Adsorption Of Chloride Ion By Magnesium Aluminum Hydrotalcite And Carbonn Nanotube Composites

Chloride ion is one of the most widespread anions in nature and it is very harmful to reinforced concrete structures.At present,the most important way to prevent chloride ions from eroding concrete components is to prevent the chloride ions from being attacked by adding the admixture to the concrete to"block"the pore structure to prevent chloride ions from invading into the concrete member.In this paper,by adding hydrotalcite materials to solidify the free chloride ions in concrete,the purpose of improving the durability of concrete is achieved.So far,the research and application of this method in the concrete field is very rare.In this paper,magnesium-aluminum hydrotalcite andmagnesium-aluminum hydrotalcite and carbon nanotube composites were prepared by one-step hydrothermal method and characterized.The ability of two materials to adsorb chloride ions in solution at different pH,adsorption time and adsorption temperature was compared.Magnesium-aluminum hydrotalcite and carbon nanotube composites were mixed into cement paste and mortar to explore the performance of solidification of chloride ions in cement paste and mortar,and the composites of magnesium-aluminum hydrotalcite and carbon nanotubes were studied.The effect on the compressive strength of the mortar.Research indicates:(1)The hydrotalcite material synthesized by one-stephydrothermal method has good crystal growth,and the whole crystal is intact.The microstructure of the magnesium-aluminum hydrotalcite and carbon nanotube composite material is a three-dimensional grade honeycomb nanostructure.Compared with magnesium aluminum hydrotalcite,the composite material with carbon nanotubes has a larger specific surface area and pore structure,and its specific surface area can reach 103.019 m~2/g.(2)The adsorption of chloride ion in magnesium-aluminumhydrotalcite and carbon nanotube composites is affected by adsorption time,adsorption temperature and pH value.The adsorption equilibrium is reached after adsorption for 100 min.The optimum adsorption temperature is 45°C.The optimum pH is 8,and the saturated adsorption amount of chloride ion is 75.58 mg/g,which is much larger than 28.56mg/g of magnesium aluminum hydrotalcite.(3)The isotherm and adsorption kinetics of chloride ionadsorptionofmagnesium-aluminumhydrotalciteand magnesium-aluminum hydrotalcite and carbon nanotube composites are in accordance with Langmuir isotherm model and quasi-secondary kinetic model,respectively.Adsorption is based on chemical adsorption.(4)Magnesium-aluminum hydrotalcite and carbon nanotubecomposites have strong curing ability for chloride ions in cement paste and mortar.The solidification amount of chloride ion is positively correlated with the curing age and chloride ion concentration.(5)The incorporation of magnesium-aluminum hydrotalcite andcarbon nanotube composite materials in cement mortar can improve the compressive strength of cement mortar,but the extent of the increase is not very obvious.