高温低氧条件下膨润土添加碳酸钠和菱铁矿试验研究

为探究处置库高温低氧条件下，添加剂对膨润土-北山水体系化学性能的影响，开展了膨润土-北山水体系中添加菱铁矿和碳酸钠的试验研究。研究了体系pH值和Eh值、胶体zeta电位和黏度、膨润土中可交换阳离子和矿物成分以及液相离子成分随碳酸钠和菱铁矿添加量的变化。结果表明，90 ℃低氧条件下膨润土中添加碳酸钠不仅可使体系的pH值维持在7.84～8.99，而且膨润土中可交换Na⁺升高至60 mmol/100 g，有效阻止了钠基膨润土向钙基膨润土的转化，同时增强了胶体的稳定性；添加菱铁矿可使体系的Eh值降低至-124 mV，并维持在还原状态；碳酸钠和菱铁矿的加入对膨润土矿物成分无很大影响。最终得出高温低氧条件下，增强膨润土化学缓冲性能的膨润土、碳酸钠、菱铁矿的最佳质量配比为400∶12∶160。

Experiment Study on Adding Na2CO3 and Siderite into Bentonite under High Temperature and Low Oxygen Condition

Tests on the bentonite-Beishan underground water system with additives of Na₂CO₃ and siderite were carried out under high temperature and low oxygen condition. Variations of pH and Eh of system, zeta potential and viscosity of colloid, exchangeable cations and mineral composition of bentonite, as well as concentration of key cations in liquid along with the additive dose were investigated. The results show that adding Na₂CO₃ could not only maintain pH value within the range between 7.84 and 8.99, but also prevent Na-bentonite from transforming into Ca-bentonite on account of improving components of exchangeable Na⁺ to 60 mmol/100 g. At meantime, the stability of colloids is strengthened. Siderite could reduce the Eh value of system to -124 mV effectively and keep the system in reduction state eventually. The mineral composition of bentonite does not change too much because of adding siderite and Na₂CO₃. Under the conditions of high temperature and low oxygen, the optimum mass ratio of bentonite, Na₂CO₃ and siderite to enhance the chemical buffer performance of Na-bentonite is 400∶12∶160.