Chlorella vulgaris-mediated sustainable biogenic synthesis of silver nanoparticles for wastewater remediation and antibacterial applications

Abstract

This investigation examines the green synthesis of silver nanoparticles (SNPs) using Chlorella vulgaris as a reducing and stabilizing agent. Algae-mediated SNPs (ASNPs) were tested for the potential application in sewage water remediation and as an antibacterial agent. Biogenic ASNPs demonstrated excellent stability and a surface plasmon resonance (SPR) peak at 440 nm. Energy dispersive X-ray (EDAX) spectroscopy analysis and Fourier transform infrared (FTIR) spectroscopy investigation indicated the role of biomolecules originating from the algal extract, which play a crucial role in the green synthesis process of ASNPs. Dynamic light scattering analysis yielded a hydrodynamic mean particle size of 200 nm and a zeta potential of around 18 mV. Observation under electron microscopy presented the morphological diversity with a prominent signature of elemental silver in ASNPs. A domestic waste sewage sample collected from a sewage treatment plant presented elevated levels of alkalinity, salinity, and biological oxygen demand (BOD). ASNP treatment normalises most of the water parameters, while algal extract alone could produce minimal effects. The antibacterial evaluations against Staphylococcus aureus and Escherichia coli, well-known opportunistic pathogens responsible for a wide range of hospital and community-acquired infections, showed dose-dependent effects. These findings highlight the dual functional role of C. vulgaris-mediated SNPs as an effective, eco-friendly solution for both wastewater remediation and antibacterial application.