Industrial wastes may contain high concentrations of valuable metals. Extraction and recovery of these metals have several economic and environmental advantages. Various studies showed positive effects of microwaves as a pretreatment method before the leaching of minerals. However, there are empty rooms for exploring simultaneous microwave and leaching (microwave-leaching) of industrial waste material for the production of valuable metals. This investigation examined the microwave-leaching method to extract copper and zinc from a copper-smelter dust (CSD). The results of microwave-leaching mechanism were compared with conventional heating leaching based on kinetics modelling. The final Cu recovery in the conventional heating and microwave irradiation was 80.88% and 69.83%, respectively. Kinetic studies indicated that the leaching reactions follow diffusion across the product layer. Based on X-ray powder diffraction (XRD) analyses, during conventional experiments sulfate; components formed with high intensity as an ash layer which prevents reagent access to the solid surface and decreases the Cu dissolution. While the sulfate components did not detect in the microwave-leaching residuals which means that microwave irradiation helped to decrease the ash layer formation. Taking all mentioned results into consider it can be concluded that microwave-leaching can be considered as an efficient method for extraction of valuable metals from waste materials.

In this study, the effect of dimensionless hydrodynamic parameters (Reynolds Number–Re, Froude Number–Fr, and Weber Number–We) and bubble surface area flux, S _b, on flotation rate constant, k, of quartz particles was investigated using laboratory mechanical flotation cell. Maximum flotation rate constant was obtained at Re = 89, 800, Fr = 2.4, and We = 1558. For either more quiescent (Re < 73, 500 and Fr < 1.61) or more turbulent (Re > 98, 000 and Fr > 2.85) conditions, flotation rate constant decreased steadily. Furthermore, the effect of Reynolds number in the k–S _b relationship was investigated, and model of was obtained.

Understanding the attachment micro process is a fundamental step toward predicting the rate constant of flotation kinetics. In this research, the effect of bubble-particle attachment efficiency on k-Sb relationship was investigated under Yoon, Stokes and Potential conditions. Maximum Stokes attachment efficiency obtained was 55.9% with particle size of -37 µm, Sbof 34.2 1/s and flotation rate of 1.65 1/min. Stokes attachment efficiency was less than Yoon efficiency and it seems to be a suitable equation for predicting attachment efficiency. Furthermore, three different models were obtained for estimating attachment efficiency usingk-Sb relationship.

The frothers are influence on the ability of bubbles to collect particles from the pulp and carry them to the froth layer. In this study the effect of type and dosage of frothers on bubble-particle collision probability and dispersion of fine particles was investigated. Therefore, collision probability of fine particles was calculated using frothers such as MIBC, Pine Oil, and Poly propylene glycol with concentration of 0, 25, 50 and 75 g/t respectively. According to this study, as the particle size increased the probability of collision increased but with using Poly Propylene Glycol, MIBC and Pine Oil, probability of collision increased, respectively. Under Potential flow conditions, Maximum collision probability was obtained 27.27% with Poly Propylene Glycol dosage of 75 g/t and particle size of 50 µm.