Trace Amounts of Aqueous Copper(II) Chloride Complexes in Hypersaline Solutions: Spectrophotometric and Thermodynamic Studies

Knowledge of the thermodynamic properties of aqueous copper(II) chloride complexes is important for understanding and quantitatively modeling trace copper behavior in hydrometallurgical extraction processing. In this paper, UV–Vis spectra data of Cu(II) chloride solutions with various salinities (NaCl, 0–5.57 mol·kg−1) are collected at 25 °C. The concentration distribution of Cu–Cl species is in good agreement with those calculated by a reaction model (RM). The simple hydrated ion, Cu2+, is dominant at low concentration, whereas [CuCl]+, [CuCl2]0 and [CuCl3]− become increasingly important as the chloride concentration rises. Moreover, the RM calculation suggests the present of a small amount of [CuCl4]2−. The de-convoluted molar spectrum of each species is in excellent agreement with our previous theoretical results predicted by time-dependent density functional theory treatment of aqueous Cu-containing systems. The formation constants for these copper chloride complexes have been reported and are to be preferred, except log10K2 ([CuCl2]0).