Electrochemical Environment
Potentiometric measurement of ionic concentration in process wastewater requires a stable salt environment to ensure that the activity coefficient of the target ion remains constant. Establishing a uniform ionic strength background minimizes the influence of varying dissolved salt levels on the electrode response. This chemical stabilization allows the sensor to register changes in concentration rather than total ionic concentration variations.
Activity Stabilization
Electrodes respond directly to the activity of specific ions, which decreases as the total salt concentration of the solution rises. By adding a high concentration of inert electrolyte to both standards and samples, the baseline ion level is kept artificially high and uniform. This addition means that any small variations in the sample’s original salt content become negligible, which stabilizes the activity coefficient.
Measurement Protocol
Practical implementation involves mixing a precise volume of ionic strength adjustment buffer with every test sample before inserting the electrode. This buffer usually contains a non-interfering salt along with pH adjustment chemicals to keep the solution within the optimal operating range of the sensor. The mixture must be stirred gently at a constant speed to maintain uniform distribution during the reading.
Boundary Condition
Highly concentrated effluent from reactive dyeing processes sometimes exceeds the buffering capacity of the adjustment solution. Under these conditions, the ionic strength background must be increased by modifying the buffer ratio.
