Degree of flocculation and viscoelastic behaviour of kaolinite-sodium chloride dispersions
Degree of flocculation and viscoelastic behaviour of kaolinite-sodium chloride dispersions
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高岭石-氯化钠分散体的絮凝度和粘弹性行为
DOI：
10.1016/j.colsurfa.2007.07.030
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发表时间：
2008
期刊：
影响因子：
--
通讯作者：
A. James
中科院分区：
文献类型：
--
作者：
M. Nasser;A. James
研究了电解质浓度和pH对高岭石分散体絮凝程度的影响。讨论了粘弹性行为，并定量地将其与絮凝程度联系起来。絮凝分散体的絮凝程度随离子强度和pH值的变化而显著变化。在低pH下，无论电解质浓度如何，高岭石分散体具有高度絮凝性（即pH<7时的强边面相互作用），沉降率高，上清浊度低。在高pH和低电解质浓度下，所有静电相互作用都是排斥性的，产生高度浑浊的上清。然而，随着电解质浓度的增加，浊度降低，沉降率增加。流变学测量表明，0.1体积分数的Bingham屈服应力在pH值2 ~ 7之间降低了一个数量级，在低离子强度下几乎保持不变，在pH值7 ~ 9之间降低速度较慢（高离子强度下）。从振荡测量中发现，弹性模量G′在酸性pH范围内较大。这些结果与蠕变实验结果表明，在pH为7时存在强弹性絮凝结构，在低离子强度下，pH进一步增加会导致絮凝体结构破坏，当离子强度增加时，会产生弱随机结构的絮凝体。
The effect of electrolyte concentration and pH on the degree of flocculation of kaolinite dispersions has been investigated. The viscoelastic behaviour is discussed and quantitatively linked to the degree of flocculation. This degree of flocculation dispersions changes significantly with both ionic strength and pH. At low pH, regardless of electrolyte concentration, kaolinite dispersions are highly flocculated (i.e. strong edge–face interactions at pH<7) having high settling rates and low supernatant turbidity. At high pH and low electrolyte concentration, all electrostatic interactions are repulsive producing a highly turbid supernatant. However as the electrolyte concentration is increased the turbidity is reduced and settling rates are increased. Rheological measurements show that, the Bingham yield stress of 0.1 volume fraction decreases up to an order of magnitude between pH 2 and 7 and remains almost constant (at low ionic strength) and has a slower rate of decrease (at high ionic strength) between pH 7 and 9. From oscillatory measurements, it is found that the elastic modulus, G′, is greater in the acid pH range. These results together with those obtained from creep experiments suggest the existence of a strong elastic, flocculated structure up to pH 7, at low ionic strength, further increase in pH causes breakdown in flocs structure and when the ionic strength is increased weak randomly structured flocs are produced.