Adsorption Of Perchlorate By Calcined Layered Double Hydroxide

Mg(NO3)2·6H2O, Zn(NO3)2·6H2O, Al(NO3)3·9H2O, NaOH and Na2CO3being raw materials, a series of Mg/Zn/Al layered double hydroxides eontainting Mg2+were synthesized by co-precipitation method and calcined at different temperature and their mixed oxides were obtained. The structure and morphology of samples were studied by XRD, BET surface area and FT-IR. By static adsorption experiment, discuss the adsorption isothermal model, dynamic model and thermodynamic parameter. The effect of calcination temperature, Mg/Zn/Al molar ratio, pH value of solution, adsorption time and dosage on the adsorption capacity of samples are studied. Mechanism were also studied. It was found that:(1) The sorbent Mg/Zn/Al Hydrotalcite-like Compounds with dieffrrent Mg/Zn/Al mol rations were prepared by co-precipitation method had strong typical diffraction peaks of hydrotalcite, crystal diffraction peak intensity and symmetry were improved with the increase of the content of Mg2+. Its layered structure was destroyed and its laminate was colla-psed after calcinated at500℃and eventually it formed a composite oxidematter of ZnO and MgAl2O4.(2) FT-IR results show that the type of hydrotalcite synthesis by inserting carbonate ions between the layers, it was said that the samples were hydrotalcite; With the increase of calcination temperature, specific surface area were increased, after calcinated at500℃the specific surface area were decline, because of it formed a composite oxidematter.(3) Through the synthetic HTLC2-500and CHT2adsorption effect of perchlorate, it showed that calcination temperature was important to absorption efficiency, the best adsoption of perchlorate was achieved at the calcinations temperature at500℃; The adsorption effect of perchlorate gradually increased with the increase of Mg2+content; With the increase of the amount of adsorbent additive, the removal rate of was increase, the roots of perchlorate adsorption capacity was decrease, adsorption using CHT2-500as adsorbate reaehes equilibrium within24h and the absorption capaeity was higher at pH4-10.(4) The adsorption equilibrium curves of perchlorate on CHT2-500could be well described by pseudo-second order kinetic; The data for perchlorate adsorption were well fitted to the Langmuir, Freundich and D-R adsorption isotherm. The adsorption of perchlorate on it was physical adsorption. Thermodynamic parameters showed that the adsorption of perchlorate on CHT2-500was spontaneous and endothermic.(5) The mechanism of removal of perchlorate using CHT2-500relies mainly on its structure memory effect to recove layer structure by adsorption perchlorate in solution. In addition, surface adsorption may also play a role in.