Electrocoalescence of emulsions in raffinate from the solvent extraction phase under AC electrical fields

Raffinate is an aqueous acid phase with low copper content obtained in the solvent extraction phase (SX). This solution, which drags a significant amount of the organic phase that forms an oil-in-water (O/W) emulsion, is recycled back to the leaching phase as an irrigation solution. In addition, the formation of emulsions can cause operational problems in the leaching phase. To solve these problems, this work is aimed to employ electrocoalescence under AC electrical fields to enhance demulsification of the emulsions that formed. The main objectives of this work were to select the most appropriate electrode and conduct laboratory tests based on a 23 factorial design to determine the variables that have the most significant effect on electrocoalescence. The variables considered were distance, frequency and voltage, while TOC removal and actual power were the response variables. The distance between electrodes is the most important parameter affecting TOC removal. In relation to actual power, the voltage applied was more significant than the distance between electrodes, the frequency and the interactions among variables. The tests to determine the optimal type of electrode identified rectangular steel plate electrodes as providing the best results. The operational parameters: a voltage of 30 V, a frequency of 400 Hz and an electrode distance of 14 cm showed the greatest efficiency. Considering these results, it is demonstrated that electrocoalescence enhances demulsification of O/W emulsions in raffinate from solvent extraction in copper processing. Keywords: O/W emulsions, Raffinate, Solvent extraction, Electrocoalescence, Factorial design, Electrode