Effect of temperature and acid concentration on lanthanum extraction from spent catalyst using organic acid

Rare earth elements (REE) are nowadays being used widely in many industries from electronics to petroleum industries as catalysts. However, their disposal caused serious problems to the environment. With the sharp growth in its usage, there is a better way to use and utilize REE from secondary sources such as their disposal rather than using new raw materials. The aim of this work is to study the potential of citric acid as a leaching agent to extract one of REE (i.e. lanthanum) in various acid concentrations and leaching temperatures. The raw material used in this work is spent catalyst from Pertamina Refinery Unit VI, Balongan, Indonesia. The spent catalyst is decarbonized with a heat treatment at 725°C for 10 minutes before the leaching process. The leaching process used 0.1; 1; and 2 M of citric acid with a varied temperature of 30, 60, and 80°C. The lanthanum recovery was calculated by comparing the mass percentage of lanthanum before leaching process and after leaching process using Energy Dispersive X-Ray Spectroscopy (EDX). The results were analyzed by response surface methodology (RSM) and are proved to be a reliable method to depict and analyze the leaching characteristics. The independent variables used in the research show significant effect on the response, especially the acid's concentration. A second order polynomial equation was used to correlate response and independent variables. The coefficient of determination (R²) shows a satisfactory result of 86.53 and the normal probability plot ensure the model's adequacy. © Published under licence by IOP Publishing Ltd.