Integration of ion exchange and non-dispersive solvent extraction processes for the separation and concentration of Cr(VI) from ground waters.

The focus of this work has been the study of simultaneous removal and recovery of Cr(VI) from ground waters with a high concentration of the metal (700 mg/l). The main objectives of water cleaning were the decrease of the Cr(VI) concentration down to the limits indicated by the Spanish regulations for discharge into channel waters (0.5 mg/l) and the recovery of the chromate compounds up to 15 g/l. The integration of two technologies: non-dispersive solvent extraction and anion exchange is presented as an environmental compatible solution. The final hybrid process allows the individual shortcomings of each technology to be overcome and leads to an optimum process configuration. Non-dispersive solvent extraction (NDSX) is used mainly for the concentration of the metal in a back-extraction solution and ion exchange (IE) is used for the depuration of the metal in the ground water down to 0.5 mg/l. The integrated process has been carried out on two different scales: laboratory and pilot plant, with satisfactory results being obtained.