Mycotoxins are secondary metabolites with a high toxicity produced by fungi and widely exist in feeding, thus reducing feed quality and affecting human-being and animal health. Montmorillonite as a feed additive can effectively reduce the risk of mycotoxin absorption by organisms, but its surface is highly hydrophilic, and the binding rate with weak/non-polar mycotoxins (such as OTA) is low. In this paper, OTA/montmorillonite composite adsorption material (i.e., CPC-MT) was prepared with pyridine salt CPC as a modifier. Its structure before and after montmorillonite modification was analyzed. The OTA adsorption behavior of modified montmorillonite was investigated through batch adsorption experiments combined with kinetic and isothermal adsorption models, so as to provide a technical scheme for effective adsorption of mycotoxins in feed.

Cetylpyridine chloride (CPC) modified montmorillonite was prepared in water bath under stirring. The modified product was obtained by centrifugal washing, drying, grinding and sieving. The layer spacing, functional groups and hydrophilicity (i.e., contact angle) of montmorillonite before and after modification were determined by X-ray diffraction (XRD), Fourior tranform infrared spectroscopy (FTIR) and contact angle measurement. In a simulated body fluid environment at different pH values, the adsorption effect of montmorillonite on OTA before and after modification was analyzed, and the adsorption mechanism was further discussed through adsorption kinetics and adsorption isotherm.

The XRD analysis shows that the crystal surface spacing of montmorillonite after CPC modification gradually increases from 1.25 nm to 1.52 nm with the increase of the amount of modifie. The layer spacing of montmorillonite at 1.5 CEC is the maximum, and gradually shifts to a lower angle as the amount of modifier increases. These results indicate that the long carbon chains entering the interlayer or CPC of CP⁺ after ion exchange with the interlayer cations of montmorillonite are combined with montmorillonite due to the electrostatic interaction. According to the organic cation chain length, the angle between the layers of montmorillonite and the layer spacing, the CPC is arranged in the interlayer of montmorillonite at an angle of 13.6°. From the FT-IR analysis, the antisymmetric and symmetric tensile vibration and shear vibration of -CH₂ in CPC and the C-H stretching vibration on CPC benzene ring appear in organic modified montmorillonite, and the intensity of the -CH₂/C-H absorption peak of CPC gradually increases, resulting in a certain degree of change in the lattice of montmorillonite. This indicates that CPC and montmorillonite are combined. From the contact angle analysis, the surface of montmorillonite changes from hydrophilic to hydrophobic, and CP⁺ between montmorillonite layers basically reaches a saturation value at 1.5CEC. The TGA analysis shows that CPC-Mt has a mass loss peak with increased decomposition of organic matter, decreased surface adsorbed water, and increased organic carbon content, which is conducive to the OTA adsorption.

The results of batch adsorption experiment show that as the amount of modifier increases the adsorption rate of X-NMt to OTA is 36.0%, and the adsorption rate of 0.5-2.0 CPC-Mt to OTA is 51.3%, 70.0%, 77.1% and 77.5%, respectively. In addition, the adsorption effect of CPC-Mt on OTA at a certain pH value of a simulated intestinal fluid is slightly better than that of gastric fluid, indicating that no OTA desorption occurs during the whole process of a simulated body fluid.

CPC entered the interlayer of montmorillonite, and the montmorillonite changed from hydrophilic to hydrophobic when using CPC modified montmorillonite. When CPC-Mt was used to adsorb OTA in simulated animal body fluids, the adsorption rate of CPC-Mt increased from 36.0% to 77.5%, compared with that of X-NMt. The adsorption behavior of OTA by CPC-Mt followed the quasi-second-order kinetic adsorption model, indicating that OTA adsorption was controlled by chemical reaction. The adsorption process followed the adsorption/distribution model, and the transformation of CPC-Mt from hydrophilic to hydrophobic played a key role in the adsorption of weak polar OTA. According to the adsorption mechanism analysis, the organic carbon chain of CP⁺ was used as a distribution medium, and the organic part of OTA was absorbed into the modified montmorillonite through hydrophobic distribution when CP⁺ was inserted into montmorillonite. OTA and CP⁺ could adsorb each other due to the electrostatic interaction.

Red mud is a solid waste generated from alumina production, its massive accumulation occupying extensive land areas and leaching alkalis and heavy metals, leading to significant environmental issues such as soil alkalization and groundwater pollution. This study responds to the current demand for sponge city construction via innovatively utilizing red mud as a raw material to produce un-sintered aggregates through a novel pelletization process that leverages similarities between red mud and permeable brick materials. High-strength un-sintered permeable bricks were prepared via integrating mixing, molding, and curing techniques. These bricks improve overall compressive strength and permeability, while drastically reducing energy consumption and environmental impact during production. This approach presents a fresh perspective on red mud utilization and sponge city development, promising the environmental and economic benefits.

The preparation of red mud-based unsintered permeable bricks involved: 1) pelletization, the aged red mud chunks were crushed, then mixed uniformly with P·O 42.5 ordinary Portland cement and water, and fed into a pelletizer for pelletization. The aggregated particles were removed and naturally cured for one week; 2) mixing, different proportions were designed based on a volumetric method, with red mud-based un-sintered aggregates, cement, water, and additives calculated and weighed according to these proportions, then added to a basin and mixed uniformly; 3) pressing, the uniformly mixed slurry was placed and pressed into a mold with the dimensions of 20 cm×15 cm×10 cm by a semi-automatic brick machine; 4) curing, the pressed permeable bricks were demolded and naturally cured for 1-2 d, then placed in a standard curing box for 28 d.

The phase structure and micro-morphology of the material were analyzed by X-ray powder diffraction (XRD) and scanning electron microscopy (SEM). The heavy metal leaching performance of the permeable bricks was analyzed according to the national standards (HJ557-2010). The concentrations of ten metal elements in the leachate were determined inductively coupled plasma mass spectrometry (ICP-MS). In addition, the environmental risk of heavy metal elements in the leachate was evaluated according to the national standards (GB/T 5085.3-2007).

The bulk density (ρ_bv) of red mud-based aggregates is 1 078.50 kg/m³, with an apparent density (ρ_ap) of 1 724.14 kg/m³ and a porosity (v) of 37.45%. The analysis of the water-cement ratio (w_c) on permeable brick performance reveals that increasing w_c from 0.20 to 0.35 gradually enhances the compressive strength. This improvement stems from the increased fluidity and adhesive properties of the cement paste at a higher w_c, facilitating a better aggregate encapsulation and thereby improving the connectivity. However, increasing w_c beyond 0.35 to 0.40 results in a significant decrease in the compressive strength likely due to excessive fluidity causing settling of the cement paste.

The results of target porosity effect on permeable bricks demonstrate a negative correlation with the compressive strength and a positive correlation with the permeability coefficient. A greater porosity leads to increased interconnected pores within the bricks, enhancing water infiltration but reducing contact points crucial for stress transmission. This leads to localized increases in pressure and higher susceptibility to fracturing, thereby impacting the mechanical properties.

The results of foaming agent content effect on permeable brick performance indicate that increasing the foaming agent from 0% (in mass fraction) to 4% slightly increases the permeability coefficient, while marginally decreasing compressive strength. This effect results from hydrogen peroxide decomposition, creating additional pores within the bricks that weaken aggregate bonding and increase porosity. A further increase in foaming agent content reduces the permeability coefficient, while gradually enhancing compressive strength.

The XRD analysis confirms CaCO₃ as a common component in red mud, cement, aggregates, and permeable bricks. The characteristic peaks of red mud and aggregates remain unchanged, indicating no alteration in primary phases of red mud under the un-sintered process. In the permeable bricks, the characteristic peaks of 3CaO·SiO₂ are absent, whereas the peaks of Ca₅(Si₆O₁₆)(OH)₂ appear. This indicates that 3CaO·SiO₂ undergoes a reaction with water under high alkalinity conditions to produce Ca₅(Si₆O₁₆)(OH)₂, consequently boosting the bricks' strength. The microstructural observation of cross-sections and vertical sections reveals abundant micro-voids crucial for permeability. The cross-sections display flaky hydration gels distributed along aggregate surfaces, while the vertical sections exhibit thinner hydration products and flocculent gels.

The results of heavy metal leaching experiments reveal chromium (Cr) as the maximum concentration metal in leachates from red mud-based un-sintered permeable bricks, exceeding 40 μg/L, while other metals are below 10 μg/L. Leachate toxicity is well below the values of the national standards (GB/T 5085.3-2007), confirming compliance with environmental safety standards and minimal environmental risk for red mud-based un-sintered permeable bricks.

Red mud-based un-sintered permeable bricks were prepared through pelletization, mixing, pressing, and curing. The water-cement ratio affected brick's performance. An increase in the water-cement ratio enhanced the fluidity of the slurry and increased compressive strength, but when the ratio exceeded 0.35, the mechanical properties deteriorated. Increasing the target porosity improved permeability but reduced compressive strength. Adding hydrogen peroxide as a foaming agent effectively increased porosity at levels below 4%, but excessive addition led to the reduced performance. The XRD analysis showed that a high alkalinity of red mud promoted the formation of C-S-H gel, enhancing compressive strength. The SEM images of the cross and vertical sections of the permeable brick revealed flaky and flocculent hydration gel products attached to the surfaces of the aggregates. The results of heavy metal leaching experiments indicated that the leaching risk of heavy metals from the permeable bricks was extremely low. This work could provide an effective approach to simultaneously address the challenges of red mud resource utilization and sponge city construction.

Zearalenone (ZEN) as an estrogenic fungal toxin produced by Fusarium graminearum widely presents in grains, corn, wheat and their by-products. The presence of ZEN seriously endangers the health of animal and humanbeing due to the reproductive toxicity, immunotoxicity, genotoxicity, carcinogenic and teratogenic effects. The adsorption method is the most effective way to remove ZEN, and the commonly used adsorbents are silicate minerals. Attapulgite is an advantageous resource in China, which is used as a feed material to enhance immune function and antioxidant capacity, promote intestinal health, and improve animal production performance and product quality. However, it is difficult to realize the efficient removal of low polarity and hydrophobic ZEN using hydrophilic and negatively charged attapulgite. It is thus indispensable to modify attapulgite with cationic surfactants to enhance their surface hydrophobicity and adsorption property toward ZEN. Imidazole ionic liquid surfactant C_nmimBr has lower critical micelle concentration, higher adsorption efficiency and better surface properties than conventional surfactants with the same carbon chain length. In this paper, attapulgite was modified with ionic liquid surfactant C_nmimBr for the efficient adsorption of ZEN.

APT (25.0 g) was dispersed in 250 mL distilled water at a stirring rate of 540 r/min to form a uniform suspension, and different types of C_nmimBr (i.e., C₁₂mimBr, C₁₄mimBr, C₁₆mimBr, and C₁₈mimBr) were added into the suspension with different concentrations (i.e., 0.5%, 1.0%, 2.5%, 3.0%, and 5.0%), respectively. The mixtures of C_nmimBr and APT were stirred at room temperature for 4 h, and then the solid products labeled as C_nmimBr-APT nanocomposites were centrifuged, washed with deionized water until no bromine ions, dried at 105 ℃ for 4 h, and ground to the fine particles below 75 µm.

The removal ratio of C_nmimBr-APT nanocomposites toward ZEN was determined via batch experiments. The influences of C_nmimBr amounts and carbon chain length on the adsorption performance for ZEN were investigated. 1.0% C₁₆mmBr-APT, 2.5% C₁₆mmBr-APT, and 5.0% C₁₆mmBr-APT were selected as adsorbents to investigate the effect of adsorption condition (i.e., adsorbent dosage, contact time, pH value, initial concentration, and coexisting nutrients) on the adsorption performance of ZEN. The adsorption process was analyzed using kinetic and thermodynamic models.

According to the Fourier transform infrared spectra, the relative intensity of C―H bonds at 2 930 cm^-1 and 2 865 cm^-1, and C=N at 1 630 cm^-1 gradually increases with the increase in the carbon chain length and added amount of C_nmimBr, indicating that C_nmimBr is anchored on the APT surface to realize the organic modification. Meanwhile, the organicization degree also increases with the increase in the carbon chain length and C_nmimBr dosage. Furthermore, the modification process does not change the crystal structure of APT, but the specific surface area reduces with the increase in the hydrophobicity, which is beneficial to the efficient removal of ZEN through hydrophobic interaction.

The in-vitro adsorption experiments indicate that the adsorption performance of C_nmimBr-APT nanocomposites is positively associated with C_nmimBr dosage and carbon chain length. The adsorption process follows the pseudo second order kinetic model and Langmuir isotherm. When the modified amount of C₁₆mimBr is 5.0%, the maximum adsorption capacity of C₁₆minBr-APT nanocomposites to ZEN is 7.45 mg·g^-1. Furthermore, pH value and co-existed nutrients (e.g., amino acids, vitamins and minerals) have little effect on the adsorption performance of ZEN.

The novel ZEN adsorbents were prepared based on the organic modification of APT using C_nmimBr with different carbon chain lengths. The results indicated that C_nmimBr modification did not change the crystal structure of APT, while the surface hydrophobicity increased with the increase in the carbon chain length of C_nmimBr. Meanwhile, the adsorption capacity of C_nmimBr-APT nanocomposites toward ZEN increased with the increase in the C_nmimBr dosage, carbon chain length, adsorbent dosage, and initial solution concentration. The adsorption mechanism was mainly due to the hydrophobic interaction between the long organic carbon chains of C_nmimBr and ZEN molecules, and C_nmimBr-APT nanocomposites presented a considerable application potential for the removal of ZEN adsorbents due to the good selective adsorption in the presence multiple nutrients.

Sulfate radical-based advanced oxidation processes (SR-AOPs) are a highly promising technology for water treatment, and their processing capacity is affected by the catalyst. However, the existing catalysts are mostly powder-based and cannot meet the requirements of recovery and mass transfer in practical applications. Catalytic filtration membrane is a functional membrane that combines catalysis and filtration. It provides a support for the catalyst to ensure its recovery, and restricts the reaction to pores, facilitating a close contact between pollutants and active sites, thereby achieving efficient utilization of peroxymonosulfate. Sepiolite is an excellent catalyst carrier because of its excellent thermal stability, great adsorption capacity, and abundant acid-base sites. In addition, sepiolite is a high-quality film-making material with fibers interwoven into a mesh structure in the same or different directions. In the paper, we prepared a CuO/sepiolite catalytic filtration membrane (CuO/sepiolite) with excellent catalytic performance via impregnation-filtering coating-drying-calcination. In addition, the performance and activation mechanism of catalyzing peroxymonosulfate method were also investigated.

0.1g sepiolite was dispersed in 20 mL of 20 mmol/L Cu(NO₃)₂ solution to obtain a suspension A. The suspension A was heated at 30 ℃ and stirred continuously for 3 h. The mixed suspension was filtrated through polyethylene (PE) microfiltration membrane (0.45 μm) and dried at 60 ℃ for 12 h to obtain a precursor. The dried precursor was placed in a muffle furnace and heated at 400 ℃ for 2 h to obtain a catalytic membrane. The catalytic membrane was cut into a circle with a diameter of 50 mm (named CS). A series of catalytic membranes were prepared at different calcination temperatures (i.e., 300, 400, 500, 600 ℃ and 700 ℃) (named CS-X, where X represents the calcination temperature).

The chemical composition of the samples was determined by X-ray fluorescence spectroscopy (XRF). The Cu content was quantitatively measured by an acid dissolution method combined with inductively coupled plasma atomic emission spectroscopy (ICP-AES). The crystal structure was analyzed by X-ray powder diffraction (XRD). The functional groups on the surface of catalytic filtration membranes were detected by Fourier transform infrared spectroscopy (FTIR). The microstructure and structural characteristics of the membrane material were determined by scanning electron microscopy (SEM) and high-resolution transmission electron microscopy.

A lab-scale catalytic filtration system was established to evaluate the catalytic performance of the CS. The inside diameter of filtration is 50 mm and the valid test area of CS is 19.6 cm². The simulated wastewater flowed through the catalytic filtration from top to bottom at a certain flow rate. Before catalytic degradation, a feed PNP solution firstly flowed through the catalytic filtration system to achieve adsorption-desorption equilibrium, and then the catalytic reaction was started by adding a specific mass of peroxymonosulfate (PMS). After a specific interval, filtrate was collected for measurement of absorbance, ion leaching concentration and TOC in alkaline conditions. The removal ratio (R) is calculated by

The catalytic filtration membrane (CS-400) has the optimum catalytic performance when the calcination temperature is 400 ℃ and the concentration of copper nitrate solution is 20 mmol/L. After the continuous catalytic degradation of 15 L of p-nitrophenol solution at a concentration of 10 mg/L, the performance of CS-400 catalytic filtration membrane does not show any degradation, and its structure is not damaged. Hydroxyl radical is the main reactive oxygen species for the degradation of p-nitrophenol in this catalytic reaction system. The CuO/sepiolite catalytic filtration membrane is a potentially valuable peroxymonosulfate catalyst with the promising applications in wastewater treatment.

A novel CuO/sepiolite catalytic filtration membrane was prepared according to the process route of impregnation-filtering-forming-drying-calcination for activating peroxymonosulfate. When the calcination temperature was 400 ℃ and the concentration of Cu(NO₃)₂ was 20 mmol/L, the prepared catalytic filter membrane (CS-400) had the best catalytic performance. After the continuous catalytic degradation of 15 L of p-nitrophenol solution at a concentration of 10 mg/L, the performance of the CS-400 catalytic filtration membrane did not show significant degradation, and its structure was not significantly corroded. The hydroxyl radical is the main reactive oxygen species for the degradation of p-nitrophenol in this catalytic reaction system, and the CuO/sepiolite catalytic filtration membrane is a potentially valuable peroxymonosulfate catalyst for the application in wastewater treatment.

Tourmaline is a kind of borosilicate mineral with complex structure and composition, which is used in the fields of functional materials, environmental protection and healthcare. Since the positive and negative charge centers of tourmaline do not coincide, tourmaline has a natural spontaneous polarization that is one of the most important properties, having its application in various fields. In previous studies, the changes of element occupancy, valence proportion of key elements and crystal structure parameters in tourmaline cause the lattice distortion, resulting in a change of spontaneous polarization intensity. It is thus of great significance to reveal the relationship among the composition, structure and property of tourmaline. In this paper, the control path along iron speciation-microstructure-spontaneous polarization of Fe-Mg tourmaline was investigated to clarify the structure-activity relationship dominated by cation occupancy in Y-site of tourmaline and propose the optimal configuration of tourmaline with the excellent performance.

Six single crystals of tourmaline samples with different Fe contents were collected from different locations in China (i.e., Hebei province, Xinjiang province, Yunnan province and Guangxi province), respectively. After digestion, the chemical compositions of the samples were determined by ICP. The natural tourmaline was crushed by a model RH-800 high-speed multifunctional pulverizer (Zhejiang Ronghao Industry and Trade, China), and ground by a model XPM-Φ100×4 planetary muller (Wuhan Prospecting Machinery Factory, China). The composition of tourmaline was determined by a model 7700x inductively coupled plasma optical emission spectrometry (ICP-OES, Agilent Co., USA). The crystallographic structure of tourmaline was examined by a model X'Pert PRO X-ray diffractometer (XRD, PANalytical B.V., the Netherlands) with Cu K_α radiation over a 2θ range between 3° and 80°. The occupancy of Fe²⁺ and Fe³⁺ at Y and Z sites of tourmaline was characterized by a model MVT-1000Mossbauer spectrometer (Wissel Co., Germany). The crystal structure of tourmaline was characterized by a model Smart APEX-CCD X-ray single-crystal diffractometer (Bruker Co., Germany) with Mo Kα radiation, and the structure refinement was completed by a crystallography software named SHELXS-97. The spontaneous polarization intensity was measured quantitatively and indirectly by an alkali solution method.

The structure difference due to different composition of tourmaline is mainly caused by the element change in Y site, in which Fe element plays a crucial role. Based on the calculation of intrinsic electric dipole moment, the spontaneous polarization intensity of tourmaline along the c-axis is more intense than that in other directions (cylinder), and the T polyhedron is the largest contributor to the intrinsic electric dipole moment of tourmaline. The intrinsic electric dipole moments generated by each polyhedron along the a and b axes cancel each other due to the toroidal symmetrical structure of tourmaline, resulting in a small total intrinsic electric dipole moment.

The intrinsic electric dipole moment and the spontaneous polarization intensity of the six tourmaline samples are in the order GX-1>YN-1>XJ-1>HB-1>XJ-2>HB-2. The more intense the polyhedral distortion is, and the larger the intrinsic electric dipole moment and the more intense the spontaneous polarization will be. For tourmalines with Fe content that is higher than Mg content, the polyhedron distortion of tourmaline and the intrinsic electric dipole moment increase with the increase of Fe²⁺ content and iron atom in Z site. For tourmalines with Fe content that is lower than Mg content, the structure distortion and the intrinsic electric dipole moment decrease with the increase of Fe content, and increases with the increase of Fe²⁺ content.

For the Fe-Mg tourmalines, the Y site is mainly occupied by Fe atoms and Mg atoms, and the change of Mg/Fe molar ratio directly affects the expansion and deformation of Y polyhedron, resulting in the change of tourmaline structure. After the intrinsic electric dipole moment of tourmaline is analyzed at different Mg/Fe ratios, the intrinsic electric dipole moment of tourmaline decreases with the decrease of Fe content when the molar ratio of Mg/Fe is less than 1. This is due to the decrease of Fe²⁺ content, leading to the weakening of structural distortion. The intrinsic electric dipole moment of tourmaline increases with the decrease of Fe content when the Mg/Fe molar ratio is greater than 1, which is consistent with the previous results. For tourmaline with Fe content that is lower than Mg content, the lower the Fe content is, and the more intense the structural distortion and the greater the inherent electric dipole moment will be. When the Mg/Fe molar ratio is greater than 2, the intrinsic electric dipole moment and the spontaneous polarization intensity of tourmaline at different Mg/Fe molar ratios become stable.

For tourmalines with Fe content that was higher than Mg content, the cell volume increased with the increase of magnesium content, and the polyhedron distortion of tourmaline and the intrinsic electric dipole moment increased with the increase of Fe²⁺ content and iron atom in Z site. For tourmalines with Fe content that was lower than Mg content, the cell volume increased with the increase of Fe content, the structural distortion and the intrinsic electric dipole moment decreased with the increase of Fe content, and increased with the increase of Fe²⁺ content. The results of spontaneous polarization test showed that the characteristic properties of tourmaline were consistent with the intrinsic electric dipole moment. The configuration structure-function relationship of tourmaline with Fe as a main factor was revealed via analyzing the variation trend of intrinsic electric dipole moment under the dominance of Y-end positive ion. The performance of tourmaline decreased with the decrease of Fe content when the Mg/Fe molar ratio was less than 1. The performance of tourmaline increased with the decrease of Fe content when the Mg/Fe molar ratio was greater than 1. The spontaneous polarization increased when the Mg/Fe molar ratio was greater than 2.

Hydrophobic organic pollutants in industrial wastewater and oil spillage have attracted wide attention. It is thus important to develop a variety of adsorbents like activated carbon, biochar, zeolite, graphene, etc.. However, carbon-based porous materials exhibit poor thermal stability and flammability, having secure risks during high-temperature applications and thermal regeneration processes. Silicon-based porous materials like zeolite are complex to prepare and difficult to effectively remove multiple organic pollutants simultaneously. Montmorillonite-based adsorbents become popular due to their low cost and environmental friendliness. However, montmorillonite as a powder has challenges in practical applications such as clogging, leakage, and recovery difficulties. It is thus effective in converting montmorillonite into fixed-form aerogel materials.

Polyurethane sponge (PU) as an ideal substrate for developing porous aerogels can enhance the mechanical properties of the adsorbents due to its biodegradability, affordability, low density, and customizable dimensions. In this paper, low-density, recyclable, and cost-effective organic montmorillonite/polyurethane sponge composite aerogels were prepared via ultrasonic swelling and freeze-drying. The composite aerogel was evaluated for its adsorption/absorption capabilities towards benzene, bisphenol A, nitrobenzene, oils, and organic solvents. In addition, the reusability and flammability characteristics of the aerogel were also analyzed.

An organic montmorillonite (i.e., C16Mnt) was prepared with cetyltrimethylammonium bromide to modify montmorillonite. 1 g C16Mnt was added to 20 mL organic solvent (the mass ratio of cyclohexane to tertiary butanol is 9∶1) to prepare a suspension C16Mnt. Chitosan sol was then introduced into the suspension C16Mnt and agitated in a water bath at 50 ℃ for 3 h, yielding a homogeneous sol. Subsequently, PU was immersed in the sol for 5 min to ensure a complete absorption. The sol-loaded PU was subsequently aged at 25 ℃ for 12 h, facilitating the transformation of the sol into a gel. The organic montmorillonite/polyurethane sponge composite aerogel (i.e., PU/CS-C16Mnt) was fabricated via freezing the gel in liquid nitrogen for 10 min and subsequently freeze-drying for 48 h. The composite aerogels, differing in densities (PU25 and PU35), were denoted as PU25/CS-C16Mnt and PU35/CS-C16Mnt, respectively.

PU has a three-dimensional porous network structure and a smooth surface on its skeleton. The pore structure of PU undergoes a significant change after loading with CS-C16Mnt. The pores are filled with numerous organic montmorillonite clusters, resulting in a rougher surface, which is favorable for enhancing the adsorption performance. The incorporation of CS-C16Mnt also improves the hydrophobicity of PU. Furthermore, the infrared spectroscopic analysis reveals that CS-C16Mnt is loaded onto the PU skeleton through covalent bonds and hydrogen bonds formed between PU and CS-C16Mnt.

The PU/CS-C16Mnt exhibits exceptional adsorption capabilities for organic pollutants, based primarily on organic distribution and pore-filling mechanisms. The adsorption results indicate that PU25/CS-C16Mnt has the maximum static adsorption performance for benzene (i.e., 682.3 mg/g). This superior performance can be attributed to the intense interactions with the benzene molecules and C16Mnt, as well as the presence of an abundance of macropores. Besides, PU25/CS-C16Mnt has excellent adsorption properties for bisphenol A and nitrobenzene, achieving adsorption capacities of 339.8 mg/g and 137.0 mg/g, respectively. The infrared spectroscopic results show that O―H and N―H in PU25/CS-C16Mnt participate in the adsorption process. The cyclic adsorption results show that the adsorption capacity of PU25/CS-C16Mnt for bisphenol A decreases from 208.4 mg/g to 154.7 mg/g, and the adsorption capacity of nitrobenzene decreases from 57.9 mg/g to 41.6 mg/g, which is still higher than that of original PU25.

Furthermore, PU25/CS-C16Mnt has good hydrophobicity and lipophilicity, which can selectively absorb oil and organic solvents with the maximum absorption capacity (i.e., 20.8~37.0 g/g) of xylene, gasoline, liquid paraffin, dimethyl silicone oil and carbon tetrachloride. After 10 repeated experiments, the absorption capacity can still maintain 82.8% of the first absorption capacity. Also, PU25/CS-C16Mnt has a good absorption performance (i.e., 7.12 g/g) for grease in actual sewage, and it is easily recyclable. The combustion behavior of PU25/CS-C16Mnt reveals that the incorporation of organic montmorillonite significantly enhances the flammable retardancy of pure PU.

Organic montmorillonite/polyurethane sponge composite aerogel with low-density (i.e., 34.61 mg/cm³), highly hydrophobic and low flammability was synthesized via ultrasonic swelling and freeze-drying. The montmorillonite/polyurethane sponge composite aerogel exhibited exceptional adsorption capabilities for organic pollutants, relying primarily on organic distribution and pore-filling mechanisms. The aerogel demonstrated a static adsorption capacity of 682.3 mg/g for benzene vapor and respective adsorption capacities of 339.8 mg/g for bisphenol A and 137.0 mg/g for nitrobenzene. The absorption capacity for various oils and organic solvents ranged from 20.8-37.0 g/g, with the excellent reusability. Furthermore, montmorillonite/polyurethane sponge composite aerogel exhibited a good adsorption/absorption performance (i.e., 7.12 g/g) for organic contaminants in actual wastewater. This aerogel could be used as a promising montmorillonite-based adsorption material for the treatment of organic pollution.

The utilization of HNT is undergoing a rapid expansion with forthcoming research prospects. In China, high-purity HNT deposits are notably scarce, with most deposits primarily consisting of mixed halloysite-kaolinite deposits. Consequently, there exists a pressing necessity for the advancement of efficient HNT beneficiation or purification methodologies to segregate HNT from kaolinite. Also, there is a growing emphasis on exploring the assembly of HNT into nanomaterials with diverse functional properties, alongside a concerted effort to unravel the influence of HNT surface characteristics, morphology, and structural attributes on the performance of composite materials. Furthermore, it is imperative to align research endeavors with national strategic imperatives, bolstering the development of HNT-based composite functional materials in harmony with the national non-metallic mineral development strategy, particularly within sectors such as information technology, biotechnology, and new energy applications.

The great interest in application of halloysite as an environmental mineral material is due to its unique physicochemical properties such as tubular structure, hydrophilicity, high specific surface area, high stability, ion exchange capacity and negatively charged external surface. The application performance of halloysite in environmental pollution control fields such as water treatment and air pollution control can be greatly improved through surface modification or nanoparticle loading. However, it is necessary to address the corresponding science and technique problems. For instance, it is difficult to achieve 100% pollutant removal efficacy by halloysite in actual complex and diverse natural environments. The recovery and regeneration of halloysite powder after use should be also considered. The large-scale purification technology and surface modification technology of halloysite need to be further optimized. The future development direction in this area includes understanding the interfacial interaction mechanism, optimizing the production process, expanding the application field, and strengthening the combination with other technologies to improve the treatment efficacy. Halloysite is a promising and cost-effective material in pollutant treatment, and future studies should pay more attentions to the improvement of operability, regeneration and processing capacity in practical applications.

Bi₂Te₃-based alloys are the most well-known thermoelectric materials for room-temperature applications. The existing Bi₂Te₃-based thermoelectric materials produced commercially are prepared by a zone melting method, resulting in highly oriented materials with high thermoelectric properties. However, the ingots produced by the zone melting method are prone to disintegration due to the weak van der Waals forces between the layers of Te atoms, leading to the poor mechanical properties and the proclivity for fracture during processing and practical applications. It is thus important to improve the mechanical properties and machinability of Bi₂Te₃-based materials with the excellent thermoelectric properties. This work was to prepare a n-type Bi₂Te_2.7Se_0.3 thermoelectric material via spark plasma sintering combined with hot extrusion (SPS+HE). The parameters affacting hot extrusion process and preparation of n-type Bi₂Te_2.7Se_0.3 materials under different process conditions were optimized, and the thermoelectric performance and mechanical properties were investigated. In addition, the machinability of the extruded Bi₂Te_2.7Se_0.3 material was also analyzed.

The commercial zone-melting crystal rods were pulverized and sintered via spark plasma sintering (SPS) at 350 ℃ and 20 MPa for 5 min. The ingot was then put into a hot extrusion mold, and treated at 390-550 ℃, extrusion speed of 0.05-0.50 mm/s, extrusion ratio of 9∶1, and extrusion angle of 30°. Under the determined hot extrusion parameters, n-type Bi₂Te_2.7Se_0.3 materials were prepared by different processes, i.e., the raw materials were ground for 1 h and then sintered by SPS and subsequent hot extrusion (HE); the raw materials were melted at 700 ℃ for 5 h and then cold-pressed (MT), and sintered by subsequent hot extrusion (HE); the raw materials were melted and cold-pressed, followed by annealing and hot extrusion (MT+AN+HE); and the raw materials were ground for 1.5 h and cold-pressed, followed by hot extrusion (BM+HE). The phase structure was analyzed by X-ray diffraction (XRD, D8 Advance, Bruker Co. Ltd., USA) at room temperature. The microstructure and fracture morphology were determined by scanning electron microscopy (SEM, Supra 55, ZEISS Co., Germany). The electrical conductivity and the Seebeck coefficient were measured by ZEM-3 (ULVAC Co. Ltd., Japan). The thermal diffusivity (λ) was measured by a laser flash method (LFA457, Netzsch Co., Germany). The thermal conductivity was calculated according to κ=λρC_p, where C_p was the heat capacity according to the Neumann-Kopp rule, and the density ρ was measured based on the Archimedes prinicple.

The results show that n-type Bi₂Te_2.7Se_0.3 thermoelectric materials can be prepared under optimum process conditions (i.e., extrusion temperature of 400 ℃ and extrusion speed of 0.05 mm/s). The XRD patterns of all the hot-extruded samples agree well with a rhombohedral structure (JCPDS 50-0954) of Bi₂Te_2.7Se_0.3. No impurity peaks appear. The SEM images reveal that Bi, Te, and Se are homogeneously distributed in the materials without any impurity phases. The electrical conductivity σ of all the samples decreases with increasing temperature, having a metallic conduction behavior. The σ of the MT+AN+HE sample is the maximum value of 1.4×10⁵ S/m. All the samples have negative Seebeck coefficients S, indicating that electrons are the major charge carriers. The S of the SPS+HE sample is the maximum value of 191.0 μV/K. At 300 K, the SPS+HE sample has the maximum power factor PF of 37.0 μW/(cm·K²). However, the PF of the material gradually decreases with the increase of temperature, which is consistent with the change of electrical conductivity and Seebeck coefficient due to the intrinsic excitation. The lattice thermal conductivity of MT+HE sample is the minimum value (i.e., 0.9 W·m^-1·K^-1). The maximum zT value reaches 0.83 at 400 K for SPS+HE sample and its Vickers hardness is 602.5 N/mm², which is twice greater than that of the zone-melting sample. This is mainly due to the dynamic recrystallization process of grain refinement during the hot extrusion process. The machinability of the extruded Bi₂Te_2.7Se_0.3 material are improved. The thermoelectric micron-sized particles with a minimum size of 147 μm can be achieved, providing a promising material for the development of Bi₂Te₃-based thermoelectric micro-devices.

The optimal hot extrusion process parameters for n-type Bi₂Te_2.7Se_0.3 thermoelectric materials were obtained (i.e., extrusion ratio 9∶1, extrusion angle 30°, extrusion temperature 400 K and extrusion speed 0.05 mm/s). A series of n-type Bi₂Te_2.7Se_0.3 thermoelectric material samples were prepared via hot extrusion under the optimum process conditions. The Bi₂Te_2.7Se_0.3 sample prepared by SPS and sebsequent hot extrusion (SPS+HE) had the maximum zT value 0.83 at 400 K, and its mechanical properties were improved. The Vickers hardness of the SPS+HE sample could reach 602.5 N/mm², which was twice greater than that of the zone-melting Bi₂Te_2.7Se_0.3 material. In addition, the machining performance was also improved, and the thermoelectric micron-sized particles with the minimum size of 147 μm could be machined for the extruded Bi₂Te_2.7Se_0.3 sample, providing a promising material for the Bi₂Te₃-based thermoelectric micro-devices.

Silicon is considered as one of the most promising lithium anode materials due to its high lithium storage capacity. However, the volume expansion effect and semiconductor properties of silicon hinder its practical application. Two effective strategies exist for mitigating this issue, i.e., reducing the size of silicon to nanoscale; and introducing non-active matrices to improve stability and conductivity. In recent decades, the incorporation of iron silicide (FeSi₂) with silicon (Si) has attracted much attention due to its high conductivity, mechanical hardness and environmental friendliness. Unfortunately, the Si/FeSi₂ nanocomposites are mainly prepared by high-energy ball milling, which has some drawbacks such as low purity, large particle size, and uncontrollable morphology, making it difficult to achieve the commercial application. Porous silica derived from clay minerals is extensively investigated for the preparation of silicon nanoparticles by magnesiothermic reduction. In addition, porous silica has a large specific surface area, which facilitates the effective dispersion and loading of iron oxides. The reduction of iron oxide and silica dioxide to Fe and Si can be achieved by magnesium. In this paper, a natural montmorillonite (Mnt) with a high content of silica (65%, in mass) was utilized as a raw material. Silicon/iron silicide (Si/FeSi₂) nanocomposites were synthesized via modification of Mnt (including acid etching and iron loading) and molten salt-assisted magnesiothermic reduction.

A porous silica (SiO₂) was prepared via leaching Mnt at a high concentration of HCl. Subsequently, a iron oxide was loaded on SiO₂ via precipitation in different Fe/Si mass ratios (i.e., 0, 10%, and 20%). Modified SiO₂ (Fe-SiO₂) was mixed with Mg and NaCl in a mass ratio of 1.00∶0.85∶3.00. Afterwards, the mixture was heated in an inert atmosphere at 650 ℃ for 5 h in a heating rate of 5 ℃/min. After cooling naturally, the product was washed with 1 mol/L HCl and 1% (in mass) HF in sequence to remove the by-product. Finally, it was rinsed with ultra-pure water until neutral and dried at 80 ℃. The sample were named as Si, Si/FeSi₂-1, and Si-FeSi₂-2, corresponding to the Fe/Si mass ratio of 0, 10%, and 20%, respectively.

The XRD patterns show that Si/FeSi₂ nanocomposites are consisted of Si and ɑ-FeSi₂. An increase in Fe content in precursors leads to a higher α-FeSi₂ content in the product. Based on the results of RIR value method and elemental composition analysis, the mass ratio of FeSi₂ to Si in Si/FeSi₂-1 and Si/FeSi₂-2 is 5% and 10%, respectively. The average grain sizes of Si, Si/FeSi₂-1, and Si/FeSi₂-2 are 20, 40 nm, and 48 nm, respectively, according to Scherrer's equation,. The grain size of silicon increases with the augmentation of Fe content in the precursor. This phenomenon analyzed by both transmission electron microscopy and scanning electron microscopy images is since the melting temperature of silicon nanoparticle is lower than that of bulk silicon (~1 410 ℃), the addition of iron greatly increases the local temperature (ΔH_Fe2O3= -309 kJ/mol vs. ΔH_SiO2= -130 kJ/mol), and the addition of Fe can effectively reduces the melting point of nanocrystalline grains in Fe/Si eutectic alloys. Moreover, the specific surface areas of Si, Si/FeSi₂-1, and Si/FeSi₂-2 are 89, 42 m²/g, and 33 m²/g, respectively. The gradual decrease in specific surface area coincides with the concurrent increase in grain size.

As anode electrodes, Si/FeSi₂ nanocomposites exhibit a higher initial coulombic efficiency, compared with Si due to the smaller specific surface area. The rate performance show that Si exhibits higher capacity than Si/FeSi₂-1 and Si/FeSi₂-2 at a low current density of 0.1 A/g. However, when the current density increases gradually, the capacity of Si is lower than that of Si/FeSi₂-1 and Si/FeSi₂-2. This phenomenon indicates that the incorporation of ɑ-FeSi₂ enhances both electron conduction and ion diffusion rates. After undergoing 500 cycles at a current of 1 A/g, the capacities of Si, Si/FeSi₂-1, and Si/FeSi₂-2 are 417, 781 mA·h/g, and 561 mA·h/g, respectively. The corresponding capacity retention rates are 35%, 77%, and 50%, respectively. The cycling performance demonstrates that Si/FeSi₂ nanocomposites have a more robust structure, compared to the Si electrode. In addition, the cyclic stability of Si/FeSi₂-1 is inferior to that of Si/FeSi₂-2, potentially due to the reduced structural stability resulting from a larger particle size.

The Si/FeSi₂ nanocomposites were prepared via modification of montmorillonite and molten salt-assisted magnesiothermic reduction. This method utilized magnesium powder to reduce Fe₂O₃ and SiO₂ for the in-situ formation of Si/FeSi₂ nanocomposites. The composition of Si and FeSi₂ nanocomposites could be adjusted via altering the ratio of Si/Fe in the precursor. Moreover, the reduction of Fe₂O₃ resulted in an increase in grain size and a decrease in specific surface area of silicon nanoparticles. As anode materials, Si/FeSi₂ composites demonstrated the superior rate performance and cycle stability, compared to Si. This phenomenon could be due to the incorporation of ɑ-FeSi₂, effectively enhancing the kinetics of lithium ions and electrons on the electrode. In addition, as an inert substance, FeSi₂ could reduce the volume expansion effect of silicon, thereby maintaining the stability of electrode structural. The structural stability of the Si/FeSi₂-2 electrode was relatively weaker than that of the Si/FeSi₂-1 electrode. Therefore, Fe content in the precursor could be of paramount importance for achieving high-performance silicon-based nanocomposite anodes.