Browsing by Author "Akpomejero, Tobore Lucky"

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    The use of potassium and magnesium thiosulphate solution for leaching of gold from disposed cell phones.
    (Department of Materials Science and Engineering, Faculty of Technology, Obafemi Awolowo University., 2024) Akpomejero, Tobore Lucky
    This study analyzed and pre-concentrated pulverized samples of printed circuit boards of disposed cell phones. The leaching condition of gold from the pre-concentrated samples was optimized using potassium and magnesium thiosulphate solutions. Electrowinning the solution of the highest gold dissolution was later carried out, followed by analysis of the obtained deposit. This was with a view to extracting gold from printed circuit boards using a less toxic lixiviant. Prior to pre-concentration and leaching, PCBs from discarded cell phones were obtained, pulverized, and analyzed using an energy dispersive spectroscopy (SEM/EDX) to determine whether gold was present. The pulverized material was then pre-concentrated using magnetic separation to eliminate ferrous components. Trioxonitrate (V) and Hydrogen tetraoxosulphate (VI) acids were used to eliminate base metals such as copper, zinc, etc. The residue was then leached separately with the use of Potassium and Magnesium thiosulphate solutions using Copper (II) sulphate and Ammonia as additives. The concentrations of the thiosulphates as well as the additives were varied in order to obtain the leachate with the highest gold dissolution. The obtained leachate was then used as the electrolyte during the electrowinning process which was done with the use of the PG Autostat 302N Potentiometer to obtain a deposit which was further analyzed with the SEM/EDX for the presence of gold. The result of the analyzed sample (before pre-concentration and leaching) showed the presence of gold during the EDX analysis. High gold dissolutions of 0.88 ppm and 0.70 ppm for Potassium and Magnesium thiosulphates respectively were obtained in both cases at the precious metal leaching stage when the maximum concentrations of thiosulphates, ammonia, and least concentration of Copper (II) sulphate were used. The result of the EDX analysis (after electrowinning using the leachate with 0.88 ppm gold dissolution and a stainless steel sample as the working electrode) showed the presence of gold from the deposit on the stainless steel sample. This study confirms that gold can be found in electronic wastes and that it can be profitably extracted with the right concentrations of additives (Copper sulphate and Ammonia) and thiosulphate (magnesium and phosphate), hence, providing a substitute for the extraction of precious metals and, eventually, help manage electronic wastes.