The supply shortage of rare earth elements (REEs) for use in numerous high-tech applications has become an incentive for the prospecting of REEs from coal and coal discard. In this study, an ...optimised leaching process for the recovery of REEs from coal using the Design Expert (DOE) is reported. Response surface methodology (RSM) was used to investigate the effect and to determine the optimal leaching parameters for the two non-calcined coal samples. An optimised REE leaching recovery of 18.95% and 41.35% was obtained for the non-calcined Run-of-Mine (ROM) coal and discard coal, respectively. This optimised recovery was obtained as the HCl concentration increased from 0.5 M to 2 M, leaching temperature increased from 30 °C to 50 °C, whilst the solid:liquid ratio decreased from 40 g/L to 10 g/L. Statistical analysis indicated that the leaching parameters studied were important and controlled the REE leaching recovery model. Optimisation results also indicate that the calcined coals at 700 °C have the highest leaching recovery of 94.73% (ROM) and 98.17% (discard), respectively. Calcination also increased the concentration of REEs in the ROM sample from 225 ppm to 347 ppm and discarded the sample from 245 ppm to 363 ppm at 700 °C. Given the effect of the lixiviants investigated, the leaching efficiency of HClO4 for REE recovery was significantly lower than HCl and HNO3 under optimal leaching conditions. The discard coal used in this study had a significantly higher potential for REE recovery than ROM coal because it had a higher REE abundance and greater recovery.
Display omitted
•Coal and coal discard have been identified as a secondary source of REEs.•Review of physical beneficiation techniques of REEs from coal and coal discard.•Pre-treatment and ...hydrometallurgical processing of REEs from coal and coal discard are discussed.•Heap leaching of coal discard dumps to recover REEs.•Summary of REEs separation and/or recovery techniques.
Given the geographical imbalance distribution and supply shortage of rare earth elements (REEs) in renewable energy processes, magnets, many high-tech technologies, etc., researchers are increasingly seeking to recover REEs from unconventional sources such as coal and coal by-products. This article provides a brief overview of the REEs mode of occurrence and its association in coal. It also discusses existing and potential beneficiation strategies for enriching REEs from coal and coal discard. Furthermore, the hydrometallurgical leaching of REEs from coal and coal discard is reviewed and a summary of recent outcomes on REEs recovery from the coal source is presented. The review validated the technical feasibility of the physical beneficiation of REE minerals from coal without a significant particle size reduction to produce high-grade REE feedstocks for leaching. Although ultrafine milling results in higher REE recovery values, additional milling costs may affect the viability of the process. Overall, the study confirms the abundance of REEs in coal, identifies gaps in knowledge, and highlighs future research that must be addressed to advance REEs recovery from these sources.
Display omitted
•The total rare earth elements contents for the high ash coal samples was ≥ 225 ppm.•LREEs exhibited a greater association with the mineral matter.•HREEs manifest a greater affinity ...for the organic fraction.•HREEs were distributed with kaolinite dispersed in cleats of the carbon matrices.•A Coutlook ≥ 0.88 for both coals suggests a potential promising REE source.
Conventional deposits of rare earth elements (REEs) cannot meet the high demand for REEs globally. Therefore, the prospecting of REEs from alternative sources like high ash coal is vital. In this study, coal discard and “Run of Mine” (ROM) coal were studied to evaluate the abundance and association of REEs in these materials. The TESCAN Integrated Mineral Analyzer (TIMA) and X-ray diffractometer (XRD) techniques were employed to determine the mineralogy of the coal samples. TIMA was further utilized to investigate the REE associations and distributions, whilst the inductively coupled plasma-mass spectrometry (ICP-MS) was used to quantify the amount of REEs in the coal samples. Quantitative analysis results revealed that the total REE content in the coal discard and ROM coal was above 225 ppm. Furthermore, the results show that the dominant REE-bearing minerals in the discard and ROM coal samples were kaolinite, pyrite, and hematite. In addition, the heavy REEs (HREEs) displayed a strong affinity for the organic macerals and were enriched in the ROM coal. The encouraging results of significantly light REEs (LREEs) relative to HREEs in both coals suggest they are viable prospects for REE extraction. Hydrometallurgical leaching is therefore recommended to assess the potential for REE recovery from these sources.
Recycling coal-based waste (CBW) into composites suitable as a building material might be a necessary response to combat its risk to the environment. Therefore, the objective of this study was to ...investigate the microstructure and performance of coal composites produced from CBW and polysiloxane polymer (SPR-212). Four types of CBW that differ in physicochemical properties were examined. Fourier transform infrared spectroscopy results indicated that the higher the intensity of the C=C bonds in the CBW, the higher the pyrolysis mass loss and shrinkage experienced by the composites during pyrolysis. The continuous operating temperature of the composites is up to 600 °C. However, at temperatures above 600 °C, composites containing carbon content greater than 36% manifested dramatic degradation. Pyrolysis mass loss in the range of 5.28 to 29.62% was obtained for all the composites. The density range of the composites is between 1.5 and 1.9 g per cubic centimetre. The water absorption of all the composites is within the range of 0 to 25% and is comparable to many building materials. Notably, the composites containing total carbon less than 10% registered a water contact angle greater than 90°, indicating the low wettability of their surface. Furthermore, composites that embodied the highest total carbon (63%) displayed the worst structural property. The findings of this study lay the foundation for further development of high-quality structural coal composites from CBW and the SPR-212 preceramic polymer through optimisation of the processing conditions.
Graphical abstract
Assessment of structural composites produced from coal-based waste and polymer-derived SiOC ceramics
Abstract only
Aims/Purpose:
The objective is to study the clinical particularities and the results therapies.
Methods:
This is a retrospective study of 15 children (25 eyes) since 2012 until 2021 at ...the paediatric ophthalmology department of the August 20 hospital from Casablanca‐Morocco.
Results:
In our study, there were 15 cases including 9 cases (13 eyes) of syndrome of Sturge weber Krabb, 2 cases (4 eyes) of Axenfield Reiger syndrome, 2 case (4 eyes) of Peters syndrome 1 case (2 eyes) of lower syndrome, 1 case (2 eyes) of polymalformative syndrome (cardiopathy, pulmonary stenosis, bilateral femoral epiphyseal dysplasia). The average age is 8 years with a sex ratio of 1.7, the notion of inbreeding exists in 43%. The warning sign was buphthalmos in 72% of cases, on clinical examination the cornea was edematous in 60% of cases with an average diameter 13.2 mm corneal, with anterior iris synechiae in 32% of cases, bilateral cataract in 4% of cases, persistence of primary vascularization in 4% of cases and an average of excavation of 7/10, an average TO at 34 mmHg. The most common systemic abnormalities were facial angioma (56%), epilepsy (41%) and mental retardation (30%).Treatment was trabeculectomy in 96% of cases associated with medical treatment in 100% of cases.
Conclusions:
It is a rare, blinding pathology, the clinical forms of which are numerous with complex ocular and general malformations, which can pose etiological and therapeutic problems that are difficult.
References
1. Kenyon KR. Mesenchymal dysgenesis in Peters' anomaly, sclerocornea and congenital endothelial dystrophy. Exp Eye Res 1975; 21: 125–42.
2. Trans Am Ophthalmol Soc 1958; 56: 507–70 ‐ PubMed.
