Photocatalytic performance and dispersion stability of nanodispersed TiO2 hydrosol in electrolyte solutions with different cations

The existence of electrolytes in aquatic environment on the photocatalytic performance and coagulation of nanodispersed TiO₂ hydrosol and the corresponding photocatalytic alteration were investigated by studying cations (Na⁺, K⁺, Ca ²⁺, Mg²⁺, and Al³⁺). The photocatalysis reactions of nano TiO₂ with different dosages of electrolytes were measured by monitoring the degradation of Rhodamine B (RhB) under ultraviolet A (UV-A) irradiation over time. The results showed that the photocatalytic performance of TiO₂ was improved by the presence of Al³⁺, while the performance was impaired by the other tested cations. The negative influences of divalent ions on the photocatalytic performance of TiO₂ were more significant than monovalent ions. The TiO₂ sol dispersed stable at nano scale at low concentration of electrolyte (< 0.01?mol/L) with slight change of pH, and coagulated into micro sizes at high concentration of electrolytes (> 0.1?mol/L) with larger increase or decrease of pH. The positive effects of Al³⁺ on the photodegradation rate of RhB might relate to the strong hydrolytic action of Al³⁺ in aquatic solutions. The photocatalytic processes of TiO₂ in the presence of all ions followed the Langmuir-Hinshelwood model, and the reaction kinetic constant was increased with the decrease of pH caused by different cations. These work suggested a new perspective about the relationship between coagulation and photocatalytic performance of TiO₂ hydrosols in electrolyte with hydrolysable cations, which demonstrated that TiO₂ hydrosols may be suitable as photocatalysts in aquatic environments.     

Construction of dual Z-scheme Bi2WO6/g-C3N4/black phosphorus quantum dots composites for effective bisphenol A degradation

In this work, a novel dual Z-scheme Bi₂WO₆/g-C₃N₄/black phosphorus quantum dots (Bi₂WO₆/g-C₃N₄/BPQDs) composites were fabricated and utilized towards photocatalytic degradation of bisphenol A (BPA) under visible-light irradiation. Optimizing the content of g-C₃N₄ and BPQDs in Bi₂WO₆/g-C₃N₄/BPQDs composites to a suitable mass ratio can enhance the visible-light harvesting capacity and increase the charge separation efficiency and the transfer rate of excited-state electrons and holes, resulting in much higher photocatalytic activity for BPA degradation (95.6%, at 20 mg/L in 120 min) than that of Bi₂WO₆ (63.7%), g-C₃N₄ (25.0%), BPQDs (8.5%), and Bi₂WO₆/g-C₃N₄ (79.6%), respectively. Radical trapping experiments indicated that photogenerated holes (h⁺) and superoxide radicals (•O₂⁻) played crucial roles in photocatalytic BPA degradation. Further, the possible degradation pathway and photocatalytic mechanism was proposed by analyzing the BPA intermediates. This work also demonstrated that the Bi₂WO₆/g-C₃N₄/BPQDs as effective photocatalysts was stable and have promising potential to remove environmental contaminants from real water samples.     

Enhanced photocatalytic activity of fish scale loaded TiO2 composites under solar light irradiation

Fish scale (FS) loaded TiO₂ composites were investigated as photocatalysts in degradation of Methyl Orange under solar light irradiation. Composites were prepared through sol-gel method by varying mass ratio of TiO₂/FS at 90:10, 70:30 and 50:50, respectively. The catalysts prepared in this study were characterized by using XRD, SEM, FT-IR and nitrogen sorption. The effects of solar irradiation, mass ratio of TiO₂/FS composites, irradiation time and catalyst loadings were studied. Synergistic effect was found in TiO₂/FS of 90:10 composite which performed higher photocatalytic degradation than synthesized TiO₂ under solar light irradiation. However, further increasing fish scale content in the composites reduced the photocatalytic activity drastically. Under solar light irradiation, all the catalysts in this study exhibited photocatalytic activity, except TiO₂/FS of 50:50 composite that only acted as a weak biosorbent without performing any photocatalytic property. Photocatalytic degradation increased with increasing catalyst loading and irradiation time but decreased with increased of initial dye concentration.     

Construction of Ag2CO3/BiOBr/CdS ternary composite photocatalyst with improved visible-light photocatalytic activity on tetracycline molecule degradation

Photocatalytic degradation was considered as a best strategy for the removal of antibiotic drug pollutants from wastewater. The photocatalyst of ABC (Ag₂CO₃/BiOBr/CdS) composite synthesized by hydrothermal and precipitation method. The ABC composite used to investigate the degradation activity of tetracycline (TC) under visible light irradiation. The physicochemical characterization methods (e.g. scanning electron microscopy (SEM), transmission electron microscopy (TEM), high resolution-transmission electron microscopy (HR-TEM), ultraviolet visible spectroscopy (UV), photoluminescence (PL) and time resolved photoluminescence (TRPL) clearly indicate that the composite has been construct successfully that enhances the widened visible light absorption, induces charge transfer and separation efficiency of electron – hole pairs. The photocatalytic activity of all samples was examined through photodegradation of tetracycline in aqueous medium. The photocatalytic degradation rate of ABC catalyst could eliminate 98.79% of TC in 70 min, which is about 1.5 times that of Ag₂CO_3, 1.28 times that of BiOBr and 1.1 times that of BC catalyst, respectively. The role of operation parameters like, TC concentration, catalyst dosage and initial pH on TC degradation activity were studied. Quenching experiment was demonstrated that ·OH and O₂^·− were played a key role during the photocatalysis process that was evidently proved in electron paramagnetic resonance (EPR) experiment. In addition, the catalyst showed good activity perceived in reusability and stability test due to the synergistic effect between its components. The mechanism of degradation of TC in ABC composite was proposed based on the detailed analysis. The current study will give an efficient and recyclable photocatalyst for antibiotic aqueous pollutant removal.     

Mechanochemical synthesis of MAPbBr3/carbon sphere composites for boosting carrier-involved superoxide species

Lead halide perovskites MAPbX₃ (MA = CH₃NH₃ or Cs; X = I, Br, Cl) are well considered to be potential candidates for photocatalytic reaction due to its excellent photoelectrical properties, but they still suffer from the low charge separation efficiency and slow catalytic reaction dynamics. To tackle the drawbacks, herein, MAPbBr₃/carbon sphere (CS) composite photocatalysts using glucose as the carbon source were elaborately designed and fabricated via a dry mechanochemical grinding process. The interfacial interaction Pb-O-C chemical bonds were constructed between MAPbBr₃ and the carbon sphere surface containing organic functional groups. By optimizing the content of CSs, the enhanced photocatalytic degradation kinetic rate of Malachite Green (MG) pollutants (92% within 20 min) for MAPbBr₃/CS_x (x = 17 wt.%) is about 3.6-fold of that for pristine MAPbBr₃, which is attributed to the corporative adsorption and enhanced carrier transportation and separation of MAPbBr₃/CS_x. Furthermore, the possible degradation mechanism was proposed on basis of the electrochemical, mass spectrometry and optical characterization results. Owing to the robust interfacial interaction, effective electron extraction rate (k_et = 4.6 × 10⁷ sec^?1) from MAPbBr₃ to CS can be established, which driven oxygen activation where superoxide radicals (?O₂^?) played an important role in MG degradation. It is expected that mechanochemistry strategy may provide a new route to design efficient lead halide perovskite-carbon or metal oxide or sulfide composite photocatalysts.     

Enhanced photocatalytic degradation of lindane using metal–semiconductor Zn@ZnO and ZnO/Ag nanostructures

To achieve enhanced photocatalytic activity for the degradation of lindane, we prepared metal–semiconductor composite nanoparticles (NPs). Zn@ZnO core–shell (CS) nanocomposites, calcined ZnO, and Ag-doped ZnO (ZnO/Ag) nanostructures were prepared using pulsed laser ablation in liquid, calcination, and photodeposition methods, respectively, without using surfactants or catalysts. The as-prepared catalysts were characterized by using X-ray diffraction (XRD), field-emission scanning electron microscopy, high-resolution transmission electron microscopy, ultraviolet–visible (UV–vis) spectroscopy, and photoluminescence spectroscopy. In addition, elemental analysis was performed by energy dispersive X-ray spectroscopy. The obtained XRD and morphology results indicated good dispersion of Zn and Ag NPs on the surface of the ZnO nanostructures. Investigation of the photocatalytic degradation of lindane under UV–vis irradiation showed that Zn@ZnO CS nanocomposites exhibit higher photocatalytic activity than the other prepared samples. The maximum degradation rate of lindane was 99.5% in 40 min using Zn@ZnO CS nanocomposites. The radical trapping experiments verified that the hydroxyl radical (·OH) was the main reactive species for the degradation of lindane.     

Photocatalytic degradation of phenanthrene on soil surfaces in the presence of nanometer anatase TiO2 under UV-light

The effect of nanometer anatase TiO₂ was investigated on the photocatalytic degradation of phenanthrene on soil surfaces under a variety of conditions. After being spiked with phenanthrene, soil samples loaded with different amounts of TiO₂ (0 wt.%, 1 wt.%, 2 wt.%, 3 wt.%, and 4 wt.%) were exposed to UV-light irradiation for 25 hr. The results indicated that the photocatalytic degradation of phenanthrene followed the pseudo first-order kinetics. TiO₂ significantly accelerated the degradation of phenanthrene with the half-life reduced from 45.90 to 31.36 hr for TiO₂ loading of 0 wt.% and 4 wt.%, respectively. In addition, the effects of H₂O₂, light intensity and humic acid on the degradation of phenanthrene were investigated. The degradation of phenanthrene increased with the concentration of H₂O₂, light intensity and the concentration of humic acids. It has been demonstrated that the photocatalytic method in the presence of nanometer anatase TiO₂ was a very promising technology for the treatments of soil polluted with organic substances in the future.     

Photocatalytic degradation of organochlorine compounds using TiO2 supported on fiberglass cloth

The feasibility of photocatalytic degradation of organochlorine compounds using TiO₂ supported on fiberglass cloth as a photocatalyst was studied. The results showed that 2.0×10^-4 mol/dm³ of dichloroethylene, trichloroethylene and tetrachloroethylene can be completely photocatalytically degraded within a short time under illumination with a 375W medium pressure mercury lamp. The effects of parameters such as illumination time, initial concentration of organochlorine compounds, amount of air flow and concentration of H₂O₂ on the photocatalytic degradation were investigated. The TiO₂ supported on the fiberglass was not easily detached and after 500h illumination there was no significant loss of photocatalytic activity of TiO₂. The passible mechanisms of photocatalytic degradation were discussed.     

Preparation and photocatalytic performance study of dual Z-scheme Bi2Zr2O7/g-C3N4/Ag3PO4 for removal of antibiotics by visible-light

At present, the high re-combination rate of photogenerated carriers and the low redox capability of the photocatalyst are two factors that severely limit the improvement of photocatalytic performance. Herein, a dual Z-scheme photocatalyst bismuthzirconate/graphitic carbon nitride/silver phosphate (Bi₂Zr₂O₇/g-C₃N₄/Ag₃PO₄ (BCA)) was synthesized using a co-precipitation method, and a dual Z-scheme heterojunction photocatalytic system was established to decrease the high re-combination rate of photogenerated carriers and consequently improve the photocatalytic performance. The re-combination of electron-hole pairs (e⁻ and h⁺) in the valence band (VB) of g-C₃N₄ increases the redox potential of e⁻ and h⁺, leading to significant improvements in the redox capability of the photocatalyst and the efficiency of e⁻-h⁺ separation. As a photosensitizer, Ag₃PO₄ can enhance the visible light absorption capacity of the photocatalyst. The prepared photocatalyst showed strong stability, which was attributed to the efficient suppression of photo-corrosion of Ag₃PO₄ by transferring the e⁻ to the VB of g-C₃N₄. Tetracycline was degraded efficiently by BCA-10% (the BCA with 10 wt.% of AgPO₄) under visible light, and the degradation efficiency was up to 86.2%. This study experimentally suggested that the BCA photocatalyst has broad application prospects in removing antibiotic pollution.     

Characteristics and sources of WSI in North China Plain: A simultaneous measurement at the summit and foot of Mount Tai

To better understand the characteristics and sources of water soluble ions (WSI) in North China Plain (NCP), fine particles (PM_2.5) were simultaneously sampled at the summit (SM) and foot (FT) of Mount Tai during May 12th to June 24th, 2017. Ion chromatography analysis showed that concentration of WSI was lower at SM (22.26 ± 16.53 μg/m³) than that at FT (31.02 ± 21.92 μg/m³). The concentration and proportion of SO₄^2? in total WSI were both lower than the values reported in previous studies. Daytime WSI concentrations were higher than that at nighttime at SM, while the opposite results were obtained at FT, possibly associated with more anthropogenic activities and higher boundary layer height (BLH) during daytimes. A severe pollution event occurred during June 14th – June 16th was documented at both FT and SM. Regional transport and topography-forced vertical transport along the slope of the mountain could explain the higher concentrations of pollutants at SM. The analyses also indicated that NH₄⁺ existed mainly in the form of NH₄HSO₄ and NH₄NO₃, but (NH₄)₂SO₄ could also exist, especially when emissions of NH₄⁺ and NH₃ were increased during daytime at FT. The results of principal component analysis (PCA) illustrated that secondary aerosols, coal/biomass burnings, sea-salts and crustal/soil dusts were the main sources at SM, and secondary aerosols and crustal/soil dusts contributed most at FT. Backward air-mass trajectories were classified into four clusters, of which air masses with the highest frequency and WSI concentrations were originated from the southwest with secondary ions (SO₄^2-, NO₃^- and NH₄⁺) as major pollutants.     

环境与人口、经济和科技发展的协同探析

本文从环境与人口、经济和科技之间的相依关系出发,探讨了诸因素相互关联的内在协同机理,简析了IPAT模型的建构与应用.嗣后,利用IPAT模型解析了中国近15年来人口、经济和科技发展对环境影响的贡献差异;指出经济规模的迅速扩展和落后技术支持下的传统生产方式是加剧环境恶化的元凶,且技术转型期的负面影响也是不可忽视的重要因素;进而提出了中国未来环境与人口、经济和科技协同演化的对策措施.     

环境与人口、经济和科技发展的协同探析

本文从环境与人口、经济和科技之间的相依关系出发，探讨了诸因素相互关联的内在协同机理，简析了IPAT模型的建构与应用。嗣后，利用IPAT模型解析了中国近15年来人口、经济和科技发展对环境影响的贡献差异；指出经济规模的迅速扩展和落后技术支持下的传统生产方式是加剧环境恶化的元凶，且技术转型期的负面影响也是不可忽视的重要因素；进而提出了中国未来环境与人口、经济和科技协同演化的对策措施。     

黄河断流对三角洲附近海域生态环境影响的研究

本文根据多年调查监测数据研究成果，以及经济和社会统计资料，论述了黄河断流的历史与现状，定性定量地评价了黄河断流对三角洲附近海域生态环境的影响，并提出了缓解和预警对策。     

论西部大开发中高等级公路建设与环境的协调发展问题——以西(宁)湟(源)一级公路为例

本文从目前我国西部大开发中所面临的各种约束条件出发，以青海省西宁市至湟源县一级公路工程为例，简要阐述了西部大开发中高等级公路在路线设计，施工过程中保护好沿线生态环境的重要性和紧迫性，初步讨论了在西部大开发中如何协调高等级公路建设与环境之间的关系。     

上游阻挡建筑间距对街谷内空气环境的影响

城市中的大部分街谷都存在上游阻挡建筑.为考察阻挡建筑对街谷内空气环境的影响,通过数值计算方法研究分析了上游阻挡建筑对街谷内空气品质的影响作用,结果表明,在常规建筑间距范围内,街谷湍流强度、平均风速和风速波动范围均随着上游阻挡建筑间距增大而减小,这将导致当上游阻挡建筑与街谷建筑间距从15m增加到60m时,街谷空间污染物平均浓度增大36%,近地空间增大41%.因此,实际设计中街谷上游阻挡建筑与临街建筑间的距离不应过大.     

徐州地区水质自动监测系统质量保证与控制现状

介绍了徐州市水质自动监测系统建成后,为保证水质自动监测系统的长期稳定运行和各项自动监测数据的准确可靠,在日常工作中所采取的质量保证与控制措施。     

论新时期中国共产党在经济发展中的执行力

执行力对执政的中国共产党来说至关重要,关乎其执政地位的巩固。中国目前是党领导一切。要认识到政党政府在宏观调控、微观参与、经济发展配套设施提供方面对经济发展不可或缺的作用,接下来的问题就是如何提升政府执行力,使政党政府通过宏观调控、微观参与行为在经济领域达到更好的效果。本文在分析我党在执行力方面存在的问题的基础上,提出了提高我党执行力的若干建议。     

论新时期中国共产党在经济发展中的执行力

执行力对执政的中国共产党来说至关重要，关乎其执政地位的巩固。中国目前是党领导一切。要认识到政党政府在宏观调控、微观参与、经济发展配套设施提供方面对经济发展不可或缺的作用，接下来的问题就是如何提升政府执行力，使政党政府通过宏观调控、微观参与行为在经济领域达到更好的效果。本文在分析我党在执行力方面存在的问题的基础上，提出了提高我党执行力的若干建议。     

胶州湾海洋动物体中重金属含量及评价

本文主要研究了胶州湾海水、海洋动物体中重金属含量，分析结果表明：沿岸河口地区海水中重金属含量较高，其重金属污染主要受沿岸工业排放废水的影响；海洋动物体中重金属含量为底栖动物大于鱼类；海洋动物体中重金属含量不仅受其所栖息海水中重金属含量的支配，而且受季节的影响；海洋动物对于铜比其它重金属具有较强的富集能力。     

区域尺度绿洲稳定性评价

论文在区域尺度上,探讨了绿洲稳定性的内涵,并以新疆三工河流域绿洲为例,从绿洲所处的地理位置、绿洲与外围荒漠和山地系统之间的相互作用等方面评价了绿洲的区域稳定性。结果表明:①冲洪积扇型绿洲稳定性最高,其次是位于地下水溢出带下方的冲积平原型绿洲,稳定性最差的是湖滨三角洲或散流干三角洲上发育的绿洲;②绿洲的冷岛效应和植被指数可较好地表征绿洲与外围荒漠和山地系统之间的相互作用和评价绿洲的区域稳定性的时间变化。绿洲规模的扩大及绿洲水分和植被的增加将加强绿洲的冷岛效应,提高绿洲的稳定性;归一化差异植被指数增加,表明绿洲内植被覆盖密度增大和植物生物量提高,绿洲的稳定性增强。