Enhanced Tetracycline Adsorption of MoS2 via Defect Introduction Under Microwave Irradiation.

Defect engineering is a promising method for improving the performance of MoS2 in various fields. In this study, sulfur-defect-enriched MoS2 (SD-MoS2) nanosheets were fabricated via a facile microwave-hydrothermal strategy in 10 min for tetracycline (TC) adsorption applications. The introduction of sulfur defects in MoS2 induced more exposed unsaturated sulfur atoms at the edge, enhancing the interaction between the adsorbent and antibiotic and improving the adsorption activity of the antibiotic. Density functional theory calculations further revealed that sulfur defects in MoS2 could alter the electronic structure and exhibited low TC adsorption energy of -2.09 eV. This work provides a new method for fabricating MoS2 nanosheets and other transition metal dichalcogenide-based adsorbents with enhanced antibiotic removal performance and a comprehensive understanding of antibiotic removal mechanisms in SD-MoS2.

Defluorination study of spent carbon cathode by microwave high-temperature roasting.

Spent carbon cathode (SCC) produced in the process of aluminum electrolysis is a typical toxic and hazardous solid waste. Therefore, the harmless treatment of SCC is extremely important for the green development of aluminum electrolysis industry. In this paper, the microwave-assisted high-temperature roasting technology was developed to remove fluorides in SCC for recycling of this cathode. The melting point, dielectric parameter, crystalline structure, surface chemical property, elemental composition, morphological structure, carbon graphitization and surface area were characterized using thermogravimetric analysis and differential scanning calorimetry, high-temperature composite conductivity analyzer, X-ray diffraction, X-ray fluorescence, X-ray photoelectron spectroscopy, scanning electronic microscopy, transmission electron microscopy, Raman spectroscopy and isothermal N2 adsorption-desorption method. The content of fluorides in raw and treated SCC was measured by ion activity meter. The results showed that the phase of sodium fluoride and cryolite would transform from solid to liquid when the temperature was higher than 1098.5 °C, and the SCC exhibited good performance on wave absorption with the action depth of 1 cm. The SCC was mainly composed of 57.94 wt% C, 14.23 wt% NaF, 1.80 wt%, CaF2, 15.06 wt% Na3AlF6, and 10.97 wt% Other. After treatment under microwave, the graphite carbon exhibited pitting structure and the fluorides could be effectively removed. In addition, the average layer spacing of graphite was increased from 0.34 to 0.36 nm. The defluorination of SCC could be enhanced with the increase of roasting temperature, which would attain 95.4% at 1500 °C. Compared with the traditional roasting method, the process under microwave showed more defects, which would provide a new guidance for the treatment and recycling of spent SCC.

Microwave hydrothermal sulfuric acid leaching of spent cathode carbon from aluminum electrolysis for high efficiency removal of insoluble calcium fluoride.

Toxic substances, like fluoride salts present in spent cathode carbon (SCC), have been a great risk to the environment and public health. Our approach involves alkali leaching to eliminate soluble fluoride, followed by microwave hydrothermal acid leaching to efficiently remove insoluble CaF2 from SCC. The optimized conditions, including a temperature of 353 K, a solid-liquid ratio of 1:20, and a 60-minute reaction time, resulted in an impressive 95.6 % removal of fluoride from SCC. Various characterization techniques were employed to analyze the composition, micro-morphology, and elemental content of the materials before and after the leaching process. Furthermore, critical process parameters on the leaching separation of insoluble CaF2 during microwave hydrothermal acid leaching were systematically investigated. The study removal mechanism revealed the transformation of insoluble CaF2 in the process of microwave oxidation insertion-hydrothermal acid leaching for SCC. The kinetic characteristics of the two-stage leaching process of CaF2 at different temperatures were analyzed according to the shrinkage kernel model. The results indicate that the two-stage leaching process of CaF2 is affected by mixing control and by diffusion control, severally. The expansion of the graphite flake layer of SCC through oxidative intercalation was identified as a critical process for the thorough removal of CaF2. Microwave hydrothermal acid leaching demonstrated a 17 % improvement over traditional hydrothermal acid leaching within the same reaction time, showcasing a noteworthy enhancement in fluoride removal. Consequently, the microwave oxidizing intercalation-hydrothermal acid leaching treatment of SCC, as explored in this study, offers an effective approach for achieving deep defluoridation of SCC.