Sedimentation characteristics of two commercial bentonites in aqueous suspensions
Sedimentation characteristics of two commercial bentonites in aqueous suspensions
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DOI：
10.1180/claymin.2008.043.3.09
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发表时间：
2008-09
期刊：
影响因子：
1.5
通讯作者：
S. Akther;J. Hwang;H. Lee
中科院分区：
文献类型：
--
作者：
S. Akther;J. Hwang;H. Lee
采用3% w/v的粘土悬浮液，在NaCl浓度（1、3.5和10%）和pH值（2、7和12）的条件下，研究了两种膨润土Tixoton（有机处理）和Montigel-F（未经处理）的沉降特性。沉降速率、絮团直径和沉积物体积通过使用Turbiscan Ma 2000仪器的透光率变化得到。两种膨润土悬浮液在NaCl溶液中均不稳定（絮凝）。沉降速率随NaCl浓度的增加而增加，并与絮凝体直径直接相关。随着NaCl浓度的增加，沉积物体积减小，这是由于离子强度增加导致双层压缩增大所致。在类似的盐浓度下，经过有机处理的膨润土（Tixoton）沉降速度要慢得多，沉降体积也更大。有机处理和未处理的膨润土悬浮液在pH 7以上都是稳定的（分散的），在酸性条件下不稳定。Tixoton在酸性条件下的沉降速率远小于Montigel-F。两种膨润土样品沉积特性的差异可能是由于Tixoton中存在阴离子聚合物（羧甲基纤维素：CMC）。对膨润土悬浮液的粘度进行了研究。粘土悬浮液的粘度与粘土在溶液中的分散性密切相关。CMC对膨润土悬浮液的粘度有很好的提高作用，但仅在中性和碱性条件下有效。
Abstract The sedimentation characteristics of two commercial bentonites, Tixoton (organically treated) and Montigel-F (untreated), were investigated using a 3% w/v clay suspension at different concentrations (1, 3.5 and 10%) of NaCl and pH values (2, 7 and 12). Settling rates, floc diameters and sediment volumes were derived from changes in light transmittance using a Turbiscan Ma 2000 instrument. Both bentonite suspensions were unstable (flocculated) in NaCl solutions. The settling rate increased with increasing concentration of NaCl and was directly related to floc diameter. The sediment volume reduced with increasing NaCl concentrations, a result of greater double layer compression caused by increased ionic strength. At comparable salt concentrations, the organically-treated bentonite (Tixoton) settled at a much slower rate and had a greater sedimentation volume. The suspensions of both organically-treated and untreated bentonites were stable (dispersed) above pH 7 and unstable in acidic conditions. The settling rate for Tixoton under acid conditions was much smaller than that for the Montigel-F. Differences in sedimentation characteristics between the two bentonite samples are probably due to the presence of an anionic polymer (carboxymethyl cellulose: CMC) in Tixoton. The viscosity of the bentonite suspensions was also studied. The viscosity of the clay suspension is closely related to clay dispersivity in solution. The CMC was highly effective in increasing the viscosity of the bentonite suspensions, but only under neutral and alkaline conditions.