Browsing by Author "Cunha, Emanoelle C."

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    Application of sodium - and biogenic sulfide to the precipitation of nickel in a continuous reactor.
    (2013) Gonzaga, Flávia Donária Reis; Silva, Adarlêne Moreira; Cunha, Emanoelle C.; Leão, Versiane Albis
    Attention has been focused in recent decades upon the precipitation of metal sulfides from acid mine drainage (AMD) and pregnant leach solutions, due to the advantages of the sulfide precipitation process over traditional methods employing hydroxides. The aim of this work was thus to explore Technologies for the precipitation of valuable metals, such as nickel using such sulfides (as either Na2S or biogenic sulfide). The recovery of nickel sulfide was improved when the initial pH of the solution containing each metal was set to 7. In such a condition the removal efficiency of nickel was 99.9%, corresponding to a residual level of 0.13 mg /L for nickel in solution. Kinetic parameters for precipitation were determined from the particle size distributions (produced in an MSMPR reactor) using the method of moments, where the growth and nucleation rates, as well the agglomeration kernel, were calculated. The precipitation of nickel at an initial pH of 7 showed a nucleation rate value of 8.16 x 1018#m^-3 s^-1, the highest volumetric growth rate (1.03 x 10^1 um^-3 s^-1) and agglomeration kernel of 9.71 x 10^-23m3 #^-1 s^-1. The biogenic sulfide was a suitable alternative to sodium sulfide for nickel removal. Both sodium sulfide and biogenic sulfide can be utilized to precipitate nickel as millerite (NiS), allowing the effluent compliant with environmental legislation.
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    Treatment of high-manganese mine water with limestone and sodium carbonate.
    (2012) Silva, Adarlêne Moreira; Cunha, Emanoelle C.; Gonzaga, Flávia Donária Reis; Leão, Versiane Albis
    Manganese is one of the most difficult elements to remove from mine waters, due to its high solubility in both acid and neutral conditions; thus it can be found in quite high concentrations, depending on the rock’s mineralogy. Metal carbonate precipitation can be an effective way for its removal, as manganese carbonate has been detected in net alkaline mine waters. However, limestone is effective in removing manganese only if the metal content is low. This research sought to study manganese precipitation from high-manganese (140 mL) content mine waters applying sodium carbonate and limestone mixtures. It was observed that besides the total carbonate concentration, pH plays a key role on manganese carbonate formation. Provided the pH solution is above 8.5, 99.9% manganese removal can be achieved with carbonate ions. Although not required for manganese precipitation, limestone acts as a solid substrate for the nucleation of fine manganese carbonate grains. Infrared spectroscopy showed manganese carbonate precipitation on the limestone surface. Magnesium was also removed from the mine water but magnesium carbonate formation was not observed.