Browsing by Author "van der Horst, Charlton"

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    Spectroscopic and voltammetric analysis of platinum group metals in road dust and roadside soil
    (MDPI, 2018) van der Horst, Charlton; Silwana, Bongiwe; Iwuoha, Emmanuel; Somerset, Vernon
    The emission of toxic compounds by increasing anthropogenic activities affects human health and the environment. Heavy road traffic and mining activities are the major anthropogenic activities contributing to the presence of metals in the environment. The release of palladium (Pd), platinum (Pt), and rhodium (Rh) into the environment increases the levels of contamination in soils, road sediments, airborne particles, and plants. These Pd, Pt, and Rh in road dusts can be soluble and enter aquatic environment posing a risk to environment and human health. The aim of this study is to determine the levels of Pd, Pt, and Rh with spectroscopy and voltammetric methods. Potential interferences by other metal ions (Na(I), Fe(III), Ni(II), Co(II)) in voltammetric methods have also been investigated in this study. At all the sampling sites very low concentrations of Pd, Pt, and Rh were found at levels that range from 0.48 ± 0.05 to 5.44 ± 0.11 ng/g (dry weight (d.wt)) for Pd(II), with 17.28 ± 3.12 to 81.44 ± 3.07 pg/g (d.wt) for Pt(II), and 14.34 ± 3.08 to 53.35 ± 4.07 pg/g (d.wt) for Rh(III). The instrumental limit of detection for Pd, Pt, and Rh for Inductively Coupled Plasma Quadrupole-based Mass Spectrometry (ICP-QMS) analysis was found to be 3 × 10−6 µg/g, 3 × 10−6 µg/g and 1 × 10−6 µg/g, respectively. In the case of voltammetric analysis the instrumental limit of detection for Pd(II), Pt(II), and Rh(III) for differential pulse adsorptive stripping voltammetry was found to be 7 × 10−8 µg/g, 6 × 10−8 µg/g, and 2 × 10−7 µg/g, respectively. For the sensor application, good precision was obtained due to consistently reproduced the measurements with a reproducibility of 6.31% for Pt(II), 7.58% for Pd(II), and 5.37% for Rh(III) (n = 10). The reproducibility for ICP-QMS analysis were 1.58% for Pd(II), 1.12% for Pt(II), and 1.37% for Rh(III) (n = 5). In the case of repeatability for differential pulse adsorptive stripping voltammetry (DPAdSV) and ICP-QMS, good standard deviations of 0.01 for Pd(II); 0.02 for Pt(II), 0.009 for Rh(III) and 0.011 for Pd, 0.019 for Pt and 0.013 for Rh, respectively.
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    Technologies for remediation of emerging contaminants in wastewater samples
    (Wiley-Blackwell, 2019) van der Horst, Charlton; Somerset, Vernon
    Introduction Various Emerging Contaminants Different Types of Bimetallic Nanoparticles Methods Used for Synthesis Techniques Used for Characterization Methods Used for Remediation Conclusions Acknowledgments
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    Voltammetric and spectroscopic determination of rare earth elements in fresh and surface water samples
    (MDPI, 2018) Makombe, Martin; van der Horst, Charlton; Silwana, Bongiwe; Iwuoha, Emmanuel; Somerset, Vernon
    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 g/L for Ce(III), and 2.10 g/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 g/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.