RESUMEN
In order to reduce the environmental hazards of red mud (RM) and realize its resource utilization, in this study, RM-based iron-carbon micro-electrolysis material (RM-MEM) were prepared by a carbothermal reduction process using RM as raw material. The influence of the preparation conditions on the phase transformation and structural characteristics of the RM-MEM were investigated during the reduction process. The ability of RM-MEM to remove organic pollutants from wastewater was evaluated. The results showed that RM-MEM prepared at a reduction temperature of 1100 °C, a reduction time of 50 min and a coal dosage of 50% had the best removal effect for the degradation of methylene blue (MB). When the initial MB concentration was 20 mg L-1, the amount of RM-MEM material was 4 g L-1, the initial pH was 7, and the degradation efficiency reached 99.75% after 60 min. When RM-MEM is split into carbon free and iron free parts for use, the degradation effect becomes worse. Compared to other materials, RM-MEM has lower cost and better degradation. X-ray diffraction (XRD) analysis showed that hematite was transformed to zero-valent iron with the increase in the roasting temperature. Scanning electron microscopy (SEM) and energy spectroscopy (EDS) analysis showed that micron-sized ZVI particles were formed in the RM-MEM, and increasing the carbon thermal reduction temperature was beneficial to the growth of zero-valent iron particles.
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Contaminantes Ambientales , Contaminantes Químicos del Agua , Aguas Residuales , Contaminantes Ambientales/análisis , Contaminantes Químicos del Agua/análisis , Difracción de Rayos X , TemperaturaRESUMEN
This study was conducted to investigate the mechanisms of enhanced microfine flake graphite (MFG) flotation by nanobubbles generated based on the principle of hydrodynamic cavitation. The effects of nanobubbles on graphite surface properties were characterized in terms of the flotation kinetics, collector adsorption behavior, Zeta potential, IR spectra, contact angle, etc. The results show that the surface nanobubbles increased the hydrophobic attraction and reduced the electrostatic repulsion between the graphite particles and collector molecules, significantly improving the flotation selectivity and the kinetic flotation rate and promoting the agglomeration of MFG.
RESUMEN
The graphite-phase carbon nitride (g-C3N4) photocatalytic materials were prepared by one-step calcination method to degrade methylene blue (MB) and potassium butyl xanthate (PBX) under visible light irradiation. The prepared g-C3N4 photocatalytic materials were investigated in detail by various characterizations, and the experiments showed that the graphitic phase carbon nitride photocatalytic materials were successfully prepared by the one-step calcination method. The material possesses excellent optical properties and strong visible light absorption, thus achieving photocatalytic degradation of MB and PBX. The catalyst dosage, pH, the initial concentration of pollutants have important effects on photocatalytic activity of MB and PBX. The photocatalytic degradation efficiency was 98.99% for MB and 96.83% for PBX under the optimal conditions (catalyst dosage, initial pollutant concentration and pH value were 500 mg L-1, 20 mg L-1 and 7, respevtively). The photocatalytic mechanisms on MB and PBX were elucidated. ·OH was the key specie for MB, while ·O2- was the key specie for PBX. This study advances the development of photocatalytic technology for mineral wastewater.
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Contaminantes Ambientales , Grafito , Catálisis , Grafito/química , Luz , Azul de Metileno/química , Nitrilos , Compuestos de Nitrógeno , Potasio , Aguas ResidualesRESUMEN
High-resolution transmission electron microscopy observations of bastnäsite from the Maoniuping rare earth element (REE) deposit at Panxi, SW China, revealed the presence of nanoparticles in the surface of bastnäsite crystal. The nanoparticles are identified as the bastnäsite nanocrystals, with 5-30 nm in length, by energy-dispersive spectrometry and fast fourier transform patterns. This represents the first observation of bastnäsite nanoparticle in nature, confirming a new form of migration and precipitation of La and Ce in the hydrothermal fluids. Meanwhile, we herein reveal that random attachment of small bastnäsite nanoparticles during aggregation-based growth initially produces large bastnäsite nanoparticles, driven by the tectonic stress. Subsequent evolution of the random aggregation and orientation of large bastnäsite nanoparticles result in bastnäsite crystal formation, driven by the tectonic stress and inherent surface stress. This underlines the bastnäsite crystallization by random aggregation and the significant role of tectonic stress in forming the bastnäsite crystal in REE deposit.
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Metales de Tierras Raras , Nanopartículas , China , Cristalización , Metales de Tierras Raras/análisis , Microscopía Electrónica de TransmisiónRESUMEN
A non-enzymatic amperometric sensor using natural molybdenite (MLN) electrodeposited with methylene blue (MB) has been fabricated and characterized and its analytical performances were investigated for the determination of ascorbic acid (AA). The surface morphology of the electrode modified by electrodeposited MB was studied by use of the Advanced Mineral Identification and Characterization System (AMICS) and laser confocal high-temperature scanning microscope (LCSM). The poly(MB) and MLN immobilized sensor showed good stability, reproducibility, sensitivity, and selectivity. It exhibited a linear performance range from 3 to 1000 µM, with a lower detection limit of 0.083 µM (signal/noise = 3) and short response time (< 5 s). No obvious decrease in the current was observed after 20 days storage. The methodology reproducibility of this sensor was 2.6%. It showed good anti-interference ability for the potential interfering compounds. The poly(MB) film not only can enhance the electron-transfer rate but also increase the lifetime of the sensor. This study demonstrated the applicability of natural molybdenite for the fabrication of non-enzymatic electrochemical AA sensor.
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Ácido Ascórbico/química , Técnicas Electroquímicas/métodos , Azul de Metileno/química , Molibdeno/química , Carbono/química , Catálisis , Electrodos , Electrólitos , Concentración de Iones de Hidrógeno , Límite de Detección , Modelos Lineales , Reproducibilidad de los Resultados , Sensibilidad y EspecificidadRESUMEN
A self-assembly method was adopted to synthesize loading architecture of ZnO/g-C3N4 heterojunction composites by hybridization of g-C3N4 nanosheets and ZnO nanoparticles utilizing a refluxing method at a low temperature. More importantly, we provided a novel route to regulate the π-π restacking thickness of the g-C3N4 nanosheets among ZnO/g-C3N4 composites by the controlling the refluxing time in the ethanol solution, which can optimize the surface hybrid structure, optical response and photocatalytic activity. Among all of samples, ZnO/g-C3N4 composites with a refluxing 12â¯h showed the enhancement of photocatalytic activity. The enhanced visible light photocatalytic activity of ZCN-12 composites can be ascribed to the synergistic effects of the construction of hybrid structures, reduction of structural defects of g-C3N4 nanosheets and suitable π-π restacking g-C3N4 nanosheets loading thickness.
Asunto(s)
Grafito , Nanocompuestos/química , Compuestos de Nitrógeno , Óxido de Zinc , Catálisis , Grafito/química , Luz , Tamaño de la Partícula , Procesos FotoquímicosRESUMEN
Molybdenite (MLN) was physically co-adsorbed with Ag nanoparticles (Ag) on a glassy carbon electrode (GCE) for selectively sensing of ascorbic acid (AA). The composite was characterized with a scan electron microscope, a high-temperature confocal laser scanning microscope, an X-ray diffractometer, an X-ray fluorescence analyzer and electrochemical methods. The prepared MLN/Ag-GCE sensor exhibited good properties including a linear range from 3.0 × 10-5 to 1.0 × 10-3 M toward AA, a low detection limit of 1.5 × 10-5 M, good selectivity, excellent reproducibility, and good stability. The synergistic effect between MLN and Ag nanoparticles results in an enhancement of the electrocatalytic activity for molybdenite.
RESUMEN
Carbon black (CB) and carbon nanotube (CNT) co-doped polyimide (PI) modified glassy carbon electrode (CB-CNT/PI/GCE) was first prepared for the simultaneous determination of ascorbic acid (AA), dopamine (DA), and uric acid (UA). The CB-CNT/PI/GCE exhibited persistent electrochemical behavior and excellent catalytic activities. Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) were used for the simultaneous detection of AA, DA, and UA in their ternary mixture. The peak separations between AA and DA, and DA and UA, are up to 166 mV and 148 mV, respectively. The CB-CNT/PI/GCE exhibited high sensitivity to DA and UA, with the detection limit of 1.9 µM and 3 µM, respectively. In addition, the CB-CNT/PI/GCE showed sufficient selectivity and long-term stability, and was applicable to detect AA, DA, and UA in human urine sample.
RESUMEN
In a multi-component homogeneous system, the relationship between partial molar and molar quantity (RPMQ) is proved to be an equivalent relation of the Gibbs-Duhem equation. The universal characteristics of a thermodynamic model to conform to the Gibbs-Duhem equation are inferred from the RPMQ. Based on the inference, an asymmetric regular solution model is suggested to deal with those systems that exhibit strong negative deviation, strong positive deviation, and both strong positive and negative deviation from ideality.