Abstract
Plant extracts were produced from Camellia sinesis (Green Tea) and Punica granatum (pomegranate), and the total concentration of polyphenols was measured in terms of equivalent concentration of Gallic acid by using the Folin-Ciocalteu method. Zero Valent Iron nanoparticles (nZVIs) were synthesized in a semi-batch reactor by mixing a pre-specified volume of plant extract or Gallic Acid solution with an aqueous solution of iron sulfate heptahydrate (FeSO4·7H2O). To monitor the kinetics of nZVI synthesis, the transient responses of solution pH and redox potential (Eh) were recorded with two probes adequately connected with a data acquisition card. The nanoparticles were characterized by a variety of techniques: Dynamic Light Scattering (DLS), ζ-potential, Attenuated Total Reflectance-Fourier Transform Infrared (ATR-FTIR) spectroscopy, Transmission Electron Microscopy (TEM). A kinetic parametric model, based on two parallel single electron transfer (SET) and hydrogen atom transfer (HAT) reactions, was suggested to quantify the dynamics of ferrous ions reduction to zero valence, and its parameters were estimated for each experimental system by matching the transient response of pH. The temporal changes of redox potential during nZVI synthesis were indicative of the reaction progress and agreed with the numerical predictions in semi-quantitative basis. The numerical model enabled us to track the temporal variation of the concentration of iron and polyphenol species, and calculate the yield of ZVI synthesis. The reactivity of nZVIs was assessed by measuring their capacity to reduce hexavalent chromium Cr (VI) in aqueous solutions prepared from potassium dichromate (K2Cr2O7).
Highlights
Nowadays, one of the main challenges is to restore and preserve the quality of soil and water
A twomechanism (SET, hydrogen atom transfer (HAT)) reaction kinetic model was developed to quantify the dynamics of ferrous ion reduction to zero Valent iron and interpret the experimentally observed behavior
The transient responses of pH were used to estimate the kinetic parameters for each reactive system that control the synthesis process
Summary
One of the main challenges is to restore and preserve the quality of soil and water. Many places all over the world face serious environmental problems, like the contamination of the subsurface, and the need for the remediation of soils and groundwater [1] Green chemistry is the layout of chemical products and approaches that lessen or remove the use of dangerous materials. The use of nanotechnologies for environmental remediation has attracted funding and interest from the service companies and scientific society. A great variety of nanomaterials have been tested in remediation studies, such as nanoscale semiconductor photocatalysts, carbon-based nanomaterials (carbon nanotubes CNT, fullerenes, graphene) bi-metallic nanoparticles. The Zero Valent Iron nanoparticles (nZVIs) has widely been used for a long time, in a variety of environmental applications, as an excellent reducing agent, due to its inexpensive and nontoxic characteristics [4]
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