Study On The Synthesis Of Hydrotalcite-like Compounds And The Adsorption Of SDBS From Aqueous Solution

The size and size distribution will be affected by many factors in the process of synthesize Mg-Al-HTlc nanoparticles using mixed co-precipitation method. Orthogonal design was used in this paper to synthesis Mg-Al-HTlc nanoparticles and to estimate the factors (such as peptizing time, peptizing temperature, aging time and alkali dosage) effect on the unit cell parameters, size and size distribution in the preparing monodispersed Mg-Al-HTlc nanopartical process. The result showed that the influence order of factors on HTlc mean size was: peptizing temperature> aging time > peptizing time > alkali dosage, the influence order of factors on HTlcs size distribution was: alkali dosage > peptizing temperature > aging time > peptizing time. The optimal condition for preparing monodispersed HTlcs was: peptizing time 48h, peptizing temperature 100℃, and alkali dosage nNH₃·H₂O/(2n_Mg²⁺+3n_Al³⁺)=1, aging time 45min.In accordance with the above optimum preparation conditions, we synthesized a series of MgAl and MgFe compounds, and were characterized using TEM, XRD and TG/DTA. The adsorption experiment was carried out using MgAl and MgFe hydrotalcite and CHT on anionic surfactants (SDBS) in aqueous solution, the experimental conditions, the main factors and the adsorption mechanism was discussed. The results showed that:(1) X-ray diffraction phase analysis showed that with increasing of metal ratio, the crystallinity of synthetic hydrotalcite was decreasing . Weight loss trend of hydrotalcits were consistent, metal ratio had little effect on the thermal stability, but impurities can reduce the thermal decomposition temperature.(2) The adsorption time of SDBS on MgAl hydrotalcite was 720min, and MgAl-A sample adsorption rate was stronger than C sample. Mg-Al hydrotalcite can effectively remove SDBS, adsorption isotherm meet the Freundlich isotherm.(3) The adsorption time of SDBS on MgAl hydrotalcite was 600min, MgFe- N1 is best of removing SDBS. Adsorption isotherm meet the Freundlich isotherm.(4) At 308K the adsorption on MgFe-N1 had maximum。With the increasing of concentration of NaCl and Na2SO4, the adsorption of SDBS was decreasing. However, with the increasing of concentration of Na3PO4, adsorption capacity of SDBS increased and then decreased.(5) The XRD patterns of MgFe -N1 and N1-SDBS showed that SDBS and N1 was only surface adsorption, and ion exchange did not occur. Comparing the adsorption isotherm of MgFe-N1 and CHT-N1, we can be obtained that the molar ratio of Mg / Fe had a strong influence on the adsorption capacity.