Faculty of Science
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Item Removal of uranium from aqueous solutions using ammonium-modified zeolite(South African Chemical Institute, 2015) Bakatula, E.N.; Mosai, A.K.; Tutu, H.Batch experiments were conducted to study the effects of contact time, pH (3 to 8), initial concentration, presence of carbonate, sulphate, and competing ions (Fe3+, Ca2+, Sr2+, Mg2+) on the adsorption of U(VI) on ammonium-modified zeolite (AMZ). The structural features of the modified zeolite were assessed by Fourier Transform Infra Red Spectroscopy (FTIR) while the metal content was determined by Inductively Coupled Plasma Optical Emission Specroscopy (ICP-OES). The removal of uranium was effective and maximal under acidic conditions (pH 3 to 5). The kinetics of adsorption of U-nitrate and U-sulphate on AMZ were described by the pseudo-second-order model (R2 ≥ 0.9820). In the presence of SO4 2- and CO3 2-, a significant reduction of 67.88 % and 71.63 %, respectively, in uranium uptake was observed. The distribution coefficient, KD (L g-1), was in the order of: U-nitrate (1.116) > U-sulphate (0.029) > U-carbonate (0.019), suggesting that AMZ had a high affinity for U-nitrate. The presence of Fe3+ enhanced the removal of U(VI) from U-nitrate, U-sulphate and U-carbonate by 20.18 %, 72.48 % and 82.43 %, respectively, while the presence of Ca2+, Mg2+ and Sr2+ reduced the removal to 19.57 %, 31.60 % and 23.65 %, respectively. AMZ is an effective adsorbent for uranium removal from aqueous solutions dominated by nitrate, carbonate and sulphate.Item Application of maghemite nanoparticles as sorbents for the removal of Cu(II), Mn(II) and U(VI) ions from aqueous solution in acid mine drainage conditions.(Springer, 2016-06) Etale, A.; Tutu, H.; Drake, D.C.The adsorptive removal of Cu(II), Mn(II) and U(VI) by maghemite nanoparticles (NPs) was investigated under acid mine drainage (AMD) conditions to assess NP potential for remediating AMD-contaminated water. The effects of time, NP and metal concentration, as well as manganese and sulphate ions were quantified at pH 3. Adsorption of all three ions was rapid, and equilibrium was attained in 5 min or less. 56 % of Cu, 53 % of Mn and 49 % of U were adsorbed. In addition, adsorption efficiencies were enhanced by >= 10 % in the presence of manganese and sulphate ions, although Cu sorption was reduced in 1: 2 Cu-to-Mn solutions. Adsorption also increased with pH: 86 % Cu, 62 % Mn and 77 % U were removed from solution at pH 9 and increasing initial metal concentrations. Increasing NP concentrations did not, however, always increase metal removal. Kinetics data were best described by a pseudo-second-order model, implying chemisorption, while isotherm data were better fitted by the Freundlich model. Metal removal by NPs was then tested in AMD-contaminated surface and ground water. Removal efficiencies of up to 46 % for Cu and 54 % for Mn in surface water and 8 % for Cu and 50 % for Mn in ground water were achieved, confirming that maghemite NPs can be applied for the removal of these ions from AMD-contaminated waters. Notably, whereas sulphates may increase adsorption efficiencies, high Mn concentrations in AMD will likely inhibit Cu sorption.