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Highlights: [•] A Ca-montmorillonite was modified with DDTMA and HDTMA through direct ion exchange. [•] The prepared organoclays were characterized by XRD and BET instruments. [•] The adsorption conditions for BPA of organoclays were systematically studied. [•] The study provides a pathway for the removal of BPA from contaminated waters. [ABSTRACT FROM AUTHOR]

Abstract In this study, adsorption and desorption performance of three mineral adsorbents (diatomite, clinoptilolite, and palygorskite) was investigated for abatement of six VOC with distinct physical and chemical properties and functional groups. Among the three mineral adsorbents, palygorskite exhibited the highest adsorption capacity for all the tested VOC as indicated by the adsorption breakthrough curves. Characterization of the adsorbents showed that palygorskite had the highest specific surface area and pore volume. The distinct adsorption capacities of minerals for VOC can be attributed to the difference of VOC's boiling point and polarity. Increasing the adsorption temperature and relative humidity decreased adsorption capacity of the minerals for VOC. Non-polar VOC showed more sensitivity to changes in temperature and relative humidity compared to polar VOC. Desorption performance of the mineral adsorbents was studied in 5-cycle adsorption/desorption experiments. The results indicated that the desorption purge gas has no significant impact on desorption efficiency. However, increasing desorption temperature clearly decreased the cumulative heel on the adsorbent. Moreover, non-polar VOC desorbed better from the mineral surface than polar VOC. Graphical abstract Unlabelled Image Highlights • Adsorption capacity of VOC was affected by its boiling point and polarity. • Polar and non-polar VOC showed different adsorption under different humidity. • Desorption purge gas has no significant effect on the desorption efficiency. • Different regeneration behaviors of polar and non-polar VOC were analyzed. [ABSTRACT FROM AUTHOR]

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]

Graphical abstract Amine functionalized opoka (OP@APTMS) were successfully fabricated via a simple method grafting with APTMS under mild reaction conditions. HCHO can be captured by the highly accessible physical and chemical adsorption sites on the OP@APTMS. The highly efficient adsorption performances for HCHO are critically attributed to the introduction of abundant amine groups on the surface of OP@APTMS. Highlights • OP@APTMS was successfully fabricated through mild reaction conditions. • OP@APTMS exhibited excellent adsorption performance towards HCHO. • The surface amine groups are favorable to the chemical adsorption of HCHO. • OP@APTMS is an excellent and safe candidate for fast removal of indoor HCHO. Abstract In this study, amine functionalized opoka (OP@APTMS) via grafting with 3-aminopropyltrimethoxysilane (APTMS) were obtained through a mild process. The surfaces of the prepared OP@APTMS are functionalized with abundant amine groups. The OP@APTMS have been proven to be effective adsorbents for fast removal of gaseous HCHO, and its adsorption rate is three times more than that of commercial activated carbon (AC). On the other hand, the desorption rate of OP@APTMS-2.0 is extremely lower than that of AC, exhibiting its potential applications as an efficient and safe adsorbent for highly efficient removal of indoor gaseous HCHO. [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]

Oxygen functionalized carbon nanocompositse (O-I@C) based on glucose and illite were obtained through mild hydrothermal process and surface oxidation. The surface properties of the prepared O-I@C were analyzed by Boehm titration, scanning electron microscopy (SEM), energy-dispersive X-ray spectrometry (EDS), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA) and Specific surface area (BET). The results showed that the surfaces of the prepared O-I@C nanocomposites were functionalized with abundant oxygen-containing functional groups (OFGs). The functionalized O-I@C nanocomposites were proven to be effective adsorbents for fast removal of congo red (CR) and methylene blue (MB) from aqueous solution within 10 min. It is demonstrated that the initial pH of dyes solution has an important influence on the adsorption process of both CR and MB, indicating that the OFGs created on the surfaces of the materials are responsible for the promoted adsorption ability. Furthermore, it is also proved that the adsorption isotherms of CR and MB obey the Langmuir model, with the maximum adsorption capacities of 238.40 mg/g and 215.28 mg/g, respectively. In addition, the used materials could be regenerated by washing with NaOH solution and reused at least four times, which exhibits potential applications as efficient and easily reusable adsorbents for the rapid removal of anionic dye CR and cationic dye MB from wastewater. [ABSTRACT FROM AUTHOR]

Carbon @ diatomite (C@DE) nanocomposite was synthesized using glucose as precursor and purified diatomite as carrier through a facile hydrothermal carbonization process. The microstructure and interface properties of the obtained nanocomposites were characterized by SEM, TEM, FTIR, XPS and zeta potential analyzer. A batch adsorption study showed that the adsorption process was very fast and the kinetic data well fitted with pseudo-second-order kinetic model. Compared to pure carbon materials, the C@DE nanocomposite exhibits higher adsorption ability for Cr (VI). This kind of nanocomposite is a promising candidate as an adsorbent for the removal of Cr (VI) ions from wastewater. [ABSTRACT FROM PUBLISHER]

A novel illite@carbon (I@C) nanocomposite adsorbent has been synthesized via a facile hydrothermal carbonization process (HTC) using glucose as carbonaceous source and illite as the carrier. The morphology, microstructure and surface properties of the prepared nanocomposite adsorbent were analyzed by FESEM, TGA, XRD, FT-IR and Zeta potential measurements. Batch experiments were carried out on the adsorption of Cr(VI) to determine the adsorption properties of the composite. The adsorption of Cr(VI) onto the I@C nanocomposite was well described by the pseudo-second-order kinetic model and Langmuir isotherm. Compared with the illite and carbon material (SC) separately, the prepared I@C nanocomposite adsorbent exhibited enhanced adsorption performance for Cr(VI) with a maximum adsorption capacity of 149.25 mg/g, which was higher than that of most reported adsorbents. In addition, the adsorption process was spontaneous and endothermic based on the adsorption thermodynamics study. The adsorption of Cr(VI) by I@C was highly pH-dependent and the optimum adsorption occurred at pH 2.0. The Zeta potential analysis results indicated that the electrostatic interactions between anionic Cr(VI) and the positively charged surface of the adsorbent might be critical to the adsorption mechanism. This study demonstrated that the I@C nanocomposite should be a promising candidate for a low-cost, environmental friendly and highly efficient adsorbent for the removal of toxic Cr(VI) from wastewater. [ABSTRACT FROM AUTHOR]

A modified inorganic bentonite (Na/Al) based on purified Ca-bentonite was prepared through exchanging Al and Na ions in the interlayer space of Ca-bentonite. The structural properties of purified and modified bentonites were characterized by XRD and SEM analysis. Batch experiments were performed for the adsorption of ammonium nitrogen and different experimental conditions were studied in order to investigate the optimum adsorption conditions. Comparative experiments were also carried out for natural Ca-bentonite (RB), unmodified purified bentonite (PB) and modified purified bentonite (MB). Through the thermodynamic analysis, the ammonium nitrogen adsorption process can be spontaneous, the standard heat was − 41.46 kJ mol − 1 , and the adsorption process based on ion exchange adsorption. The ammonium nitrogen adsorption capacity of MB (46.904 mg/g) was improved compared to raw bentonite (RB) (26.631 mg/g), which was among the highest values of ammonium nitrogen adsorption compared with other adsorbents according to the literatures. The described process provides a potential pathway for the removal of ammonium nitrogen at low concentrations encountered in most natural waters. [ABSTRACT FROM AUTHOR]

Diatomite, a porous non-metal mineral, was used as support to prepare TiO 2 /diatomite composites by a modified sol–gel method. The as-prepared composites were calcined at temperatures ranging from 450 to 950 °C. The characterization tests included X-ray powder diffraction (XRD), scanning electron microscopy (SEM) with an energy-dispersive X-ray spectrometer (EDS), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), and nitrogen adsorption/desorption measurements. The XRD analysis indicated that the binary mixtures of anatase and rutile exist in the composites. The morphology analysis confirmed the TiO 2 particles were uniformly immobilized on the surface of diatom with a strong interfacial anchoring strength, which leads to few drain of photocatalytic components during practical applications. In further XPS studies of hybrid catalyst, we found the evidence of the presence of Ti–O–Si bond and increased percentage of surface hydroxyl. In addition, the adsorption capacity and photocatalytic activity of synthesized TiO 2 /diatomite composites were evaluated by studying the degradation kinetics of aqueous Rhodamine B under UV-light irradiation. The photocatalytic degradation was found to follow pseudo-first order kinetics according to the Langmuir–Hinshelwood model. The preferable removal efficiency was observed in composites by 750 °C calcination, which is attributed to a relatively appropriate anatase/rutile mixing ratio of 90/10. [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]

• TiO 2 /diatomite calcined at 550 °C exhibited enhanced VOC degradation efficiency. • Optimal degradation conditions are RH = 0%, flow rate = 1 L/min, and VOC = 10 ppm. • VOC has a high value degradation rate when the composite dosage was 3.76 mg/cm2. • Key parameters had obvious impact on the VOC adsorption and degradation. The TiO 2 /diatomite composites with excellent adsorption and photo-degradation performances were leveraged to investigate the influences of calcination temperature and operating factors on their properties. The results showed that the calcination temperature was closely bound up with the crystallization of TiO 2 and the specific surface area of composite. The composite with calcination temperature of 550 °C exhibited enhanced photocatalytic owing to the high surface area and small TiO 2 crystallite size. A series of dynamic degradation experiments were conducted to investigate the effect of various operating parameters on acetone and p -xylene adsorption/degradation performances of the composite. The results illustrated that when the relative humidity (0–70%), gas flow rate (1–4 L/min), and VOC concentration (10–40 ppm) were set as the low values, the high total organic carbon degradation rate could be acquired. The total organic carbon degradation rate reached to a high value when the composite dosage was 3.76 mg/cm2. With the increase of light intensity (0.48–1.33 mW/cm2), the total organic carbon degradation rate presented an upward trend and then kept stable. The absorbent-photocatalyst hybrid TiO 2 /diatomite composite could be the promising VOC purification materials. [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]