Experimental Study on PCDD/Fs Adsorption onto Nano-Graphite

The adsorption of the 17 toxic 2,3,7,8-substituted dioxin congeners onto graphite was investigated using a laboratory-scale fixed-bed adsorption system. First, the morphology and microstructure of graphite were characterized by Scanning Electron Microscopy and Brunauer-Emmer-Teller surface estimation. Removal efficiency of the 17 toxic PCDD/Fs varies from 89.31% to 99.96% and the amount adsorbed on graphite is a linear function of the inlet concentration of PCDD/Fs, as it was varied from 2.3–20.7 ng I-TEQ Nm–3. Operating over 3 hours, it is observed that the saturation time of fixed-bed adsorbers is less when the inlet concentration is higher. The removal efficiency of dioxin depends on vapour pressure and rises strongly with increasing chlorine substitution number. Removal efficiencies strongly correlate with vapour pressure, with R2 0.96 for PCDDs and 0.99 for PCDFs, respectively. The removal efficiency of dioxin decreases linearly as the temperature increased (R2 = 0.99). Possibly, π-π interactions between PCDD/Fs and graphite sheets lead to a high adsorption capacity of dioxin. The high mesopores volume and pore structure of graphite are critical factors when adsorbing dioxin.