| The cheap magnesium nitrate,aluminium nitrate and iron nitrate were used to prepare Mg/Al hydrotalcite compounds(Mg/Al-HTs) and Mg/Al/Fe hydrotalcite-like compounds(Mg/Al/Fe-HTLCs) under mild reaction conditions via coprecipitation method,the products(Mg/Al-HTCs-500 and Mg/Al/Fe-HTLCs-500) were obtained when they were calcined at 500 ℃,their strutures were all characterized by X-ray diffraction.Mg/Al-HTCs-500 and Mg/Al/Fe-HTLCs-500 were used to remove sulfate ions in the aqueous solution,it was studied the time,dosage,pH,other anions and initial concentration of the solution influenced the adsorption of sulfate ions by Mg/Al-HTCs-500 and Mg/Al/Fe-HTLCs-500.It is also simply studied the result for adsorption of sulfate ions by Mg/Al-HTCs-500 and Mg/Al/Fe-HTLCs-500 in practical use,the adsorption mechanism was preliminarily studied,whether the addition of iron caused difference in structure and adsorption property of Mg/Al-HTCs-500 and Mg/Al/Fe-HTLCs-500 was analysised.The results showed Mg/Al-HTs and Mg/Al/Fe-HTLCs had noticeable features and good layered structure,but the addition of iron caused the Mg/Al/Fe-HTLCs’s crystallinity and layer spacing were smaller than Mg/Al-HTs, Mg/Al-HTs and Mg/Al/Fe-HTLCs formed medal oxides after high temperature calcination.Time,dosage,other anions and initial concentration of sulfate solution have the same influence rule for adsorption of sulfate ions by Mg/Al-HTCs-500 and Mg/Al/Fe-HTLCs-500,the only difference was individual numerical,for example,The time of equilibrium for adsorption of sulfate ions by Mg/Al-HTCs-500 was 4h,but for Mg/Al/Fe-HTLCs-500 it was 3h.There was great difference when pH influenced adsorption of sulfate ions by Mg/Al-HTCs-500 and Mg/Al/Fe-HTLCs-500,the adsorption of sulfate ions on Mg/Al-HTCs-500 had a maximum adsorption quantity when the pH was 2,but Mg/Al/Fe-HTLCs-500’s adsorption quantity suddenly reduced,Mg/Al-HTCs-500 and Mg/Al/Fe-HTLCs-500 had great difference for the low pH’s influence. The adsortion process is consistant with pseudo-seccond-order kinetics model and langmuir adsorption isotherm model for Mg/Al-HTCs-500 and Mg/Al/Fe-HTLCs-500 and controlled by intraparticle diffusion mechanism and chemical reaction.The two roasted products have homogeneous surface,the adsorption on the surface is monolayer. Mg/Al-HTCs-500 and Mg/Al/Fe-HTLCs-500 had good adsorption property for sulfate ions and could remove sulfate ions in the practical use.The two roasted products’ adsorption mechanism for sulfate ions is regaining the layer structure by adsorping sulfate ions and putting it as interlayer anion.It can be concluded by comparing the result of the adsorption of sulfate ions by the two roasted products the addition of iron dosen’t cause substantial changes,the two main aspects influenced are Mg/Al/Fe-HTLCs-500’s adaptive capacity for pH and adsorption capacity for sulfate ions are smaller than Mg/Al-HTCs-500. |
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