Adsorption Of Representative Perfluorinated Octane Compounds On Mesoporous Carbon Nitride And Magnetic Mesoporous Carbon Nitride

Perfluorooctane sulfonate (PFOS) and perfluorooctane acid (PFOA) with high-energy carbonefluorine (C-F) bonds are representative perfluorinated octane compounds in the wastewater. Because of its exceptionally high stability, PFOS and PFOA are difficult to decompose by heat, light, oxidation and reduction, biological degradation. Adsorption is an effective and economical method to remove PFOS from wastewater. Mesoporous carbon nitride (MCN) and Magnetic mesoporous carbon nitride (MMCN) were successfully prepared. The overall appearance, internal structure, chemical composition and magnetic properties of MCN and MMCN were evaluated using X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), N2adsorption-desorption analysis, Fourier transform infrared (FT-IR) spectroscopy, X-ray photoelectron spectroscopy (XPS), element analysis, zeta potential and Boehm titration analysis. The adsorption behaviors of perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) on MCN or MMCN were studied.In the calcination temperature at673K,773K and873K, the highly ordered mesoporous structure of MCN were successfully synthesized, and the average pore diameter was about4.2nm. Nitrogen content of MCN decreased with increasing the calcination temperatures. Adsorption results showed that the adsorption capacities of PFOS decreased as the calcination temperatures. Moreover, the adsorption capacities of MCN for PFOS were affected by adsorption time, solution concentrations, solution pH, solution temperatures and co-existing ions, and the solution pH was the most significant factor. After saturating MCN with PFOS,0.1mol/L NaOH solution had a high desorption efficiency. In the study of dynamic experiment, the adsorption effect of adsorption column was strongly depended on the column high, solution flow rate and solution concentrations.When the mass ratio of magnetic particles and MCN-763was1:5, the obtained material kept the mesoporous structure of matrix and had a strong magnetic property. The main components of the magnetic particles were magnetite (Fe3O4), magnetic hematite (γ-Fe2O3) and hematite (a-Fe2O3), which mainly deposited on the surface or inside hole of the matrix. The maximum adsorption capacities of PFOS and PFOA were454.55mg/g and370.37mg/g.0.1mol/L NaOH solution had a high desorption efficiency for the saturated MMCN-673(1:5) with PFOS, whereas0.07mol/L NaOH solution had a high desorption efficiency for the saturated MMCN-673(1:5) with PFOA. After five cycles of adsorption/desorption regeneration, the removal rate of PFOS and PFOA were96.14%and91.96%, respectively, and the adsorbent maintained high magnetic property. The adsorption column was easy to be penetrated and the adsorption was reached saturation with the increase of adsorbent dosage, solution flow rate and solution concentration.