Abstract
Abstract Because of its priority to remove anions, nano-layered double hydroxide (LDH) was incorporated to improve the sulfate attack corrosion resistance of cement-based materials. Herein, the synthesis of high-efficiency LDH for removal of SO 4 2 − {\text{SO}}_{4}^{2-} is necessary. In this study, LDH with different Mg/Al ratios was synthesized under different dual solvent systems (water and ethylene glycol/ethanol/tetrapropylammonium hydroxide). Based on the adsorption experimental results, the LDH synthesized with n(Mg:Al) = 2:1 under water and ethanol solvent systems (ET2.0) exhibits the best adsorption capacity. The d (003) of LDH synthesized with n(Mg:Al) = 2:1 under different dual solvent systems are 0.7844, 0.7830, and 0.7946 nm, respectively. Three LDH belong to LDH- NO 3 − {\text{NO}}_{3}^{-} . The results indicated that their surface charges show obvious difference synthesized under different dual solvent systems, which leads to differences in adsorption performance. The adsorption experimental results show that ET2.0 followed pseudo second-order kinetics and Langmuir model. The ET2.0 removed SO 4 2 − {\text{SO}}_{4}^{2-} through anion substitution and electrostatic interaction and exhibited excellent adsorption rate with the maximum adsorption capacity of 95.639 mg/g. The effects of pore solution anion (OH−, Cl−, and CO 3 2 − {\text{CO}}_{3}^{2-} ) on the removal of SO 4 2 − {\text{SO}}_{4}^{2-} by the ET2.0 are limited.
Highlights
During the service period of concrete, temperature, load, electric field, ion erosion, etc. all have adverse effects on the durability of concrete, which greatly shorten the service period of concrete and cause huge safety problem [1]
The synthesis of high-efficiency layered double hydroxide (LDH) for removal of SO42− is rarely considered and the effect of anions that may exist in the pore solution of cementbased materials on the adsorption of SO42− by the LDH was rarely explored
To determine the optimal synthesis method, the removal of SO42− by LDH with various n(Mg:Al) ratios under different dual solvent systems was studied by the batch adsorption experiments
Summary
During the service period of concrete, temperature, load, electric field, ion erosion, etc. all have adverse effects on the durability of concrete, which greatly shorten the service period of concrete and cause huge safety problem [1]. The synthesis of high-efficiency LDH for removal of SO42− is rarely considered and the effect of anions that may exist in the pore solution of cementbased materials on the adsorption of SO42− by the LDH was rarely explored. Both factors affect the ability of LDH to adsorb sulfate, which is closely related to the sulfate corrosion resistance of cement-based materials mixed with LDH. The effect of anions that may exist in the pore solution of cement-based materials on the adsorption of SO42− by the LDH is rarely considered and worthy of further exploration [33]. The effects of pH, Cl−, and CO32− on the adsorption of SO42− were explored
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