Detection And Degradation of Endocrine Disruptors Using Zno Nanoparticles

Abstract

Globally, the major concern is alarming levels of EDCs resulted due to rapid industrialization and urbanization. Industries produce these compounds for every aspect of our life, such as mobility, gadgets, health, agriculture and cosmetics. The inappropriate use or disposal of these products led to contamination of the water ecosystem and became a threat to human health. Thus, there is a constant need to develop detection methods for EDCs and further cleanup technology to eliminate those pollutants from the water ecosystem. In this aspect, ZnO nanoparticles were synthesized by chemical and biological approaches for the detection and degradation of EDCs, i.e., p-NP and BPA have been reported. For biological synthesis, a zinc metal tolerant endophytic fungus C. geniculatus was isolated from the medicinal plant Nothapodytes foetida and its ability to synthesize proteins that can aid in the synthesis of ZnO nanoparticles was evaluated. The discrete, polydisperse and quasi-spherical hexagonal wurtzite structured ZnO nanoparticles with an average size of 5.25 ± 1.43 nm were synthesized. The removal efficiency of 78.57 % and 85.18 % was obtained in the photocatalytic degradation of p-NP and BPA, respectively, under optimum reaction conditions. The experimental results with COD and TOC analysis exhibit 60 % and 50.9 % of the mineralization degree for p-NP (25 mg/L) and 63.6 % and 63.6 % for BPA (10 mg/L). The photocatalytic degradation of p-NP and BPA follows first- order reaction kinetics. Moreover, the degradation reaction of p-NP and BPA were found to be initiated and dominated by •OH and h+ radicals. Subsequently, the intermediates and products of photocatalytic degradation of p-NP and BPA were identified through LC-MS analysis and the degradation pathway was proposed. Furthermore, the detection limit was found to be 17.9 μM and 0.35 μM for p-NP and BPA, respectively, using a fluorescence spectrophotometer. The hypothetical sensing mechanism for p-NP and BPA is ascribed to static and dynamic quenching, respectively. A yellow fluorescent, APTES@ZnO and β- CD@ZnO QDs were synthesized by co-precipitation method for detection of p-NP and BPA, respectively. The lower detection limit of functionalized QDs for p-NP and BPA was estimated to be 0.089 μM and 0.19 μM, respectively. Moreover, the hypothetical sensing mechanism in detection was ascribed to the partially inner filter effect of p-NP towards APTES@ZnO QDs, and the transfer of excited state electrons of the APTES@ZnO QDS to p-NP. In the case of BPA, the quenching mechanism was ascribed to electron transfer between β-CD-functionalized ZnO QDs and BPA due to inclusion complex formation.