Tetracycline removal using green synthesized bimetallic nZVI-Cu and bentonite supported green nZVI-Cu nanocomposite: A comparative study

Antibiotics, one of the most abundant contaminants in the natural water systems possess various difficulties to remediate through conventional water treatment methods. Tetracycline (TC) remains one of the most widely used antibiotics for human and veterinary applications because of its broad-spectrum antibacterial activity. In the current study, we have employed nano zero-valent technology-based antibiotic remediation. In a first of its kind work, we applied bimetallic nZVI-Cu nanoparticles synthesized using pomegranate rind extract for remediation. TC removal of 72 +/- 0.5% (initial TC concentration 10 mg/L) was obtained with the nZVI-Cu concentration of 750 mg/L at pH 7. To overcome the colloidal instability and enhance TC removal further, the bimetallic nanoparticles were formed in-situ over bentonite. The bentonite supported composite (B/nZVI-Cu) was used to treat TC an initial concentration of 10 mg/L and the results confirmed significant enhancement in removal with a substantially decreased nanoparticle loading. Using only 150 mg/L of B/nZVI-Cu at pH 7, 95 +/- 0.05% of TC could be removed. The nanoparticles and the composites were characterized by SEM, FT-IR, and XRD analyses. The removal process was followed by UV-Visible analyses in conjunction with TOC, ORP and LCMS measurements. For treatment using B/nZVI-Cu, the reusability of the composite was established up to three cycles of operation, and the process was validated in the real water systems. Substantially decreased residual toxicity of the composite treated TC solution lends credence to the environmental sustainability of the process.