With excessive consumption of sulfide ores, using low-grade Pb-Zn mixed ores to obtain Zn has attracted more attention. Acid leaching is an effective method for Zn recovery; however, a high ...concentration of inorganic acid brings severe environmental issues, including acidic wastewater, contaminated soil, etc. Compared with inorganic acid, organic acid showed lower acidity and toxicity. Herein, we applied an effective method for Zn recovery from carbonate-type Pb-Zn mixed ore (CMO), by combining organic acid leaching with mechanical activation. Among the organic acids applied (lactic, malonic, citric, amber, acetic, and tartaric one), lactic acid was selected for its high leaching efficiency. The optimum condition was identified via response surface methodology, with a lactic acid concentration of 1.15 mol/L, L/S ratio of 20, leaching time of 75 min, and temperature of 75 °C. The effect of mechanical activation on Zn leaching was further investigated. The leaching efficiency increased to 90.1% after mechanical activation, which was the highest leaching efficiency for organic acid leaching. Mineralogical characterization showed that the bulk minerals were milled into small particles while the proportion of amorphization increased. Such activation effects improved the acid-solubility of Zn speciation. This work provided a potential green method for metal recovery from low-grade sources.
Elemental sulfur is an important non-metallic material that is widely used in various fields including chemical, metallurgical and sulfuric acid industries. Polymetallic sulfur slag (PSS) is an ...important secondary resource for the recovery of sulfur. However, separation of sulfur from PSS is difficult due to the tight binding of some thiophilic metals to sulfur. Herein, we proposed a recrystallization method for the effective separation of sulfur and metals by using organic solvents to control the particle size of sulfur crystals. It was suggested that the particle size of sulfur recovered in the close to saturation state of toluene is about 2000 μm, while the purity is as high as 99.6%. Moreover, the recovery rate is over 95%, which is more than the current commonly used flotation method. The growth mechanism of sulfur crystals under different saturation conditions lays a foundation for the deepening of the growth theory of large-size sulfur crystals. This method realized the effective separation of sulfur from metal sulfides such as FeS2 and ZnS, which provided an important guidance for the recovery of sulfur resources through a novel method of recrystallizing regulation.
Highly efficient photocatalysts have great development prospects in wastewater treatment, especially in the degradation of organic pollutants and reduction of inorganic heavy metal ions. Herein, a ...Z-scheme ZnTiO3/Zn2Ti3O8/ZnO ternary photocatalyst was prepared by the solvothermal-calcination method and the influence of the content of tetrabutyl titanate precursor and different reaction temperature on the crystal phase structures, photoelectrochemical properties and photocatalytic activities of the samples were investigated. Due to its unique Z-scheme structure and suitable band gap position, which is favorable for the efficient migration and separation of photo-generated electrons and holes and the improvement of photocatalytic redox reaction capability, the samples show excellent performance for the degradation of organic pollutants and reduction of heavy metal Cr(VI) ions. Based on a series of characterization analyses, a possible Z-scheme photocatalytic mechanism is proposed. This work provides a simple preparation method for fabrication of multivariate heterojunction photocatalyst for degradation of organic pollutants and removal of heavy metal ions.
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•A two-step route for building ZnTiO3/Zn2Ti3O8/ZnO nanostructure was developed.•Experiment parameters on the crystal structure and photocatalytic performance were optimized.•The excellent removal efficiency for organic pollutants and Cr(VI) ions were obtained simultaneously.•A unique Z-scheme could illuminate the high removal performance.
Semiconductor photocatalysts are extensively applied in environmental treatment and energy conversion. However, one of their major disadvantages is their relatively low photocatalytic performance ...owing to the recombination of generated electron-hole pairs. The presence of the phase junction is an effective way to promote the photocatalytic activity by increasing the separation efficiency of the electron-hole pairs. Accordingly, extensive research has been conducted on the design of phase junctions of photocatalysts to improve their charge transfer properties and efficiencies. Therefore, for the design of an appropriate phase junction and the understanding of the mechanism of electron-hole separation, the development of the photocatalytic phase junction, including the preparation methods of the heterogeneous materials, is tremendously important and helpful. Herein, the commonly used, externally induced phase transformation fabrication techniques and the primary components of the semiconductors are reviewed. Future directions will still focus on the design and optimization of the phase junction of photocatalytic materials according to the phase transition with higher efficiencies for broadband responses and solar energy utilization. Additionally, the most popular phase transformation fabrication techniques of phase junctions are briefly reviewed from the application viewpoint.
Applications of the low-cost and efficient phase junction pathway for the construction of nanophase junctions in photocatalysis.
•Cu NPs deposition brings about strong visible light absorption and fast separation of the photogenerated carriers.•The synergistic effect between the plasma effect of Cu NPs and single Z-scheme.•The ...superior photocatalytic performance for hydrogen production, dye decomposition, and Cr(VI)reduction.
Cu NPs loaded over Z-scheme mechanism over ZnTiO3/Zn2Ti3O8/ZnO resulted in a strong visible light absorption and fast separation of photogenerated electrons and holes. Thus, a superior photocatalytic performance for hydrogen production, dye decomposition, and Cr(VI)reduction was obtained. Display omitted
Metal nanoparticles (NPs) deposition is an effective strategy to enhance the photocatalytic performance. Here, we developed a non-noble Cu NPs deposition strategy to largely boost the overall photocatalytic performance of a ternary Zn-based composite photocatalyst (ZnTiO3/Zn2Ti3O8/ZnO, ZTO). The physicochemical properties of copper-deposited ZTO were extensively analyzed by a series of techniques such as XRD, BET, FT-IR, XPS, TEM, PL, and photoelectrochemical tests. And the free radical and light absorption properties of copper-deposited ZTO were examined by ESR and UV–vis DRS, respectively. The photocatalytic performance for hexavalent chromium reduction removal, dye decomposition, and water splitting for hydrogen production without noble metal cocatalyst were investigated. The results show that with suitable Cu content (3%~ 4.7%), the Cu-ZTO samples showed high activity for Cr(VI) reduction (3.2 times reduction rate of ZTO), dye decomposition(5.3 times degradation rate of ZTO), and hydrogen generation (19 times of the H2 production rate of ZTO). The synergistic effect between the plasma effect of Cu NPs and single Z-scheme mechanism over ternary ZTO results in a strong visible light absorption and fast separation of photogenerated electrons and holes. Thus, a superior photocatalytic performance was obtained over this novel Cu-ZTO photocatalyst system.
A series of robust AgCl/WO3 composite microrods (0.1–0.2 μm) with different Ag/W molar ratios (0.25, 0.50, 0.75, 1.00, 1.25) were synthesized via hydrothermal-calcination process. The obtained ...samples were characterized by XRD, SEM, TEM, FT-IR, UV-vis DRS, PL, BET, Raman, transient TPRT and EIS. The photocatalytic test for organic dyes degradation showed that AgCl/WO3 microrods possess much higher photocatalytic activities and stability than bare AgCl and WO3. With optimal AgCl/WO3 molar ratio (0.75∼1), 2∼5 times increase in dye decomposition efficiency was obtained over AgCl/WO3 microrods. The formation of intimate WO3/AgCl heterojuction (interface) largely enhanced the separation efficiency of photogenerated carriers. This investigation suggested that AgCl/WO3 microrods could a promising photocatalyst for environmental remediation.
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•100∼200 nm AgCl/WO3 composite nanorods were synthesized.•With molar ratio of 0.75∼1(AgCl/WO3), 2∼5 times increase in activity was obtained.•The WO3/AgCl interface boosted the separation of photo-induced carriers.
Thermostability and band gap deeply influence the photocatalytic activity of the photocatalysts. In this article, BiOBr and La-doped BiOBr photocatalysts were synthesized via a solvothermal process. ...The obtained samples were calcinated at different temperatures. X-ray diffraction (XRD), N2-physical adsorption, scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetry analysis (TGA) and differential thermal analysis (DTA) were utilized to characterize the effect on thermostability after La doping. UV–Visible spectroscopy, X-ray photoelectron spectroscopy (XPS), photoluminescence (PL) spectroscopy, Electrochemical Impedance Spectroscopy (EIS), transient photocurrent spectroscopy and Mott-Schottky (M-S) plots were utilized to analyze the band gap and band edge positions of the samples. The results presented that La doping not only enhanced thermostability of BiOBr but also regulated the band gap of heterojunction to advantageous status for promoting the activity. These results could open a new way to tune the heterojunction with rare earth doping by heat treatment.
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•La doping enhances thermostability of BiOBr at low temperature region (200°C–400°C).•La doping brings fast phase transformation of BiOBr at high temperature.•La doping regulates the band gap of BiOBr during thermo-transformation to form advantage status heterojunction.
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•A novel Ag3VO4/Zn3(VO4)2/Zn2V2O7/ZnO photocatalyst was constructed for pollutants degradation.•This photocatalyst shows high degradation rates (>70%for phenols, >50% for azo ...dyes).•This photocatalyst can be used to remove organic pollutants in water.
High efficient solar-light-driven heterogeneous photocatalysts are crucial for utilizing solar energy to deal with environmental problem. Herein, a novel Ag3VO4/Zn3(VO4)2/ Zn2V2O7/ZnO quaternary heterojunction (Ag3VO4/Zn-V-O) was constructed by a phase transformation and in-situ precipitation process. This quaternary heterojunction photocatalyst was applied to efficiently remove some typical organic pollutants, e.g. phenols (bisphenol A, p-chlorophenol, phenol) and azo dyes (rhodamine B, methyl orange, acid orange II and methylene blue). The well matched energy level structure among Ag3VO4, Zn3(VO4)2 and Zn2V2O7 semiconductors greatly strengthened the light harvesting and suppressed the recombination of photoinduced electron-hole pairs in Ag3VO4/Zn -V-O quaternary heterojunction, producing more OH and O2− radicals to participate in decomposing the organic pollutants. Under simulate solar light illumination, Ag3VO4 and Zn-V-O almost show no activity for phenols decomposition, however, 86%, 70% and 80% degradation rates were obtained over 50%Ag3VO4/Zn -V-O for bisphenol A, phenol and p-chlorophenol. Similar very high activity was observed over 50%Ag3VO4/Zn -V-O for azo dyes degradation (95% for RhB, 50% for MO, 78% for orange II and 100% for MB). This work could afford interesting insight into designing advanced photocatlysts for applying solar light to environmental purification.
Highly efficient photocatalysts have great development prospects in wastewater treatment, especially in the degradation of organic pollutants and reduction of inorganic heavy metal ions. Herein, a ...Z-scheme ZnTiO
/Zn
Ti
O
/ZnO ternary photocatalyst was prepared by the solvothermal-calcination method and the influence of the content of tetrabutyl titanate precursor and different reaction temperature on the crystal phase structures, photoelectrochemical properties and photocatalytic activities of the samples were investigated. Due to its unique Z-scheme structure and suitable band gap position, which is favorable for the efficient migration and separation of photo-generated electrons and holes and the improvement of photocatalytic redox reaction capability, the samples show excellent performance for the degradation of organic pollutants and reduction of heavy metal Cr(
) ions. Based on a series of characterization analyses, a possible Z-scheme photocatalytic mechanism is proposed. This work provides a simple preparation method for fabrication of multivariate heterojunction photocatalyst for degradation of organic pollutants and removal of heavy metal ions.
Phase Coded Waveform Set Design for MIMO Radar Using SPS-JADE Liu, Tianqu; Zhang, Hongbo; Chen, Fanyun ...
2022 15th International Congress on Image and Signal Processing, BioMedical Engineering and Informatics (CISP-BMEI),
2022-Nov.-5
Conference Proceeding
Phase coded waveform set is one of the most extensively studied MIMO radar waveform sets with good application prospects. The goal of the MIMO radar waveform set design is making the peak ...cross-correlation function ratio (PCCR) and peak auto-correlation function side-lobe ratio (PASR) as low as possible. Existing phase coded waveform set design algorithms include the following two categories, one is cyclic iteration algorithms, and the other is intelligent optimization algorithms. Because of the insufficient mathematical properties of the correlation functions, the performances of the cyclic iterative algorithms have hit a bottleneck. With the development of computing power, the intelligent optimization algorithms are capable of obtaining good results within a short time at the cost of more computing resources. This paper establishes an optimization model of the MIMO radar phase coding waveform set design problem. Then an improved differential evolution algorithm based on successful parent selection framework (SPS-JADE) is used to solve this optimization problem. For some parameters, numerical results show that the values of the PCCR and PASR metrics obtained by SPS-JADE are 3.21 dB and 1.92 dB lower than those obtained by Multi-CAN algorithm on average, respectively. Furthermore, the convergence speed of SPS-JADE is much higher than that of GA algorithm.
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