Synthesis of copper nanoparticles using grape stalk and spent coffee extract

Abstract

Nanotechnology has great potential in improving waste water treatment. Physical and chemical methods of obtaining nanoparticles have already been explored a great deal. They have however some drawbacks such as hazardous reaction conditions and expensive reagents. Green nanotechnology is a new way of producing nanoparticles which has a less drastic reaction and is eco-friendly. Green synthesis of nanoparticles can be achieved by using for example microorganisms or plant extracts. In this study, biosynthesis of metal nanoparticles was done using grape stalk (waste from winery) and spent coffee (after production of soluble coffee) waste. These agrofood wastes contain a high concentration of reducing agents such as polyphenols and sugars that could be adequate to reduce the metals in solutions to zero-valent and obtain the nanoparticles. The grape stalk and spent coffee extracts were obtained using Milli-Q water as a solvent. Temperature, contact time, ratio solvent/waste and particle size were conditions that were examined to obtain the highest concentration of reducing agents possible. The concentration of reducing agents in the extracts was analysed. The extract was then added to a synthetic copper solution to obtain the nanoparticles. The effects of temperature, pH, contact time and ratio metal/extract were examined. The nanoparticles were characterized by using scanning electron microscopy (SEM) coupled with EDX and UV-Vis absorption