Silver nanoparticles (AgNPs) have antibacterial properties and are widely used for water disinfection. This technology is commercially applied in point-of-use water treatment as a post-treatment for filtrate water. However, the current process of synthesizing AgNPs has several disadvantages including the use of hazard chemicals, consumption of a large amount of energy and the formation of hazardous byproducts. In this work, we report an alternative and green synthesis using plant extracts. In this work, the plant extracts came from radish (R) and tea (T), and the AgNPs were derived from a microwave irradiation method. The AgNPs synthesized by chemical-based microwave irradiation (Ag-C) were also performed as a control material. The novel method produced a smaller size of nanostructures with good dispersion ability and less agglomeration than those from chemical synthesis. The antibacterial properties of AgNPs on gram-negative bacteria Escherichia coli (or E. coli) and Gram-positive bacteria Staphylococcus aureus (or S. aureus) were investigated. The results revealed that both AgNPs from green synthesis and chemical based methods inactivated both types of bacteria. The green synthesized-AgNPs from radish juice provided a higher percentage of inhibition of E. coli than that of S. aureus. The inactivation rates of the AgNPs increased with increasing concentration of AgNPs. As the concentration of the Ag/AgCl-R and Ag-R increased from 150 μg/mL to 300 μ/mL, the complete inactivation required a shorter time for the reaction from 300 minutes to only 30 minutes. Finally, the Ag/AgCl-R and Ag-R offered high antibacterial activity while the Ag-T provided the lowest antibacterial activity. This work provides an alternative method for the eco-synthesis of anti-bacterial nanomaterials for water treatment.
- green nanomaterials
- water treatment
- First received 5 February 2015.
- Accepted in revised form 29 July 2015.
- © IWA Publishing 2015