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BACKGROUND: In order to investigate the correlation between the pore size distribution of biomass activated carbon adsorbents (BACAs) and VOCs (volatile organic compounds) adsorption/desorption performance. Four BACAs with same specific surface area but different pore size distribution were prepared under different experimental conditions and processes. RESULTS: The impact of the pore size distribution of BACAs on the adsorption/desorption performance of benzene, toluene and xylene was investigated. The results indicated that the adsorption ability of the prepared BACAs for benzene, toluene and xylene was mostly affected by the pore sizes distributed in the 2.60 ~ 3.25, 2.68 ~ 3.35and 4.20 ~ 4.90 nm ranges, respectively, when the studied BACAs had similar specific surface area (SBET ≈ 1080 m2 g−1). However, the desorption amount of adsorbed benzene molecules mainly relied on the pore structures of BACAs having pore sizes in the 3.95 ~ 4.60 nm range. CONCLUSION: The pore structures of BACAs distributed in different pore size ranges have various effects on the phenyl VOCs adsorption capacity. Benzene adsorption on the BACAs was mainly affected by the microporous structures. The pore structure with larger pore size was more favorable for the desorption of the adsorbed toluene and xylene molecules compared to the adsorbed benzene molecules. Benzene, toluene and xylene had low residual rates in the studied activated carbon adsorbents attesting to their superior regenerative properties. This work could provide an important reference for the design, preparation, and selection of activated carbon adsorbents for the adsorption capacity of benzene, toluene and xylene. © 2024 Society of Chemical Industry (SCI). [ABSTRACT FROM AUTHOR]

Waste Zanthoxylum bungeanum branches were used to prepare activated carbon adsorbents with high mesopore ratio by H3PO4 staged activation method with adding KNO3 additive. The prepared activated carbon adsorbents were characterized by SEM, BET, FT-IR, and XRD. The adsorption properties of the prepared activated carbon adsorbents were evaluated by the toluene adsorption/desorption in air. The quasi-first-order, quasi-second-order, and Bangham models were used to fit the obtained toluene adsorption results. The oxidative etching of KNO3 additive improved the pore-forming ability of the H3PO4 activator to enhance the activation pore-forming effects of the selected biomass raw material. The secondary pore-forming effects of K atoms promoted the effective expansion of the pore diameter in the activated carbon preparation process to prepare activated carbon adsorbents with high mesopore proportion. The specific surface area and mesopore proportion of the activated carbon adsorbents prepared by adding KNO3 additive exceeded 1100 m2/g and 71.00%, respectively, and the toluene adsorption capacity exceeded 370.00 mg/g. The rich mesopore structures can effectively reduce the toluene mass transfer resistance, which can promote the corresponding activated carbon adsorbent to be regenerated by low-temperature (40 °C) thermal desorption. The toluene adsorption on the prepared activated carbon adsorbents includes surface adsorption and diffusion in pore structures, and the toluene adsorption mechanism is more consistent with the Bangham kinetic model. [ABSTRACT FROM AUTHOR]

The CoxOy/AC catalysts were prepared by wet impregnation method for toluene oxidation removal from air. The thermal stability of cobalt nitrate and Co oxide on the activated carbon (AC) support surface was analysed by thermal analysis. The physicochemical properties of the prepared catalysts were characterised by XRD, SEM, H2-TPR, and XPS. AC support with high specific surface area and developed pore structure can promote the dispersion of Co species on its surface to form highly dispersed Co oxide species. The participation of AC supports can promote the partial reduction of Co3O4 species to CoO species to coexist in the prepared CoxOy/AC catalyst. The Co2+/Co3+ ratio was significantly affected by the calcination temperature, and the appropriate Co2+/Co3+ ion pairs in the studied CoxOy/AC catalyst is helpful to the activity of O2 molecules to form reactive oxygen species. The oxygen species composition on the catalyst surface is obviously affected by the calcination temperature, which plays an important role in toluene oxidation reaction. The studied CoxOy/AC catalysts exhibited excellent toluene oxidation removal performances. The conversion of toluene exceeded 97% and 99% at 240°C and 250°C, respectively, and maintained good stability within 700 min. That is to say, the concentration of toluene in the air can be reduced from 10,000 ppm to less than 40 ppm by using the CoxOy/AC catalyst. [ABSTRACT FROM AUTHOR]

Activated carbon adsorbents were prepared by chemical activation with waste Zanthoxylum bungeanum branches as raw materials and H3PO4/H2SO4 as composite activator under different dosages of the auxiliary activator H2SO4. The prepared samples were characterized by scanning electron microscopy (SEM), Brunauer–Emmett–Teller (BET) specific surface area test, Fourier transform infrared spectroscopy (FT-IR), and X-ray diffraction (XRD). The adsorption/desorption performances of low concentration toluene in the air were evaluated, and its reusability was evaluated by the adsorption/desorption cycle. Adsorption results were fitted using the quasi-first, quasi-second, and Bangham models. The adsorption properties of activated carbon adsorbent for toluene in the air show a "volcanic-type change trend" with the increase of H2SO4 dosage. The toluene adsorption properties of the prepared activated carbon adsorbents from high to low are as follows: BAC02 > BAC05 > BAC01 > BAC10 > BAC00. When the mass fraction of auxiliary activator H2SO4 was 2.0%, the adsorption amount of toluene on the prepared BAC02 activated carbon adsorbent increased by 51%, reaching 511 mg/g. After thermal desorption at 200℃, the adsorption performance of toluene was regenerated. The adsorption process of toluene conforms to the quasi-first-order model and Bangham model. The whole adsorption process can be divided into three stages: outer surface adsorption, intra-channel diffusion, and adsorption equilibrium. The addition amount of H2SO4 significantly affected the specific surface area, pore volume, and pore size distribution of the prepared activated carbon adsorbent. [ABSTRACT FROM AUTHOR]

Activated carbon adsorption has been considered the most efficient technology toward VOC removal. The waste biomass as alternates solved the problems of high price and nonrenewable of traditional raw materials. The waste Zanthoxylum bungeanum branches were firstly selected as raw materials to prepare activated carbons. Interestingly, the pore structure and surface chemistry can be successfully controlled by adjusting the heating rate. The hierarchical porous carbons exhibited great potential for toluene adsorption. The micro-mesopore structure possessed unique spatial effect; micropores played a dominant role in adsorption process, especially narrow micropores (pore size ≤ 1.0 nm) emerged stronger adsorptive force toward toluene molecules due to overlapping attractive forces from neighboring pore walls. And mesopores not only displayed excellent transport diffusion but also provided adsorption sites. Additionally, the high graphitization degree enhanced the interaction between graphene layer equipped electron-rich regions and π-electrons on the aromatic ring by the π-π conjugated effect. The hydroxyl and carbonyl functional groups served as chemisorption sites and led to higher adsorption amounts. Fortunately, the regeneration can be achieved by thermal treatment at the low temperature (≤ 150 °C) or even gas purging at room temperature (20 °C), which avoided an explosion accident in the process of high-temperature regeneration. [ABSTRACT FROM AUTHOR]

The catalytic properties of Co-supported activated carbon (AC) catalysts for ethyl acetate catalytic elimination in air were investigated. Results showed that air atmosphere promoted the generation of high-valence state cobalt oxides, and promote the production of reactive oxygen species (ROS) in the Co 3 O 4 /AC catalyst. ROS crucially functioned in improving the catalytic activity of Co 3 O 4 /AC catalysts. Therefore, CoACA catalyst prepared in air exhibited higher catalytic activity than CoACN catalyst prepared in nitrogen, and CoACA catalyst led to high ethyl acetate conversion (>93%) and stability at a low reaction temperature (210 °C). [ABSTRACT FROM AUTHOR]

A series of activated carbon adsorbents with super-high specific surface areas (SHAC) (S BET ≥ 2500 m2 g−1) was prepared and used to adsorb storage hydrogen. The results indicated that the structure of activated carbon adsorbents and hydrogen storage capacity are affected by preparation conditions. The influence of preparation conditions on hydrogen storage capacity can be attributed to changes in the structure of the prepared activated carbon adsorbents. The prepared adsorbents had high hydrogen storage capacity, reaching 5.65 wt % and 4.98 wt % when the adsorption temperatures were 0 °C and 25 °C, respectively, and the pressure was 9.0 MPa. [ABSTRACT FROM AUTHOR]

Abstract: The catalytic properties of Ni, Co, and Co-Ni supported activated carbon (AC) catalysts for oxidation for the removal of carbon monoxide (CO) in H2-rich gas are investigated. Results show that Co x O y /AC and CoO–NiO/AC exhibit higher catalytic activity than NiO/AC and that CoO–NiO/AC gives high CO conversion of above 99.5% at a wide reaction temperature region of 413–463K. The addition of nickel oxide (NiO) can lead to enriched CoO species on the surface of CoO-NiO/AC. The higher catalytic activity and selectivity of CoO-NiO/AC compared with Co x O y /AC can be attributed to NiO playing an important role. [Copyright &y& Elsevier]

The waste biomass was used as raw materials to prepare activated carbon adsorbents with micro-mesoporous structure. And the prepared activated carbon adsorbents were used to adsorption remove toluene from air, which can achieve the goal of "treat waste with waste". In this paper, biomass activated carbon adsorbents with micro‒mesoporous structure were prepared by two-stage process of "low temperature carbonization‒high temperature activation" using waste biomass as raw materials and H 3 PO 4 as activator. The obtained results show that the activation temperature can significantly affect the structural characteristics, graphitization degree and surface chemical properties of the prepared adsorbents, and the toluene adsorption and regeneration performances of the adsorbent are significantly affected by its physicochemical properties. High thermal desorption temperature (100 °C) can destroy the strong interaction between the oxygen atoms of the oxygen-containing functional groups on the surface of the adsorbent and the p -electrons of toluene aromatic ring, thus realizing the desorption of corresponding adsorbed toluene molecules. The low heat treatment temperature of 60 °C can destroy the strong adsorption from narrow micropores for toluene and π ‒ π conjugation effect between the adsorbent and toluene molecules, which can realize the corresponding adsorbed toluene molecules to be desorbed. When the activation temperature is 650 °C, the activated carbon adsorbent with surface area of 1006.2 m2/g, micro-mesoporous structure and mesoporous proportion of 65.5% can be prepared. The adsorption capacity of toluene can reach 417.0 mg/g, and the toluene thermal desorption regeneration can be realized at 60 °C. The results indicate that it is a promising adsorbent material for toluene removal from air [Display omitted] • Biomass activated carbons with typical micro−mesopore structure were prepared. • The spatial effect from micro-mesopore structure can promote toluene adsorption. • Surface composition and pore structure can affect toluene adsorption/desorption. • Toluene adsorption capacity can reach 417.0 mg/g. [ABSTRACT FROM AUTHOR]

Abstract: The present work investigates the catalytic properties of the Ni, Co and Co-Ni supported activated carbon (AC) catalysts for the selective oxidation of carbon monoxide in an excess hydrogen gas. The results shows that Co/AC and Co-Ni/AC exhibit a higher catalytic activity than Ni/AC, meanwhile, Co-Ni/AC gives a high CO conversion in a wide reaction temperature region of 130–150°C, the CO conversion can reach up to above 99.5%. The X-ray power diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) characterizations show that Co3O4 is the main cobalt oxide phase in Co/AC and Co-Ni/AC catalysts. The XRD and temperature-programmed reduction (TPR) results indicate that Co3O4 species of Co-Ni/AC exhibits a higher dispersion than that on Co/AC. Based on the XPS results, the function of nickel oxide in Co-Ni/AC is to enrich Co3O4 species, and decrease the electronic cloud density of cobalt. Therefore, we conclude that Co3O4 species is an important catalytic active center, the higher activity of Co-Ni/AC in comparison with Co/AC is attributed to the higher dispersion of active Co3O4 species and the lower electronic cloud density of cobalt on the surface of Co-Ni/AC. [Copyright &y& Elsevier]

We used an impregnation method to prepare CuO/AC (activated carbon) composite materials of different CuO content and characterized them via scanning electron microscope (SEM), Brunauer–Emmett–Teller (BET), and Fourier transform infrared spectroscopy (FT-IR). The effect of CuO content on toluene adsorption/desorption was evaluated. We explored the reusability of AC and AC03 (CuO modified AC with CuO loading 0.3 wt.%) adsorbents via toluene adsorption/desorption cycle testing. We used quasi-first- and quasi-second-order models, the Bangham model, and the Weber–Morris model to fit the toluene adsorption data. The introduction of CuO species evidently improved the adsorption performance of activated carbon toward toluene. The CuO content markedly affected the specific surface area, CuO dispersal, the numbers of oxygen-containing functional groups on the surface, and adsorption performance of the prepared composite adsorbents. Low CuO content was not favorable for the formation of active adsorption sites, while high content greatly reduced the specific surface area, and even covered active adsorption sites. The toluene adsorption performance varied in the order AC03 > AC02 > AC05 > AC08 > AC01 (AC03, AC02, AC05, AC08 and AC01 are CuO modifying AC with CuO loading 0.3, 0.2, 0.5 0.8 and 0.1 wt.%, respectively). The breakthrough time and toluene adsorption capacity of the AC03 composite adsorbent were 94 min and 701.8 mg/g, respectively, and the recycling efficiency was 92.8% after thermal desorption at 200°C. The adsorption process was best described by the Bangham model and adsorption could be divided into three stages. Unlabelled Image [ABSTRACT FROM AUTHOR]

Waste biomass is used as raw material to prepare activated carbons for the volatile organic compounds (VOCs) adsorption elimination, which is an effective way to solve the waste biomass resource utilization and air pollution problems. Zanthoxylum bungeanum branches activated carbons with rich micropore structures were prepared by adopting H 3 PO 4 low-temperature hydrothermal pretreatment activation method. The prepared activated carbons were characterized by Brunauer-Emmett-Teller (BET), Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD). The toluene adsorption/desorption performances and reusability were also tested to evaluate the application value of the prepared activated carbons. The toluene adsorption capacity increased with the rising of hydrothermal pretreatment temperature. When hydrothermal pretreatment temperature increased from 100 °C to 180 °C, the specific surface area of the prepared activated carbons increased from 956.0 to 1290.9 m2/g. And the micropore ratio of the prepared activated carbons markedly increased from 30.55 % to 63.35 %. Interestingly, the linear fitting results of toluene adsorption capacity and pore structures showed that the micropore volume and toluene adsorption capacity had maximum correlation. The micropore volume increased from 0.40 to 0.56 cm3/g, and the toluene adsorption capacity increased from 309.80 to 532.89 mg/g with the increase of hydrothermal pretreatment temperature. Toluene adsorption results were fitted by quasi-first, quasi-second, and Bangham models to analyze the toluene diffusion mechanism. The toluene adsorption process of all studied samples conformed to the Bangham kinetic model, which indicated that the diffusion mechanism of toluene adsorption process mainly followed intra-particle diffusion. Besides, the toluene adsorption capacity of the prepared biomass activated carbons could be regenerated at relatively low thermal desorption temperature (≤150 °C). [Display omitted] • The activated carbon pore structures are obviously affected by the hydrothermal pretreatment temperature. • H 3 PO 4 hydrothermal pretreatment activation can prepare activated carbons with high micropore ratio. • Toluene adsorption capacity of the biomass activated carbons could be regenerated at low temperature. • The toluene adsorption process mainly was intra-particle diffusion. [ABSTRACT FROM AUTHOR]