Electrochemical and optical protocols for the detection and removal of an antibiotic drug rifaximin from wastewater

Abstract

Improper disposal of pharmaceutical drugs is increasing the pollution level of water reservoirs which in turn adversely impacts the ecosystem. The current study presents an electrochemical scaffold that comprises a glassy carbon electrode modified with amino-functionalized multiwalled carbon nanotubes (NH₂-fMWCNTs) for the detection of a pharmaceutical drug rifaximin in wastewater. Electrochemical impedance spectroscopic characterization revealed efficient charge transport through the modified electrode surface. Square wave voltammetry was employed for probing the electro-oxidation of antibiotic rifaximin. Under optimized experimental conditions, the designed sensor demonstrated the qualities of sensitivity, repeatability, and reproducibility as required for the practical applicability of the sensing device. After the detection of a contaminant, its removal from water is imperative. In this regard an adsorption method using ZnO nanoparticles as adsorbents was developed that led to the removal of rifaximin from wastewater. At lower adsorbate concentration, adsorption was found to occur according to the Langmuir model while at higher concentration adsorption data followed the Freundlich model. The rate of rifaximin adsorption over ZnO nanoparticles followed pseudo-second-order kinetics.