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This study was performed in two phases of work. In the first stage, alkaline leaching of lead and zinc from an Iranian low-grade oxide ore was examined and the influence of the operating variables including stirring speed, leaching temperature, NaOH concentration and liquid to solid ratio was determined experimentally. The optimum condition was found to be NaOH concentration of 4 M, liquid to solid ratio of 20 ml/g, temperature of 80 °C and a stirring speed of 500 rpm for lead and 400 rpm for zinc, in the range of investigated parameters. Under these conditions, the highest recovery of lead and zinc was obtained to be 72.15 and 85.52%, respectively. In the second stage, the dissolution kinetics of lead and zinc was evaluated by the shrinking core models. The finding reveals that diffusion through the fluid film was the leaching kinetics rate controlling step of lead and zinc. The activation energy was found to be 13.6 kJ/mol for lead and 13.92 kJ/mol for zinc. Equations representing the leaching kinetics of lead and zinc were achieved to be 1 − (1 − x)2/3 = 0.7272 × e(−13.6/(8.314×T)) × t and 1 − (1 − x)2/3 = 0.9686 × e(−13.92/(8.314×T)) × t, respectively. Keywords: Alkaline leaching, Kinetics modeling, Shrinking core models, Low-grade ore, Recovery

This work was aimed to study the relative floatability of phosphate flotation by means of kinetic analysis. The relative floatability is important to determine how selectively the phosphate is separated from its impurities. The effects of pulp pH, solid content, reagents dosage (depressant, collector and co-collector) and conditioning time were investigated on the ratio of the modified rate constant of phosphate to the modified rate constant of iron (relative floatability). The results showed that a large dosage of depressant associated with a low value of collector resulted in a better relative floatability. Increasing the co-collector dosage, conditioning time and pH increased the relative floatability up to a certain value and thereafter resulted in diminishing the relative floatability. Meanwhile, the results indicated that increment of solid concentration increased the relative floatability in range investigated. It was also found that that maximum relative floatability (16.05) could be obtained in pulp pH, 9.32, solid percentage, 30, depressant dosage, 440 g/t, collector dosage, 560 g/t, co-collector dosage, 84.63 g/t and conditioning time, 9.43 min. Keywords: Phosphate, Relative floatability, Kinetics, Rate constant, Separation

This study was aimed to investigate the effects of individual variables and their interactions on weight loss of grinding ball using the SEM/EDX analysis and RSM model. The results SEM/EDX analysis indicated that corrosion mechanism type for steel balls is pitting. In addition, abrasive corrosion was observed on high carbon chromium steel ball surface. It was also found that steel balls were formed from corrosion phases of Fe, O, S and Si. The results of RSM model showed that the linear effects of all factors and the quadratic effects of solid concentration and charge weight of balls were significant parameters on wear rate. Also, it was observed no interactions between factors. Furthermore, results indicated that degree of influence of factors on the wear rate was in the order of ball type > solid percentage > pH > solid percentage2 > charge weight2 > grinding time > rotation speed of mill > charge weight > throughout.