Treatment of Uraniferous Effluents by an Activated Carbon Produced from Nut Shells

This preprint presents a study on the synthesis and characterization of activated carbon from pecan shells and its application for the adsorption of uranium from aqueous solutions. The activated carbons were synthesized by combined chemical activation with phosphoric acid and thermal activation at 400 °C. Texture, chemical, and granulometric analyses were performed using nitrogen adsorption/desorption (BET), FTIR spectroscopy, and laser granulometry. Batch adsorption experiments were conducted to investigate the influence of pH, contact time, amount of adsorbent, and initial uranium concentration. Kinetic studies showed that the adsorption process follows a pseudo-second-order model, and the equilibrium data are best described by the Freundlich isotherm. The maximum adsorption capacity (q_max) of the optimized sample (CA-A) was 24.63 mg/g. A central composite design (CCD) was used to model and optimize the adsorption process. Optimal conditions were determined at a pH of 4.64, an adsorbent mass of 0.39 g, and a uranium concentration of 159.41 mg/L. The study demonstrates that activated carbon derived from pecan shells is a promising, cost-effective bioadsorbent for uranium removal from contaminated water and thus has potential applications in environmental remediation. This version is an unpublished preprint and has not yet been peer-reviewed.