Physicochemical properties of nano-pore adsorbents to remove volatile organic compounds in aqueous phase

Abstract

The nano-pore adsorbents, which were waste-reclaimed (WR), shale-based (S), red clay-based (R), and blue kaolin-based (B), were investigated for their physicochemical characteristics to remove benzene, toluene, ethylbenzene and xylene (BTEX). The BET and SEM-EDS analysis showed that WR, which was a mixture of bottom ashes from a power plant and dredged soil, had the larger surface area (i.e. 14.56 m2 g-1), the rougher surface topography, and the higher total iron (i.e. 5.46 wt% of Fe) than others. Moreover, the XRD analysis indicated that all adsorbents contained aluminum-silica complexes and particularly, both S and WR also contained the iron complexes. The iron complex on S was identified as hercynite (FeAl2O4) while two types of iron oxides (i.e. hematite (α-Fe2O3) and maghemite (γ-Fe2O3)) existed on the surface of WR. Langmuir model generally predicted BTEX adsorption on nano-pore adsorbents and the calculated adsorption capacities (Q0) of WR for BTEX were 0.752, 3.793, 1.678, and 4.902 mg g-1, respectively. In addition, the more BTEX was removed in H2O2/WR system than others. This relatively high BTEX removal by H2O2/WR could be explained by both the larger surface area and catalytic property, which was mainly from the coexistence of hematite and maghemite. Moreover, even though S had hercynite, it did not show much catalytic properties to degrade BTEX in solution.