The effect of the chloride ion on chemical degradation of LIX 984N extractant

Abstract

Water supply is becoming an increasingly important aspect of hydrometallurgical operations due to water deficiency. This problem may significantly lessen if the extraction processes can incorporate the usage of saltwater throughout the whole hydrometallurgical operation. In this research, the effect of chloride ion on the chemical degradation of LIX 984N was investigated. It was shown that chloride does not directly degrade LIX 984N. However, it has a catalytic effect on the hydrolysis and nitration of the extractant. The synergic effect of chloride on the extractant degradation through hydrolysis and nitration mechanism was assessed at different acidities and mixing times for up to three months. The presence of chloride ion accelerated the degradation of LIX 984N through both hydrolysis and nitration processes. Additionally, the impact of degradation processes on copper maximum loading, extractant viscosity, copper extraction, impurity entrainment, extraction selectivity, and copper stripping were assessed. The structure of the degraded extractant and its compositional changes was studied using Fourier transform infrared spectroscopy (FT-IR) and gas chromatography-mass spectrometry (GC–MS) analysis. Degradation of the extractant resulted in a decrease in maximum copper loading, increasing entrainment of impurities, increasing extractant viscosity, lower copper extraction, and less efficient stripping of copper. Samples degraded in the presence of chloride functioned less efficiently in comparison to samples degraded in the absence of chloride. Moreover, structural changes were more noticeable in samples mixed with an aqueous solution containing chloride.