Enhanced Ozone Oxidation by a Novel Fe/Mn@γ−Al2O3 Nanocatalyst: The Role of Hydroxyl Radical and Singlet Oxygen

Catalytic ozonation is a potential alternative to address the dye wastewater effluent, and developing an effective catalyst for catalyzing ozone is desired. In this study, a novel Fe/Mn@γ−Al2O3 nanomaterial was prepared and successfully utilized for catalytic ozonation toward dye wastewater effluent components (dimethyl phthalate and 1−naphthol). The synthesized Fe/Mn@γ−Al2O3 exhibited superior activity in catalytic ozonation of dimethyl phthalate and 1−naphthol in contrast to Fe@γ−Al2O3 and Mn@γ−Al2O3. Quench and probe tests indicated that HO° contributed to almost all removal of dimethyl phthalate, whereas O3, HO°, and singlet oxygen participated in the degradation of 1−naphthol in the Fe/Mn@γ−Al2O3/O3 system. The results of XPS, FT−IR, and EPR suggested that HO° and singlet oxygen were generated from the valence variations of Fe(II/III)and Mn(III/IV). Moreover, the Fe/Mn@γ−Al2O3/O3 system could also have excellent efficacy in actual water samples, including dye wastewater effluent. This study presents an efficient ozone catalyst to purify dye wastewater effluent and deepens the comprehension of the role and formation of reactive species involved in the catalytic ozonation system

Enhanced Ozone Oxidation by a Novel Fe/Mn@γ−Al₂O₃ Nanocatalyst: The Role of Hydroxyl Radical and Singlet Oxygen

Catalytic ozonation is a potential alternative to address the dye wastewater effluent, and developing an effective catalyst for catalyzing ozone is desired. In this study, a novel Fe/Mn@γ−Al2O3 nanomaterial was prepared and successfully utilized for catalytic ozonation toward dye wastewater effluent components (dimethyl phthalate and 1−naphthol). The synthesized Fe/Mn@γ−Al2O3 exhibited superior activity in catalytic ozonation of dimethyl phthalate and 1−naphthol in contrast to Fe@γ−Al2O3 and Mn@γ−Al2O3. Quench and probe tests indicated that HO° contributed to almost all removal of dimethyl phthalate, whereas O3, HO°, and singlet oxygen participated in the degradation of 1−naphthol in the Fe/Mn@γ−Al2O3/O3 system. The results of XPS, FT−IR, and EPR suggested that HO° and singlet oxygen were generated from the valence variations of Fe(II/III)and Mn(III/IV). Moreover, the Fe/Mn@γ−Al2O3/O3 system could also have excellent efficacy in actual water samples, including dye wastewater effluent. This study presents an efficient ozone catalyst to purify dye wastewater effluent and deepens the comprehension of the role and formation of reactive species involved in the catalytic ozonation system

Industrial agglomeration, spatial structure and economic growth: Evidence from urban cluster in China

The industrial agglomeration and spatial structure characteristics play important roles in the economic development and improvement of competitiveness for urban cluster. The article constructs a C-D model using panel data of 130 cities in 13 urban clusters in China from 2006 to 2015, then constructs regression equations of the relationship between industrial agglomeration, spatial structure and economic growth through fixed-effects regression models, and finally analyzes the influence of industrial agglomeration and spatial structure on economic growth of urban clusters. The research results indicate that the economic structure of urban clusters is affected by both the level of industrial agglomeration and spatial structure of urban clusters. The higher the level of industrial agglomeration, the more obvious the economic effect of urban clusters. From the perspective of the spatial structure of urban clusters, the impact of monocentric spatial structure of urban clusters on economic growth shows a positive correlation. Human capital, physical capital, economic openness and resident population have significant positive effects on the economic growth of urban clusters, while transportation infrastructure is not significant. At this moment, we should further promote the industrial agglomeration, and continuously optimize the internal spatial structure of urban clusters with the linkage mechanism of land and household registration to improve the comprehensive competitiveness of urban clusters

Comparison of Different Enhanced Coagulation Methods for Azo Dye Removal from Wastewater

Printing and dyeing wastewater (PDW) is considered to be one of the most difficult industrial wastewaters to treat because of its large quantities, high pH values, and high color and toxicity, which may endanger the lives of animals and humans. In this study, we assessed the chemical decolorization process of Congo Red in azo dyes using response surface methodology (RSM), and the effect of different enhanced coagulation pretreatment processes (ECPPs) on the microbial community structure of PDW using high-throughput sequencing technology. We concluded that, based on the initial concentration and pH of Congo Red, different decolorants can be selected for decolorization reactions. In addition, it was found that the microbial community of the wastewater after three different ECPP treatments was similar to the raw wastewater and the oxidation ditch wastewater from a treatment plant. We also found that the ECPPs with polymeric iron sulfate had the smallest effect on the microbial community. In practical applications, these findings provide a reference for an established link between the physicochemical and biochemical treatment of PDW

A High Flux Electrochemical Filtration System Based on Electrospun Carbon Nanofiber Membrane for Efficient Tetracycline Degradation

In this work, an electrochemical filter using an electrospun carbon nanofiber membrane (ECNFM) anode fabricated by electrospinning, stabilization and carbonization was developed for the removal of antibiotic tetracycline (TC). ECNFM with 2.5 wt% terephthalic acid (PTA) carbonized at 1000 °C (ECNFM-2.5%-1000) exhibited higher tensile stress (0.75 MPa) and porosity (92.8%), more graphitic structures and lower electron transfer resistance (23.52 Ω). Under the optimal condition of applied voltage 2.0 V, pH 6.1, 0.1 mol L−1 Na2SO4, initial TC concentration 10 ppm and membrane flux 425 LMH, the TC removal efficiency of the electrochemical filter of ECNFM-2.5%-1000 reached 99.8%, and no obvious performance loss was observed after 8 h of continuous operation. The pseudo-first-order reaction rate constant in flow-through mode was 2.28 min−1, which was 10.53 times higher than that in batch mode. Meanwhile, the energy demand for 90% TC removal was only 0.017 kWh m−3. TC could be converted to intermediates with lower developmental toxicity and mutagenicity via the loss of functional groups (-CONH2, -CH3, -OH, -N(CH3)2) and ring opening reaction, which was mainly achieved by direct anodic oxidation. This study highlights the potential of ECNFM-based electrochemical filtration for efficient and economical drinking water purification

Simultaneous removal of Ni(II) and fluoride from a real flue gas desulfurization wastewater by electrocoagulation using Fe/C/Al electrode

Large amounts of anions and heavy metals coexist in flue gas desulfurization (FGD) wastewater originating from coal-fired power plants, which cause serious environmental pollution. Electrocoagulation (EC) with Fe/C/Al hybrid electrodes was investigated for the separation of fluoride and nickel ions from a FGD wastewater. The study mainly focused on the technology parameters including anode electrode type, time, inter-electrode distance (5–40 mm), current density (1.88–6.25 mA/cm2) and initial pH (4–10). The results showed that favorable nickel and fluoride removal were obtained by increasing the time and current density, but this led to an increase in energy consumption. Eighty-six percent of fluoride and 98% of Ni(II) were removed by conducting the Fe/C/Al EC with a current density of 5.00 mA/cm2 and inter-electrode distance of 5 mm at pH 4 for 25 min and energy consumption was 1.33 kWh/m3. Concomitant pollutants also achieved excellent treatment efficiency. The Hg, Mn, Pb, Cd, Cu, SS and chemical oxygen demand were reduced by 90%, 89%, 92%, 88%, 98%, 99.9% and 89%, respectively, which met stringent environmental regulations

A High Flux Electrochemical Filtration System Based on Electrospun Carbon Nanofiber Membrane for Efficient Tetracycline Degradation

In this work, an electrochemical filter using an electrospun carbon nanofiber membrane (ECNFM) anode fabricated by electrospinning, stabilization and carbonization was developed for the removal of antibiotic tetracycline (TC). ECNFM with 2.5 wt% terephthalic acid (PTA) carbonized at 1000 °C (ECNFM-2.5%-1000) exhibited higher tensile stress (0.75 MPa) and porosity (92.8%), more graphitic structures and lower electron transfer resistance (23.52 Ω). Under the optimal condition of applied voltage 2.0 V, pH 6.1, 0.1 mol L−1 Na2SO4, initial TC concentration 10 ppm and membrane flux 425 LMH, the TC removal efficiency of the electrochemical filter of ECNFM-2.5%-1000 reached 99.8%, and no obvious performance loss was observed after 8 h of continuous operation. The pseudo-first-order reaction rate constant in flow-through mode was 2.28 min−1, which was 10.53 times higher than that in batch mode. Meanwhile, the energy demand for 90% TC removal was only 0.017 kWh m−3. TC could be converted to intermediates with lower developmental toxicity and mutagenicity via the loss of functional groups (-CONH2, -CH3, -OH, -N(CH3)2) and ring opening reaction, which was mainly achieved by direct anodic oxidation. This study highlights the potential of ECNFM-based electrochemical filtration for efficient and economical drinking water purification