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Naphthalene (NAP) is a typical gaseous polycyclic aromatic hydrocarbons (PAHs) pollutant that displays toxicological effects on biosystems. Ordered mesoporous carbon has relatively adequate adsorption capacity; however, the attached hydrophilic functional groups were proven to affect the adsorption performance in the presence of moisture. In this paper, trimethylchlorosilane (TMCS) is used to carry out the hydrophobic modification of ordered mesoporous carbon FDU-15, and the adsorption and desorption properties of FDU-15 were studied. Furthermore, the adsorption isotherms of naphthalene on FDU-15 and modified FDU-15 were fitted by L-F equation, and the kinetic parameters of desorption of naphthalene on modified FDU-15 were analyzed based on the method of temperature programming desorption (TPD). The results showed that the micropore volume and specific surface area of FDU-15 were significantly increased after hydrophobically modified by TMCS, and the polar functional groups of the hydrophobically modified FDU-15 were significantly reduced. Furthermore, the adsorption of naphthalene by FDU-15 before and after modification conformed to the L-F equation (R2 > 99%), and the adsorption of naphthalene by modified FDU-5 at low concentration was significantly improved due to the increase of micropores. Based on desorption kinetic performance study of modified FDU-15, it can be seen that the adsorption kinetic characteristics of naphthalene on the modified FDU-15 conform to the mechanical function of the JMA equation. When the mass ratio of TMCs to FDU-15 is 1:10 in the modification process, the pore structure and surface hydrophobicity of the modified FDU-15 reach an excellent balance. At this time, the adsorbent had the optimum desorption performance under experimental conditions, and the desorption activation energy was decreased from 60.98 kJ/mol of FDU-15 to 50.28 kJ/mol. [ABSTRACT FROM AUTHOR]

Modelling dynamic adsorption of sulfur dioxide (SO 2 ) on activated carbons (ACs) is significant in guiding practical desulphurization processes and making highly efficient use of adsorbents in terms of the adsorption rate which largely depends on particle size. In this work, models derived from the Vermeulen and an improved linear driving force (LDF) rate equation were studied for the first time on SO 2 adsorption over AC particles with different sizes. For larger particles (≥3 mm), breakthrough curves predicted by the Vermeulen equation showed good agreement with experimental data, demonstrating that intraparticle diffusion resistance varied with particle size, feed concentration, adsorption time and location. For smaller particles (1 mm), a correction on the volume-averaged adsorption capacity as a function of adsorption time and saturation in the rate equation was developed to avoid the underestimation of adsorption rate due to the inappropriate parabolic concentration profile inherent in the conventional LDF model. By providing a concentration gradient and adsorption rate closer to actual values, the improved LDF equation was confirmed to provide excellent prediction results on 1-mm particles. Different modelling characteristics of the two models indicates varying effects of intraparticle diffusion on adsorption rate with particle size regarding the specificity of SO 2 physisorption on ACs. [ABSTRACT FROM AUTHOR]

The kinetics of the thermal desorption of CO2 adsorbed on zeolite 13X were obtained using a differential thermogravimetric analyser under two different carrier gas conditions. The varying heating rates were set as 8, 12, 16, and 20 K min−1, respectively. The desorption activation energy of the physisorption sites for this experiment evaluated by an integral method without prediction of the reaction order ranged from 12.15 to 14.12 kJ mol−1 (CO2 as the carrier gas) and 43.32 to 50.42 kJ mol−1 (Ar as the carrier gas), respectively. The desorption activation energy of the chemisorption sites ranged from 57.95 to 58.53 kJ mol−1 (CO2 as the carrier gas) and 74.02 to 79.92 kJ mol−1 (Ar as the carrier gas), respectively. [ABSTRACT FROM AUTHOR]

Adsorption is a promising technology for simultaneously capturing nitrogen oxides (NO x) from flue gases and recycling NO 2 as a profitable chemical, for which a robust and efficient adsorbent provides the key step for success in practical applications. This work reports the enhancement of NO x adsorption performances with less cost of desorption energy on Cu-ZSM-5 zeolites prepared by a facile and rapid (690 s) modification method, the incipient-wetness impregnation coupled with microwave drying (IM). In comparisons to H-ZSM-5, Na-ZSM-5 and conventionally liquid-phase ion-exchanged counterparts under sub-1000 ppm NO x feed concentrations and room temperature, the IM sample renders a record NO x adsorption capacity (q t,NOx) of 0.878 mmol/g from dry gas stream on zeolites, and an applicable q t,NOx of 0.1 mmol/g from wet gas stream with a proper copper loading (2.1 wt%). The temperature programmed desorption of NO x on the optimal IM sample saturated with NO x from wet gas stream exhibit primary peak temperature lower than reported Cu-ZSM-5 and significant NO 2 proportion (72.6 %) in desorbed NO x. Deeper insights into advantageous NO x oxidative adsorption over the properly-loaded Cu-ZSM-5 in terms of diverse adsorbate states and competitiveness towards H 2 O were gained, showing IM method a promising sorbent improvement strategy for practical use. [Display omitted] • Cu-ZSM-5 is prepared by incipient-wetness impregnation coupled with microwave drying. • A record NO x adsorption capacity at sub-1000 ppm dry gas feed on zeolites is obtained. • Applicable NO x adsorption capacity at wet feed is gained on properly-loaded Cu-ZSM-5. • Lower NO x desorption temperature and higher NO 2 proportion in desorbed gas are shown. • Advantageous NO x oxidative adsorption competing with H 2 O on Cu-ZSM-5 is revealed. [ABSTRACT FROM AUTHOR]

Adsorption is a promising technology for capturing nitrogen oxides (NO x) from humid flue gases, for which as the preferred NO x adsorbent, zeolite with an appropriate silica to alumina (Si/Al) ratio provides the key step for success in practical applications. In this work, the effects of Si/Al ratio, temperature, relative humidity (RH), and feed gas (NO x -H 2 O(g)–CO 2 –O 2 -N 2) compositions on NO x sorption behavior on HZSM-5 zeolites were systematically investigated, based on a series of characterizations, fixed-bed adsorption and temperature programmed desorption (TPD) tests. The low-silica HZSM-5(25) showed the best performance (326.6 μmol/g and 39.2 μmol/g at dry and 90%RH) as compared to others with higher Si/Al ratios at each RH, in which the roll-up effect was positively correlated with the Si/Al ratios and humidity. O 2 enhanced NO x adsorption and reached an optimal adsorption capacity at the concentration of 14%, while CO 2 had little effect on NO x adsorption. The decrease in temperature increased NO x adsorption capacity on HZSM-5(25), benefitting from NO 2 physisorption as well as satisfactory NO oxidation within the active adsorbent structure. The facile thermal desorption of NO x and significant NO–NO 2 conversion on HZSM-5(25) was exhibited by bimodal TPD peaks at 343–353K and 533–543K respective for NO and NO 2 , in contrast to those on Silicalite-1. A potential "water-resistant" strategy via the enhancement of NO x adsorption competitiveness was revealed, providing a theoretical guideline for NO x adsorbent screening in industrial applications. [Display omitted] • Influential rules of multiple factors on NO x adsorption are systematically explored. • Low-silica HZSM-5 shows the best NO x adsorption performance at each condition. • Contributions of NO oxidation and NO 2 physisorption at varying temperatures are shown. • Greater regenerability of NO x from NO x -H 2 O(g)–CO 2 –O 2 -N 2 feed on HZSM-5 is demonstrated. • A "water-resistant" strategy for enhancing NO x adsorption competitiveness is proposed. [ABSTRACT FROM AUTHOR]

Capturing and recovering naphthalene as a profitable chemical from hot flue gas are of significance in terms of environmental protection with economic benefits, for which the adsorption technology using high-performance sorbents provides the key step for success in practical applications. Carbonaceous materials with hydrophobic natures have been shown to render high affinities with non-polar naphthalene, but remain challenging due to difficulties in tackling the trade-off between adsorption and desorption. This work reports a systematic investigation with deeper insights into adsorption equilibria, kinetics and regenerabilities of gaseous naphthalene on typical carbonaceous sorbents originated from different texture properties, including ordered mesoporous carbons (CMK-3, CMK-5 and FDU-15), carbon nanotubes (SWCNT and MWCNT) and a coconut-shell-based activated carbon (AC). The adsorption isotherm and breakthrough curves at wide feed concentration ranges and temperature programmed desorption curves for each sorbent were obtained along with series of theoretical model fitting. FDU-15 and CMK-5 were demonstrated as superior sorbents with high maximum adsorption capacities (1.13 and 1.735 mmol/g) and low desorption activation energy (62.66 and 72.68 kJ/mol), respectively exhibiting advantages of the 3-dimensional diffusion-controlled desorption upon a hexagonal pore arrangement and the efficient adsorption upon a reasonable mesopore-micropore hierarchical structure, in contrast to poor kinetics on pure microporosity (AC) and 1-dimensional topologies (CNTs). Deeper insights into the morphology-affinity relationship revealed advantageous naphthalene transport behaviors over 3-dimensional ordered mesoporosities with appropriate coexisting microporosities and narrower primary size (2–5 nm) or diverse forms of mesopore, which contribute toward reaching comprehensive balances of sorption performances. [Display omitted] • Adsorption equilibria of gaseous naphthalene on carbonaceous sorbents are obtained. • Regenerability with desorption kinetic triplet for each sorbent is quantified. • Ordered mesoporous carbons, FDU-15 and CMK-5, are demonstrated as superior sorbents. • 3-dimensional ordered mesoporosities with narrower primary size (2–5 nm) are favored. • Micropore-mesopore hierarchical structure gives high adsorption/desorption kinetics. [ABSTRACT FROM AUTHOR]

Conventional flue gas nitrogen oxides (NO x) abatement technologies commonly convert NO x into harmless compounds, while less effort has been made to recycle NO 2 as a profitable chemical in many industries. Towards this end, adsorption is a promising technology for which an advanced technique for NO 2 desorption and efficient sorbent regeneration provides the key step for success in practical applications. This work reports a novel cyclic adsorption process for NO x removal with recycling of NO 2 from iron-ore sintering flue gas of a steel plant. This process using self-prepared and validated pelletized Na-ZSM-5 zeolites as low-cost sorbents involves NO x catalytic adsorption and reversible desorption using multiple hot gas circulations (GC) within the enclosed fixed bed followed by scavenging and purge at mild conditions. In comparison to conventional cyclic processes, greater amount of recyclable NO 2 was obtained, rendering the NO x recovery of >92% and the mean NO 2 concentration of >2% significantly enriched from original 20 ppm in feed gas. A robust adsorption-desorption performance with appreciable NO x working capacity was achieved for up to 16 cycles. The key role of the segmentation of GC in boosting NO x regenerability was addressed, providing an economical three-tower strategy for continuous NO 2 production for practical use. ga1 • NO x removal and with recycling of NO 2 from flue gas was studied through field tests. • Comparisons among different adsorption cycles in NO x removal and recycling were made. • A novel technique for efficient NO 2 desorption and sorbent regeneration was proposed. • NO x recovery of 92% and recyclable desorbed NO 2 concentration of >2% were obtained. • Robust cyclic performance with NO x working capacity of >0.1 mmol/g was demonstrated. [ABSTRACT FROM AUTHOR]

The adsorption of three typical polycyclic aromatic hydrocarbons (PAHs), naphthalene, phenanthrene, and pyrene with different ring numbers, on a common mesoporous material (MCM-41) was simulated based on a well-validated model. The adsorption equilibriums (isotherms), states (angle distributions and density profiles), and interactions (radial distribution functions) of three PAHs within the mesopores were studied in detail. The results show that the simulated isotherms agreed with previous experimental results. Each of the PAHs with flat molecules showed an adsorption configuration that was parallel to the surface of the pore, in the following order according to the degree of arrangement: pyrene (Pyr) > phenanthrene (Phe) > naphthalene (Nap). In terms of the interaction forces, there were no hydrogen bonds or other strong polar forces between the PAHs and MCM-41, and the O–H bond on the adsorbent surface had a unique angle in relation to the PAH molecular plane. The polarities of different H atoms on the PAHs were roughly the same, while those of the C atoms on the PAHs decreased from the molecular centers to the edges. The increasing area of the π-electron plane on the PAHs with the increasing ring number could lead to stronger adsorption interactions, and thus a shorter distance between the adsorbate and the adsorbent. [ABSTRACT FROM AUTHOR]

• The properties of ECSCs are controllable by adjusting the fuel in SCS process. • The superb S bet , V P, and V meso of ECSCs are beneficial to improve the naphthalene adsorption capacity. • ECSCs exhibit unprecedented high capacity, fast kinetics, and low desorption energy. Sorptive capture and recycling of gaseous naphthalene from industrial emissions are of both environmental significance and economic benefit. Constructing carbonaceous sorbents with matchable pore size and adequate active sites is significant towards the trade-off between adsorption and desorption for naphthalene. In this study, we developed a series of porous carbonaceous sorbents (ECSCs) using facile, inexpensive, and effective solution combustion synthesis (SCS) with subsequent calcination and pickling. The MgO@C precursors were fabricated via a fast and self-exothermic combustion reaction, and after calcination and MgO removal by pickling, the tailored pore structure was created. The morphology, porous structure, and surface chemical properties of ECSCs are precisely controlled by adjusting the type and content of fuel in combustion. For the optimized ECSC-G14 prepared on fuel-balanced condition, its layer-by-layer network facilitates adsorption mass transfer, and its high specific surface area (1987 m2·g−1) and abundant 3–6 nm mesoporosity promotes the accessibility of active sites. Consequently, an unprecedented high naphthalene uptake (3.075 mmol·g−1 at 398 K) and fast kinetics (∼1.43 × 10−2 s−1 at 2.82 × 10−3 mol·m−3 feed concentration) were achieved. Combined characterization and molecular calculation revealed the synergistic contribution of O and N to reversible adsorption with superb regenerability (E a of 42.71 kJ·mol−1) and cyclic properties. This study provides an effective strategy and theoretical support to customize the properties of porous carbons, overcoming the adsorption–desorption dilemma for gas purification. [ABSTRACT FROM AUTHOR]

[Display omitted] • Development of oxygen generation from air over zeolite by PSA was reviewed in this work. • Mechanisms of O 2 separation from N 2 over zeolite by adsorption were discussed. • Requirements for zeolite adsorbents to improve the O 2 purity were analyzed. • Effect of impurities in air on the nitrogen–oxygen separation was concluded. The adsorptive generation of oxygen from air has become increasingly important in the chemical and medical industries due to the growing demand for O 2 with high purity. Among the commonly used three methods of cryogenic distillation, pressure swing adsorption (PSA) and membrane separation for N 2 /O 2 separation, PSA has received much attention due to the advantages of small volume, low management cost, and short start-up time, etc. Zeolites, with their unique pore structure, highly polarized pore environment, and abundant ion exchange sites, are widely employed as an efficient adsorbent in N 2 /O 2 separation. Hence, in this work, a review about the application of zeolites in O 2 generation via PSA was performed. In detail, the common PSA techniques applied for O 2 generation were summarized and compared from both the characteristics and application scenarios firstly. Then, the main mechanisms of O 2 separated from N 2 in air over zeolite by adsorption were summarized from three aspects of the steric effect, kinetic effect and equilibrium effect. Based on above, the requirements for silica-alumina zeolite adsorbents to improve the O 2 purity clarified from skeleton topology, extra-framework cations as well as physical & chemical properties. Moreover, the operation conditions and impurities having a significant effect on the product O 2 quality were discussed. Finally, both the challenges and prospects of air separation and O 2 generation are proposed based on existing research results. [ABSTRACT FROM AUTHOR]

An eruptive solution combustion synthesized carbonaceous sorbent (ECSC) with unprecedented naphthalene adsorption and desorption performances is generated by introducing rational mesoporosity and nitrogen groups into a layer-by-layer porous carbon network. The integration of all key elements via careful tuning of morphological, porous, and chemical properties during the synthesis of ECSC opens up vast possibilities to overcome the adsorption–desorption dilemma for low-volatile or large-molecular gases, which offers great opportunities for gas separation and purification applications. [Display omitted] • Carbon sorbent was derived with an facile eruptive solution combustion strategy. • Layer-by-layer network, rational mesoporosity, and reversible sites were integrated. • Unprecedented high adsorption capacity and kinetics for naphthalene were achieved. • Good regenerability with low naphthalene desorption activation energy was obtained. • Moderate sorption affinity of naphthalene-pyridinic N π–π bonding was proposed. Capturing naphthalene as a valuable chemical from waste gases via adsorption on porous sorbent materials is a promising approach to tackle such an environmental health issue with additional economic benefits. However, very few sorbents have simultaneously high adsorption capacity and good regenerability for the large-molecular and low-volatile naphthalene. Here we attempt to address this challenge by integrating key fabrication elements of a layer-by-layer network, rational mesoporosity, and highly reversible sites into a carbonaceous adsorbent (ECSC) using a facile and fast eruptive solution combustion synthesis method. Adsorption breakthrough and temperature-programmed desorption experiments show that the ECSC achieves all-round superior naphthalene capture performance with unprecedented high capacity, fast kinetics, and low desorption energy. The combination of in situ DRIFTS, XPS, and DFT calculations reveals the moderate adsorption affinity of mitigated π–π stacking bonding between tilted naphthalene molecule and surface pyridinic N. This work affords new insights for designing next-generation adsorbents for naphthalene removal and presents a way of overcoming the adsorption–desorption dilemma for gas purification. [ABSTRACT FROM AUTHOR]

Adsorptive removal of gas phase low concentration macromolecular organic component, represented by naphthalene, from the enclosed space using ordered mesoporous carbon (OMC) has been studied by molecular simulation and experimental investigation. The simulation results indicated that both adsorption capacity and adsorption stability of the OMCs for naphthalene decreased with the increase of pore sizes from 2 nm to 8 nm. Characterizations showed that the prepared OMCs had the pore structure similar to the simulated OMCs except for the rough surface. In particular, the adsorption performance of the prepared OMCs was significantly lower than that of the simulated OMCs when pore size was 2 nm and 3 nm, which was attributed to the rough inner surface of these adsorbents, blocking the narrow pore channels and significantly reducing the pore volume. OMC with pore size of 4 nm had the highest adsorption amount for naphthalene. The co-adsorption experiments in the presence of both naphthalene and toluene, acetone or water showed the adsorption performance of OMCs for naphthalene were almost unaffected by the presence of low concentration toluene and acetone, as well as high relative humidity. [Display omitted] • Adsorption of naphthalene by OMCs were investigated by simulation and experiment. • Realistic molecular models for OMCs were constructed by "delete atom" method. • The impact of pore structure on the adsorption of naphthalene was revealed. • OMC with pore size of 4 nm has the highest adsorption capacity for naphthalene. • OMCs show excellent adsorption selectivity and good moisture resistance. [ABSTRACT FROM AUTHOR]

• Influence of coexisting nanoparticles on toluene adsorption was studied. • Competition between gas and particles in interaction with zeolites was addressed. • Reduction of toluene adsorption capacity by particles was up to 16.0 % on K-ZSM-5. • Reduction of toluene adsorption rate by particles was up to 20.3 % on Li-ZSM-5. • Adsorption site occupation and steric hindrance could be caused by nanoparticles. Adsorption as one of the most important air cleaning methods has been extensively applied during which the coexisting airborne nanoparticles (NPs) with sizes close to adsorbent pore sizes could inevitably influence gas adsorption processes. In this work, the influence of sub-20 nm NPs on toluene adsorption on ZSM-5 zeolites exchanged with different cations (Li+, Na+ and K+) were studied based on gas-and-particle coexisting adsorption/filtration tests. Affinities for both toluene and NPs on adsorbents follow Li-ZSM-5 > Na-ZSM-5 > K-ZSM-5 regarding the orders of charge density, pore size, and internal and external specific surface areas. The toluene adsorption was shown to be impaired by coexisting NPs from perspectives of thermodynamics and kinetics. For Li-ZSM-5, Na-ZSM-5 and K-ZSM-5, significant relative reductions of 10.4 %, 10.5 % and 16.0 % in toluene adsorption capacity at the lower feed concentration, and of 20.3 %, 15.2 % and 2.3 % in mass transfer coefficient at the higher feed concentration were observed, respectively. The influential mechanisms regarding competitiveness between toluene and NPs in interaction with cationic and porous surfaces were accordingly proposed, which are of practical significance for selecting robust adsorbents under realistic harsh air conditions. [ABSTRACT FROM AUTHOR]