Microwaves and Functional Materials: A Novel Method to Continuously Detect Metal Ions in Water

Abstract

Protecting water from chemical pollutants is a major societal goal. Metal ion dispersion from abandoned mines is a global concern and one of the principal causes of metal pollution in water. Toxic metals are a particular concern because they are not degraded by normal biogeochemical cycles and cause adverse environmental and human health effects even with low concentrations if there is long-term exposure. Current laboratory-based methods are not suitable for monitoring adequately water pollution in the environment. Consequently, it is necessary to develop and deploy new sensing systems to investigate water quality continuously. Microwave spectroscopy has been demonstrated as an effective method for offering continuous measurement of material properties, nevertheless, this method suffers from a lack of selectivity and sensitivity (Zarifi et al. Sens Actuators B Chem 255:1561–1568 (2018), [1]). This chapter presents a feasibility study using unique functionalised electromagnetic (EM) sensors for continuous monitoring of zinc in water. The reaction between Zn and a Bi2O3 based thick film that is screen-printed onto a planar interdigitated electrode (IDE) sensors starts within 30 s, and the adsorption equilibrium was attained within 10 min. The response is faster during the initial stage and slows as equilibrium is reached. Results show good linear correlations between C (capacitance), S11 (reflection coefficient) and Zn concentration. Also, the recovery time of sensors is evaluated to be 100–150 s demonstrating the sensors reusability and potential for continuous monitoring.