Study on the Synthesis, Microstructure and Adsorption Performance of Nano-meter Mg-Al Hydrotalcite
Nano-meter Mg-Al hydrotalcite was prepared by precipitation method using Mg(NO3)2·6H2O and Al(NO3)3 · 9H2O as the raw material and Na2CO3 and NaOH as precipitator and pH regulator.The effects of pH value,reaction temperature and the ratio of magnesium and aluminum on the microstructure and the growth of LDHs were investigated systematically by the means of X-ray diffraction (XRD),scanning election microscopy (SEM) and energy dispersive spectrometer (EDS).Simultaneously,its growth mechanism was discussed using ligand theory.Furthermore,methyl orange acted as the simulated wastewater,adsorption mechanism and property of the calcined LDHs synthesized under the optimum synthesis conditions were studied.The results reveal that the increase of pH and temperature was helpful to prepare the Mg-Al-LDHs with single structure,better crystalline and regularity.Besides,as pH and temperature increases,grain size and the ratio of thickness and diameter presents an increasing trend.When the temperature is equal or greater than 80 ℃,the increase of temperature had fewer effect on the morphology of LDHs.However,the ratio of magnesium and aluminum influenced the crystallization and growth of LDHs.At the ratio of 3∶ 1,Mg-Al-LDHs with size of about 70-100 nm and thickness of about 20 nm were obtained and showed the best regularity and uniformity.When the ratio was 1∶ 1,the particle diameter obviously decreased,which is about 30 nm.Otherwise,the calcined nano-meter Mg-Al-LDHs synthesized under the optimum condition have good adsorption performance.The decolorization rate gradually increased with the time.In 70 min,the adsorption equilibrium of LDO reached and the decolorization efffect is more than 90％.Adsorption dynamics study indicated that the adsorption process of LDHs fitted well with the pseudo-first-order kinetics rate equation and Langmuir adsorption model.
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