Browsing by Author "Asiam, Elias Kwasi"

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    Arsenic Adsorption by Some Iron Oxide Minerals: Influence of Interfacial Chemistry
    (Ghana Mining Journal, 2020-12-12) Koomson, Bennetta; Asiam, Elias Kwasi
    The dramatic increase in hydrometallurgical extraction of gold from arsenic bearing gold ores has inevitably resulted in the release of arsenic into the environment worldwide. Residual arsenic minerals in tailings storage facilities can be oxidised and mobilise arsenic into the environment. This can contaminate soils, ground and surface waters and eventually biota. In spite of well-established technologies and recent advances in arsenic remediation, there are limited knowledge and understanding of the iron oxide substrate (goethite, hematite and magnetite) mineralogy and the fate of arsenic on the surface charge of these iron oxide substrates in an aqueous media during adsorption. The aim of the present study was to investigate the influence of interfacial chemistry on arsenic adsorption onto selected iron oxide particles to assist in developing a better understanding and new knowledge in arsenic removal from contaminated waters. Bulk mineralogy and partial chemical composition of selected iron oxide minerals were obtained using quantitative x-ray diffractometry (QXRD) and acid digestion followed by metal determination using inductively coupled plasma optical emission spectrometry (ICP-OES) respectively. Zeta Potential measurements involving iron oxide particles as arsenic adsorbents were carried out to elucidate the influence of interfacial chemistry on the adsorption behavior of arsenic from solution. The study confirmed that the iron oxide minerals were predominantly hematite, magnetite and goethite with goethite containing significant amounts of quartz. Arsenic adsorption was pH dependent and strongly influenced the zeta potential and isoelectric point (IEP) of the iron oxide particles. The zeta potential of all substrates studied was strongly positive at pH 2 but indicated a reversal at pH ~ > 9. The interaction between substrates, arsenic and its hydrolysable products resulted in significant decrease in the magnitude of zeta potential and change in IEP indicating specific adsorption.
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    Ascertaining the Quality of Water for Irrigation and Its Impact on Vegetable Quality: A Case Study Along the Bibini River in Kumasi.
    (Environment & Ecosystem Science (EES), 2021-06-23) Kyeame, Gifty; Koomson, Bennetta; Asiam, Elias Kwasi
    Farmers in peri-urban areas use diluted wastewater for irrigation. Over time, heavy metals may accumulate in agricultural soils and food crops causing health problems when consumed. Physicochemical, heavy metals (cadmium, lead and chromium) and microbial analysis of water, soil and vegetables were conducted to ascertain the quality of water and vegetables using standard methods. The results of the study showed that the water quality indicators; dissolved oxygen, biochemical oxygen demand and water temperature were not within the recommended standards of Ghana’s Environmental Protection Agency. The presence of heavy metals in the water, soil and vegetables were in the order of; soil (1.47 ± 0.017 of cadmium, 0.0019 ± 0.00011 of chromium and 0.541 ± 0.017 of lead) > vegetable (1.472 ± 0.044 of cadmium, 0.0020 ± 0.00010 of chromium and 0.474 ± 0.021 of lead) > water (0.068 ± 0.009 of cadmium, 0.0047 ± 0.00037 of chromium and 0.110 ± 0.014 of lead). Cadmium, chromium and lead concentrations in soil, vegetables and water varied significantly. Cadmium and lead concentrations as well as coliform counts in water and vegetables exceeded Food and Agriculture Organization/ World Health Organization’s maximum permissible levels. Soil samples from the control site showed almost negligible concentrations of heavy metals (0.00017 mg/kg of cadmium, 0.00014 mg/kg of chromium and 0.0011 mg/kg of lead) whereas farm sites had heavy metals as a result of long-term wastewater irrigation. Cadmium and lead concentrations in the water and vegetables makes them toxic and microbial populations of faecal coliform in water and lettuce indicated faecal contamination. Therefore, the quality of vegetables produced using the Bibini river is low and unsafe for human consumption.
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    Beneficiation of Iron Oxides from Cupola Furnace Slags for Arsenic Removal from Mine Tailings Decant Water
    (Ghana Mining Journal, 2022-06-20) Koomson, Bennetta; Koomson, John Ato; Asiam, Elias Kwasi
    Large volumes of ferrous metallurgical slags (FMS) are generated annually as waste materials from metal extraction, purification, casting and alloying processes worldwide. Some attempts have been made to use bulk FMS in metal precipitation and concrete works but little success has been achieved because of unstable precipitates and volume expansion of concrete structures. As a result, significant quantities of FMS are still disposed in landfills. This disposal leads to land conflicts and poor environmental practices. The present study focuses on the characterization and separation of iron oxide from selected bulk FMS (Cupola Furnace Slag - CFS) obtained from Ghana into constituent components for use as engineering materials. Quantitative X-ray diffractometry was used to determine the mineralogy of CFS. Iron oxide morphology and spot composition in the CFS were determined using scanning electron microscopy, combined with energy dispersive spectroscopy. The inductively coupled plasma-optical emission spectrometry was used to ascertain the chemical composition of CFS after acid digestion. Wet low intensity magnetic separation technique was employed for beneficiating iron oxides from the CFS. It is shown that the CFS is amorphous and consist of ferrous and non-ferrous material. Results of the investigation confirmed that ferrous materials in the slags can be separated using magnetic separation technique. The study further confirmed that fine grinding (- 75 μm) liberates the magnetic portions of the slag efficiently, and as such, they can be recovered using a low magnetic field. The recovery was 99.04 % and the concentrates obtained from the beneficiation process consist primarily of pigeonite, quartz, magnetite and jacobsite. The beneficiated concentrates have the capacity to adsorb arsenic from mine effluent. This study has demonstrated that, slags can be utilized as secondary resources rather than a waste.
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    Studies on Arsenic Release and its Mitigation from Tailings Dam Using Nanomagnetite Particles
    (Ghana Mining Journal, 2013-06) Koomson, Bennetta; Asiam, Elias Kwasi
    Knowledge of the geochemistry of As in tailings material after beneficiation of gold-bearing sulphidic ores is necessary to comprehend the nature, stability and mobilization of As into the geo-environment and its subsequent mitigation during storage. In this study, XRD combined with reflected light microscopy and SEM-EDX were employed to carry out studies on the mineralogical composition of As in a tailings material. Arsenic-rich solutions were generated from the tailings material using deionised water to ascertain As mobilisation. The remediation kinetics of the soluble As was carried out using nanomagnetite (Fe3O4). The XRD and SEM- EDX analyses showed that the major source of As in the tailings material is arsenopyrite (FeAsS). The study further confirmed that the residual As mineral in the tailings material is capable of decomposing during storage and can be subsequently mobilised into the geo-environment. It was established that nanomagnetite can efficiently remove As from tailings leachates; preferably at pH between 6 and 7 and Langmuir isotherm best described the sorption process while the Gibbs free energy of the sorption was found to be -12.1026 KJ/mol. Thus, nanomagnetite can be used to mitigate arsenic foot-prints from tailings dam.
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    Understanding the Mechanism of Arsenic Mobilisation and Behaviour in Tailings Dams
    (Ghana Mining Journal, 2017-06-20) Koomson, Bennetta; Asiam, Elias Kwasi; Skinner, William; Addai-Mensah, Jonas
    This study was carried out on leaching of tailings at 30 ᵒC and 40 ᵒC. The mineralogical and chemical composition of the tailings material were determined by Quantitative X-Ray Diffractometry (QXRD) and Scanning Electron Microscopy combined with Energy Dispersive Spectroscopy (SEM-EDAX). The study revealed that the tailings contain sulphides (arsenopyrite and pyrite) which can leach to produce arsenic (As) and other ions in solution. The acid released during leaching depends on the temperature of leaching. More acid was produced at higher temperature (40 ᵒC) than lower temperature (30 ᵒC). It was established that arsenic precipitation from solution was higher at higher temperature (40 ᵒC) than lower temperature (30 ᵒC). Mimicking the study in a typical tailings environment, it could be proposed that As mobilisation will be enhanced at lower temperature (30 ᵒC) than at higher temperature (40 ᵒC).