Preparation And Adsorption Properties Of Modified Montmorillonite For Uranium(â…¥)

The fast and efficient separation of uranium from the waste water was very important for both human living environment and recycling of resources, so the development of new materials which were suitable for the separation of uranium from underground water was the key to solve the problem. In order to separate the uranium-carbonate or calciumcarbonate complex compounds from waste water, the montmorillonite(MT) was chose as the substrate to design and prepare the hydroxy aluminum pillared montmorillonite(OH-AlMT) and organic montmorillonite(CTAB-MT). Based on that, the liquid phase reducing method of sodium borohydride was selected to prepare nano zero-valent iron column braced organic montmorillonite(nZVI-CTAB-MT) materials. In this paper, the thermodynamics, isotherms and sorption mechanism of three new separation materials which adsorbed uranyl were discussed.OH-Al-MT was obtained with the hydroxy aluminum as the pillaring reagent. The results of FT-IR and SEM showed that, OH-Al was successfully intercalated into the MT layer with the MT hydrophobicity enhancing and the MT surface roughness increasing respectively. Besides, XRD results indicated that the introduction of OH-Al increased the MT interlayer spacing from 1.491 nm to 1.522 nm. In the neutral aqueous solution, the increases of total carbonate substances and the soluble calcium weakened the OH-Al-MT adsorption properties. In addition, the existing of humic acid inhibited the adsorption of uranium(VI). The adsorption of uranium(VI) on the OH-Al-MT observed the pseudosecond order kinetics model with the control of the chemical reaction and the Freundlich isotherm model for the surface of the non-uniform adsorption. The adsorption of uranium(VI) on the OH-Al-MT and Na-MT was a spontaneous process.MT-CTAB was obtained with the CTAB as the pillaring reagent. FT-IR, SEM and XRD results indicated that the introduction of CTAB into the MT interlayer, increased its spacing from 1.491 nm to 1.905 nm improving the dispersion properties of the MT. In neutral aqueous solution, the total carbonate substances, soluble calcium and humic acid impeded the adsorption properties of CTAB-MT for uranium(VI). The adsorption process of uranium(VI) on the CTAB-MT was in line with the quasi-second order kinetics, which was controlled by the chemical reaction. Both of the Langmuir and Freundlich isotherm model could describe the spontaneous adsorption process of uranium(VI) on the CTAB-MT that was in fact a monolayer and non-uniform surface adsorption. The properties of CTAB-MT were superior to that of OH-Al-MT.With the CTAB-MT as a support material, the n ZVI-CTAB-MT was prepared by the method of sodium borohydride liquid reduction. FT-IR results showed that the n ZVI was successfully intercalated into the CTAB-MT. The SEM results indicated that the spherical nZVI was dispersed into the CTAB-MT. XRD results showed that the nZVI was pillared into the CTAB-MT. In the neutral aqueous solution, the adsorption properties of uranium(VI) on the nZVI and nZVI-CTAB-MT could be weakened by the total carbonate substances, soluble calcium and humus. The adsorption processes of uranium(VI) on the n ZVI and nZVI-CTAB-MT controlled by the chemical reaction were in accord with the model of quasi-second order kinetics. Langmuir and Freundlich isotherm could be used to describe the spontaneous adsorption process of n ZVI-CTAB-MT that included a monolayer and nonuniform surface adsorption.In the condition of 50 mg·L-1 initial uranium concentration, the ionic strength of 0.01 mol·L-1 NaClO4, 4.0 mmol·L-1 total carbonate concentration, 1.0 mmol·L-1 calcium ion concentration, pH = 7, and T = 298.15 K, the maximum adsorption capacities of uranium(VI) on the OH-Al-MT, CTAB-MT, nZVI and nZVI-CTAB-MT were approximately 54.07 mg·g-1, 184.11 mg·g-1, 29.56 mg·g-1 and 254.09 mg·g-1 respectively. On the same conditions, the adsorption capacity of nZVI-CTAB-MT is eight times of nZVI revealing the excellent adsorption performance of nZVI-CTAB-MT. Besides, on the same conditions, the material performances for uranium(VI) adsorption followed the order of nZVI-CTAB-MT> CTABMT> OH-Al-MT> n ZVI.