Antimony film sensor for sensitive rare earth metal analysis in environmental samples

Improved borate fusion technique for determination of rare earth elements in electronic waste components

The information regarding the abundance of rare earth elements (REEs) in electronic waste components (EWC) helps the recycling industry. However, after the end of use, improper disposal may be detrimental to the environment by releasing toxic substances. An optimised alkaline borate fusion method for REEs determination in electronic waste (e-waste) was developed. It is divided into three phases. Firstly, the sample preparation stages were investigated. Secondly, the optimisation of experimental particulars comprises the choice of oxidiser, flux composition, non-wetting agents, fusion time, and sample to flux ratio. The third phase consists of spectroscopic determination by inductively coupled plasma optical emission spectroscopy (ICP-OES) and X-ray fluorescence (XRF) spectroscopy. The highest REEs recovery (mg/g of e-waste) were found more in fine fractions of less than 0.09 mm compared to gross fractions. The optimum and safe fusion conditions for e-waste were achieved after slow thermal decomposition up to 550°C, pulverisation to 90% of -53 µm, flux composition (90%LiBO₂ + 10% Li₂B₄O₇), 3:1 oxidant ratio of Na₂CO₃: NaNO₃, LiBr as the non-wetting agent. Also, a sample to flux ratio of 1:15 and a total fusion time of 10 min was optimised. The newly improved alkaline fusion results compared better to those obtained from classical mineral acid dissolution with at most 5% RSD on REEs studied. The alkaline borate fusion results in smartphones e-waste were at least 15% and 25% higher than in four acid digest and microwave-assisted digest techniques, respectively. The results indicated enrichment of REEs in smartphones followed by non-smartphones and computer waste.

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

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.