| In the past few years, the heavy metal pollution in water and soil environment has been more serious and become a hot topic with wide focus. Clay minerals paly an important role in the treatment of heavy metal polluted water and remediation of heavy metal polluted soil. However, clay minerals have some limitations such as low sorption selectivity and stability, low sorption amounts and huge application dosage. The surface modification of clay minerals by surface grafting or intercalation can increase their sorption amounts for heavy metals. But grafting method in organic solvent reflux has low efficiency. It was important for the developments of treatment or remediation of heavy metals to research surface modification of clay minerals and their application in sorption of heavy metal.Sepiolite and palygorskite were selected to prepare mercapto functionalized sepiolite and palygorskite, and amino functionalized palygorskite using high speed shear sol-gel method based on their rheological properties. The functionalized minerals were characterized by XRD, FTIR, SEM/TEM, 29 Si CP/MAS NMR. The results confirmed that the organic groups were grafted on the surface of clay mineral with covalent bond. The high speed shear sol-gel methods was more effective than grafting in organic solvent reflux. The surface modification can significantly increase the sorption amount for heavy metals. The sorption thermodynamics and sorption kinetics were studied in detail and the sorption mechanisms were analyzed with the aid of XPS and 29 Si NMR and other spectroscopies. It was found that sorption of Pb2+ on mercapto functionalized sepiolite was depend on the complexation of Pb2+ and mercapto group, meanwhile with minor physical adsorption with surface hydroxyl group. The sorption mechanism of Cd2+ on amino functionalized palygorskite was precipitation of CdCO3 and complexation of Cd2+ and amino groupsMeanwhile nano iron supported montmorillonite was prepared through ionexchange-reduction effects. Sorption of Pb2+ on nano iron supported montmorillonite was studied in detail and the sorption mechanism was mainly surface complexation and reduction effect. |
