TY - JOUR
T1 - Simultaneous determination of rees in coal samples using the combination of microwave-assisted ashing and ultrasound-assisted extraction methods followed by icp-oes analysis
AU - Zuma, McEliseni C.
AU - Nomngongo, Philiswa N.
AU - Mketo, Nomvano
N1 - Publisher Copyright:
© 2021 by the author. Licensee MDPI, Basel, Switzerland.
PY - 2021/10
Y1 - 2021/10
N2 - The world during the COVID-19 pandemic has led to extensive use of virtual activities by means of electronic devices, which are made up of rare earth elements (REEs). This means that quantitative knowledge of REEs in various resources is crucial for the development of effective recovery methods. Therefore, this report describes a simple microwave assisted ashing followed by ultrasound-assisted extraction (MAA-UAE) for quantitative determination of REEs in coal samples using inductively coupled plasma-optical emission spectroscopy (ICP-OES). Firstly, coal samples were ashed at 55 °C for 4.5 h to form white ashes, which were then treated with dilute HNO3 acid under ultrasonication to enhance the extraction of REEs. The quantitative recoveries (86–120%) of REEs were obtained when 1 mol L−1, 0.1 g, 40 °C, 20 min, and high frequency were applied for [HNO3], sample mass, ultrasonic bath temperature, extraction time, and ultrasonic bath frequency, respectively. The method detection limits of the proposed MAA-UAE method were between 0.0075 and 0.59 µg g−1 with satisfactory precision (<5%). The concentration levels of REEs in South African coals ranged from 1.4 to 105 µg g−1, suggesting that this coal can be a resource for REEs.
AB - The world during the COVID-19 pandemic has led to extensive use of virtual activities by means of electronic devices, which are made up of rare earth elements (REEs). This means that quantitative knowledge of REEs in various resources is crucial for the development of effective recovery methods. Therefore, this report describes a simple microwave assisted ashing followed by ultrasound-assisted extraction (MAA-UAE) for quantitative determination of REEs in coal samples using inductively coupled plasma-optical emission spectroscopy (ICP-OES). Firstly, coal samples were ashed at 55 °C for 4.5 h to form white ashes, which were then treated with dilute HNO3 acid under ultrasonication to enhance the extraction of REEs. The quantitative recoveries (86–120%) of REEs were obtained when 1 mol L−1, 0.1 g, 40 °C, 20 min, and high frequency were applied for [HNO3], sample mass, ultrasonic bath temperature, extraction time, and ultrasonic bath frequency, respectively. The method detection limits of the proposed MAA-UAE method were between 0.0075 and 0.59 µg g−1 with satisfactory precision (<5%). The concentration levels of REEs in South African coals ranged from 1.4 to 105 µg g−1, suggesting that this coal can be a resource for REEs.
KW - Coal
KW - Inductively coupled plasma-optical emission spectroscopy
KW - Microwave-assisted ashing
KW - Rare earth elements
KW - Ultrasound-assisted extraction
UR - http://www.scopus.com/inward/record.url?scp=85116573618&partnerID=8YFLogxK
U2 - 10.3390/min11101103
DO - 10.3390/min11101103
M3 - Article
AN - SCOPUS:85116573618
SN - 2075-163X
VL - 11
JO - Minerals
JF - Minerals
IS - 10
M1 - 1103
ER -