The Research Of Adsorption And Catalytic Oxidation Technology With Carbon Xerogels For The Removal Of Pollutants In Micro-polluted Water

Application of carbon xerogels is one of the hottest subjects in the field of material research. In our work a series of metal-doped and non-metal-doped xerogels were synthesized by the sol-gel method and their performance was evaluated for the catalytic ozonation and the adsorption of simulated micro-polluted water containing orth-dichlorobenzen (o-DCB) and humic acid (HA), respectively.The obtained samples were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), nitrogen adsorption and desorption, and mercury porosimetry. The results were as follows:as to non-metal-doped xerogels, the size of surface xerogel particles increased with the increase of R/C values (the stoichiometric molar ratio of organic precursor and catalyst). When the R/C value was 800, the surface area of the xerogel was 546 m2/g, the pore size distribution was within the region of 20-80 nm, and the mesopore volume was up to 1.31 cm3/g. As to metal-doped xerogels, Fe3+ oxides and Mn3+ oxides existed in Fe-doped xerogel (XFe) and Mn-doped xerogel (XMn), respectively, and the metallic particles were well distributed over the xerogel supports.The performance of non-supported carbon xerogels was evaluated for adsorption of target pollutants. The kinetic adsorption and equilibrium adsorption results indicated that the adsorption ability of o-DCB onto non-supported carbon xerogels depended on the surface area of the adsorbent, and the three carbon xerogel (CX200, CX800 and CX1500) with the surface area of 518-546 m2/g were good adsorbents of o-DCB. However, as to HA, the adsorption capability was related to the mesopore volume, and the carbon xerogel CX800 with more mesopore was the most efficient adsorbent within the three carbon xerogels. Meanwhile, CX800 showed better adsorption property of HA than activated carbon and carbon nanotubes. Therefore, CX800 is a promising adsorbent for HA.The performance of metal-doped xerogels was evaluated for the catalytic ozonation of target pollutants. The results indicated that the removal rate of o-DCB increased to 58% and 72% with catalytic ozonation using XFe and XMn, respectively, while it was 44% with single ozonation. And the usage of turt-butyl alcohol approved the existence of hydroxyl radical species. The good catalytic abilities of XFe and XMn were due to the existence of Fe3+ oxides and Mn3+ oxides in XFe and XMn, respectively, along with the better distribution of metallic particles over the xerogel supports. Meanwhile, the metal leaching from the metal-doped xerogel to the water solution was determined in order to test the stability of the catalysts, and about 2% and 8% metal leaching for XFe and XMn was reached within 5 h, which suggests that metal-doped xerogels are promising catalysts for ozonation process.