Eco-friendly synthesis and optimization of CuNPs using a non-pathogenic bioflocculant from Kytococcus sedentarius

Abstract

Nanotechnology is being used to solve a variety of environmental issues, including wastewater treatment. In the present study, a rapid eco-friendly method was applied to biosynthesize and optimize copper nanoparticles (CuNPs) from Kytococcus sedentarius. The CuNPs characteristics were identified using X-ray diffractometer (XRD), scanning electron microscope (SEM), Fourier Transform infrared (FT-IR), Transmission electron microscope (TEM), Thermogravimetric analysis (TGA) and UV–Vis spectroscope (UV–Vis). To determine the maximum metabolic yield, the optimum dosage size, pH, temperature, salinity and cations were evaluated. The antibacterial activity of the samples against Gram-negative and Gram-positive isolates was assessed using the Kirby-Bauer Disk Diffusion Test. 28.3 nm was the average crystallite size of CuNPs revealed through XRD analysis. The SEM and TEM analysis depicted the CuNPs to be agglomerated in various sizes and forms. Elements such as Carbon (25.23 % wt), Cu (23.37 % Wt) and Oxygen (20.13 % Wt) were found in CuNPs. The nanoparticles had functional groups and a Cu–O bond at 559 cm ⁻¹. The CuNPs retained 70 % of its weight whereas the bioflocculant retained only 50 % when heated at a range of 100 °C–900 °C. The samples exhibited a UV–Vis spectra between 250 and 300 nm, at a range of 200–1400 nm. The flocculating effeciency of CuNPs was optimal at 0.2 mg/mL (92 %) and cation independent (92 %). pH 7 was the peak maximum as 98 % of the flocculating activity was obtained. The CuNPs were thermally stable than the bioflocculant as over 80 % of its flocculating activity was retained even at high temperatures (121 °C). The CuNPs were not affected by the increase in NaCl concentration with the highest NaCl concentration (35 g/L) having the highest flocculating activity of 90 %. CuNPs exhibited antimicrobial activity against both bacterial strains, with greater susceptibility observed in S. aureus as compared to the bioflocculant. Thus, CuNPs have a potential to be applied in wastewater treatment to replace traditional flocculants.