Synthesis of Zinc Oxide Nanoparticles by Ecofriendly Routes: Adsorbent for Copper Removal From Wastewater.

Julia De O Primo,Verônica C Teixeira,Silvia Jaerger,Ayrton Sierra-Castillo,Carla Bittencourt,Selene Acosta,Fauze J Anaissi,Jean-François Colomer

doi:10.3389/fchem.2020.571790

Abstract

Zinc Oxide nanoparticles have been synthesized by two simple routes using Aloe vera (green synthesis, route I) or Cassava starch (gelatinization, route II). The XRD patterns and Raman spectra show that both synthesis routes lead to single-phase ZnO. XPS results indicate the presence of zinc atoms with oxidation state Zn2+. SEM images of the ZnO nanoparticles synthesized using Cassava starch show the presence of pseudo-spherical nanoparticles and nanosheets, while just pseudo-spherical nanoparticles were observed when Aloe vera was used. The UV-Vis spectra showed a slight difference in the absorption edge of the ZnO particles obtained using Aloe vera (3.18 eV) and Cassava starch (3.24 eV). The ZnO nanoparticles were tested as adsorbents for the removal of copper in wastewater, it is shown that at low Cu2+ ion concentration (~40 mg/L) the nanoparticles synthesized by both routes have the same removal efficiency, however, increasing the absorbate concentration (> 80 mg/L) the ZnO nanoparticles synthesized using Aloe vera have a higher removal efficiency. The synthesized ZnO nanoparticles can be used as effective and environmental-friendly metal trace absorbers in wastewater.

Highlights

The fast growth of the human population and the further development of industries have direct consequences on the environment, leading to the depletion of natural resources, with an emphasis on freshwater resources
The E2low mode is attributed to the vibrations of zinc sublattice in ZnO and E2high mode is assigned to the oxygen vibration (Cuscó et al, 2007; Stankovicet al., 2012), the strong E2high mode indicates the high crystallinity of the oxide (Jothilakshmi et al, 2009), the same vibrational mode has been identified for the zinc oxide nanoparticles obtained via the Starch-assisted synthetic route, reported by Carp et al (2015)
ZnO nanoparticles have been successfully synthesized by an eco-friendly procedure based on a polysaccharide, without using any surfactant, organic solvent and at low calcination temperature

Summary

INTRODUCTION

The fast growth of the human population and the further development of industries have direct consequences on the environment, leading to the depletion of natural resources, with an emphasis on freshwater resources. The solution was washed, filtered and the resulting Aloe vera gel broth extract was stored under refrigeration (2◦C) Two different routes, both easy to reproduce, were used for synthesizing Zinc oxide nanoparticles. In the route II (gelatinization method): first starch (ST) was extracted from 100 g of natural Cassava starch in 300 ml of distilled water under mechanical stirring for 2 h It was sieved, and in the colloidal starch suspension was added 9.40 g of zinc nitrate. To investigate the efficiency of the ZnO nanoparticles as adsorbents for the removal of copper metal ions from water, an adsorption test was performed. The residue was washed with deionized water followed by oven drying at 60◦C

RESULTS AND DISCUSSION

CONCLUSIONS

DATA AVAILABILITY STATEMENT