Biocarbón a partir del raquis de banano aplicando adsorción en columna para la recuperación de itrio en soluciones acuosas.

Abstract

This research evaluated the use of biochar obtained from banana stems as an adsorbent material for the recovery of yttrium (Y³⁺) in aqueous solutions. The precursor material from banana stems was synthesized by incorporating PEG and CMC and subjected to a pyrolysis process at 800°C, thus obtaining biochar with properties suitable for adsorption studies. The banana stem biochar (BRB) was characterized by FTIR spectroscopy and proximate analysis to determine moisture, ash, volatile matter, and fixed carbon. Its yttrium adsorption capacity was evaluated at pH 4 and 5, as well as its selectivity against rare earths and heavy metals. In addition, column tests were performed to study continuous-flow adsorption. Desorption studies were also conducted with different reagents at temperatures of 25°C and 80°C to determine yttrium recovery efficiency. The experimental study was carried out at pH 5, obtaining a higher adsorption capacity (55.09 mg/g); however, pH 4 was used to prevent Y³⁺ precipitation. Selectivity with rare earths showed greater affinity toward Neodymium, with an adsorption capacity of 35.45 mg/g; and among heavy metals, the BRB showed high selectivity toward Yttrium, with an adsorption capacity of 40.30 mg/g. In the fixed-bed column study, breakthrough times were 4 hours at a flow rate of 0.05 L/h, while at a flow rate of 0.01 L/h, the path time was 39 hours, indicating that a lower flow rate results in greater adsorption by the BRB. Desorption was limited to a single cycle. At a temperature of 25°C, the best desorbent was hydrochloric acid (HCl), and at a temperature of 80°C, the best desorbent was aluminum sulfate (Al2(SO4)3). These results demonstrate that biochar derived from banana agro-industrial waste can be a sustainable alternative for the recovery of elements such as yttrium, promoting the circular economy.