Synthesis Of Magnetic Mesoporous Carbon And Its Application In Remediation Of Water Pollution

Recently, water pollution has become increasingly serious. Because of the superiorities of mesoporous carbons on adsorption and magnetic nanoparticles on solid-liquid separation, a series of magnetic mesoporous carbons nanocomposites were prepared and applied to treat wastewater containing heavy metal and organics. In this study, three mesoporous carbons including magnetic iron doped mesoporous carbon, nitrogen-functionalized magnetic mesoporous carbon and magnetic mesoporous carbon incorporated with polyaniline were successfully synthesized using the hard template method, and several techniques were utilized to characterize their physicochemical properties. The application in wastewater treatment was investigated and the relevant mechanisms were proposed.Chapter 2 of the paper investigated the preparation and application of magnetic iron doped ordered mesoporous carbon(Fe/CMK-3). Specifically, Fe/CMK-3 was firstly prepared via the template method and nano co-casting technology. Then, TEM, FTIR and XPS methods were used to study the morphology, structure and component of the resultant solid. The result indicated that the resultant carbon material maintained ordered mesostructure, high surface area of 679.4 m2/g and excellent magnetic property. Batch experiments were conducted to investigate the removal performance. Fe/CMK-3 exhibited higher Cr(VI) removal efficiency(97%), broader p H scope of application and easier separation compared with pristine ordered mesoporous carbon(CMK-3). The kinetics data were well described by pseudo-second-order kinetic model, and Langmuir model fitted the sorption isotherms commendably. Moreover, the Cr loaded Fe/CMK-3 could be regenerated by 0.01 mol /L Na OH solution, and the removal capacity still reached 70% in the seventh cycle. XPS analysis demonstrated that the Cr(VI) r emoval was a adsorption and synergistic reduction process owing to Cr(III) occurring on the surface of Fe/CMK-3. The results suggested that Fe/CMK-3 had potential superiority in removal of Cr(VI) from wastewater.Chapter 3 of the paper was mainly centered in nitrogen-functionalized magnetic mesoporous carbon. In this chapter, a novel nitrogen-functionalized magnetic ordered mesoporous carbon(N-Fe/OMC) with uniform pore size(3.8 nm) and excellent magnetic property(8.46 emu/g) was fabricated through simple impregnation then polymerization and calcination. The resultant adsorbent exhibited more preferential sorption toward Pb(II) and phenol than simple equivalent mixture of magnetic ordered mesoporous carbon(Fe/OMC) and pristine ordered mesoporous carbon(O MC). Binary adsorption showed that the coexistence of Pb(II) and phenol at low concentrations would slightly accelerate their jointly adsorption because of partial complexation between Pb(II) and phenol. While at high concentrations, Pb(II) adsorption would be inhibited in relation to the competition from phenol, but phenol adsorption was scarcely affected due to the directly phenol molecular adsorption pattern. Pb(II) adsorption was more suitable in alkaline solution and affected by ionic strength on account of electrostatic interaction, whereas phenol adsorption was better in neutral p H and hardly interfered by ionic strength as the adsorption was a physical combination process. Thermodynamics indicated that the uptakes of Pb(II) and phenol were endothermic and exothermic processes, respectively. Moreover, N-Fe/OMC could be regenerated effectively and recycled by using dilute Na OH and acetone solutions. These superior properties demonstrate that N-Fe/OMC is attractive for practical applications in treatment of water contamination by Pb(II) and phenol.Chapter 4 of the paper discussed the application of magnetic mesoporous carbon incorporated with polyaniline(PANI–Fe/OMC) in removal of Cr(VI). Several physicochemical techniques including TEM, FTIR and XPS an alyses confirmed that magnetic iron nanoparticles and amino groups have been successfully bound on the mesoporous matrix. The adsorption capacity of the functionalized material is two- and ten- folds of the magnetic mesoporous carbon(Fe/OMC) and pristine mesoporous silicon(SBA-15), respectively. Solution p H exhibited a remarkable impact on the Cr(VI) adsorption and the maximum uptake amount(172.33 mg/g) occurred at p H 2.0. The well fitting of adsorption process using pseudo –second–order and Langmuir models indicated the chemisorption process of Cr(VI) removal. The regeneration study revealed that PANI–Fe/OMC can be reused without loss of their activity in repetitive adsorption tests. Moreover, the resultant adsorbent can be effectively applied in actual wastewater treatment due to the excellent removal performance in fixed–bed column and real water samples. The interaction between Cr(VI) and PANI–Fe/OMC was investigated by FTIR and XPS analyses. The results indicated that the amino groups on the surface of PANI–Fe/OMC are involved in Cr(VI) uptake, and simultaneously some toxic Cr(VI) were reduced to non –toxic Cr(III) during the removal process.