Cationic-ratio-regulated surface chloride adsorption of layered double hydroxides

IF 10.9 1区 工程技术 Q1 CONSTRUCTION & BUILDING TECHNOLOGY
Qinglu Yu , Xing Ming , Peixian Huo , Guoxing Sun
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Abstract

Layered double hydroxides (LDHs) have emerged as an effective ingredient for enhancing the durability of cement-based materials against chloride-contaminated coastal or marine environments. Yet, the relationship between the surface chemistry and consequential adsorption affinity, which mainly constitutes chloride binding capacity of LDHs, still remain elusive, especially in alkaline cement pore solutions. Herein, we investigate Mg-Al-CO3-LDHs to demonstrate the cationic-ratio- (MII/MIII-) regulated surface chloride adsorption in alkaline solutions through a series of progressively in-depth means. The regulatory mechanism of the cationic ratio is microscopically operated through diverse composition and proportion of hydroxylated clusters with varying deprotonation reactivity of bonded hydroxyl on the surface. DFT calculations combined with multiple surface characterization techniques indicate that the varying reactivity is determined by the ionic bonding characteristics of HO bond and the electrostatic attraction ability of different clusters. The LDH with Mg/Al ratio of 2.0 exhibits the optimal surface chloride adsorption among ratios ranging from 1.6 to 3.8 in alkaline solutions due to the strong resistance to nucleophilic attack from OH of Mg2Al-OH cluster while maintaining high electrostatic attraction ability. Our findings advance the comprehension of surface interactions of LDHs with alkaline environments while underscoring the role of cationic ratio in surface chloride adsorption.

受阳离子比例调节的层状双氢氧化物表面氯化物吸附现象
层状双氢氧化物(LDHs)已成为提高水泥基材料耐受氯化物污染的沿海或海洋环境的有效成分。然而,层状双氢氧化物的表面化学性质与吸附亲和力之间的关系(主要构成了层状双氢氧化物的氯化物结合能力)仍然难以捉摸,尤其是在碱性水泥孔溶液中。在此,我们对 Mg-Al-CO3-LDHs 进行了研究,通过一系列逐步深入的方法证明了在碱性溶液中阳离子比例(MII/MIII-)对表面氯化物吸附的调控作用。阳离子比例的调节机制在微观上是通过表面键合羟基的不同去质子化反应性的羟基化团簇的不同组成和比例来实现的。DFT 计算结合多种表面表征技术表明,不同的反应活性是由 HO 键的离子键特性和不同团簇的静电吸引能力决定的。在碱性溶液中,镁/铝比例为 2.0 的 LDH 在 1.6 至 3.8 的比例范围内表现出最佳的表面氯化物吸附性,这是因为 Mg2Al-OH 团簇在保持高静电吸引能力的同时,还能很好地抵抗来自 OH- 的亲核攻击。我们的发现加深了人们对 LDH 与碱性环境的表面相互作用的理解,同时强调了阳离子比例在表面氯化物吸附中的作用。
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来源期刊
Cement and Concrete Research
Cement and Concrete Research 工程技术-材料科学:综合
CiteScore
20.90
自引率
12.30%
发文量
318
审稿时长
53 days
期刊介绍: Cement and Concrete Research is dedicated to publishing top-notch research on the materials science and engineering of cement, cement composites, mortars, concrete, and related materials incorporating cement or other mineral binders. The journal prioritizes reporting significant findings in research on the properties and performance of cementitious materials. It also covers novel experimental techniques, the latest analytical and modeling methods, examination and diagnosis of actual cement and concrete structures, and the exploration of potential improvements in materials.
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