Synthesis of CaFeAl layered double hydroxides 2D nanosheets and the adsorption behaviour of chloride in simulated marine concrete

Chloride-induced reinforcement corrosion in marine concrete structures adversely impacts its durability, which leads to the decrease of the actual service life of concrete. Three kinds of layered double hydroxides (LDHs), CaFe–NO3 LDHs (LDHs-CF), CaAl–NO3 LDHs (LDHs-CA) and CaFeAl–NO3 LDHs (LDHs-CFA), were synthesized to bind chloride. The results showed that all of the synthetized LDHs could effectively adsorb chloride from simulated concrete pore solutions (SCPSs) and artificial seawater (ASW) through the surface adsorption and ion exchange. The maximum chloride adsorption capacity of the LDHs-CFA was 3.18 mmol g−1. The adsorption process could be described by the Langmuir isotherm and pseudo-second-order kinetic models. For the chloride desorption experiments, the chloride desorption rate of the LDHs-CF (29.20%) and LDHs-CFA (39.31%) were lower than that of the LDHs-CA (47.45%), because the presence of Fe3+ in LDHs suppressed the concentration of dissolved metals, and a crystal transformation occurred to form 3CaO·Fe2O3·0.5CaSO4·0.5CaCl2·10H2O, exhibiting excellent stability for LDHs-CF and LDHs-CFA. In conclusion, LDHs show excellent chloride binding behaviour, which makes it promising to achieve the goal of high efficiency and stability of chloride binding for marine concrete by LDHs.