Abstract:
Since dye effluents discharged from different industries lead to environmental contamination,
their treatment and environmental remediation are highly desired. Due to the limitations of
physical treatment methods like adsorption, photocatalytic degradation was used because of its
capability to complete the degradation of dyes. On the other hand, most microbial species have
shown resistance to antibiotic drugs. Concerning this, nanomaterials have been found to be a
promising candidate to overcome such a problem. Metal oxide-based nanostructures are widely
used in photochemical processes and antimicrobial agents due to their unique properties. But
single-nanostructure metal oxide materials might suffer from low efficiency under visible light.
This fact makes it important to have efficient and reliable nanocomposites for the photochemical
processes. The combination of different nanomaterials to form a composite configuration can
produce a material with new properties. The new properties, which are due to the synergetic
effect, are a combination of the properties of all the counterparts of the nanocomposites. The
main objective of this research was to synthesize ZnO NPs and Co/ZnO NCs by precipitation
using red onion peel plant aqueous extract for photocatalytic and antimicrobial applications.
Co/ZnO NCs were prepared from red onion peel plant aqueous extract , Zn(NO3)2 .6H2O) and
Co(NO3)2.6H2O solution at 65 0C for 2 h and ZnO NPs were prepared in the same way, but
without the addition of Co(NO3)2.6H2O solution. The synthesized ZnO NPs and Co/ZnO NCs
were characterized by UV-Vis, XRD, FT-IR, and SEM techniques. From the UV-Vis absorption
spectrum, the peaks of ZnO NPs and Co/ZnO NCs were detected at 369 and 375 nm,
respectively. The XRD data showed the crystalline nature of the NPs and NCs, and the average
crystallite size of ZnO NPs and Co-ZnO NCs is 27.47 and 33.97, respectively. The FT-IR result
revealed the presence of important functional groups like tannins and phenolics, which were also
observed in the phytochemical screening test experiment. The SEM result showed hexagonal
wurtzite and spherical-like morphologies for ZnO Nps and Co/ZnO NCs, respectively. The in
vitro antimicrobial test of NMs showed good antimicrobial activity, especially at high
concentrations. The result indicates that Co/ZnO NCs showed enhanced antimicrobial activity
compared to ZnO NPs. The photocatalytic performance of Co/ZnO NCs was further assessed by
the degradation of MB dye as a model pollutant under irradiation of natural sunlight and
compared with that of bare ZnO NPs. The effect of some parameters like pH, catalyst dosage,
irradiation time, and initial dye concentration of MB dye on the activity of Co/ZnO NCs was also
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investigated. 98.5% and 89.3% of MB dye were degraded by Co/ZnO NCs and ZnO NPs at 60
min, which is a promising future application of solar light driven photocatalytic degradation of
organic pollutants.
