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Graphical abstract Highlights • Natural porous minerals were used as VOCs adsorbents. • Adsorption capacity of mineral is linearly related to its specific surface area. • Models fit breakthrough curves, isotherm and kinetic processes well. • The acid stellerite could be a promising adsorbent for VOC adsorption. Abstract The abundance of natural porous minerals and their low cost make them the potential adsorbents for VOCs (volatile organic compounds). In this paper, three natural minerals (diatomite, stellerite and vitric tuff) and their corresponding acid-treated minerals were used as adsorbents. The adsorption performances of minerals were investigated by the adsorption breakthrough curves of VOCs. The results indicated that the properties of organic compounds such as boiling point and polarity and the surface area and pore volume of minerals had obvious effects on the adsorption of VOCs over minerals. Increasing adsorption temperature and relative humidity would have negative effects on the VOC adsorption of minerals. The adsorption capacity of 2-heptanone over acid stellerite decreased by 7.2% as the temperature rose from 25°C to 45°C. The adsorption capacity of acid stellerite for 2-heptanone reduced by 60.9% when relative humidity increased from 0% to 75%. Minerals were tested for five adsorption-regeneration cycles to study the reusability. Better fittings of Thomas model, pseudo-first order kinetics model, and Freundlich model were showed in fitting the adsorption. Overall, porous minerals with high specific surface area and pore volume have promising prospect in VOCs adsorption. [ABSTRACT FROM AUTHOR]

This study evaluated the adsorption of five volatile organic compounds (VOCs) on Opoka, precipitated silica, and palygorskite, to elucidate the effect of their pore size on VOCs adsorption. The adsorption capacity of these adsorbents is not only highly correlated with their surface area and pore volume, but also notably improved by the presence of micropores. The variation in adsorption capacity for different VOCs was primarily influenced by their boiling point and polarity. Palygorskite, which had the smallest total pore volume (0.357 cm3/g) but the largest micropore volume (0.043 cm3/g) among the three adsorbents, exhibited the highest adsorption capacity for all tested VOCs. Additionally, the study constructed slit pore models of palygorskite with micropores (0.5 and 1.5 nm) and mesopores (3.0 and 6.0 nm), calculated and discussed the heat of adsorption, concentration distribution, and interaction energy of VOCs adsorbed on different pore models. The results revealed that the adsorption heat, concentration distribution, total interaction energy, and van der Waals energy decrease with increasing pore size. The concentration of VOCs in 0.5 nm pore was nearly three times that in 6.0 nm pore. This work can also provide guidance for further research on using adsorbents with mixed microporous and mesoporous structures to control VOCs. [Display omitted] ● Adsorption behavior and related mechanisms of 3 adsorbents on VOCs were studied. ● The adsorption capacity was influenced by boiling points and polarities of VOCs. ● The micropores of an adsorbent can greatly improve its ability to adsorb VOCs. ● Effect of palygorskite pore size on VOCs adsorption was studied by simulation. [ABSTRACT FROM AUTHOR]

This work aims to prepare and characterize novel organo-montmorillonites (OMts) using a nonionic surfactant - octylphenol polyoxyethylene ether (OP-10), and apply the materials for the removal of cationic organic dyes. The nonionic surfactant OP-10 can be successfully intercalated into the interlayer of montmorillonite and the obtained OMts still keep cation exchange capacity. The structural configuration of surfactant molecules between clay mineral layers varies from the surfactant loadings. Moreover, OMts with higher surfactant loadings have higher organic carbon content but lower specific surface area. The prepared OMts showed enhanced adsorption capacities towards cationic organic dye methylene blue (MB), and the adsorption amount increases with an increase of surfactant loading. The high adsorption capacity can be attributed to the fact that the novel OMts still keep cationic exchange capacity and OP-10 has plentiful polyoxyethylene ether chains in its molecule structure, which can capture MB molecules through hydrogen bonding. A probable mechanism for the removal of MB was proposed to be a synergistic effect of ion exchange, partition adsorption, hydrogen bonding and electrostatic interactions. Kinetic and isotherm data could be fitted with pseudo-second order model and Langmuir isotherm. The adsorption thermodynamics study has proved the spontaneous and endothermic nature of the adsorption process. The nonionic surfactant modified OMts could be promising candidate adsorbents for the removal of cationic organic dyes. [ABSTRACT FROM AUTHOR]

Mesoporous silica MCM-41 was synthesized by a facile hydrothermal treatment using sodium silicate extracted from natural Opoka as the Si source. The dynamic adsorption and desorption of organic vapors mixture on the MCM-41 were investigated. Characterization of the textural properties of the samples showed that the sample synthesized with a molar ratio of CTAB/Si = 0.16 possessed the largest specific surface area (988 m2/g) and pore volume (1.02 cm3/g), also uniform pore size distribution centered at 2.8 nm. The adsorption capacity of this sample for organic vapors mixture improved remarkably over raw Opoka and reached 158.5 mg/g at 20 ℃, which is comparable to that of commercial activated carbon. The reusability of the adsorbent was tested by 5 adsorption and regeneration cycles. Obtained results demonstrate that the MCM-41 adsorbent can be easily regenerated by thermal desorption in air, and the cumulative heel on the adsorbent can be markedly reduced by increasing the desorption temperature, making it a promising adsorbent for VOCs abatement. ga1 • MCM-41 was prepared from natural Opoka via hydrothermal treatment. • Effect of template on the microstructure of MCM-41 was studied. • Synthesized MCM-41 has a much higher surface area compared to the raw opoka. • MCM-41′s VOC adsorption capacity is comparable to activated carbon. • MCM-41 can be regenerated more efficiently and easily than activated carbon. [ABSTRACT FROM AUTHOR]

Mycotoxins contamination has been a worldwide long-standing issue, which poses tremendous threats to human health and food security. However, the detoxification of various mycotoxins, especially apolar species, is still a big challenge at present. In this study, carbon nanoparticles derived from biopolymer chitosan (Cts) and rectorite supported Cts carbon nanocomposite (Cts@Rec) were fabricated via hydrothermal treatment as efficient mycotoxin adsorbents for apolar zearalenone (ZER). Microstructural analysis revealed that Cts nanoparticles with smaller sizes uniformly distributed on the surface of rectorite, forming the Cts@Rec biocomposite. The obtained two adsorbents contained high organic carbon contents and large specific surface areas, which exhibited superior adsorption efficiency towards ZER. Kinetic study indicated that the adsorption of ZER on Cts and Cts@Rec reached equilibrium within 120 min, and the adsorption process fitted pseudo-second-order kinetic model better. The adsorption isotherms of ZER on both adsorbents matched obviously with linear model, which implied the existence of adsorption/partition model mechanism. The adsorption capacities were found to be positively correlated to the organic carbon contents and specific surface areas, suggesting that organic matter functioned as partition medium for ZER and the enhanced specific surface areas provided sorption sites for ZER. Furthermore, no desorption happened when changed the simulated pH based on the values from gastric fluid to intestinal fluid, confirming the feasibility of resultant Cts and Cts@Rec biocomposite as mycotoxins adsorbents in vivo. Unlabelled Image • Rectorite supported chitosan biocomposite (Cts@Rec) were easily fabricated. • Cts@Rec showed superior adsorption efficiency towards apolar ZER. • The adsorption performance of Cts@Rec kept stable from pH = 3.5 to 6.5. • Hydrophobic interaction charged for the adsorption process of Cts@Rec. [ABSTRACT FROM AUTHOR]