Quantitative analysis of silver and gold nanomaterials in industrial wastewater

The emergence of nanotechnology has resulted in fast production and wide usage of engineered nanomaterials (ENMs) in consumer products and industrial applications globally. The current levels of pollution arising from industrial and commercial activities in South Africa appear to have reached crisis proportions, and concerns have been raised about their safety and their health impact Therefore, a simple and precise method for identifying and quantifying ENMs in various industrial wastewater is required. ENMs made of silver (Ag) and gold (Au) precursors have been investigated using ultraviolet–visible spectrophotometry as the element of interest in industrial-categorized nano-wastewater samples. Firstly, Ag and Au NPs were synthesized and characterized to get an insight into the characteristics of the categorized wastewater. The as-synthesized Ag and Au NPs and Ag and Au-categorized wastewater samples were characterized using Ultra-Violet (UV) visible spectrometer, Energy-dispersive X-ray Fluorescence (ED-XRF), inductively coupled plasma-optical emission spectroscopy (ICP-OES), transmission electron microscopy (TEM), and zeta potential techniques. The quantification results by XRF show the presence of Ag and Au with 832 and 41 ppm respectively. The ICP-OES analysis confirmed the presence of Ag and Au in wastewater with 710.06 and 47.269 ppm concentrations respectively. SPR peaks were detected for the as-synthesized Ag and Au NPs at 412 nm and 529 nm, respectively. The presence of Au NPs in the Au-categorized waste was confirmed by an SPR peak at 527  nm and TEM showed spherical shapes at various sizes. No distinct peak was observed for the Ag-categorized waste however TEM revealed aggregated particles. The Au NP concentration in Au-categorized waste was found to be 0.066 mM.