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Chemically activated carbon microspheres (CACms) are synthesized by sulfonation and carbonization of PVA (polyvinyl alcohol) microspheres, which is prepared by hydrothermal method with the assistance of FeCl 3 . The as-prepared samples are characterized by SEM, XRD and FTIR measurement. Functional carbon microspheres with sulfonic group are found to be excellent adsorbents for cation dye removal with a higher adsorption capacity. Methylene blue (MB) as a typical kind of cation dye is chosen to investigate the adsorption performance of CACms. The parameters, such as pH, temperature, contact time, concentration of adsorbate, are employed to study the influence for adsorption capacity. The obtained results suggest that CACmc can effectively adsorb methylene blue with adsorption capacity increasing from 474.6 to 602.4 mg g − 1 as the initial concentration increases from 20 to 300 mg/L in a wide pH range. The kinetics, isotherms and adsorption mechanism of functional CACms adsorption are discussed in detail. The adsorption data onto CACms can be fitted to pseudo-second-order model better than the pseudo-first-order model. The Langmuir adsorption model agrees well with the experimental data and the maximum adsorption capacity can reach 925.9 mg g − 1 at 45 °C. Temperature change is found to have a significant effect on the adsorption process. The thermodynamic parameters such as the free energy, enthalpy and entropy of adsorption are evaluated and it was found that the adsorption was endothermic and spontaneous. In addition, the as-prepared CACms exhibit selective adsorption ability for MB.

Mesoporous carbon nanofibers (MCNFs) were prepared using ferric-nitrilotriacetate (Fe-NTA) nanofibers as the precursors via annealing under enclosed condition at 500 °C. The precursors were synthesized by hydrothermal method with FeSO 4 ⋅7H 2 O and nitrilotriacetic acid as the raw materials. The obtained mesoporous carbon nanofiber materials were characterized by means of X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), transmission electron microscope (TEM) and nitrogen adsorption–desorption measurement. Characterization results indicated that the mesoporous carbon nanofiber samples with long fibrous morphology, high surface area and mesoporous structure. Due to the porous structure, the obtained MCNFs exhibited excellent performance for the adsorption of methylene blue (MB) and methyl orange (MO) from aqueous solution. The adsorption kinetics and isotherms of the adsorbent were investigated in detail. The experimental equilibrium data of MB and MO were well fitted to the Langmuir isotherm model. The adsorption kinetic data of both dyes were found to follow the pseudo-second order kinetic. The calculated thermodynamic parameters namely Gibbs free energy (Δ G o ), enthalpy (Δ H o ) and entropy (Δ S o ) showed that the adsorption process of MB and MO onto MCNFs was spontaneous and endothermic in nature.

We propose a Multi-Objective Shuffled Frog-Leaping Algorithm (MOSFLA) and Genetic Algorithm (GA) based task assignment and sequencing method, for multi-Unmanned Aerial Vehicles (multi-UAVs) plant-protection operation optimization. Based on full coverage of spray area, a dual decision model of non-operation flight distance and total operation time is developed considering energy consumption and operation efficiency. The proposed optimization method is hybridized using MOSFLA and GA: we first use modified MOSFLA for multi-UAVs operation assignment optimization, shrinking multi-UAVs operation cost including fields allocation, non-operation flight distance and operation time difference; we then employ GA for fields operation sequencing optimization, reducing the total operation time. Considering multi-UAVs’ take-off preparation delay effect, we established a latency time calculation model to determine total operation time for multi-UAVs. The test results show that: ① the non-operation flight distance cost for multi-UAVs using MOSFLA is less than that of single-UAV, which also performs better than that for multi-UAVs in traditional modes; ② the total operation time shrinks by using GA with known assignment matrix (including MOSFLA), which could save over 20 min compared with traditional modes; ③ the total operation time cost in MOSFLA–GA is less than that in traditional modes and optimized traditional modes, with same UAV number and preparation time for take-off; ④ the minimum iteration when assignment fitness value of MOSFLA attains maximum is small (

Li4Ti5O12 and Li4Ti5O12-rutile TiO2 nanosheet composite were synthesized by a facile solvothermal method with further calcination. The addition of rutile TiO2 does not affect the crystal structure, particle size, morphology of spinel Li4Ti5O12. XRD shows that the molar ratio of Li/Ti has much influence on the chemical composition of the products. TEM indicates that both Li4Ti5O12 and Li4Ti5O12-rutile TiO2 samples are composed of nanoplates with particle size of 50–100 nm. CV and EIS imply that Li4Ti5O12-rutile TiO2 has higher reversible intercalation and deintercalation of Li+, larger lithium-ion diffusion coefficient and smaller charge transfer resistance corresponding to a much higher conductivity than those of Li4Ti5O12 corresponding to the extraction of Li+ ions. Li4Ti5O12-rutile TiO2 material exhibits excellent cycling stability and rate capability in relevant lithium-ion batteries, which can retain a capacity of 120.5 mAh g−1 after 150 cycles at 5 C charge–discharge rate cycled between 1.0 and 2.5 V. This performance is much better than that of pristine Li4Ti5O12 (82.2 mAh g−1), whose capacity fades seriously. Li4Ti5O12-rutile TiO2 also exhibits a good rate performance in a broad voltage window. The capacities of Li4Ti5O12-rutile TiO2 and Li4Ti5O12 charge-discharged at 12 C rates remains at 125.4 and 50.2 mAh g−1 cycled between 0.0 and 2.5 V after 200 cycles, respectively. The enhanced performance of Li4Ti5O12-rutile TiO2 is ascribed to the improved electronic conduction and the reduced polarization resulting from the rutile TiO2 modification together with nanosized structure.

The bowknot-like ZnFe2O4 superstructures have been synthesized by the decomposition of the zinc ferrioxalate microstructures, which are prepared by facile method at room temperature. The obtained products are characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), and nitrogen sorption measurements. The adsorption performances of bowknot-like ZnFe2O4 superstructures are tested with the removal of typical pollutants of Cr(VI) from simulated wastewater. The results show that the as-prepared bowknot-like ZnFe2O4 superstructures can effectively remove Cr(VI) from the wastewater. Kinetics of the Cr(VI) removal is found to follow pseudosecond-order rate equation. The adsorption isotherms of bowknot-like ZnFe2O4 superstructures can be described very well by the Langmuir equation. Therefore, the as-obtained bowknot-like ZnFe2O4 superstructures are promising absorbents for wastewater treatment.

In this study, 3D hierarchical porous iron oxides were prepared by a precursor thermal conversion method and their adsorption properties for Congo red were reported. The products were characterized by X-ray powder diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), electron microscopy (EM) and nitrogen adsorption–desorption isotherms. Results demonstrated that the 3D magnetic bowknot-like iron oxides were constructed by three-dimensional self-assembly of nanorods with porous nanostructures. The effect of experimental parameters including polymer concentration, reaction temperature, reaction time and heat treatment atmosphere were studied. Bowknot-like α -Fe 2 O 3 , Fe 3 O 4 and γ -Fe 2 O 3 superstructures were obtained by the thermal transformation of the oxalate precursor under the various atmosphere. These porous iron oxide superstructures exhibited ferromagnetic property at room temperature. Adsorption of Congo red (CR) onto the as-prepared samples from aqueous solutions was investigated and discussed. The results indicated that pseudo-second-order kinetic equation model can better describe the adsorption kinetics of CR onto α -Fe 2 O 3 and γ -Fe 2 O 3 , and Lagergren-first-order kinetic model is better fitted for the adsorption of CR onto Fe 3 O 4 . The hierarchically α -Fe 2 O 3 bowknots showed better adsorption ability for CR than Fe 3 O 4 and γ -Fe 2 O 3 superstructure.

Magnetic carbon spheres have been successfully prepared by the synchronous carbonation and activation of the 8-quinoliolato Fe(III) complexe with sphere morphology, which has been synthesized by solovthermal method. The obtained composite possesses relatively even pore diameter of 3.8 nm, high surface area of 335.59 m 2 /g with 52.67 wt.% Fe 3 O 4 coated, and a saturation magnetization (Ms) of 35.27 emu/g. Dye separation performance of the magnetic carbon spheres is investigated using methylene orange and methylene blue as modle. The resluts show that the maxium adsorption capacity for methylene orange and methylene blue is 128.70 mg g −1 and 151.29 mg g −1 , respectively, and the process can rapidly reach adsorption equilibrium within 5 min, which is important for the application of the as-prepared magnetic carbon spheres.

Mesoporous NiO microspheres with the average diameters of 1.5 μm, 2 μm, 5 μm and 10 μm were successfully prepared by the direct thermal transformation of nickel oxalate microspheres as the sacrificial oxalate template, which was facilely synthesized by simple precipitation reaction with controllable size in the control of polyvinyl alcohol. The obtained samples were characterized by X-ray diffraction (XRD), transmission electron microscope (TEM), scanning electron microscopy (SEM) and nitrogen adsorption–desorption measurement. Specific surface area of the mesoporous NiO microspheres with the average diameters of 10 μm was calculated as 110.2 m 2 g −1 by BET method. The mesoporous NiO microspheres as adsorbents exhibited rapid adsorption rate for methyl orange and high adsorption capacity of 113.64 mg g −1 for methyl orange. Batch kinetic experiments showed that pseudo-second-order kinetic equation can better describe the adsorption kinetics, and the experimental data of equilibrium adsorption fitted very well to Langmuir model. The thermodynamic parameters of Δ G °, Δ H ° and Δ S ° showed that adsorption of methyl orange on mesoporous NiO microspheres was an exothermic and spontaneous in nature.

Spinel Li4Ti5O12 materials are synthesized and characterized as anode materials for high rate lithium-ion batteries. Li4Ti5O12 material by ethanol-assisted hydrothermal synthesis shows much better capacity retention at high C-rate than the one by solid-state synthesis in the voltage range between 1.0 and 2.5 V. Li4Ti5O12 materials by ethanol-assisted hydrothermal synthesis show the discharge capacity of 122 mAh g−1 at a high charge–discharge C-rate of 5 C after 150 cycles. The improved cycling behavior and higher reversible capacity of the Li4Ti5O12 material by ethanol-assisted hydrothermal synthesis compared to the one by solid-state synthesis could probably be due to an improved structural stability, lithium ion diffusion and ionic conductivity.

Well-defined submicron Li4Ti5O12-Li3xLa(2/3)−xTiO3 (LTO-LLTO) materials have been synthesized by a solid-state reaction followed by hydrothermal procedure. Li4Ti5O12-Li3xLa(2/3)−xTiO3 materials show much improved rate capability and specific capacity compared with pristine Li4Ti5O12 when used as anode materials for lithium-ion batteries. The results here give clear evidence of the utility of Li3xLa(2/3)−xTiO3 (LLTO) to improve the kinetics of Li4Ti5O12 toward fast lithium insertion/extraction. LTO-LLTO (10 wt%) shows a high capacity of 101 mAh g−1 even at a charge-discharge rate of 5 C in the 150th cycle, about 150% that of pristine Li4Ti5O12 particles (68 mAh g−1). The improved high-rate capability, cycling stability, fast charge-discharge performance of LTO-LLTO composites can be ascribed to the improvement of electrochemical reversibility, lithium ion diffusion and ionic conductivity by LLTO modifying.

Three-dimensional CoFe 2 O 4 superstructures are prepared by the controlled thermal decomposition of the complex oxalate with various hierarchical nanostructures, which are obtained via poval (PVA) mediated precipitation reaction. The influence of experimental parameters including the concentration of PVA, reaction temperature, and reaction time was systematically investigated to study the possible formation mechanism of the superstructure. The as-prepared samples are characterized by X-ray powder diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy, transmission electron microscopy, and high-resolution transmission electron microscopy. The catalytic property of the as-prepared superstructure is also carried out. The results show that the hierarchical structure presents superior catalytic activity for ammonium perchlorate by decreasing its decomposition temperature to as low as 290 °C and more decomposition occurs at the low temperature phase (LTD) stage.

The Mo-doped LiNi 0.5 Mn 1.5 O 4 cathodes are successfully synthesized by citric acid-assisted sol–gel method. The result demonstrates that the Mo-doped LiMn 1.4 Ni 0.55 Mo 0.05 O 4 cathodes present the improved electrochemical performance over pristine LiNi 0.5 Mn 1.5 O 4 . At the 2 C rate after 80 cycles, the discharge capacities are 68.5 mAh g −1 for the pristine LiNi 0.5 Mn 1.5 O 4 material (53.9% of the capacity at 0.1 C), 107.4 mAh g −1 for the LiMn 1.425 Ni 0.5 Mo 0.05 O 4 material (82.1% at 0.1 C), and 122.7 mAh g −1 for the LiMn 1.4 Ni 0.55 Mo 0.05 O 4 material (90.5% at 0.1 C). Mo-doping is favorable for reducing the electrode polarization, suggesting that Mo-doped LiNi 0.5 Mn 1.5 O 4 electrodes have faster lithium insertion/extraction kinetics during cycling. Mo-doped LiNi 0.5 Mn 1.5 O 4 electrodes show lower charge-transfer resistance and higher lithium diffusion coefficients. In addition, LiMn 1.4 Ni 0.55 Mo 0.05 O 4 cathode exhibits the smallest particle size, the lowest charge-transfer resistance and the highest lithium diffusion coefficient among all samples, indicating that it has a high reversibility and good rate capability.