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Wet scrubbing is a low-cost process for disposing of air pollutants. Nevertheless, this method is rarely used for the treatment of volatile organic compounds (VOCs) because of their poor water solubility. In this study, we used a unique wet scrubbing system containing H 2 O 2 and activated carbon (AC)-supported iron oxychloride (FeOCl) nanoparticles to remove airborne dichloroethane (DCE). The operating conditions of the wet scrubber were optimized, and the mechanism was explored. The results showed that the adsorption of dissolved DCE onto AC promoted its transfer from air to water, while the accumulation of DCE on AC facilitated its oxidation by •OH generated on FeOCl catalyst. The wet scrubber performed well at pH 3 and low H 2 O 2 concentrations. By pulsed or continuous dosing H 2 O 2 , the cooperative adsorption-catalytic oxidation allowed long-term DCE removal from air. Benefiting from satisfactory cost-effectiveness, avoidance of toxic byproduct formation, and less corrosion and catalyst poisoning, wet scrubbers coupled with cooperative adsorption and heterogeneous advanced oxidation processes could have broad application potentials in VOC control., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

[Display omitted] Chlorinated volatile organic compounds (CVOCs) are a recalcitrant class of air pollutants, and the strongly oxidizing reactive oxygen species (ROS) generated in advanced oxidation processes (AOPs) are promising to degrade them. In this study, a FeOCl-loaded biomass-derived activated carbon (BAC) has been used as an adsorbent for accumulating CVOCs and catalyst for activating H 2 O 2 to construct a wet scrubber for the removal of airborne CVOCs. In addition to well-developed micropores, the BAC has macropores mimicking those of biostructures, which allows CVOCs to diffuse easily to its adsorption sites and catalytic sites. Probe experiments have revealed HO• to be the dominant ROS in the FeOCl/BAC + H 2 O 2 system. The wet scrubber performs well at pH 3 and H 2 O 2 concentrations as low as a few mM. It is capable of removing over 90% of dichloroethane, trichloroethylene, dichloromethane and chlorobenzene from air. By applying pulsed dosing or continuous dosing to replenish H 2 O 2 to maintain its appropriate concentration, the system achieves good long-term efficiency. A dichloroethane degradation pathway is proposed based on the analysis of intermediates. This work may provide inspiration for the design of catalyst exploiting the inherent structure of biomass for catalytic wet oxidation of CVOCs or other contaminants. [ABSTRACT FROM AUTHOR]

Wet scrubbing coupled with adsorption-enhanced heterogeneous advanced oxidation processes (AOPs) are promising approaches to the treatment of chlorinated volatile organic compounds (CVOCs). However, microporous activated carbon-based adsorbents and catalyst supports have the disadvantage of difficult molecule diffusion. Herein, we have demonstrated that porous graphitized carbon (PGC) allowed faster intra-particle diffusion of organic molecules due to its well-developed mesoporous structure. Therefore, a wet scrubbing system containing H 2 O 2 and a PGC-supported FeOCl catalyst has been developed to effectively remove gaseous dichloroethane, trichloroethylene, dichloromethane and chlorobenzene. The scrubber performed well at pH 3.0 using a FeOCl/PGC dosage of 0.2 g/L and initial H 2 O 2 concentration of 40 mM. Its good long-term performance was achieved by replenishing H 2 O 2 to maintain a suitable concentration. The degradation pathways of dichloroethane have been proposed using a combination of intermediate analysis and density functional theory calculations. PGC-supported catalysts may be desirable bifunctional adsorbent-catalyst materials for wet scrubbing of CVOCs. [Display omitted] • Porous graphitized carbon (PGC) has well-developed mesopores. • Mesopores allows for easy intra-particle diffusion of dissolved CVOCs. • Wet scrubber containing FeOCl/PGC and H 2 O 2 efficiently removes gaseous CVOCs. • Long-term wet scrubbing performance is achieved by replenishing H 2 O 2. • HO• plays a dominant role in FeOCl/PGC-catalyzed peroxide oxidation of CVOCs. [ABSTRACT FROM AUTHOR]

Structured catalysts and reactors have wide applications in environmental remediation and production of important energy-related chemicals. In thermal catalytic processes, external heater are often required to raise the temperature and ignite the reactions, which might lead to huge setups. Herein, we introduce a novel Joule-heat-ignition catalytic reactor. Using Fe-Cr-Al alloy as catalyst substrate, electric currents can pass directly through the substrate, generating Joule heat and bringing the catalysts to the target temperatures. Therefore, the setup can be simplified by omitting the additional heater; the heat produced inside the substrates can be transferred directly to the catalyst coat to achieve rapid ignition; and the reaction temperature can be flexibly controlled by adjusting the input power. In this work, we loaded manganese oxide catalyst onto an alloy wire and used it to build a Joule-heat-ignition reactor for the catalytic oxidation of carbon monoxide and toluene. The anodization pretreatment generated channels on the alloy surface, which effectively enhanced the catalyst loading. The use of alumina as a secondary support also favored catalyst loading and promoted catalyst dispersion. By adding proper amounts of zirconium, the mechanical stability of the catalyst layer increased. The Joule-heat-ignition catalytic system might provide some inspiration in related environmental catalysis. [ABSTRACT FROM AUTHOR]

[Display omitted] • Bamboo-derived porous graphitized carbon is prepared from biomass using simple chemical reagents. • BPGC can have a high specific surface area while having a good degree of graphitization. • The mechanism of BPGC's excellent adsorption effect was revealed by DFT calculation. • BPGC maintains high VOCs adsorption capacity and good recycling performance even under hydrophobic conditions. Biomass-derived activated carbons (BACs) are often used as green adsorbents for the removal of VOCs, however, their abundant surface functional groups severely reduced their adsorption selectivity under humid conditions. In this study, hydrophobic bamboo-derived porous graphitized carbons (BPGCs) were prepared using a combined catalytic graphitization method. The optimal micro-mesoporous BPGC had a large specific surface area of 2181 m2/g and a low surface O/C ratio of 0.038. Under dry conditions, its adsorption capacities for toluene, cyclohexane and ethanol were 6.7, 3.8 and 2.4 mmol/g, respectively. At 80 % relative humidity, its adsorption capacities for toluene and cyclohexane remained 82 % and 66 %, while the uptake of ethanol even increased by 33 %. In the two-component adsorption test, BPGC showed a high selectivity for toluene adsorption over ethanol, with 198 times more toluene than ethanol. The adsorption mechanism at the microscopic molecular level was revealed by DFT calculation. The abundant π electrons and high polarizability of BPGC allow for strong π-π interactions and dispersion forces with non-polar organics, while the abundant oxygen-containing groups on BAC have strong adsorption force on water. The absorption of ethanol by capillary condensed water in mesopores of BPGC may contribute to its increased uptake under humid conditions. BPGC allowed for faster adsorption kinetics than activated carbon. More than 90 % of the adsorbed toluene was desorbed from BPGC at 90 °C. Owing to abundant renewable raw materials, excellent hydrophobicity and desirable textural properties, BPGCs may be promising adsorbents. [ABSTRACT FROM AUTHOR]

Nanosized Co 3 O 4 catalyst was prepared through a dispersion–precipitation method involving a reaction between wet cobalt hydroxide and acetic acid, which forms a colloidal dispersion, and subsequent dilution, which destabilizes and precipitates the colloidal particles. The catalyst had a particle size of 5–15 nm and a specific surface area of 82 m 2 /g. Compared with the analogue prepared by conventional alkali-induced precipitation method, the nanosized catalyst was more reducible and contained a larger amount of active surface oxygen species, as revealed by experiments using temperature-programmed reduction in hydrogen and temperature-programmed desorption of oxygen. The oxygen species could contribute to the observed higher activity in the catalytic oxidation of carbon monoxide and propane. In addition, a kinetics study revealed that the apparent activation energies for carbon monoxide and propane oxidation over the catalyst were 34.0 and 49.5 kJ/mol, respectively, much lower than those over the analogue (54.7 and 71.1 kJ/mol, respectively). Furthermore, a long-term test (76 h) showed that the nanosized catalyst is highly stable. [ABSTRACT FROM AUTHOR]

[Display omitted] • Porous graphitized carbon fiber (PGCF) is prepared from activated carbon fiber. • PGCF has enhanced hydrophobicity and can effectively remove VOCs from humid air. • Toluene-adsorbed PGCF is easily regenerated by low-temperature thermal desorption. Activated carbon fibers (ACFs) are a popular class of adsorbents for volatile organic compounds (VOCs), however, their abundant hydrophilic functional groups greatly limit their selective adsorption capacity for organics under humid conditions. In this work, porous graphitized carbon fibers (PGCFs) with enhanced hydrophobicity were prepared by KOH-promoted catalytic graphitization of viscose-based ACF, and their adsorption capacity for representative VOCs was investigated. Characterizations showed that the PGCFs had reduced O/C ratios, high specific surface areas exceeding 2200 m2/g, and micro-mesoporous structure. Under dry conditions, the adsorption capacity of a typical PGCF for toluene, cyclohexane and ethanol reached 7.2, 4.6 and 2.0 mmol/g, respectively. At 80 % relative humidity, the adsorption capacity for toluene and cyclohexane retained 92 % and 85 %, respectively, while that for ethanol even increased by 54 %. The abundant π electrons and high polarizability of the PGCF strengthened the π-π interaction and dispersion force with non-polar organics, thereby enhancing their removal. The capillary condensed water in mesopores could act as absorbate for the uptake of polar ethanol under humid conditions. The toluene-adsorbed PGCF was effectively regenerated at a low temperature of 80 °C. Benefiting from their excellent adsorption capacity and moisture-resistance, PGCFs may be promising adsorbents to remove VOCs from air. [ABSTRACT FROM AUTHOR]

[Display omitted] • Porous graphitized carbon was prepared through Ni-KOH treatment of activated carbon. • Graphitized carbon features enhanced adsorptive affinity for organics. • π-π interaction allows intensive adsorption of aromatics. • Improved hydrophobicity contributes to enhanced humidity-resistance. • Developed mesopores facilitate mass-transfer of VOC molecules. Generally, air moisture strongly competes with airborne volatile organic compounds (VOCs) when activated carbons (ACs) are used as adsorbent, and the exclusively microporous texture of ACs hinders the mass transfer of the VOCs, lowering the sorbents' efficiency. Here, we introduced a porous graphitized carbon (PGC) with improved hydrophobicity and well-developed mesopores, thereby overcoming the drawbacks. Through Ni-catalyzed graphitization of AC and KOH activation, we fabricated the PGC, having a surface area >1200 m2·g−1. Characterization through X-ray photoelectron spectroscopy and Boehm titration confirmed that PGC exhibited significantly reduced surface oxygen-containing groups over the pristine AC. Thus, PGC features enhanced adsorptive affinity for VOCs, especially the nonpolar ones. In particular, PGC achieved the highest dynamic adsorption capacity (4.63 mmol·g−1) at 298 K toward toluene, attributed to the π-π interactions between the graphene sheet and the aromatic ring. Furthermore, PGC maintained over 70% of its adsorption capacity at a high relative humidity (RH) of 80%, even for a polar VOC (methyl ethyl ketone). Besides, PGC exhibited superior overall mass transfer coefficients and shortened mass transfer zone than AC. Through facile synthesis, the derived PGC could be a promising adsorbent for VOC removal, especially under humid conditions. [ABSTRACT FROM AUTHOR]