This study investigates the colloid systems and interfaces stability of cerium oxide nanoparticles in aqueous environments as a function of pH, monovalent cations (Na⁺) and divalent cations (Ca²⁺), and humic substances (humic acid (HA) and fulvic acid (FA)). Results show that the solution chemistry affected the colloidal stability and aggregation kinetics of CeO₂ NPs. The pH point of zero charge (pH_PZC) of CeO₂ NPs was measured at pH 10.2 with diameter of CeO₂ NPs aggregates of ∼1,700 nm. The effects of Na⁺ and Ca²⁺ and HA and FA on the magnitudes and rates of aggregation were pH-dependent. In addition, when salts were present in the aqueous systems, although the CeO₂ NPs were stable at pH < pH_PZC (expect for 1 mM of NaCl/CaCl₂) and pH > pH_PZC (except for 0.5 mM CaCl₂), the aggregation was enhanced at pH = pH_PZC, with the diameter of CeO₂ NPs in the ∼1,300–3,600 nm range. HA also stabilized CeO₂ NPs under pH > pH_PZC with an enhanced aggregation of pH = pH_PZC with the diameter of CeO₂ NPs in the ∼1,500–1,900 nm range, and in the presence of 0 and 1 mM of NaCl/CaCl₂ at pH < pH_PZC. At three pH levels (8.2, 10.2, and 12.2) and under all different electrolyte concentrations (0–1 mM of NaCl or CaCl₂), FA (0.14 mg/L) exhibited a greater degree of efficiency in stabilizing CeO₂ NPs than HA (5 mg/L), with CeO₂ NPs aggregates growing at low rates and resulting in diameter of ∼95–115 nm.

中文翻译：

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水环境中氧化铈纳米颗粒的胶体系统和界面稳定性：pH、离子组成以及苏瓦尼河腐殖酸和黄腐酸的影响

本研究研究了氧化铈纳米颗粒在水性环境中的胶体系统和界面稳定性与 pH、一价阳离子 (Na ⁺ ) 和二价阳离子 (Ca ²⁺ ) 以及腐殖质（腐殖酸 (HA) 和黄腐酸 ( F A））。结果表明，溶液化学影响了 CeO ₂ NPs 的胶体稳定性和聚集动力学。CeO ₂ NPs 的零电荷 pH 点 (pH _PZC )是在 pH 10.2 下测量的，CeO ₂ NPs 聚集体的直径约为 1,700 nm。^{Na +}和Ca ²⁺以及HA 和FA 对聚集程度和速率的影响取决于pH。此外，当水体系中存在盐时，尽管 CeO _{2 NP 在 pH < pH PZC （1 mM NaCl/CaCl 2}除外）和 pH > pH _{PZC （0.5 mM CaCl 2}除外）下稳定，但当 pH = pH _PZC时，聚集增强，CeO ₂纳米颗粒的直径在~1,300–3,600 nm 范围内。HA还在 pH > pH _PZC下稳定了 CeO ₂ NP ，并增强了 pH = pH _{PZC的聚集，CeO 2} NP的直径在~1,500–1,900 nm 范围内，并且存在 0 和 1 mM NaCl/CaCl ₂在 pH < pH _PZC时。在三个 pH 水平（8.2、10.2 和 12.2）和所有不同电解质浓度（0-1 mM NaCl 或 CaCl _{2 ）下，FA (0.14 mg/L) 在稳定 CeO 2} NP方面表现出比 HA 更高的效率(5 mg/L)，CeO ₂ NPs聚集体以低速率生长，导致直径为∼95–115 nm。