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The relationship among intrinsic surface reaction constant (K) in 1-pK model, point of zero net charge (PZNC) and structural charge density (σst) for amphoteric solid with structural charges was established in order to investigate the effect of σst on pK. The theoretical analysis based on 1-pK model indicates that the independent PZNC of electrolyte concentration (c) exists for amphoteric solid with structural charges. A common intersection point (CIP) should appear on the acid-base titration curves at different c, and the pH at the CIP is pHPZNC. The pK can be expressed as pK=-pHPZNC log[(1 2αPZNC)/(1-2αPZNC)], where αPZNC≡σst/eNANs, in which e is the elementary charge, NA the Avogadro‘s constant and Ns the total density of surface sites. For solids without structural charges, pK=-pHPZNC. The pK values of hydrotalcite-like compounds (HTlc) with general formula of [Mg1-xFex(OH)2](Cl,OH)x were evaluated. With increasing x, the pK increases, which can be explained based on the affinity of metal cations for H^- or OH^- and the electrostatic interaction between charging surface and H^- or OH^-. 相似文献
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混合碳链烷基聚葡糖苷中相微乳液的研究 总被引:6,自引:0,他引:6
用Winsor型相图、δ—γ“鱼状”相图和改进的ε—β“鱼状”相图研究了混合碳链烷基聚葡糖苷(APG:C8/10G1.31和C12/14G1.43)中相微乳液的相行为,结果表明,随醇浓度的增加,微乳液类型发生Winsor Ⅰ→Ⅲ→Ⅱ的转变,从Winsor型相图直接观察到醇浓度增加时,微乳液三种类型的变化、各相体积以及中相微乳液形成和消失时醇的浓度,从“鱼状”相图除得到中相微乳液形成和消失时的组成,以及单相微乳液形成时的组成外,还可得到平衡界面膜的组成、表面活性剂单体分子和醇在油相中的溶解度及表面活性剂形成单相微乳液的效能等,在比较上述两种相图优缺点的基础上,我们首次提出了改进的“鱼状”相图,把两者的优点集中于该图中,既能直观地观察出体系相态的变化,又能得到平衡界面膜的组成等其它性质,为理论和实际应用提供更多信息和方便。 相似文献
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通过电泳淌度、流变参数和中压滤失量的测定,研究了KCl和AlCl3对带永久负电荷的蒙脱土与带永久正电荷的氢氧化铝镁/甘油形成的混合悬浮体胶体性能的影响,并对影响机理进行了深入探讨 相似文献
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通过羟基喜树碱(HCPT)的10位羟基与聚乙二醇单甲醚(MPEG)之间的成醚反应, 制备了MPEG化学偶联的HCPT(MPEG-HCPT); 采用1H NMR和FTIR等进行了结构表征. 考察了MPEG偶联后对HCPT药物的水溶性和内酯环稳定性的影响, 研究了MPEG-HCPT在水溶液中的聚集行为. 结果表明, MPEG-HCPT中HCPT原药的质量分数约为33%, 在37 ℃, pH=4.8和7.2的缓冲溶液中的溶解度分别为5.23和7.90 mmol/L, 明显高于HCPT原药(0.0026和0.035 mmol/L). 该偶联药物在37 ℃下的pKah=7.12(Kah为表观水解反应平衡常数), 高于HCPT原药(6.67), 说明MPEG的偶联对HCPT内酯环结构具有一定的稳定作用. 研究还发现, 该偶联药物具有明显的表面活性, 在水溶液中可形成疏水药物为内核、 亲水聚乙二醇为外壳的聚集体, 其临界聚集浓度约为0.46 mmol/L. 相似文献
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