Determination of Stoichiometric and Equilibrium Data for Reactive Extraction of Cobalt with D2EHPA

Abstract

Modern development is the need of present to achieve the aspiration of sustainable world. The advancement of modern development is significantly reliant on metals, serving as a fundamental resource. From a small pin to huge skyscrapers or com-plex electronic gadgets, metals form the backbone of cutting-edge technology. While metals possess a wide array of properties, their most notable advantage lies in their potential to recycle continuously. To bolster sustainability and contribute to develop-ment, the emphasis should be on metal recycling and seeking environmentally friend-ly methods to achieve this. Solvent extraction is the technique that emerges as a promising technique for recycling of metals with the minimal environmental impact. In this process, metals dissolved in an aqueous solution are extracted selectively into an organic phase. This master thesis has employed this technology for the determi-nation of stoichiometric and equilibrium data for reactive extraction of cobalt with D2EHPA. The initial step involves the construction of extraction curves. These curves illustrate the variation of the degree of extraction as a function of the equilibrium pH of the reaction. The process entails introducing an organic phase containing an extractant and solvent to an aqueous solution of the desired metal. Prior adjustments are made to the pH of the aqueous solution. The phases were mixed in a thermostatic bath to attain equilibrium of the reaction and then were allowed to settle. The phases were then separated and collected. Later, back-extraction of the cobalt present in organic phase was performed. An acidic aqueous solution was mixed with the loaded organic phase to re-extract the metal towards the new aqueous phase. The aqueous phases obtained from both procedures were subjected to analysis. Numerous experiments were conducted at different pH allowing to build extraction curves. Experiments with varying extractant concentrations were also performed to enable the determination of the stoichiometry and the equilibrium constant of the extraction reaction. The devised protocol developed for creating extraction curves has been validated for the case study of cobalt extraction with 10% D2EHPA. After the experiments, it can be inferred that this technique has good potential for the study of cobalt extraction with D2EHPA, even if a few precisions are still required. A few samples showed turbidity at higher pH which created problem in spectroscopy analysis. Too high HCl concentrations created precipitation during back-extraction but too low concentrations were not sufficient to back-extract entirely the metal for all the samples.