Valorisation of sulphate rich effluents by electrodialysis

As part of a route for the valorisation of liquid effluents from copper metallurgical plants, the recovery and generation of sulphuric acid using electrodialysis from synthetic sulphate-rich solutions, similar to those of copper electrometallurgy, was investigated. Sulphate-bearing solution, having sulphuric acid ranging from 45 to 180 g/L and copper from 0 to 40 g/L, and having impurities of Co (0.2 g/L) and Fe (3.0 g/L), were electrodialysed at various current densities at several temperatures. A recovery of sulphuric acid of 0.5 kg/h/m² was obtained at 300 A/m² and 55°C, with a final concentration of 216 g/L of high purity H₂SO₄ with a SEC of 1.95 kWh/kg. Electrodialysis at 700 A/m² resulted in an acid rate recovery of 1.5 kg/h/m², with a final concentration of 328 g/L, and a SEC of 2.46 kWh/kg. The mass transport of metal ions and the effect of solution’s viscosity on acid recovery are discussed.