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 laborator y 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 supplement ed 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. Becau se of this fact, the variables of the system are interrelated, making the p rediction of the behavior of the whole system difficult. Because of this co mplexity, in this work, the behavior of a NDSX pilot plant has been experim entally 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 mathemat ical model consists of nonlinear partial differential equations which are s olved using the process simulator gPROMS. Once the suitability of the propo sed model and parameters for the description of removal and concentration o f Cr(VI) in the NDSX pilot plant was checked, the simulation was used to pe rform a sensitivity analysis to operating variables such as flow rates, vol umes, total carrier concentration, and initial complex species concentratio n. The theoretically predicted behavior was checked with some experimental results, and a satisfactory performance of the pilot plant was achieved.