Continuous monitoring of Zn in water with bismuth oxide thick-film using microwave and electric techniques

Assuring a high quality of water and protecting it from chemical contamination is a major societal goal in the European Union and worldwide. Zinc is a metal, which when present in water in high concentrations, could cause adverse health effect with long-term exposure. Metal ion dispersion from abandoned mines is a global concern and one of the principle cause of metal pollution in water. Consequently, it is necessary to develop and deploy new sensing systems able to monitor continuously the water quality. In this work, the feasibility of using eight-pair interdigitated (IDE) sensors coated with bismuth oxide based film for continuous monitoring of zinc in water is assessed with microwave and electric techniques. The reaction between zinc in the concentration range 0–100 mg/l in deionised water and bismuth oxide based thick film screen-printed on planar IDE sensors starts after 30 seconds and the adsorption equilibrium was attained within 10 minutes; the response is faster during the initial stage and slows as equilibrium is reached. Furthermore, results show good linear correlations between C (capacitance) and S11 (reflected power) and zinc concentration, respectively about R2=0.99 and R2=0.97 at 5 and 10 minutes. In addition, the recovery time of sensors is evaluated to be 100–150 sec demonstrating the sensor reusability and potential for a continuous monitoring.