posted on 2023-03-18, 02:29authored byZhiang Hou, Xiaoqiang An, Kai Zhu, Qingwen Tang, Huachun Lan, Huijuan Liu, Jiuhui Qu
The
adsorption of contaminants by porous carbon has been extensively
studied by conventional isotherm and kinetic methods. However, the
co-adsorption behavior and sorption sites of multiple contaminants
in different-sized pores remain unclear. Herein, the nuclear magnetic
resonance (NMR) approach is performed to investigate the adsorption
mechanism of toluene and cetane in the confined space of carbon at
the molecular level. The ring current effect induces the variation
in the NMR chemical shifts of in-pore adsorbed toluene and cetane,
realizing the identification of pore-dependent adsorption sites for
contaminant removal. Cetane has a slower adsorption kinetic but a
higher binding energy than toluene, which could squeeze toluene from
micropores to larger pores with increasing adsorption quantity. This
leads to a stronger competitive adsorption effect in small micropores
than in mesopores. Accordingly, hierarchical porous carbons are determined
to be the most effective adsorbents for the adsorption of coexisting
contaminants. This study not only provides an effective NMR method
to reveal the adsorption mechanism in the confined space of porous
carbon at the molecular level but also offers new insights into the
pore size-dependent adsorption of activated carbon for petroleum contaminant
treatment.