Photocatalytic degradation of tetracycline and ciprofloxacin antibiotic residues in aqueous phase by biosynthesized nZVI using Sal (Shorea robusta) leaf extract

Conventional treatments for antibiotic residues in effluents are inefficient and do not lead to complete removal. Though effective and feasible degradation of antibiotics using nanoparticles has been reported by several scientists, chemically synthesized nanoparticles have their own disadvantages. Thus, in this study, nZVI was biosynthesized using leaf extract of Shorea robusta and precursor FeSO4·7H2O for photocatalytically degrading tetracycline (TC) and ciprofloxacin (CIP). The characterization of nZVI was performed using SEM, TEM, AFM, EDX, FTIR, and XRD to test their properties, which revealed iron-rich, well-dispersed, spherical, crystalline nanoparticles. Photocatalytic degradation of TC and CIP under UV illumination revealed 88 and 84% optimum efficiency at antibiotic concentrations 15 and 25 mg L−1, 0.014 and 0.0175 g L−1 doses of nZVI, respectively in the pH range 4–6 in 70 min. The degradation was further verified using mass spectrometry, which confirmed the degradation of antibiotics into the breakdown products. Toxicity assay of the degraded antibiotic solution proved it non-toxic for bacteria and safe for discharge into water bodies. The cost analysis of antibiotic degradation using nZVI proved very economical, costing around 1.5 USD per 1,000 L of wastewater.