Lanthanum recycling from spent FCC catalyst through leaching assisted by electrokinetic remediation: Influence of the process conditions on mass transfer

• The EKR system recovered up to 80 % of lanthanum content of spent FCC catalysts. • EKR is an alternative for recycling rare earth metals from catalysts. • A low electric field promoted electrokinetic transport phenomena of La ions. • The La ions go to the electrolytic chambers to be recovered after the treatment. • The best conditions to reduce energy and reagent consumptions were defined. The electrokinetic remediation assistance on the leaching of spent FCC catalysts demonstrated satisfactory performance as an alternative method to the traditional leaching method, aiming to recycle rare earth elements from this solid waste, by former studies. The present work identified the process conditions that improved the mass transfer performance of lanthanum by electrokinetic phenomena, by means of a central composite design and variance analysis. Thereby, the system that operated with the sulfuric acid concentration in the electrolyte of 1 mol/l and the applied electric field of 0.15 V/m, for 8 h of the experiment, was the best in terms of energy and acid consumption per mass of lanthanum recovered, amid the tested conditions.