The role of normal and activated bentonite on the pelletization of barite iron ore concentrate and the quality of pellets

The essential parameters affecting the pelletization process of high barite iron ore concentrate were studied using the Egyptian normal and activated bentonite as binder materials. The metallurgical properties of green, dried and fired pellets were studied using chemical and X-ray analyses. The average strength of fired pellets 1.5% normal bentonite and fired 1300 °C for 25 min exceeded 200 kg/pellet. Using activated bentonite produced a lower kg/pellet value. Meanwhile, the productivity of green pellets decreased when the last binder was used.     

氢氧化镁/膨润土协同阻燃聚丙烯的研究

进一步探究了改性氢氧化镁与其他阻燃剂的协同使用对聚丙烯材料性能的影响。结果表明:阴离子改性膨润土与氢氧化镁具有良好的协同阻燃作用,两者的比例影响其协同效果。当氢氧化镁和膨润土的质量比为37:3时,协同效果最好,材料的阻燃性能和机械性能都有改善。当协同阻燃剂的填充量为45%时,材料极限氧指数达到27.8,拉伸强度达到29 MPa。     

膨润土在废水处理中的应用进展

介绍了膨润土及改性膨润土的基本组成和基本性质,阐述了膨润土的改性方法,论述了膨润土及改性膨润土在废水处理中的应用及展望.     

改性膨润土在废水处理中的应用

概述了膨润土的主要特性，研究了膨润土的主要改性方法以及改性膨润土在废水处理中的应用，讨论了改性膨润士用于废水处理中存在的问题和今后的研究方向。     

Long-term consolidation mechanisms based on micro–macro behavior and in situ XRD measurement of basal spacing of clay minerals

An important issue in the area of geological disposal of high-level radioactive waste (HLW) is to demonstrate the long-term mechanical stability of the buffer. In particular, it has to be clarified whether a waste package would continue to sink in the buffer over a long time period, resulting in a significant decrease in the buffer thickness. The candidate buffer material in Japan is a mixture of silica sand and bentonite. Consolidation tests have revealed that the bentonite shows secondary consolidation phenomena similar to clay in general. Therefore, it is important to investigate the mechanism of secondary consolidation behavior.Bentonite is a microinhomogeneous material consisting of clay minerals, macrograins (mainly quartz) and others. The unique combination of molecular dynamics (MD) and homogenization analysis (HA) procedures, termed the unified MD/HA method, has been proposed for estimating the micro to macro behavior of such an inhomogeneous material (Ichikawa, Y., Kawamura, K., Nakano, M., Kitayama, K., Kawamura, H., 1998. Unified molecular dynamics/homogenization analysis for water flow in bentonite. Proc. 1998 Int. High-Level Radioactive Waste Management Conf., Las Vegas. American Nuclear Society, La Grange Park, IL, pp. 422–428). In this study, the unified MD/HA method is applied to bentonite in order to understand its long-term consolidation mechanism. Thus, it was found that the permeability decreases significantly with a decrease in the void ratio due to the evolution of consolidation. It was therefore assumed that secondary consolidation is governed by drainage from the interlayer pores (micropores) with very low permeability, and that this is the reason why secondary consolidation is very slow.This paper also documents the result of an X-ray diffraction (XRD) experiment on bentonite under consolidation (in situ XRD), which was performed in order to validate the assumption mentioned above. It was observed that interlayer space starts to decrease after the latter half of primary consolidation. This finding strongly supports the long-term consolidation mechanism presumed above from a microscopic point of view.One-dimensional consolidation analyses of the bentonite, into which the relationship between the void ratio and the permeability determined using the unified MD/HA method was introduced, were performed for comparison with a long-term consolidation test. The good agreement between the analytical result and the test result including secondary consolidation behavior also supports the long-term consolidation mechanism presumed above.     

Modelling bentonite–water interactions at high solid/liquid ratios: swelling and diffuse double layer effects

Previous experimental studies on bentonite–water interactions have demonstrated the importance of ion exchange and surface complexation reactions occurring at the clay surface as well as dissolution/precipitation reactions of mineral impurities. Based on these findings, thermodynamic models have been widely used to derive porewater compositions for the compacted bentonite used as backfill material for nuclear repositories. Conventional models typically neglect phenomena important in compacted clays such as anion exclusion induced by swelling of the expandable clay fraction and by the formation of electrical double layers on charged edge surfaces. In this study, we evaluate such phenomena by applying a refined diffuse double layer (DDL) approach to model porewater composition in a compacted bentonite backfill surrounded by argillaceous host rock, as foreseen for the Swiss high-level waste repository. Model calculations also include the effect of water incorporation in the structural interlayers.The results indicate that the conventional model and the refined DDL model without distinction between interlayer and external water only differ slightly. The main buffering reactions include ion exchange of Ca for Na, calcite and gypsum dissolution and deprotonation of surface hydroxyl groups. On the other hand, the calculation accounting for the distinction of external and interlayer water indicates significant anion exclusion effects on the external water composition. Most notably, this leads to an increased salinity and drop in pH.From a performance assessment perspective, however, the differences induced by the inclusion of swelling and diffuse double layer effects are not very significant relative to uncertainties related to system variables, such as the pCO₂ of the host rock. Finally, it should be emphasised that significant uncertainties related to the thermodynamic properties of water in compacted clays, e.g., dielectric constant, are still unresolved and deserve further investigations.     

富铁膨润土的脱色性能研究

对矿产粗制富铁膨润土进行了金属元素分析。通过对矿产粗制膨润土进行研磨、筛分取小于160目的细微颗粒进行酸处理以脱除膨润土中的金属杂质(主要是铁)。经水洗、过滤并用硫氰化钾检验处理效果、干燥、焙烧等步骤最终以焙烧产品的色泽确定对产品的脱色效率。考察了酸种类、浓度、处理温度和时间以及焙烧温度对脱色效果的影响。结果表明,在膨润土脱色过程中,在室温下,8mol/L的浓硝酸,酸处理16h,焙烧温度为550℃,焙烧时间为2h,在该条件下制备的产品颜色由原始的棕红色脱变为乳白色,白度值由43.0提高到81.6。     

黄原胶/AMPS/膨润土制备油田堵水剂的研究

通过水溶液法制备了一种黄原胶/2-丙烯酰胺基-2-甲基丙磺酸（AMPS）/膨润土三元复合型油田堵水剂,考察了2-丙烯酰胺基-2-甲基丙磺酸、膨润土、交联剂以及引发剂质量分数等因素对堵水剂吸水率的影响,测试了不同温度下堵水剂的吸水倍率和保水值,研究了堵水剂对不同质量分数NaCl溶液的吸水性能。结果表明,最佳的制备工艺：膨润土的质量分数为15%,AMPS的质量分数为3%,交联剂的的质量分数为2%,引发剂的质量分数为2.5%,在60℃的温度下反应4h,在最佳工艺下,环境温度20℃时,堵水剂的吸去离子水的倍率最高达到1 677g/g,吸质量分数0.9%NaCl溶液的倍率为165g/g;环境温度80℃的高温下仍保持着1 590g/g的吸水倍率,12h后仍能保水20%以上,具有良好的热稳定性和耐盐性。     

钠基膨润土对氨氮废水的处理

研究了经氯化钠改性的膨润土对氨氮废水的处理,比较了经不同浓度的氯化钠溶液改性的膨润土在各种条件下对氨氮废水的处理效果。实验表明,经1%的氯化钠溶液改性的膨润土在搅拌时间为40min,膨润土用量为5g,pH值为8～9,室温时处理浓度为160mg/L的氨氮废水100mL效果最佳,最高去除率可达93.78%,处理后的氨氮废水可达到国家一级排放标准(15mg/L)。同等条件下,用该方法改性的膨润土对氨氮废水的处理效果好于粉煤灰。     

型砂砂粒间粘土膜的流变特性

用一台自己设计的仪器对型砂砂粒间粘土膜进行了测试。结果分析显示：粘土膜的流变特性可以用宾汉体－开尔文体流变模型，亦即Ｂ－Ｋ模型表达；同时观察到，在其变形过程中有应力松弛及触变现象。文中讨论了它们在型砂紧实过程中可能起作用的程度。