Construction of rGO-Bi2Sn2O7-NiFe2O4 nanoheterojunction system for the enhanced photodegradation of doxycycline: A brief insight on degradation kinetics and toxicological evaluation on Allium cepa

Abstract

In this study, the rGO-Bi2Sn2O7-NiFe2O4 nanocomposite (RBN NCs) was fabricated using an in-situ hydrothermal method and applied for the effective aqueous degradation of doxycycline (DOX). Various analytical techniques were employed to characterize the physicochemical properties of the fabricated nanoparticles, including TEM, UV–Vis, PL, FE-SEM, ESR, DRS, XPS, XRD, and N2 adsorption and desorption analysis. The efficiency of DOX degradation by the RBN system under different conditions was evaluated. Under optimal conditions (RBN concentration = 50 mg/L and pH = 7.0), the NCs removed 99.1% of DOX (10 mg/L) within 270 min under visible light irradiation. ESR and scavenging tests illustrated that the developed system produced O2⦁- radicals, which played a dominant role in the complete degradation of DOX. The mineralization of DOX was confirmed by total organic carbon results. The RBN system displayed exceptional reusability over six consecutive cycles and could be easily removed from treated water due to its magnetic properties. The toxicity of the end-product after degradation was assessed against Escherichia coli (gram-negative) and Bacillus subtilis (gram-positive). Additionally, GC-MS analysis was conducted to predict the possible photodegradation pathway of DOX, providing a better understanding of the degradation process. Toxicity of intermediate products was also estimated computationally using the ECOSAR software. The fabricated RBN was further investigated for genotoxicity towards Allium cepa. This study provides new insights into the RBN system for environmental remediation.