Study of the adsorption of Nickel ions on Sodium alginate polymeric membrane in hydrometallurgical effluents

Abstract

Mining extraction activities in the Democratic Republic of Congo result in the production of hydrometallurgical effluents containing varying concentrations of metallic ions. These effluents are often discharged into the environment without proper treatment, leading to ecological imbalances and severe illnesses in animals and humans. It is crucial to treat these effluents before releasing them into the natural environment. This study presents a technical approach for developing polymeric membranes capable of adsorbing metallic ions from aqueous solutions of hydrometallurgical effluents. A sodium alginate polymeric membrane was synthesized and characterized using various techniques including X-Ray Diffraction, Fourier Transform Infrared Spectroscopy, X-Ray Fluorescence, Transmission Electronic Microscopy, Differential Scanning Calorimetry, and Mechanical Traction. Adsorption experiments were conducted using aqueous solutions of nickel sulphate prepared in the laboratory and hydrometallurgical aqueous solutions from a factory. The results showed that the adsorption of nickel (Ni2+) ions on the polymeric membrane is faster in the hydrometallurgical solution compared to the nickel sulphate solution. This phenomenon appears to be mainly governed by short-range forces such as Van der Waals forces. The Hill-Langmuir model was used to describe the adsorption experiments, and the analysis of the model parameters indicated that the adsorption of Ni2+ ions on the sodium alginate polymeric membrane is more efficient in solutions containing only one type of ion compared to complex aqueous solutions. This is due to the competition between different metallic ions present in complex solutions, which are not the case in the nickel sulphate solution where only Ni2+ ions are present. Furthermore, the analysis showed that the coordination number (n) for Ni2+ ions in a "receiving" site of the polymeric membrane is smaller in the nickel sulphate solution (2.22) compared to the hydrometallurgical aqueous solution (2.85).