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| Permeability of sodium polyacrylate modified calcium bentonite in acid-base salt solution |
Qi-zhen KANG1,2( ),Jing-jing LI3,Yu-chao LI1,2,*(),Shi-yuan YAO1,2,Yun-min CHEN1,2 |
1. Key Laboratory of Soils and Geoenvironmental Engineering, Ministry of Education, Zhejiang University, Hangzhou 310058, China
2. Institute of Geotechnical Engineering, Zhejiang University, Hangzhou 310058, China
3. Zhejiang Fenghong New Materials Limited Company, Huzhou 313300, China |
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Abstract Sodium polyacrylate (PAA-Na) was used to modify sodium calcium bentonite to improve swelling and impermeability aiming at the problem that the anti-fouling effect of bentonite in high-salt or strong acid-base solutions deteriorates due to the reduction of bentonite’s swelling and impermeability. The effect law of different concentrations of NaCl solution and acid-base solution on sodium polyacrylate modified calcium bentonite PB2, PB5, PB10, PBHV5 and Wyoming bentonite’s swelling characteristics and permeability characteristics was explored by free swelling test and improved fluid loss test. Results show that the swelling characteristics and permeability of PB10 in acid-base salt solution are better than that of Wyoming bentonite, while these characteristics of PBHV5 are similar to Wyoming bentonite. The swelling and impermeability of PBHV5 and PB10 were decreased by strong acid condition with pH = 2 and strong alkali condition with pH = 12. The permeability coefficients of the three kinds of bentonites increase with the increase of the swelling index and the void ratio in the acid-base solutions and low concentration (≤20 mmol/L) salt solution, which is speculated to be the reason for the delamination of the crystal layer structure. The swelling of bentonites become smaller and more seepage channels are formed in the medium and high concentration (>20 mmol/L) salt solution. The permeability coefficients increase with the decrease of the swelling index and the void ratio. In the studied polymer content range (2%~10%), the larger the polymer content is, the better the impermeability and chemical compatibility of bentonite are. The polymer content should not be less than 5% if the goal is to achieve better characters than Wyoming natural sodium bentonite.
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Received: 23 November 2020
Published: 27 October 2021
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| Fund: 国家自然科学基金资助项目（42077241）；国家重点研发计划资助项目（2019YFC1806000） |
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Corresponding Authors:
Yu-chao LI
E-mail: kangqizhen@zju.edu.cn;liyuchao@zju.edu.cn
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PAA-Na改性膨润土在酸碱盐溶液中的渗透性
针对高盐或强酸碱溶液中以膨润土为主材的防污屏障的阻控效果因膨润土膨胀性和抗渗性的降低而劣化的问题，采用聚丙烯酸钠（PAA-Na）对国产钠化钙基膨润土进行改性，提高膨胀性和防渗性. 通过自由膨胀试验和改进滤失试验，研究不同浓度的NaCl溶液和酸碱溶液对聚丙烯酸钠改性膨润土PB2、PB5、PB10、PBHV5和美国怀俄明天然钠基膨润土的膨胀特性、渗透特性的影响规律. 结果表明，在酸碱盐溶液中PB10的膨胀特性和渗透性优于怀俄明膨润土，PBHV5与怀俄明膨润土相近. pH=2的强酸条件和pH=12的强碱条件会降低PBHV5和PB10的膨胀性和抗渗性，pH=3~11的酸碱溶液对两者的影响很小. 在酸碱溶液和低浓度（≤20 mmol/L）盐溶液中，由于晶层结构层剥离，3种膨润土渗透系数随着膨胀指数和孔隙比的增大而增大；在中高浓度（>20 mmol/L）盐溶液中，膨润土膨胀性降低，渗流通道增多，产生了渗透系数随膨胀指数和孔隙比的减小而增大的现象. 在所研究的聚合物掺量（2%~10%）下，膨润土抗渗性和化学相容性随着聚合物掺量的增大而提高，若目标取得优于美国怀俄明天然钠基膨润土的特性，聚合物掺量须不低于5%.
关键词：
改性膨润土,
聚丙烯酸钠（PAA-Na）,
渗透系数,
膨胀指数,
酸碱盐溶液,
化学相容性
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