Tanaydın, Mehmet Kayra; Bakıcı Tanaydın, Zümra; Demirkıran, Nizamettin

The leaching behavior of Tunceli smithsonite ore in nitric acid was evaluated in two study steps including optimization of leaching process and kinetics modeling. The individual and synergistic effects of effective parameters such as nitric acid concentration, solid-to-liquid ratio, stirring speed, and temperature on the dissolution rate of zinc were investigated using central composite design. Four factors including temperature (30–50 °C), nitric acid concentration (0.2–0.5 mol/L), stirring speed (350–600 rpm), and solid-to-liquid ratio (0.004–0.01 g/L) were investigated. The dissolution percent of zinc (97%) was obtained in 120 min of leaching time: acid concentration 0.5 mol/L, temperature 50 °C, stirring speed 500 rpm, and solid–liquid ratio 2/500 g/mL at the optimum conditions obtained using the central composite design. The dissolution kinetics of smithsonite was examined according to heterogenous models and it was found that the dissolution rate was controlled by ash layer diffusion process. It was found that the leaching rate increased with increasing temperature, stirring speed, and acid concentration as well as decrescent particle size and solid/liquid ratio. The trial data were analyzed by statistical and graphical methods and the activation energy of this leaching process was determined to be 28.63 kJ·mol−1. Graphical Abstract: [Figure not available: see fulltext.].

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Karacahan, Mehmet Kayra; Demirkiran, Nizamettin; Ince, Muharrem; Bakıcı Tanaydın, Zümra

This study, the effectiveness of perlite for the removal of Cu (II) and Cd (II) ions from aqueous medium was investigated by adsorption method. Using perlite adsorbent, parameters such as initial concentration, initial pH, adsorbent dosage and contact time affecting Cu (II) and Cd (II) ions adsorption from aqueous solutions were investigated. Initial concentration of copper (II) ions, initial pH value, adsorbent amount, contact time respectively 3.2 ppm, natural pH 6.49, 2 g, during the 180 minutes adsorption 94% of copper ions adsorbed, the initial concentration of cadmium (II) ions solution, initial pH, adsorbent amount, contact time 5.6 (ppm), natural pH 5.25, 2 g, 180 minutes, respectively, 77% adsorbed. It was determined that the adsorption data fit the Langmuir isotherm for copper ions and Freundlich isotherm for cadmium ions, and the kinetic data of copper and cadmium ions fit the false second order model. Including the thermodynamic parameters of adsorption, Gibbs free energy change (ΔG°), enthalpy (ΔH°) and entropy (ΔS°) values calculated at 20oC are for copper 3.1 kJ mol-1, -55.52 kJ mol-1, -0.2 kJ mol-1 K-1 , respectively and for cadmium, 7.14 kJ mol-1, -28.02 kJ mol-1, -0.12 kJ mol-1 K-1, respectively. The results showed that the adsorption of these metal ions on the perlite is exothermic and feasible at 20-50°C.

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