This review addresses the recovery of metals from all the main types of spent batteries (including Li-based, Zn-based, and Ni-based batteries) using bioleaching processes. Traditional processes are based on pyrometallurgical and hydrometallurgical methods and can be costly and, in some cases, cannot effectively recover the metals used in battery manufacture. Biobased hydrometallurgy may circumvent some of these drawbacks. This review presents a classification of batteries based on chemical composition from a recycling point of view. The bacterial and fungal leaching for each type of battery is reviewed. The research outputs are compared in each section, and chemical and biological mechanisms are presented. In addition, the catalytic effect of metals on the bioleaching process is reviewed for each battery. The results indicated that the main bioleaching mechanisms are the reactions of metals with metabolites, acid dissolution, and their combinations with oxidation-reduction reactions. The reactions presented in the literature are assessed and modified thermodynamically. The advantages and disadvantages of batteries bioleaching are discussed, and a future perspective is drawn. Although battery bioleaching has high efficiency and is an environmentally friendly method, with no gas emission and low energy consumption, slow kinetics and low pulp densities are among the major limiting factors hindering bioprocessing development from pilot to commercial scale.

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.

This investigation examined various kinetic and equilibrium models for gold (Au) and silver (Ag) adsorption from cyanide leach solution, onto surface of granular activated carbon (GAC) with 10, 35, 70 and 100% activities. Results indicated that the initial rate for Au and Ag adsorption is similar and increases by increasing the GAC activities. Outcomes showed that the adsorption for low activity GAC is proportional to the number of adsorption sites while the rate-limiting can be chemisorption for GAC with high activity. Thus, even low amount of contaminations on the fresh GAC can significantly decrease the capacity of precious metals adsorption.