Evaluation of Solubility and Thermodynamic Properties of Synthetic Nickel Hydroxide Carbonate

Abstract

Knowledge of the values of the thermodynamic functions of natural minerals of transition elements has important applications in the study of the processes of their formation and geochemical migration with groundwater; when developing methods to prevent corrosion of non-ferrous alloys in fresh and sea water; when immobilizing heavy metals in mine drainage and industrial waters, etc. Also, these values are in demand when calculating reactions and developing methods for producing synthetic analogs of minerals, many of which exhibit magnetic, catalytic, photochemical, and other properties. However, in scientific literature, there is a lack of detailed data on the thermodynamic properties of nickel hydroxysalts. A sample of basic nickel carbonate with the theoretical formula Ni₃[CO₃](OH)₄·3H₂O was obtained using the hydrothermal synthesis method. The structure of the compound was verified by X-ray diffraction and infrared spectroscopy. Experiments were carried out on sample dissolution in order to measure the solubility constant (solubility product): log₁₀ K_SP =  − 45.8 ± 1.8. Based on the data obtained, the thermodynamic parameters of the reaction of dissolution of the compound were determined and the main thermodynamic functions were determined: Gibbs free energy of formation Δ_fG° =  − 1554 ± 6 kJ·mol⁻¹; enthalpy of formation Δ_fH° =  − 1798 ± 9 kJ·mol⁻¹; standard entropy S° = 260.6 ± 7.8 J·mol⁻¹·K⁻¹.