Automated pH Monitoring and Control of TALSPEAK and Advanced TALSPEAK Processes

Maintaining pH in an operable range is key in many industrial processes, where automating pH correction and control can enable significant advances in process efficiency. One such process is solvent extraction. In solvent extraction, the pH can directly influence separation by altering the extraction of different species. Solvent extraction procedures for separating components of used nuclear fuel, such as TALSPEAK and Advanced TALSPEAK, are examples of this. In these processes, the extraction of trivalent lanthanides and actinides is pH-dependent, with more acidic conditions causing greater metal extraction. However, the pH can be challenging to control. Here, automated pH control has been demonstrated using robust, Raman-based pH measurement that informed the control software connected to programmable logic controllers (PLCs). The use of Raman spectroscopy paired with a chemometric model has been applied to the feed solutions for TALSPEAK and Advanced TALSPEAK processes and is used to demonstrate effective, robust, and near instantaneous pH measurement. The result of this measurement was then fed into a PLC instrument that had been programmed to maintain a constant pH. When the pH was purposely perturbed by adding an acid or base, the PLC was able to automatically correct the pH and, consequently, control the desired extraction of metal ions. The analytical approach and performance to automated, real-time process control are described here.