Latest ArticlesGeological polymer (zinc slag/Metakaolin geopolymer, ZMG) was synthesized by using zinc slag and metakaolin as raw materials and phosphoric acid as activating agent. The effects of the ratio of raw materials on the mechanical properties, formation of mineral phases, microstructure and pore size distribution of geopolymers were studied. The geopolymer was employed as Fenton-like catalyst for degradation of direct copper salt blue 2R simulated dye wastewater. The effects of the ratio of raw materials, catalyst dosage, pH value and H2O2 concentration on dye degradation rate were systematically investigated. The results showed that the 7-day compressive strength of ZMG-50 geological polymer with a zinc slag proportion of 50% (in mass fraction) could reach 19.9 MPa. Zinc slag can eliminate mechanical pores, improve mesoporous structure and increase specific surface area of geopolymer. The catalytic results showed that ZMG-50 had the best catalytic performance under the conditions of catalyst dosage of 8 g/L, pH value of 2.5 and H2O2 concentration of 0.32 mmol/L, the degradation rate of direct copper salt blue 2R dye could reach 96.2% after 42 min reaction, and it had good stability and reuse performance.
Octahedral cations of acid-treated palygorskite clay (Pal) were partially replaced by Cu2+ via hydrothermal method to achieve lattice reconstruction (Cu-Pal). CuO quantum dots (CuO QDs) were grown in situ on the surface of Cu-Pal by adjust the pH and thermal treatment in case of excess Cu2+, which led to the formation of CuO QDs/Cu-Pal nanocomposite toward photocatalytic nitrogen fixation. The influence of Cu2+ content on the microstructure, optical property and band gap structure of Pal were studied. Results showed that the Cu substitution narrowed the band gap of Pal which extended the light response range from ultraviolet light to visible light. When the Cu2+ content exceeded 5% (in mass fraction), CuO QDs on the Cu-Pal surface effectively promoted the absorption of NIR light due to its rather low band gap (1.2 eV). 20% Cu-Pal formed the best-matched Type-I heterostructure and demonstrated the highest photocatalytic nitrogen fixation performance due to the enhanced charge separation.
Attapulgite and wollastonite powders modified by a mechanochemical method were added to polytetrafluoroethylene (PTFE), and then the mineral/polymer composite was prepared by mechanical stirring and cold pressing sintering. The physical and chemical properties, friction and wear characteristics of the composite were investigated X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, thermogravimetry-differential scanning calorimetry, polarized microscopy, X-ray photoelectron spectroscopy, Shore hardness test and ring block friction and wear test, respectively. The results show that the crystallinity and glass transition temperature of the PTFE composite decrease, the hardness increases, the friction coefficient increases slightly, and the wear rate decreases significantly after adding attapulgite and wollastonite into the composite. It is indicated that attapulgite and wollastonite are beneficial to the formation of the transfer film on the surface of the metal friction pair, thus effectively improving the self-adaptability of the friction interface between the PTFE composite and the counter metal friction pair and reducing the wear rate of the friction pair.
Clustered crystals of Silicalite-1 forming spherical-like structures were synthesized by a solvent-free solid-state method using activated carbon as a hard template. The influence of activated carbon dosage on the Silicalite-1 zeolite was explored by X-ray diffraction, specific surface area analysis, scanning electron microscopy, transmission electron microscopy, infrared spectroscopy, and X-ray photoelectric spectroscopy. The results show that the C—O—Si bond is formed between hydroxyl groups on the surface of activated carbon and silicic acid, growing and aggregating along the activated carbon and formed spherical-like Silicalite-1 zeolites after calcination. The spherical-like Silicalite-1 prepared with 10% (in mass fraction) activated carbon has a greater crystallinity with great specific surface area and pore volume as well as uniform particle size.
The integrity of the seed layer was improved by adding SiO2-ZrO2 nano-sized sol into the seed solution on macroporous α-Al2O3 carrier for the preparation of high-performance mordenite membranes. The effect of SiO2-ZrO2 sol amount added in the seed crystal on the seed layer and zeolite membrane was investigated. The results show that the pervaporation performance of mordenite membranes is improved by the addition of SiO2-ZrO2 sols. The flux and separation factor decreases slightly as the concentration increases. When 0.5% (in mass fraction) SiO2-ZrO2 sol is added into the seed crystal, the permeation flux and separation factor can reach 0.94 kg/(m2·h) and 5 285 by a pervaporation of 90% (in mass fraction) acetic acid/water solution at 75℃. It is indicated that SiO2-ZrO2 sol improves the dispersion of the seed in the solution. The mordenite membrane prepared by this method has good repeatability and acid resistance.
Cation exchange capacity (CEC) is an essential physicochemical index of clayey soil, which can characterize the physicomechanical properties of clayey soil, and methylene blue method can quickly determine the CEC of clayey soil. Therefore, methylene blue method (MB method), ammonium chloride ammonia water exchange method (ammonia method), and barium chloride buffer method (barium method) were used to measure the CEC of several typical clayey soils, to explore the applicability of MB method. The results show that the ammonia method and barium method are consistent, but MB method is different from ammonia method and barium method; The test result is low when the CEC is low, and the test result is high when the CEC is high. The adsorption behavior of methylene blue to clayey soil was analyzed by X ray diffraction test, which was found that methylene blue molecules were adsorbed on the surface when the CEC was lower (less than 40mmol/100g); When the CEC was higher (greater than 40 mmol/100 g), a large number of methylene blue molecules were absorbed between layers. Combined with the results of X ray diffraction, the results of the MB method are modified by the change of basal spacing (d001). The results of the MB method are modified by empirical relation at low CEC and modified by d001 at high CEC, and good results are obtained.
A SiO@TiO2/C composite was synthesized by a sol-gel method and a subsequent high-temperature solid-phase method. The results show that SiO@TiO2/C material exhibits an excellent cycling and rating performance due to the promotion of TiO2 on the interface stability and lithium-ion diffusion process. A high specific capacity of 710 mA·h/g is achieved after 150 cycles at a current density of 1 A/g, and the reversible capacity is 430 mA·h/g at a high current density of 4 A/g.
Si/C@graphene(GR)/graphite(G) composite anode materials were prepared by a simple and easy-to-operate wet coating method with silicon nanoparticles and graphite as main raw materials, fatty alcohol polyoxyethylene ether as a surfactant and graphene. The effect of allocation ratio on the composition, morphology and electrochemical performance of the composite materials was investigated. The results show that the prepared composite materials exhibit a superior cycling stability, and the volume expansion alleviates. When the silicon nanoparticles content is 10%, the initial discharge capacity is approximately 730 mA·h/g. After 100 cycles at a current density of 100 mA/g, the discharge capacity can stably maintain at 500 mA·h/g. The initial coulomb efficiency reaches 87.27%, revealing a great improvement in comparison with the efficiency of pure silicon material (i.e., less than 70%).
This review represented recent work on minerals application in electrochemical energy storage, i.e., the use of minerals in electrodes, electrolytes and separators of secondary batteries or supercapacitors. In addition, the existing problems, challenges and future development in this field were also described.
Different amounts of NaH2PO2 were used to treat lithium-rich cathode materials. The results show that the material treated by 4% (in mass fraction) NaH2PO2 exhibits an excellent cycle stability with 85.3% of capacity retention after 150 cycles at 0.5 C and a high Coulombic efficiency. The enhanced electrochemical performance is attributed to the two following aspects. One aspect is that NaH2PO2 pyrolysis produces reducing PH3 gas, which reacts with the active oxygen in the surface layer of the lithium-rich cathode materials to yield oxygen vacancy, thus effectively reducing the irreversible capacity loss in the first charge process. Another is that NaH2PO2 pyrolysis treatment induces Na+ doping, which can effectively stabilize the lattice structure and inhibit phase transition, and accelerate Li+ diffusion and reduce the electrochemical impedance. In addition, the formed Na4P2O7 coating can protect the electrode material and reduce the dissolution of the transition metal, thereby improving the cycle stability.
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