Particle size, pH and Fe(III) ions affect the process of bioleaching of copper from chalcopyrite ores. In the study presented herein a copper sulfide ore was subjected to bioleaching process using a mixed microbial consortium obtained from a biotrickling filter treating high loads of H 2 S at different mineral particle size, distinct medium pH and various additional Fe(III) ion concentrations as leaching agent. After 1300 hours of operation, the total copper recovery achieved a value of 50 % in the most acidic conditions. A decrease of 2.5 units of pH implied an increase in the efficiency of 35%. It was also observed an optimal particle size (between 2 and 3 mm), considerably higher than previous reported studies, meaning a decrease in operational cost to mill material. Finally, results indicate that there is a threshold concentration of ferric ion from which the system is not sensitive (500 ppm).

Prediction of breakthrough curves for continuous sorption characterization is generally performed by means of simple and simplified equations. These expressions hardly have any physical meaning and, also do not allow extrapolation. A novel and simple approach, based on unsteady state mass balances, is presented herein for the simulation of the adsorption of Cr(III) ions from aqueous onto a low-cost adsorbent (leonardite). The proposed model overcomes the limitations of the commonly used analytical solution-based models without the need for complex mathematical methods. A set of experimental breakthrough curves obtained from lab-scale, fixed-bed columns was used to calibrate and validate the proposed model with a minimum number of parameters to be adjusted.

Copper recovery from printed circuit boards (PCB) from waste mobile phones was investigated using a two-step bioleaching process. The method consists of a first step where Fe(II) ions are biologically oxidised to Fe(III) by Acidithiobacillus ferrooxidans. Later, Fe (III) ions are put in contact with the PCBs for copper solubilisation. At the conditions tested in the present work, the Fe(II) bio-oxidation (first step) was almost completed in 48 h. Two different methods (filtration and sedimentation) for biomass separation before the second step were tested. No significance differences between both separation methods were observed in terms of the overall process efficiency. In both cases, using 7.5 g/L of e-waste concentration, copper recovery of 95-100% were obtained in only 48 hours. In order to test an inexpensive and environmental friendly method to recovery the copper from the leachate solution, cementation of Cu (II) with metallic iron was performed. The copper powder obtained had purity of 64.8%.

The suitability and limits of bioleaching for copper recovery from printed circuits boards has been stated with new strategies and methodologies. The process has been tested using a continuous column reactor simulating those conditions found at industrial scale. The new strategy developed improved the kinetic reaction rate and overcomes transport limitations for the leaching solution, thus improving copper recoveries from 50% to 80% in only 6 hours. This drastically reduced the time required by previous studies to achieve the same copper recovery. Inhibition effects of the biological process due to the release of metals from E-waste has been identified by means of microrespirometric monitoring tests. This systematic study allowed identifying that nickel, copper and aluminum impact the microorganisms' activity, inactivating them in specific scenarios (depending on the concentration and the time exposed).Including the time exposure as variable, this work demonstrated that metal concentrations that have been reported as non-toxic to microorganisms, resulted toxic when the required leaching contact time was considered. Besides high iron concentrations also produce inhibitory effect on the microorganisms' growth, despite being the energy source for their metabolism.

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