Recuperação de cério e lantânio de soluções sintéticas e lixiviados utilizando carvões ativados obtidos a partir de matérias primas alternativas como adsorventes

Abstract

The high demand for rare earth elements (REEs) has led to a search for different alternatives to obtain them. In particular, cerium and lanthanum are highlighted due to their wide application. In this context, the use of phosphogypsum as a secondary source of these elements is promising. The literature has already shown that the leaching of REEs from phosphogypsum is possible. However, REEs must be further recovered from these leachates and, for this purpose, adsorption is a high-potential alternative. Regarding adsorption, one of the most relevant aspects is the development of efficient and low-cost adsorbents. Activated carbon is one of the most widely used adsorbents, mainly due to its excellent textural properties. In addition, this adsorbent can be obtained from various raw materials, including biomass waste. Besides representing a low-cost raw material, the use of biomass waste for activated carbon production is a good alternative to add value to it. Therefore, considering the abovementioned, the main of this work was to produce activated carbons from two alternative biomasses waste, soybean pod waste and vine pruning waste, and apply them as adsorbents for the recovery of Ce(III) and La(III) from synthetic solutions and phosphogypsum leachates. The characterization analyzes showed that both materials produced presented good textural properties, with surface areas of 614 m2 g-1 and 467 m2 g-1 for the activated carbon obtained from soybean pods and for the activated carbon obtained from vine pruning waste, respectively. Furthermore, by determining the point of zero charge, it was verified that the surface of both materials maintains a negative charge over a wide pH range. The activated carbon obtained from soybean pods presented maximum adsorption capacities of 107.7 mg g-1 and 127.2 mg g-1 for Ce(III) and La(III), respectively. On the other hand, the material obtained from grape pruning residues showed maximum adsorption capacities of 48.45 mg g-1 and 53.65 mg g-1 for Ce(III) and La(III), respectively. Regarding the adsorption mechanism, pore filling, ion exchange, and surface complexation were proposed as dominant mechanisms. Finally, both activated carbons showed a good potential for recovery of Ce(III) and La(III) from real phosphogypsum leachate.