RESUMEN
Normally, the acidic impurities in hemihydrate phosphogypsum (HPG) must be neutralized when HPG is utilized, and a little amount of calcium hydroxide (CH) is the best choice. In this paper, the effects of excessive CH (5 wt.%, 10 wt.%, 15 wt.% and 20 wt.% of HPG) for carbonation curing on the performance of hardened HPG paste were studied. According to the results of macro tests and microanalyses of XRD, TG, SEM-EDS, MIP and N2 physisorption, it could be verified that CaF2, Ca3(PO4)2 and a large amount of nanoscale CaCO3 crystals were produced as a result of neutralization and carbonation, and the compressive strength and the water resistance of carbonated HPG + CH paste were significantly improved due to the effects of nanoscale CaCO3 crystals on pore refinement and the coverage on the surfaces of gypsum crystals of the hardened paste. Therefore, this study suggests a feasible and green method for recycling HPG/PG, with the collaborative effects of neutralization, performance enhancement and reductions in CO2 emissions.
RESUMEN
Cobalt is a strategic and critical mineral whose demand is expected to grow rapidly. This study aims to provide a comprehensive summary of cobalt extraction and recovery research from 2012 to 2021 in the form of bibliometric analysis. The work was based on the Science Citation Index Expanded (Web of Science) and carried out using the InCites of Clarivate for bibliometric data analysis and the software VOSviewer for science mapping. By analyzing a dataset of 4967 publications, the most influential journals, countries, authors, institutions, and publications were identified, and the keyword co-occurrence networks were mapped. The China mainland produced the most publications, while the USA had the highest average number of citations per publication and the UK was the most collaborative with other countries. The keyword analysis shows that the research hotspots gradually shifted over time from early means and methods for determination of cobalt in solution to recovery of cobalt from spent lithium batteries, smelting slag, copper-cobalt ore, etc. The research will be focused on further improvement and optimization of the separation, extraction, and recovery processes of cobalt from spent batteries in recent and future years, and three approaches were promoted to facilitate economization and industrialization of the processes in this field.
