CST, DST, and EST samples. The presence of emulsified droplets increased the setting time and prevented water molecules from evaporating, causing an increase in the pore size of SPT. The porosity increased with increasing TBP/OK content. The results demonstrate that TBP/OK was efficiently encapsulated in SPT and met the nuclear authorities’ acceptance criteria for waste storage applications.

3.5条。实验误差探讨

为保证固化试样的抗压强度、流动度、收缩、抗压强度损失等数据的可靠性，每组各准备6个试样进行测试。取每组实验中数值的算术平均值作为结果。如果一组中的某个测试值大于或小于算术平均值的15%，则该组中的所有值都将被丢弃。抗压强度的标准差分别为8.91%、6.44%、7.28%、6.82%，收缩的标准差分别为0.35%、0.29%、0.36%、0.31%。流动性的标准差范围为0.58% ~ 0.94%。浸压强度损失的标准差为0.34% ~ 0.61%，冻融处理后的标准差为1.17% ~ 3.02%。设置时间测试，每个测试重复4次，取算术平均值。每组6个样品测定TBP/OK的浸出率和孔隙率。选择每个实验的算术平均值作为结果。表中TBP/OK的浸出率1和表中的孔隙率2是算术平均数。

4。结论

固化与基于酸式磷酸酯的地质聚合物花费TBP / OK有机液体的方法进行了研究。这项研究的主要发现可以总结如下。

TBP / OK有机液体可以PAG被固化，并在磷酸盐酸溶液，并在地质聚合物粘贴TBP / OK乳液的混合过程中的稳定性允许高TBP / OK内容包封在复合物（高达18％）。

The compressive strength of the SPT was up to 59.19 MPa when the content of TBP/OK was 18%. The loss of compressive strength of SPT was less than 10% after immersion and less than 25% after freeze-thaw treatment.

The fluidity of fresh SPT is 15.5 mm, the final setting time was 40.0 h, and the shrinkage of SPT was nearly 3% when the content of TBP/OK is 18%.

浸出试验证明了非常有限的TBP / OK的量从PAG-凝固TBP / OK样品释放。TBP / OK凝固可以通过物理封装发生。

数据可用性

支持本研究结果的数据可从通讯作者处获得。

利益冲突

作者宣称，他们没有利益冲突。

致谢

作者非常感谢由华南地区，中国的教育局研究基金会（批准号18K075）和国家大学生创新平台和创业培训项目，中国（批准号201810555001）的支持。

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