Solid–Liquid Equilibrium and Process Design of CuSO₄ + NaCl + (H₂O or H₂SO₄/H₂O) Systems at 298.15 K

Abstract

The low availability of fresh water in Chilean deserts has encouraged research into new alternative water sources in the mining industry. One of alternative is the use of saline water; however, there are few data about this new approach. For the production of copper sulfate pentahydrated (CuSO 4 ·5H 2 O) crystals, the effect of NaCl in the crystallization area must be known; therefore, the solid−liquid equilibrium of the CuSO 4 + NaCl + (H 2 O or H 2 SO 4 /H 2 O) system at 298.15 K was experimentally determined by the wet residue method. The density and refractive index of saturated solutions were also measured. The addition of NaCl has a clear effect on the solid−liquid equilibrium, promoting the formation of solid phases. In the phase equilibrium diagram that includes sulfuric acid, the pH affects the solubility curve. Using the information of the new phase diagrams, six simulation cases, varying in NaCl content and the addition of sulfuric acid in the feed, were evaluated in terms of mass and energy balance. The addition of sulfuric acid increases the total fluxes but decreases the heat requirement. Contrary to the expected results, the yields for the cases that include sulfuric acid were lower. The best results were obtained using a 50% NaCl pulp, which produced the lowest total flux and a high yield of 75.6%. ■ INTRODUCTIONThe mining activity with respect to the main mineral products of the Antofagasta region, copper and saline systems, is growing. This highly arid region and its water scarcity present an opportunity to develop new approaches for mining processes.The use of seawater has become a viable alternative in the mining industry. Many large mining companies, such as Minera Esperanza, Minera Michilla S.A., 1 and Las Luces (from the Las Cenizas group 2 ), have incorporated seawater into their processes with successful results. Moreno et al. 2 have described the Las Luces mineral process with seawater in milling and flotation in detail. Their operational results show that after 15 years, the metallurgic results remained unaffected by the salinity of the seawater and that the increase in the concentration of dissolved salts is mainly due to evaporation and water recirculation.Considering the equilibrium data for the ions involved in this system, Christov 3 presented a thermodynamic study of the quaternary Na−Cu−Cl−SO 4 −H 2 O system at 298.15 K, including solubility simulations. The crystallization of simple salts CuCl 2 ·2H 2 O and CuSO 4 ·5H 2 O was assessed. The Pitzer model is also used for the thermodynamic simulation of the (NaCl + CuCl 2 )(aq), (Na 2 SO 4 + CuSO 4 )(aq), and (CuCl 2 + CuSO 4 )(aq) systems, in good agreement with the experimental solubility isotherms.Druzhinin and Kosyakina 4 also studied quaternary systems composed of the same ions, finding the crystallization zone of the double salt CuSO 4 ·Na 2 SO 4 ·2H 2 O in the ternary CuSO 4 + Na 2 SO 4 + H 2 O system at 298.15 K. The double salt CuCl 2 ·NaCl·2H 2 O was present in the CuCl 2 + NaCl + H 2 O ternary system. Nine crystallizatio...

The effect of 2-propanol, ferrous sulfate and copper chloride on the solubility and physicochemical properties of acidic copper sulfate solutions at 298.15K

“…Fig. 8 shows the previously published phase equilibrium diagram for the system CuSO 4 + NaCl + (0.1 g H 2 SO 4 /g H 2 O) at 298.15 K [16]. In this previous work, Rocha et al found that adding NaCl has a clear effect on the solid-liquid equilibrium, promoting the formation of solid Table 5).…”

“…However, the study did not involve the size and shape of the product, which could be affected by the addition of ethanol. Rocha et al [16] studied the solid-liquid equilibrium of the CuSO 4 + NaCl + (H 2 O or H 2 SO 4 /H 2 O) system at 298.15 K by the wet residue method. The density and refractive index of saturated solutions were also measured.…”

“…Phase diagram for the CuSO 4 + NaCl + (0.1 g H 2 SO 4 /g H 2 O) system at 298.15 K, (&) experimental equilibrium data, (-) solubility curve, in mass fraction, both from[16].…”

Solubilities and Physical Properties of Saturated Solutions in the Copper Sulfate + Sulfuric Acid + Seawater System at Different Temperatures

“…Therefore, mining industries are developing new methods to optimize water use (Torres et al, 2013). In northern Chile, for example, certain mining companies are using raw seawater in their production processes (Rocha et al, 2013) and purified seawater by reverse osmosis (Philippe et al, 2010). In a mining process, the solid−liquid equilibrium and physical properties of solutions change upon seawater incorporation, especially the density and viscosity; which are used in pipe-sizing and pumping calculations.…”