Abstract
Adsorption is a consequence of surface energy distribution, and the existence of electrostatic bonding suggests that the presence of an external electric field may affect adsorbate/adsorbent interactions. Nevertheless, this aspect has been poorly studied in the literature, except under non-thermal plasma or corona discharge conditions. After having demonstrated in our previous work that the adsorption kinetics of gaseous organic compounds can be enhanced by the presence of an external applied electric field, in this study, we focus on the influence of the electric field on adsorbent and adsorptive interactions. By using a commercially available activated carbon cloth, in addition to increasing the adsorbent mass transfer coefficient by virtue of the increasing intensity of the applied electric field, the results suggest that adsorbent morphology is only influenced by the formation of new surface functional groups. Moreover, enhanced adsorption kinetics and capacity may result from the electrohydrodynamic force induced by the movement of charged and neutral particles towards the adsorbent, as confirmed by the reversibility of the process. Such enhancement results in a negligible increase, of about 3%, in adsorption capacity (i.e., from 91 mmol m−2 Pa−1 for only adsorption to 94 mmol m−2 Pa−1 in the presence of the applied electric field), but also in a dramatic doubling of adsorption kinetics (i.e., from 0.09 min−1 for only adsorption to 0.19 min−1 in the presence of the applied electric field). In reality, the application of an electric field to an activated carbon cloth leads to faster adsorption kinetics, without substantially altering its adsorption capacity.
Highlights
The application of an electric field to separate particles from a gaseous stream is generally known as electrostatic precipitation, and it is a widely adopted technique for removing particulate matter from industrial emissions
We investigated the possibility of coupling such process with the photocatalytic process in order to remove nitrogen oxides (NOx) [5] and volatile organic compounds (VOCs) [6], by using different support materials [7], focusing on the feasibility and on the efficiency of such novel hybrid process
The lower ID /IG ratio of the treated activated carbon cloth (ACC) may suggest the amorphization of the carbon, as reported in the three-stage model reported by Ferrari and Robertson [53]
Summary
The application of an electric field to separate particles from a gaseous stream is generally known as electrostatic precipitation, and it is a widely adopted technique for removing particulate matter from industrial emissions. Electrostatic precipitators (ESPs) are based on Coulombic attractions between charged particles and a collecting plate. That gives the principle of operation: a discharge electrode gives the particles an electrical charge, and they are forced to pass through an electric field. Particles are deflected by the electric field to the collector electrode [1,2]. As an electric field is formed from the application of an electric potential difference to the ESP discharge electrodes, the strength of this electric field is a critical factor in ESP performance. The adsorption process is a conventional technique for removing pollutants from a fluid stream
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