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Prospective on the recovery of waste iron phosphate: Structure regulation by calcination and dissolution kinetics in acid solution
No full textThe regeneration of waste iron phosphate has not been achieved. In this study, a calcination-assisted structure regulation-solution purification process was proposed to recover waste iron phosphate based on the dissolution performance of various iron phosphate. It has been demonstrated that iron phosphate dihydrate can transform from monoclinic to hexagonal and trigonal structures at 573 K and 773 K, respectively. The removal of crystal water changes the stable structure coordinated by octahedron to the metastable structure coordinated by tetrahedral. The structure conversion leads to a change in acid dissolution performance. The dissolutions of iron phosphate dihydrate and anhydrous iron phosphates are all controlled by chemical reactions but with various apparent activation energy, 70.84 kJ/mol for iron phosphate dihydrate, 56.15 kJ/mol for tridymite FePO4, and 44.36 kJ/mol for alpha-quartz FePO4. The dissolution efficiency was increased from 0.23% (iron phosphate dihy-drate) to 64% (tridymite FePO4) and 86% (alpha-quartz FePO4) at 293 K, and from 4% (iron phosphate dihydrate) to 89% (tridymite FePO4) and 88% (alpha-quartz FePO4) at 353 K, in 2 h. Guided by this dissolution behavior, the waste iron phosphate was calcined at 473 K, dissolved in 1 mol/L sulfuric acid, and hydrothermally treated at 393 K. Iron phosphate dihydrate that met the battery standard was regenerated. The research has provided an effective strategy to recover the waste iron phosphate
Facile synthesis of N-rich carbon nanosheets derived from antibiotic mycelial dregs as efficient catalysts for peroxymonosulfate activation
No full textNitrogen-rich carbon nanosheets using hazardous waste penicillin mycelial dregs (PMD) as the sole precursor were successfully synthesized amid molten salt-assisted pyrolysis and applied as catalysts for peroxymonosulfate (PMS) activation to degrade acid orange 7 (AO7). The structural properties and the associated catalytic per-formances of carbon nanosheets were precisely regulated by molten salt (NaCl/KCl) mass ratios and pyrolysis temperatures. Carbon nanosheets prepared at a molten salt ratio of 6 and a pyrolysis temperature of 800 degrees C possessed an optimized catalytic performance, achieving both high effective and efficient decolorization of AO7 than activated carbon catalysts. It was likely attributed to the combination of high graphitic N content and defective carbon structures from nanosheets through quantitative structure-activity relationships analysis. Both radical and non-radical pathways were recognized to be responsible for AO7 degradation, while surface-bound radicals generated from catalyst surface-PMS complexes in non-radical pathways were the main reactive oxygen species. This work offers a green and facile method to prepare high graphitic N content and defect-rich carbon nanosheets from nitrogen-rich biowastes, highlighting its promising catalytic properties for environmental remediation, synchronously expanding the means of resourceful and harmless treatment of PMD to improve the sustainability of antibiotic pharmaceutical production
China Central Guidance on Local Science and Technology Development Fund of Henan Province[Z20221343028]
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Selective extraction and separation of REEs from NdFeB magnets scrap using co-chlorination and water leaching
No full textAn approach of co-chlorination followed by water leaching to achieve the selective extraction of rare earth elements (REEs) from NdFeB magnets scrap (scrap) was studied. Co-chlorination refers to the synergistic effect of direct and indirect chlorination reactions. The feasibility of direct and indirect chlorination was explored from both theoretical and practical standpoints. The transformation between NdCl3 and NdOCl during the chlorination roasting process was discovered by X-ray diffraction (XRD) analysis combined with Scanning Electron Microscopy-Energy Dispersive X-Ray Spectroscopy (SEM-EDS) as well as chemical analysis. The formation of NdOCl was prevented by regulating FeCl3 center dot 6H(2)O dosage, chlorination temperature and chlorination time, then the negative impact from the hydrolysis of NdOCl was avoided. As a result, the complete chlorination of REEs was successfully achieved by using co-chlorination and water leaching. The results showed that 96.51% REEs and 64.29% Co can be synchronously extracted into the leaching solution under appropriate conditions. After the separation of REEs and iron, 92 wt% iron oxide was obtained. This work offers an effective method for recovering REEs from NdFeB magnets scrap
