Time-Frequency Aliased Signal Identification Based on Multimodal Feature Fusion.

The identification of multi-source signals with time-frequency aliasing is a complex problem in wideband signal reception. The traditional method of first separation and identification especially fails due to the significant separation error under underdetermined conditions when the degree of time-frequency aliasing is high. The single-mode recognition method does not need to be separated first. However, the single-mode features contain less signal information, making it challenging to identify time-frequency aliasing signals accurately. To solve the above problems, this article proposes a time-frequency aliasing signal recognition method based on multi-mode fusion (TRMM). This method uses the U-Net network to extract pixel-by-pixel features of the time-frequency and wave-frequency images and then performs weighted fusion. The multimodal feature scores are used as the classification basis to realize the recognition of the time-frequency aliasing signals. When the SNR is 0 dB, the recognition rate of the four-signal aliasing model can reach more than 97.3%.

Fe-pillared montmorillonite functionalized chitosan/gelatin foams for efficient removal of organic pollutants by integration of adsorption and Fenton degradation.

A Fe-pillared montmorillonite (Fe-MMT) functionalized bio-based foam (Fe-MMT@CS/G) was developed by using chitosan (CS) and gelatin (G) as the matrix for high-efficiency elimination of organic pollutants through the integration of adsorption and Fenton degradation. The results showed that the mechanical properties of as-obtained foam were strengthened by the addition of certain amounts of Fe-MMT. Interestingly, Fe-MMT@CS/G displayed efficient adsorption ability for charged pollutants under a wide range of pH. The adsorption processes of methyl blue (MB), methylene blue (MEB) and tetracycline hydrochloride (TCH) on Fe-MMT@CS/G were well described by the Freundlich isotherm model and pseudo-second-order kinetic model. The maximum adsorption capacities were 2208.24 mg/g for MB, 1167.52 mg/g for MEB, and 806.31 mg/g for TCH. Electrostatic interactions, hydrogen bonding and van der Waals forces probably involved the adsorption process. As expected, this foam could exhibit better removal properties toward both charged and uncharged organic pollutants through the addition of H2O2 to trigger the Fenton degradation reaction. For non-adsorbable and uncharged bisphenol A (BPA), the removal efficiency was dramatically increased from 1.20 % to 92.77 % after Fenton degradation. Additionally, it presented outstanding recyclability. These results suggest that Fe-MMT@CS/G foam is a sustainable and efficient green material for the alleviation of water pollution.

Versatile CO2-responsive Sponges Decorated with ZIF-8 for Bidirectional Separation of Oil/Water and Controllable Removal of Dyes.

The complex wastewater containing water-soluble dyes and water-insoluble oils has given rise to significant environmental concerns that demand urgent remediation. Herein, a novel "smart" multifunctional sponge (ZIF-8@PMS) stepwise decorated with ZIF-8 nanoparticles and CO2-responsive copolymer (poly(2-(diethylamino) ethyl methacrylate-co-3-(trimethoxysilyl)propyl acrylate-co-stearyl methacrylate) was successfully prepared for CO2 controllable oil/water separation and dyes removal. The results revealed that the sponge coated with CO2-responsive copolymer for three cycles (ZIF-8@PMS-3) exhibited optimal comprehensive properties. The ZIF-8@PMS-3 had excellent compressive-resilient characteristics and chemical stability. As expected, it displayed tunable wettability and charged state under the regulation of CO2. Based on these features, ZIF-8@PMS-3 presented highly efficient removal of oil and dyes, even for the dye-containing oil/water emulsions, via a synergistic combination of adsorption and separation methods. The adsorption capacity for oil and various organic solvents ranged from 21.3 to 50 g g-1. The maximum adsorption capacities toward anionic dyes: methyl orange with 1205.89 mg g-1 and methyl blue with 880.00 mg g-1 in the presence of CO2 through electrostatic interaction. In the absence of CO2, it achieved maximum adsorption capacities for cationic dyes, including malachite green with 1246.15 mg g-1 and rhodamine B with 203 mg g-1, primarily driven by π-π interactions. According to distinct adsorption mechanisms, ZIF-8@PMS-3 could selectively adsorb either anionic or cationic dyes by exploiting CO2 as a trigger. Furthermore, the separation efficiencies for both types of oil/water emulsions surpassed 99.9%, with respective fluxes of 1566.99 L m-2 h-1 (water-in-oil emulsion) and 310.37 L m-2 h-1 (oil-in-water emulsion). Additionally, the as-prepared sponges exhibited remarkable antibacterial properties and exceptional recyclability. Therefore, the ZIF-8@PMS-3 holds substantial promise for potential applications in practical industrial wastewater treatment.

Study on degradation of diesel pollutants in seawater by composite photocatalyst MnO2/ZrO2.

In this paper, the effectiveness of the composite photocatalyst was studied by using manganese dioxide (MnO2)/zirconium dioxide (ZrO2) to degrade diesel pollutants in seawater under visible light.The MnO2/ZrO2 photocatalyst was prepared by co-precipitation and characterized by scanning electron microscopy, X-ray powder diffraction, energy-dispersive spectroscopy and UV-Vis diffuse reflectance spectroscopy analysis. This is the first report on a comprehensive analytical study on the effect of various physio-chemical parameters on diesel degradation using the synthesized MnO2/ZrO2 photocatalysts. The effects of doping ratio of MnO2/ZrO2, dosage, initial diesel concentration, calcination temperature, concentration of H2O2 solutions and illumination time on the diesel degradation were investigated. The degradation of diesel pollution in seawater was optimized by orthogonal experiment. According to the results, the prepared samples were monoclinic form and the MnO2 was successfully doped into the bulk ZrO2. The absorption edge of the MnO2/ZrO2 photocatalysts exhibited red shift, and this red shifts imply enhanced photon absorption under visible light compared with the pure ZrO2. The results showed that under optimum reaction conditions, the degradation rate can reach 92.92%. The result of this study will enable ZrO2 to make more effective use of sunlight and improve the actual value of photocatalytic technology in the field of contaminant treatment.

Application of Fe2O3/ZrO2 loaded polyhedron ball on photocatalytic degradation of diesel pollutants in seawater under visible light.

Fe2O3/ZrO2 nanocomposite photocatalyst was successfully prepared by coprecipitation method for the degradation of diesel pollutants in seawater under visible light. The effects of doping ratio, calcination temperature, photocatalyst dosage, initial diesel concentration, H2O2 concentration, and reaction time on the photocatalytic removal efficiency were investigated. Moreover, the optimal conditions for Fe2O3/ZrO2 nanocomposite photocatalyst to degrade marine diesel pollution were determined. The removal efficiency of diesel by nanocomposite photocatalyst could reach 97.03%. A photocatalyst-loaded polypropylene polyhedral ball was prepared, and the removal efficiency of diesel by photocatalyst-loaded polypropylene polyhedral ball decreased from 99.35 to 68.84% after four recycling cycles.

Photocatalytic degradation of marine diesel oil spills using composite CuO/ZrO2 under visible light.

Diesel oil spills in marine environments pose a severe threat to both aquatic and terrestrial ecosystems. Photocatalysis is an environment-friendly method for marine oil remediation; however, its practical usage is limited due to several issues. In this study, we demonstrate the enhanced efficacy of doped CuO/ZrO2 photocatalyst at degrading marine diesel in comparison to undoped ZrO2. The photocatalysts were prepared using co-precipitation method, and their physical and chemical properties were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and ultraviolet-visible spectroscopy (UV-Vis). XRD analysis showed that the photocatalytic crystallite size of ZrO2 and CuO/ZrO2 was 28.80 nm and 40.32 nm, respectively. Both catalysts exhibited stable crystalline forms. UV-Vis analysis showed that doping of ZrO2 with CuO significantly reduced its band gap from 4.61 eV to 1.18 eV, thus enhancing the utilization of visible light. The effect of catalyst dosage, doping ratio, and initial diesel concentration on the degradation rate of diesel was investigated by performing single-factor experiments. The optimization experiment results showed that 96.96% of diesel could be degraded under visible light. This study laid an experimental foundation for expanding the practical applications of photocatalytic technology.

Adsorption of chlortetracycline from aquaculture wastewater using modified zeolites.

In this study, lanthanum modified zeolite (La-Z) was used to adsorb chlortetracycline (CTC) from aquaculture wastewater. La-Z was characterized by SEM, TEM, EDS, XRD, FTIR and BET. The effects various factors on the adsorption of CTC by La-Z were investigated, including the lanthanum modification concentration on zeolites, the dosage of La-Z, solution pH and reaction time. Orthogonal experiments were performed to determine the optimal adsorption conditions. Adsorption kinetics were studied by quasi-first-order model, quasi-second-order model, Weber-Morris, Boyd and Bangham models, while isotherms were analyzed by the Langmuir and Freundlich models. The removal rate reached 98.4%, when the modified concentration was 0.02 mol/L, the adsorbent dosage was 0.04 g, the initial concentration of CTC was 5 mg/L, the adsorption time was 20 min, and the pH was 7. The initial CTC concentration had the greatest influence on the adsorption process. The kinetic results showed a significant linear correlation between the experimental results and the quasi-second-order kinetic model. From the results of the internal diffusion model, it was found that the La-Z adsorption rate was controlled by both internal diffusion and external diffusion, in a multi-step process. The adsorption isotherm conforms to the Langmuir model, with the maximum adsorption quantity reaching 127.55 mg/g. Thermodynamic analysis showed that the adsorption process was an endothermic process of entropy increase, which occurs spontaneously.

Photocatalytic degradation of chlortetracycline hydrochloride in marine aquaculture wastewater under visible light irradiation with CuO/ZnO.

A CuO/ZnO photocatalyst nanocomposite was successfully prepared by co-precipitation and characterized by investigating its chemical and physical properties by X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, UV-vis diffuse reflectance spectroscopy and photoluminescence spectroscopy. The average particle size of CuO/ZnO composite was found to be around 80 nm. The degradation of chlortetracycline hydrochloride pollutants in marine aquaculture wastewater using ZnO and CuO/ZnO was compared and it was found that CuO/ZnO nanocomposite is more efficient than ZnO. The effects of external factors on the photocatalytic effectiveness of nanocomposite were investigated under visible light. Also, the photocatalytic conditions for the degradation of chlortetracycline hydrochloride by the nanocomposite were optimized. Based on both ability and efficiency of degradation, and on the cost and availability, 10:2 molar ratio of Zn2+/Cu2+ and 0.7 g/L nanocomposite, was found to be optimal, in which case the average photocatalytic degradation rate of chlortetracycline hydrochloride reached 91.10%.

Photocatalytic degradation of oxytetracycline hydrochloride pollutants in marine aquaculture wastewater under visible light.

A CuO/ZnO nanocomposite for use as photocatalyst was successfully prepared by co-precipitation method. Its chemical and physical properties were evaluated by X-ray diffractometry, scanning electron microscopy, EDS, UV-vis diffuse reflectance spectroscopy and photoluminescence spectroscopy. The average particle size of CuO/ZnO composite was found to be around 80 nm. The degradation of oxytetracycline hydrochloride pollutants in marine aquaculture wastewater using ZnO and CuO/ZnO was compared. CuO/ZnO nanocomposite was found to be more efficient than ZnO. The effects of external factors on the photocatalytic efficiency of the nanocomposite were investigated under visible light. Moreover, conditions for the degradation of oxytetracycline hydrochloride using CuO/ZnO nanocomposite were optimized. Based on both, the ability and efficiency of degradation, 10:1 molar ratio of Zn2+/Cu2+ and 0.4 g L-1 nanocomposite, were found to be optimal, using which the average photocatalytic degradation rate of oxytetracycline hydrochloride reached 90%.