Mineralogical evidence of alkaline corrosion of montmorillonite in GMZ bentonite
During the operation of underground repository of high-level radioactive waste, the highly alkaline solution generated by groundwater corroding lining concrete will diffuse into the bentonite buffer barrier, resulting in the degradation of barrier property. The KOH solution with different pH values...
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| Format: | Article |
| Language: | English |
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SCIENCE PRESS , 16 DONGHUANGCHENGGEN NORTH ST, BEIJING, PEOPLES R CHINA, 100717
2022-11-01
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| Series: | Rock and Soil Mechanics |
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| Online Access: | http://rocksoilmech.whrsm.ac.cn/EN/10.16285/j.rsm.2021.7174 |
| _version_ | 1797855923716227072 |
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| author | TONG Yan-mei ZHANG Hu-yuan ZHOU Guang-ping LI Xiao-ya |
| author_facet | TONG Yan-mei ZHANG Hu-yuan ZHOU Guang-ping LI Xiao-ya |
| author_sort | TONG Yan-mei |
| collection | DOAJ |
| description | During the operation of underground repository of high-level radioactive waste, the highly alkaline solution generated by groundwater corroding lining concrete will diffuse into the bentonite buffer barrier, resulting in the degradation of barrier property. The KOH solution with different pH values was used to simulate the alkaline solution, and a one-year contact diffusion test at room temperature was conducted. Then, X-ray fluorescence spectroscopy (XRF), X-ray diffraction (XRD), scanning electron microscope (SEM) and energy dispersive spectrometry (EDS) were performed to investigate the effect of slow diffusion on the mineralogy of bentonite. The XRF test results show that when the pH of KOH solution was greater than 12.6, the content of silicon began to decrease, that is, montmorillonite, quartz, cristobalite and other Si-containing minerals in bentonite were dissolved. At the same time, the content of K increased, indicating that the bentonite had an ion exchange reaction with the alkaline solution, a large amount of K+ ions in the solution entered the montmorillonite crystal layer. The XRD test results show that the 001 peak of montmorillonite mineral started to shift to the right at pH=12.6, the peak widths widened, and the peak intensity reduced considerably. When the pH>13, the crystal interlayer space decreased from 1.385 3 nm (13.853 Å) to 1.221 0 nm (12.210 Å), indicating that the crystal layer of montmorillonite was compressed. With the increase of the pH value, the content of minerals such as montmorillonite and quartz decreased significantly, and the contents of illite, clinoptilolite and feldspar minerals increased slightly. The SEM test results show that part of the montmorillonite crystal layer overlapped with the pH of the solution increasing, and then some cracks and holes were generated. As a result, the cracks can accelerate the dissolution of montmorillonite. In the one-year contact diffusion test, the diffusion depth of the KOH solution with pH=13.8 exceeded 7.5 mm, and the newly formed illite crystallites were observed on the contact surface between the alkaline solution and the bentonite. It is confirmed that the strong alkaline solution will cause montmorillonite dissolution and illitization. |
| first_indexed | 2024-04-09T20:31:49Z |
| format | Article |
| id | doaj.art-14dd241bdfc64ec49eb3e802c312bd9b |
| institution | Directory Open Access Journal |
| issn | 1000-7598 |
| language | English |
| last_indexed | 2024-04-09T20:31:49Z |
| publishDate | 2022-11-01 |
| publisher | SCIENCE PRESS , 16 DONGHUANGCHENGGEN NORTH ST, BEIJING, PEOPLES R CHINA, 100717 |
| record_format | Article |
| series | Rock and Soil Mechanics |
| spelling | doaj.art-14dd241bdfc64ec49eb3e802c312bd9b2023-03-30T15:02:57ZengSCIENCE PRESS , 16 DONGHUANGCHENGGEN NORTH ST, BEIJING, PEOPLES R CHINA, 100717Rock and Soil Mechanics1000-75982022-11-0143112973298210.16285/j.rsm.2021.7174Mineralogical evidence of alkaline corrosion of montmorillonite in GMZ bentonite TONG Yan-mei0ZHANG Hu-yuan1ZHOU Guang-ping2LI Xiao-ya31. School of Civil Engineering and Mechanics, Lanzhou University, Lanzhou, Gansu 730000, China1. School of Civil Engineering and Mechanics, Lanzhou University, Lanzhou, Gansu 730000, China 2. Key Laboratory of Mechanics on Disaster and Environment in Western China, The Ministry of Education, Lanzhou University, Lanzhou, Gansu 730000, China1. School of Civil Engineering and Mechanics, Lanzhou University, Lanzhou, Gansu 730000, China1. School of Civil Engineering and Mechanics, Lanzhou University, Lanzhou, Gansu 730000, China During the operation of underground repository of high-level radioactive waste, the highly alkaline solution generated by groundwater corroding lining concrete will diffuse into the bentonite buffer barrier, resulting in the degradation of barrier property. The KOH solution with different pH values was used to simulate the alkaline solution, and a one-year contact diffusion test at room temperature was conducted. Then, X-ray fluorescence spectroscopy (XRF), X-ray diffraction (XRD), scanning electron microscope (SEM) and energy dispersive spectrometry (EDS) were performed to investigate the effect of slow diffusion on the mineralogy of bentonite. The XRF test results show that when the pH of KOH solution was greater than 12.6, the content of silicon began to decrease, that is, montmorillonite, quartz, cristobalite and other Si-containing minerals in bentonite were dissolved. At the same time, the content of K increased, indicating that the bentonite had an ion exchange reaction with the alkaline solution, a large amount of K+ ions in the solution entered the montmorillonite crystal layer. The XRD test results show that the 001 peak of montmorillonite mineral started to shift to the right at pH=12.6, the peak widths widened, and the peak intensity reduced considerably. When the pH>13, the crystal interlayer space decreased from 1.385 3 nm (13.853 Å) to 1.221 0 nm (12.210 Å), indicating that the crystal layer of montmorillonite was compressed. With the increase of the pH value, the content of minerals such as montmorillonite and quartz decreased significantly, and the contents of illite, clinoptilolite and feldspar minerals increased slightly. The SEM test results show that part of the montmorillonite crystal layer overlapped with the pH of the solution increasing, and then some cracks and holes were generated. As a result, the cracks can accelerate the dissolution of montmorillonite. In the one-year contact diffusion test, the diffusion depth of the KOH solution with pH=13.8 exceeded 7.5 mm, and the newly formed illite crystallites were observed on the contact surface between the alkaline solution and the bentonite. It is confirmed that the strong alkaline solution will cause montmorillonite dissolution and illitization. http://rocksoilmech.whrsm.ac.cn/EN/10.16285/j.rsm.2021.7174bentonitemontmorillonitekoh solutionph valuediffusion testcorrosion |
| spellingShingle | TONG Yan-mei ZHANG Hu-yuan ZHOU Guang-ping LI Xiao-ya Mineralogical evidence of alkaline corrosion of montmorillonite in GMZ bentonite Rock and Soil Mechanics bentonite montmorillonite koh solution ph value diffusion test corrosion |
| title | Mineralogical evidence of alkaline corrosion of montmorillonite in GMZ bentonite |
| title_full | Mineralogical evidence of alkaline corrosion of montmorillonite in GMZ bentonite |
| title_fullStr | Mineralogical evidence of alkaline corrosion of montmorillonite in GMZ bentonite |
| title_full_unstemmed | Mineralogical evidence of alkaline corrosion of montmorillonite in GMZ bentonite |
| title_short | Mineralogical evidence of alkaline corrosion of montmorillonite in GMZ bentonite |
| title_sort | mineralogical evidence of alkaline corrosion of montmorillonite in gmz bentonite |
| topic | bentonite montmorillonite koh solution ph value diffusion test corrosion |
| url | http://rocksoilmech.whrsm.ac.cn/EN/10.16285/j.rsm.2021.7174 |
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