Study on site energy of phosphate adsorption by layered double hydrotalcites with mesoporous morphologies
Phosphorus pollution in water bodies is an urgent environmental problem,which threatens biological health and destroys ecological balance.In this paper,Mg-Al layered double hydrotalcites with CO32-type stacking lamellae,CH2CHCOO-type intercalated rock-like,and CH2CHCOO-type recombined funnel-shaped and rock-like were prepared re-spectively by hydrothermal method.The interaction between different interlayer ions and hydrotalcite lamellae was studied by density functional theory.Through isothermal adsorption experiment and site energy distribution theory based on Toth model and DA model,the phosphate adsorption characteristics of hydrotalcites with different morphology and structure were analyzed.The experimental results showed that the adsorption sites of funnel-shaped hydrotalcite were distributed in high energy region,while the sites of the other two hydrotalcites were distributed in low energy region.With the increase of tem-perature,the site distribution of the three hydrotalcites shifted to the high energy region,and the average site energy was in-creased by 12.04%to 14.26%.Funnel-shaped hydrotalcite obtained by acrylic acid regulation had more high-energy adsorp-tion sites,larger specific surface area and stronger ligand exchange.At the same time,with the increase of temperature and concentration,the energy distribution of funnel-shaped hydrotalcite sites changed most significantly,indicating that funnel-shaped hydrotalcite had advantages in phosphate adsorption.This study provided a theoretical basis for the regulation of mesoporous hydrotalcite and the study of phosphate adsorption mechanism of hydrotalcite through site energy distribution theory.
layered double hydrotalcitemorphological structureadsorptionphosphatesite energy distribution