Different strategies for recovering metals from CARON process residue

http://dx.doi.org/10.1016/j.jhazmat.2011.03.048The capacity of Acidithiobacillus thiooxidans DMS 11478 to recover the heavy metals contained in the residue obtained from the CARON process has been evaluated. Different bioreactor configurations were studied: a two-stage batch system and two semi-continuous systems (stirred-tank reactor leaching and column leaching). In the two-stage system, 46.8% Co, 36.0% Mg, 26.3% Mn and 22.3% Ni were solubilised after 6 h of contact between the residue and the bacteria-free bioacid. The results obtained with the stirred-tank reactor and the column were similar: 50% of the Mg and Co and 40% of the Mn and Ni were solubilised after thirty one days. The operation in the column reactor allowed the solid–liquid ratio to be increased and the pH to be kept at low values (<1.0). Recirculation of the leachate in the column had a positive effect on metal removal; at sixty five days (optimum time) the solubilisation levels were as follows: 86% Co, 83% Mg, 72% Mn and Ni, 62% Fe and 23% Cr. The results corroborate the feasibility of the systems studied for the leaching of metals from CARON process residue and these methodologies can be considered viable for the recovery of valuable metals

Split regeneration of chelating resins for the selective recovery of nickel and copper

The management of spent acids containing heavy metals has been traditionally carried out by neutralization-precipitation technologies that often fail to provide the required selectivity for metal recovery. This work proposed a split elution process using H2SO4 and NH4OH solutions to regenerate bispicolylamine-based chelating resins (Puromet™ MTS9600) employed in a previous work to separate nickel and copper from spent sulfuric acid effluents. Operation variables namely S/L ratio, concentration of the regeneration agents and process configuration were analysed to select the best conditions to optimize the metal unloading and their selective recovery in independent solutions. It was found that 43% of nickel was eluted from the resin by H2SO4 2.0 M and recovered with purities of 98% while 47% of copper was desorbed with NH4OH 2.0 M and recovered with purities of 97%. The long-term assessment evidenced that copper removal and metal recovery were not affected after 10 adsorption-regeneration cycles, while the nickel adsorption efficacy decreased about 10%.This research was developed in the framework of the projects CTM2017-87740-R (Spanish Ministry of Science, Innovation and Universities), RTI2018-093310-B-I00 (Spanish Ministry of Science, Innovation and Universities), TEC2016-76021-C2-2-R) (AEI/FEDER, UE & PID2019-107270RB-C21/AEI/10.13039/501100011033), and grant BES-2017-080076