介孔形貌的LDH吸附磷酸盐的位点能量研究

Study on site energy of phosphate adsorption by layered double hydrotalcites with mesoporous morphologies

水体磷污染是一个亟待解决的环境问题,威胁生物健康并破坏生态平衡。通过水热法制备了分别具有CO_(3)^(2-)型堆积片层状、CH_(2)CHCOO^(-)型插层岩石状和CH_(2)CHCOO^(-)型重组漏斗孔型岩石状的水滑石。使用密度泛函理论研究了不同层间离子与水滑石片层的作用关系。通过等温吸附实验,并采用基于Toth模型和DA模型的位点能量分布理论分析了不同形貌结构的水滑石对磷酸盐的吸附特性。结果表明:漏斗孔型水滑石的吸附位点分布在高能量区,其余两种水滑石的位点分布在低能量区;随温度升高,3种水滑石的位点分布向高能量区偏移,平均位点能量增加了12.04%~14.26%。通过丙烯酸调控得到的漏斗孔型水滑石具有更多的高能吸附位点数量、更大的比表面积和更强的配体交换作用,同时随着温度和浓度增加,漏斗孔型水滑石位点能量分布变化最为显著,表明漏斗孔型水滑石在磷酸盐吸附中具有优势。该研究对水滑石的调控及通过位点能量分布理论研究水滑石为磷酸盐的吸附机制提供了理论依据。

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 CO_(3)^(2-)type stacking lamellae,CH_(2)CHCOO^(-)type intercalated rock-like,and CH_(2)CHCOO^(-)type recombined funnel-shaped and rock-like were prepared respectively 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 temperature,the site distribution of the three hydrotalcites shifted to the high energy region,and the average site energy was increased by 12.04%to 14.26%.Funnel-shaped hydrotalcite obtained by acrylic acid regulation had more high-energy adsorption 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 funnelshaped 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.