Voltammetric and Spectroscopic Determination of Rare Earth Elements in Fresh and Surface Water Samples

Martin Makombe,Bongiwe Silwana,Charlton Van Der Horst,Vernon Somerset,Emmanuel Iwuoha

doi:10.3390/environments5100112

Abstract

The increasing demand for rare earth elements in green technology, electronic components, petroleum refining, and agricultural activities has resulted in their scattering and accumulation in the environment. This study determined cerium, lanthanum and praseodymium in environmental water samples with the help of adsorptive differential pulse stripping voltammetry (AdDPSV) and inductive coupled plasma-optical emission spectroscopy (ICP-OES). A comparison of the results of these two analytical techniques was also made. The accuracy and precision of the methods were evaluated by spiking water samples with a known amount of REEs. The detection limit obtained for the stripping analysis was 0.10 μg/L for Ce(III), and 2.10 μg/L for combined La(III) and Pr(III). The spectroscopic method of determination by ICP-OES was applied to the same samples to evaluate the effectiveness of the voltammetry procedure. The ICP-OES detection limit obtained was 2.45, 3.12 and 3.90 μg/L for Ce(III), La(III) and Pr(III), respectively. The results obtained from the two techniques showed low detection limits in voltammetry; the ICP-OES method achieved better simultaneous analysis. This sensor has been successfully applied for the determination of cerium, lanthanum, and praseodymium in environmental water samples, offering good results.

Highlights

Rare earth elements (REEs) make possible the high-tech world we live in today—from the miniaturization of electronics, to the enabling of green energy and medical technologies, to supporting a myriad of essential telecommunication and defense systems
Most rare earth elements consist of radioactive materials, which impose the risk of radioactive dust and water emissions [3]
The water samples were collected from streams and boreholes that are in close proximity to the rare earth mining activities at the Zandkopsdrift rare earth project in the Namaqualand region of Northern Cape Province, South Africa

Summary

Introduction

Rare earth elements (REEs) make possible the high-tech world we live in today—from the miniaturization of electronics, to the enabling of green energy and medical technologies, to supporting a myriad of essential telecommunication and defense systems. These elements have become irreplaceable in the world of technology, owing to their unique magnetic, phosphorescent, and catalytic properties [1]. Innovations in crop quality after the 1970s were a result of the use of rare earth micro fertilizers This led to largescale application of the fertilizers for crops such as wheat, rice, maize and mungbean [5], resulting in a large

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