Experimental and theoretical analysis of a nondispersive solvent extraction pilot plant for the removal of Cr(VI) from a galvanic process wastewaters

The scale-up of a chemical process from the results obtained in a laboratory scale involves a high degree of uncertainty. Experimental tests in pilot plants are therefore necessary in order to decrease that uncertainty. When the processes are not simple, these experimental tests should be supplemented by simulation studies which are a highly useful tool in the analysis of a chemical plant. A nondispersive solvent extraction (NDSX) plant includes two processes, extraction and stripping, coupled by an organic phase. Because of this fact, the variables of the system are interrelated, making the prediction of the behavior of the whole system difficult. Because of this complexity, in this work, the behavior of a NDSX pilot plant has been experimentally and theoretically analyzed. The removal and recovery of chromium(VI) from wastewaters of a galvanic process have been used as a case study for the simulation and experimental analysis of the NDSX process. The mathematical model consists of nonlinear partial differential equations which are solved using the process simulator gPROMS. Once the suitability of the proposed model and parameters for the description of removal and concentration of Cr(VI) in the NDSX pilot plant was checked, the simulation was used to perform a sensitivity analysis to operating variables such as flow rates, volumes, total carrier concentration, and initial complex species concentration. The theoretically predicted behavior was checked with some experimental results, and a satisfactory performance of the pilot plant was achieved.