Ion selective electrodes for flue gas desulfurization wastewater monitoring: Effects of ionic strength on selective ions

Abstract

Ion selective electrodes (ISE) were evaluated for use in a flue gas desulfurization (FGD) wastewater monitoring system. Calcium, chloride, nitrate, and nitrite ISE's were calibrated in a broad range of concentrations that were designed to model an actual FGD wastewater sample that was obtained from an industrial partner. Ideal Nernst, Modified Nernst, and a multiparameter regression analysis was performed for each electrode and evaluated on general fit and sensitivity at anticipated operating conditions. The Ideal Nernst equation, even with correction for ionic strength, was not able to properly model actual electrode performance. The multiparameter regression was able to model the electrode performance with relative errors of 10-25% when ionic strengths were below 0.1 M. Through the evaluation of real-time sensor usage at real conditions, a methodology of washing and sampling rate is suggested to minimize error in the readings.