Síntesis de perlas de quitosano funcionalizadas con polietilenimina, hierro y ferrita magnética aplicadas a la adsorción de dicianoaurato.

Abstract

In the present titration work, the main objective is to synthesize and characterize chitosan beads functionalized with polyethylenimine (PEI) and iron-related compounds, evaluating their capacity as an alternative for the selective adsorption of dicyanoaurate from aqueous solutions. Efficient and sustainable gold recovery is a critical challenge in the metallurgical industry. In Ecuador, the high demand for this precious metal requires the development of advanced methods for its extraction and purification. Chitosan, a biopolymer derived from chitin, is presented as a promising material due to its biocompatibility and abundance. However, to improve its adsorbent properties, it needs to be chemically modified. Chitosan beads were synthesized by incorporating PEI by its amino groups and iron compounds such as ferric chloride hexahydrate (FeCl₃-6H₂O) or manganese ferrite (MnFe2O4). The material characterization was performed the technique called Fourier transform infrared spectroscopy (FTIR) and zero charge point (pHpzc). Several operational parameters were evaluated, including pH, initial dicyanoaurate concentration as well as contact time, to determine the optimum adsorption capacity of the developed material. The functionalized chitosan beads showed high adsorption capacity and selectivity for dicyanoaurate. Adsorption was found to be most efficient at pH 9, with significantly enhanced adsorption capacity due to PEI immobilization and incorporation of iron compounds. The adsorption data fitted optimally to the Freundlich isotherm model, indicating adsorption on heterogeneous surfaces. The mathematical model for the adsorption kinetics that adequately described the process is the pseudo-second order model, suggesting that chemical interaction is the dominant mechanism in dicyanoaurate adsorption. This study demonstrates that the functionalization of chitosan with PEI and iron compounds is an effective strategy to improve its adsorptive properties. Modified chitosan beads present great potential for applications in the recovery of gold from aqueous solutions, offering a viable alternative to conventional precious metal extraction techniques. The research also suggests that optimizing the operating conditions and scaling up the process to an industrial level could contribute significantly to the efficiency of metallurgical processes.