Desarrollo de carbón activado a partir de raquis de banano aplicado a la separación de oro en solución cianurada.

Abstract

This study addresses the need to develop sustainable adsorbent materials for gold recovery in metallurgical processes. Activated carbon (AC) was developed from banana rachis, an abundant agricultural waste in banana-producing regions of Ecuador, through a double pyrolysis process and chemical activation with potassium hydroxide (KOH). Unactivated carbon (CSA) and a commercial activated carbon (CC) were compared with AC to evaluate their physical and chemical characteristics, as well as their adsorption capacity (Qe) toward the dicyanoaurate complex Au(CN)2- in a synthetic gold solution at different pH values (10, 11, 12). Characterization included Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), attrition tests, and determination of the zero-charge point (pHpzc). Adsorption analysis data were obtained using inductively coupled plasma optical emission spectroscopy (ICP-OES). KOH activation increased porosity and oxygenated functional groups in AC and improved its mechanical strength (22.3% weight loss) compared to CSA (55.8% weight loss), though it was lower than that of CC (10.5% weight loss). The pHpzc of AC was close to 10, indicating that at pH values below this, the material's surface would be positively charged, favoring the adsorption of the dicyanoaurate complex. Adsorption analysis results showed that AC achieved its highest adsorption capacity (Qe) of 12.75 mg/g at pH 12, which decreased as the pH decreased. At all tested pH levels, AC exhibited lower performance compared to CSA and CC. It is concluded that banana rachis is indeed a viable precursor for producing activated carbon capable of adsorbing gold from a cyanide solution, as evidenced by the results obtained in this study.