Applicability of a bipolar electrode arrangement involving ion-selective electrodes in vertical farming, with the self-controlled supply of macro- and microcomponents

Abstract

All-solid-state potentiometric ion-selective electrodes (ISEs) with plastic membranes are attractive analytical tools due to the simplicity of the apparatus and their ease of use. The implementation of ISEs into a bipolar electrode system working in self-powered mode would open new and attractive possibilities, far beyond typical analytical purposes. In the present work, the applicability of such systems for vertical farming, e.g., in hydroponics, is evaluated as a proof of concept. This approach can be used for long-term monitoring of the concentration of electrolytes (macrocomponents, e.g., potassium or chloride ions) in solutions. Another innovative application proposed herein utilizes the properties of the bipolar electrode system to allow for self-adjustment of the concentrations of components via spontaneous charge transfer processes occurring at both poles of the bipolar electrode. We demonstrate that a self-powered bipolar electrode system composed of an active metal (zinc) and an ISE can be applied for the controlled release of minute amounts of microelements, in this case, zinc ions. The ion flux is selectively controlled by a chemical stimulus, namely, the composition and concentration of a neutral electrolyte (macrocomponents), as well as the properties of the bipolar electrode system.