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

Jun Wang,Zhongyang Mao,Yu Wang,Bei Huang

doi:10.3390/ma14040994

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.

Highlights

Chloride ion erosion firstly rusts the reinforcement of reinforced concrete, leading to cracks along the reinforcement of concrete; secondly, chloride solution migrates to the concrete surface with the continuous drying of concrete, which generates frost or crystallizes in the pores of the concrete surface and produces crystallization expansion stress, which leads to concrete-surface peeling and cracks [1]
layered double hydroxides (LDHs) is prepared by a simple hydrothermal synthesis method, and the structure and properties 5
Of Conclusions the materials are analyzed by modern micro-analysis techniques, including phase analysis, observation, The mainmorphology conclusions are as follows:and infrared spectroscopy

Summary

Introduction

In the marine environment, concrete structures are damaged, and the main causes of damage are steel corrosion and salt erosion. The essence of its erosion is that sulfate ions in the environment invade into concrete and react with hydration products to produce ettringite, gypsum, and other expansive substances, and at the same time, it causes cracking and spalling of concrete under the action of sulfate crystallization expansion. Jone [7] used hydrotalcite materials to remove complex anions of some metal ions in solution by using the ion exchange method. Jone [7] used calcined hydrotalcite materials to remove Ni(CN)4 2− , CrO4 2− , and other complex anions from some metal ions in solution. Ulibarri [9] used calcined hydrotalcite to remove trichlorophenol and trinitrophenol from wastewater

Methods

Results

Conclusion