Biosynthesis of copper nanoparticles using a bioflocculant from Alcaligenis faecalis, characterization and its application

Abstract

Nanotechnology offers a great deal of possibility for the efficient removal of pollutants in the area of water purification. Most common method used for nanoparticles formation such as physical (condensation evaporation) and chemical (oxidation and reduction) are very efficient traditional methods. However, both methods have been found to have some shortcomings. One may require a large amount of energy and the other may involve the use of toxic and expensive chemicals which may results in the binding of the nanoparticles on the surface of these chemicals. Naturally occurring secretion secreted by microorganisms (bioflocculants), have attracted considerable interest due to their harmlessness, biodegradability, and negligible secondary pollution. Therefore, in this present study, biosynthesis of copper nanoparticles was successfully achieved by using a bioflocculant from Alcalegenis feacalis and copper sulphate salt. Nanoparticles were characterized using a scanning electron microscope equipped with elementary detector (SEM), UV-visible absorption, Thermogravititional analysis (TGA), Fourier Transform Infrared Spectrophotometer (FT-IR) and transmission electron microscopy (TEM). This new synthesis method shows excellent stability and is eco-friendly. Scanning electron microscopy (SEM) images revealed that the huge significant increase of copper compared to the bioflocculant. The synthesized nanoparticles showed a 35.8% copper and 37% oxygen concentration. This was an indication that nanoparticles were successful synthesized. The synthesized copper nanoparticles were shown to have higher flocculating activity and removal efficiency of both BOD and COD when compared with the bioflocculant and commercial flocculant. Moreover, the potential of CuNPs was also observed when compared to the bioflocculant and iron chloride in kaolin clay, mine water, industrial waste water and domestic waste water. The highest flocculating activity was achieved with the lowest concentration of CuNPs (0.002g/L) with 96% and the least activity was 80% at 0.01g/L. The synthesized copper nanoparticles (CuNPs) are cation independent with 96% flocculating activity following 1% behind the most effecting cations (K+, Mn2+ and Li+) which had 97%. It functioned the best at pH with 7 with 96% FA. It was not as effective at pH 3 as it was least effective with 55% FA. Furthermore, the nanoparticles were found to be thermostable with a flocculating activity was above 90% in a temperature range of 50-100 ℃. A temperature of 100 ℃ was the least effective with 91% flocculating activity. The synthesized copper nanoparticles are also high in removal efficiency of staining dyes, such as safranin (92%), carbol fuchsine (94%), malachite green (97%) and methylene blue (85%). Furthermore, the synthesized CuNPs were shown to possess high removal efficiencies for elements such as sulphur, calcium, aluminium and phosphorus both in mine and waste water. Nutrients such as nitrate (NO3-) were also removed effectively by the CuNPs. Removal efficiency for both COD and BOD was also high compared to that of FeCl3 and the pure bioflocculant, with a RE of 76% and 80% respectively.