Drastically boosting volatile acetone capture enabled by N-doping activated carbon: An interesting deep surface digging effect

Investigation on removal of multi-component volatile organic compounds in a two-stage plasma catalytic oxidation system - Comparison of X (X=Cu, Fe, Ce and La) doped Mn2O3 catalysts

Mn₂O₃-X catalysts (X = Cu, Fe, Ce and La) were prepared based on γ-Al₂O₃ for the mixture degradation of muti-component volatile organic compounds (VOCs) composed of toluene, acetone, and ethyl acetate. The catalysts were characterized, and the density functional theory (DFT) simulation of ozone adsorption on Mn₂O₃-X were carried out to investigate the influence of adsorption energy on catalytic performance. The results showed that the removal efficiency (RE) of each VOC component was similarly improved by Mn₂O₃-X catalysts, and the greatest increase in VOCs' removal efficiency was obtained (7.8% for toluene, 86.2% for acetone, and 82.5% for ethyl acetate) at a special input energy (SIE) of 700 J L^-1 with Mn₂O₃-La catalyst. Characterization results demonstrated that Mn₂O₃-La catalyst had the highest content of low valence Mn elements and the greatest O_ads/O_latt ratio, as well as the lowest reduction temperature. Mn₂O₃-La catalyst also presented superior catalytic effect in improving carbon balance (CB) and CO₂ selectivity ( [Formula: see text] ). The CB and [Formula: see text] were increased by 47.7% and 12.61% respectively with Mn₂O₃-La at a SIE of 400 J L^-1 compared with that when only γ-Al₂O₃ was applied. The DFT simulation results of ozone adsorption on Mn₂O₃-X catalysts indicated that the adsorption energy of catalyst crystal was related to the catalytic performance of the catalyst. The Mn₂O₃-La/γ-Al₂O₃ catalyst, which had the highest absolute value of adsorption energy, presented the best performance in improving VOCs' RE.

Adsorption/desorption characteristics of low-concentration semi-volatile organic compounds in vapor phase on activated carbon

The adsorption/desorption behaviors of semi-volatile organic compounds (SVOCs: 1,2,3,4-tetrachlorobenzene (TCB) and phenol) in vapor phase by activated carbon (AC) were investigated by the experiments and density functional theory calculation. Investigations showed that at 100-160 °C, the adsorption capacities of TCB and phenol on AC were in the range of 176.6-342.0 mg/g and 24.0-66.4 mg/g, respectively. Increasing the temperature inhibited the SVOCs adsorption. TCB tended to be adsorbed on AC surface by monolayer, whereas the phenol was multilayer adsorption. The stronger interaction between SVOCs and active sites resulted in a higher desorption temperature (TCB: 255-689 °C; phenol: 200-369 °C). The SVOCs adsorption on AC was fitted well by the pseudo-first-order kinetic model, their lower concentration and larger molecular structure influenced the AC external mass transfer and intraparticle diffusion. TCB and phenol were adsorbed on graphite layer by a parallel manner, their highest adsorption energies were -75.59 kJ/mol and -55.00 kJ/mol, respectively. Oxygen-containing groups altered the charge distribution of the atoms at the edge of the graphite layer, which improved the SVOCs adsorption through enhancement of electrostatic interactions and formation of hydrogen bonds. The carboxyl and lactone groups played a critical role in improving the TCB adsorption capacity, while the carboxyl was important for phenol adsorption.