Recovery of Rare Earth Elements by Carbon-Based Nanomaterials—A Review

et al. 2020

Sustain Environ Res

Rare earth elements (REE) are essential for the production of technological devices. However, their high demand and low availability, together with an increase in electronic waste generation, compel the development of efficient, economic and green methods for recovering these elements from electronic waste. In this work, a facile method for selective recovering of REE from Liquid Crystal Display (LCD) screen wastes, employing ultrasound assisted leaching is presented. The screen wastes were milled and sieved to pass through a − 325 mesh sieve (44 μm). The milled powder was subjected to ultrasound-assisted leaching in an aqueous medium, at room temperature (25 °C) and pH 6 for 60 min. Subsequently, a magnetic separation was applied to the leach residue. Inductively coupled plasma was employed to quantitatively analyze the composition of the LCD powders and determine the effectiveness of the extraction process. Scanning Electron Microscopy/Energy Dispersive X-Ray Spectroscopy allowed qualitative chemical analysis of the solid materials. The results show that the LCD screen wastes are formed, mainly, by amorphous oxides of Si, Fe, In, Sn and REE. The amount of Gadolinium (Gd) and Praseodymium (Pr) in the wastes were 93 and 24 mg kg− 1, respectively, which justifies their recovery. X-ray diffraction analysis of the magnetic portion of the leached residue, confirmed the presence of an amorphous phase together with crystalline metallic iron alloy. The magnetic behavior, obtained by Vibration Sample Magnetometry, helped to understand the nature of the residues. The formation of this metallic alloy is attributed to the effect of high power ultrasonic during the leach. It was confirmed that the magnetic residue concentrates and recovers 87 wt% of Gd and 85 wt% of Pr contained in the original material. Therefore, ultrasound-assisted leaching is a selective and facile method for recovering Gd and Pr from waste LCD.

Section: Resultsmentioning

confidence: 95%

Facile method for the selective recovery of Gd and Pr from LCD screen wastes using ultrasound-assisted leaching

et al. 2020

Sustain Environ Res

“…The results are shown in Table 1 as the percentages of the total element in the initial LCD powder in each of the following states: present in the leach liquor, remaining in the LCD powder (nonmagnetic residue) or recovered in the magnetic residue. According to these results, the magnetic material (0.3 g) is composed mainly of Fe, Pr and Gd, corresponding to 94.5%, 86.8% and 85.4%, respectively, of the total amount of each element contained in the LCD screens; this represents an important concentration of these elements, with a higher recovery compared to conventional leaching [34]. On the other hand, 98.6% of the In, 73.9% of the Sn and 84.34% of the Er remained in the non-magnetic solid (2.58 g).…”

Section: Resultsmentioning

confidence: 95%

Facile method for the selective recover of Gd and Pr from LCD screen wastes using ultrasound-assisted leaching

et al. 2020

Preprint

Rare earth elements (REE) are essential for the production of technological devices. However, their high demand and low availability, together with an increase in electronic waste generation, compel the development of efficient, economic and green methods for recovering these elements from electronic waste. In this work, a facile method for selective recovering of REE from Liquid Crystal Display (LCD) screen wastes, employing ultrasound assisted leaching is presented. The screen wastes were milled and sieved to pass through a -325 mesh sieve. The milled powder was subjected to ultrasound-assisted leaching in an aqueous medium, at room temperature (25 °C) and pH 6 for 60 minutes. Subsequently, a magnetic separation was applied to the leach residue. ICP was employed to quantitatively analyze the composition of the LCD powders and determine the effectiveness of the extraction process. SEM-EDS allowed qualitative chemical analysis of the solid materials. The results shown that the LCD screen wastes are formed, mainly, by amorphous oxides of Si, Fe, In, Sn and REE. The amount of Gadolinium (Gd) and Praseodymium (Pr) in the wastes were 93 mg kg-1 and 24 mg kg-1, respectively, which justifies their recovery. X-ray diffraction analysis of the magnetic portion of the leach residue, confirmed the presence of an amorphous phase together with crystalline metallic iron alloy. The magnetic behavior, obtained by Vibration Sample Magnetometry, helped to understand the nature of the residues. The formation of this metallic alloy is attributed to the effect of high power ultrasonic during the leach. It was confirmed that the magnetic residues concentrates and recovers 87 wt. % of Gd and 85 wt. % of Pr contained in the original material. Therefore, ultrasound-assisted leaching is a selective and facile method for recovering Gd and Pr from waste LCD.

“…The chemical composition of the leach liquor and the solid residues (magnetic and non-magnetic) were quantified by ICP; the results are shown in Table 1. According to these results, the magnetic material (0.3 g) is composed mainly of Fe, Pr and Gd, which corresponds to 94.5%, 86.8% and 85.4%, respectively, of the total amount of each element in the LCD screens; this represents an important concentration of these elements, which is higher leaching efficiency comparing with conventional leaching [34]. On the other hand, 98.6% of the In, 73.9% of the Sn and 84.34% of the Er remained in the non-magnetic solid (2.58 g).…”

Section: Resultsmentioning

confidence: 97%

Facile method for the selective recover of Gd and Pr from LCD screen wastes using ultrasound-assisted leaching

et al. 2020

Preprint

Rare earth elements (REE) are essential for the production of technological devices. However, their high demand and low availability, together with an increase in electronic waste generation, compel the development of efficient, economic and green methods for recovering these elements from electronic waste. In this work, a facile method for selective recovering of REE from Liquid Crystal Display (LCD) screen wastes, employing ultrasound assisted leaching is presented. The screen wastes were milled and sieved to pass through − 325 mesh sieve. The milled powder was summited to ultrasound-assisted leaching in aqueous medium, at room temperature (25 °C) and pH 6 for 60 minutes. Subsequently, a magnetic separation was applied into the leach residue. ICP was employed to quantitatively analyze the composition of the LCD powders and the effectiveness of the extraction process. SEM-EDS allowed qualitatively analyzing the chemical composition of the solid materials. The results shown that the LCD screen wastes are formed, mainly, by amorphous oxides of Si, Fe, In, Sn and REE. The amount of Gd and Pr in the wastes were 93 mg/kg and 24 mg/kg, respectively; It represents enough reason to recover it. X-ray diffraction analysis of the magnetic portion of the leaching residue, confirmed the presence of an amorphous phase together with crystalline metallic iron alloy. The magnetic behavior, obtained by Vibration Sample Magnetometry, helped to understand the nature of the residues. The formation of this metallic alloy is attributed to the effect of high power ultrasonic during the leaching. It was confirmed that the magnetic residues concentrates and recovers 87 wt. % of Gd and 85 wt. % of Pr of the total content of these REE in the magnetic residue. Therefore, ultrasound-assisted leaching is a selective and facile method for recovering Gd and Pr from a screen wastes.