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Öğe Direct conversion of alkaline earth metal hydroxides and sulfates to carbonates in ammonia solutions(Oficyna Wydawnicza Politechniki Wroclawskiej, 2022) Ehsani, Ilhan; Ehsani, Arman; Ucyildiz, Ayse; Obut, AbdullahIn this study, the direct conversion behaviors of different alkaline earth metal solids (the hydroxides and the sulfates of alkaline earth metals Ca, Sr, Ba and Mg) to their corresponding carbonates in dissolved carbonate-containing pregnant solutions obtained by direct leaching of a smithsonite (ZnCO3) ore sample in aqueous ammonia solutions having different concentrations (4 M, 8 M and 13.3 M NH3) were investigated by using X-ray diffraction analyses at alkaline earth metal to dissolved carbonate mole ratios of 1:1 and 1:2, for revealing the conversion possibilities of dissolved carbonate in the pregnant solutions to solid carbonate by-products. The results of direct conversion experiments showed that Ca(OH)(2), CaSO4 center dot 2H(2)O, Sr(OH)(2)center dot 8H(2)O and Ba(OH)(2)center dot 8H(2)O converted to their corresponding carbonates, SrSO4 partially converted to SrCO3 as observed by the presence of unreacted SrSO4 peaks in X-ray diffraction patterns of the converted solids, and BaSO4 did not convert to BaCO3 because of its lower solubility with respect to BaCO3. On the other hand, it was observed that Mg(OH)(2) did not convert to MgCO3, but MgSO4 center dot 7H(2)O converted dominantly to an uncommon phase, which was tentatively identified as Mg5Zn3(CO3)(2)(OH)(12)center dot H2O. In the study, a complete discussion on the conversion behaviors of alkaline earth metal solids to their corresponding carbonates was given considering the differences between their solubility product constants and the changes in the free energies of the theoretical conversion reactions. In addition, infrared spectra and scanning electron microscope images of some of the converted solids were also presented for characterization purposes.Öğe Preparation of different zinc compounds from a smithsonite ore through ammonia leaching and subsequent heat treatment(Oficyna Wydawnicza Politechniki Wroclawskiej, 2021) Ehsani, Arman; Ehsani, Ilhan; Obut, AbdullahIn this study, firstly, the effects of ammonia concentration, leaching time and solid/liquid ratio on the leaching behaviour of zinc from a smithsonite (ZnCO3) ore sample in aqueous ammonia solutions were investigated at room temperature by chemical, X-ray diffraction (XRD) and Fourier-transform infrared (FT-IR) spectroscopy analyses. It was found that leaching ratio of zinc steeply increased from 30.1 to 76.2% with increasing ammonia concentration from 1.0 to 4.0 M and maximum zinc leaching ratio of 79.7% was reached after leaching in 13.3 M NH3 solution. The XRD pattern of the residue obtained after leaching in 4.0 M NH3 solution for 90 min at solid/liquid ratio of 0.15 g/mL, the optimum condition, showed that smithsonite phase in the ore sample almost completely dissolved whereas the gangue minerals goethite and calcite remained unaffected, confirming the selectivity of ammonia solution for zinc dissolution. Together with zinc, leaching ratios of cadmium were also determined. In second part of the study, precipitation tests (by complete drying at different temperatures) were conducted on dissolved zinc, carbonate and ammonia containing pregnant solutions obtained after selected leaching experiments. By complete drying of the pregnant solutions at low temperatures, i.e. 50 degrees C, relatively pure solid zinc ammine carbonate (Zn(NH3)CO3) precipitates and at higher temperatures, i.e. 150 degrees C, quite pure solid zinc carbonate hydroxide (Zn-5(CO3)(2)(OH)(6)) precipitates could be prepared. High-temperature heating of Zn(NH3)CO3 and Zn-5(CO3)(2)(OH)(6) precipitates at 450 degrees C yielded single-phase zinc oxide (ZnO). The chemical compositions, FT-IR spectra and scanning electron microscope (SEM) photographs of some of the precipitates were also presented.