Study on Adsorption Properties of Calcined Mg–Al Hydrotalcite for Sulfate Ion and Chloride Ion in Cement Paste

Abstract

In the marine environment, sulfate ions and chloride ions are abundant. Therefore, sulfate attack and chloride ion attack are common failure forms of marine concrete. Mg–Al hydrotalcite is a layered bimetallic hydroxide, which can be used as guest molecular adsorbent. In this experiment, we synthesized Mg–Al hydrotalcite, and the crystal state, surface morphology, and composition of this adsorbent were investigated by modern micro-analysis technology. Mg–Al hydrotalcite was added into the prepared target ion solution, to explore the influence of various factors on the adsorption performance of Mg–Al hydrotalcite, and then calcined Mg–Al hydrotalcite was added into cement paste, to study the mechanical properties and durability of the paste samples. The experimental results show that the optimum conditions for adsorption of chloride ions by calcined Mg–Al hydrotalcite are an adsorption time of 4 h, temperature of 35 °C, LDO (calcined Mg-Al hydrotalcite) dosage of 3.5 g/L, and a pH of 8. The adsorption effect of sulfate ion is best when the adsorption time is 6 h, the temperature is 35 °C, the dosage of LDO is 4 g/L, and the pH = 8. The optimal adsorption conditions of calcined Mg–Al hydrotalcite for chloride ion and sulfate ion are not completely the same, and the adsorption of these two ions in mixed solution shows competitive adsorption. Compared with the common paste specimens without Mg–Al hydrotalcite, the mechanical properties and deformation properties of cement specimens can be significantly improved by adding Mg–Al hydrotalcite.

pH‐Triggered Release and Degradation Mechanism of Layered Double Hydroxides with High Loading Capacity

“…Layered double hydroxides (LDHs) are a type of cationic layered compounds with exchangeable anions between the layers that possess certain alkalinity, which mainly include hydrotalcite, hydrotalcite‐like compounds, and their intercalation chemical products, pillared hydrotalcite. [ 1–3 ] The general chemical formula of LDHs can be expressed as follows: [M 2+ 1–x M 3+ x (OH) 2 ] + (A n− ) x/n · mH 2 O, where M 2+ and M 3+ are divalent and trivalent metal cations, respectively, A n− represents the exchangeable interlayer anion, x expresses the molar ratio of M 3+ /(M 2+ + M 3+ ) and m is the number of interlayer water molecules. While, M 2+ , M 3+ , and A n− can be adjusted to tailor them for different applications.…”

“…Layered double hydroxides (LDHs) are a type of cationic layered compounds with exchangeable anions between the layers that possess certain alkalinity, which mainly include hydrotalcite, hydrotalcite-like compounds, and their intercalation chemical products, pillared hydrotalcite. [1][2][3] The general chemical formula of LDHs can be expressed as follows:…”

Durability of Blast-Furnace Slag Cement Concrete With Different Curing Methods

“…When there is enough moisture and temperature, strength gains continue beyond 28 days [14]. Sulfate attack occurs when sulfate ions in the pore solution of concrete react with concrete components, resulting in the formation of novel reaction products with a large molar volume [15,16]. Several studies have been undertaken to reduce the attack and increase the service life of concrete structures exposed to sulfate conditions [15,17].…”

Mechanical Properties and Damage Evolution of Concrete Materials Considering Sulfate Attack

“…Sulfate attack is an important factor affecting the service life and durability of concrete buildings and structures [ 1 , 2 , 3 , 4 ]. Soils containing a large amount of sulfate are common in saline areas of Northwest China, seawater in coastal areas, and groundwater.…”