Abstract Description

Increasing industrial activity is posing a challenge to the supply and availability of safe water for living organisms. The textile, printing and food industries are known for releasing wastewater containing dyes into the environment causing pollution to natural water bodies. These dyes are mostly toxic and have a negative impact on the environment and human health. The exploration of metal nanoparticles for the removal of dyes in wastewater has become a hot topic over recent years as an alternative to the conventional methods for dye degradation. Nanoparticles being an integral part for the foundation of nanotechnology are nanomaterials with sizes between 1-100 nm possessing a unique set of physicochemical properties such as their small sizes and morphologies, large surface area to volume ratio and magnetization. However, the hazardous effects of their production have become a setback due to the toxic reagents required for synthesis, high cost of production, high energy consumption and pollution during synthesis. This has highlighted the need for alternative nanoparticle synthetic strategies that will not be harmful to the environment. The synthesis of nanoparticles using green synthesis methods has opened a door to create easy, cost effective approaches towards producing nanoparticles while also being considerate of the environment. The study aimed to use a green synthetic strategy to synthesise metal nanoparticles. The study involved the green synthesis of silver and gold nanoparticles using aqueous extracts of Aloe africana Mill. Aloe plants are known for their therapeutic and curative properties. The phytochemicals present in the extract acted as reducing and stabilizing agents for nanoparticle synthesis. The biosynthesised metal nanoparticles were characterised using ultra-violet visible spectroscopy (UV-vis), transmission electron microscopy and energy dispersive X-ray spectroscopy (TEM-EDX) analysis and zeta potential. UV-vis spectroscopy analysis of the silver nanoparticles showed characteristic peaks at the wavelengths of 480 nm. The size, shape and elemental composition of the nanoparticle samples were confirmed using TEM-EDX analysis. The zeta potential analysis showed that the metal nanoparticles were moderately stable and moderately dispersed. The silver nanoparticles were used as catalysts for the degradation of methyl orange. The nanoparticles exhibited up to ±40 % methyl orange degradation in 10 minutes. The p-iodonitrotetrazolium chloride (INT) colorimetric assay was used to determine the antibacterial activity of the nanoparticles against Escherichia coli, Enterococcus faecalis, Pseudomonas aeruginosa and Staphylococcus aureus. The biosynthesised metal nanoparticles displayed broad-spectrum antibacterial activity. Overall these silver nanoparticles show promise as dye degradation and antibacterial agents.