Abstract:
Waste water released to the environment is causing adverse effect on our ecosystem.
There are various toxic heavy metals that are released with industrial waste water to the
environment, hence worsening the life of biodiversity and increasing environmental
pollution. Hexavalent Chromium (Cr(VI)) is a highly toxic pollutant which needs to be
removed from the waste water. Conventional methods for remediation of Cr(VI) are
usually costly and difficult to operate. Green synthesis provides advancement over
chemical and physical method because it is cost effective, environmentally friendly, easily
scaled up for large scale synthesis. In this study, zero valent iron, a strong reducing
agent that transforms Cr(VI) to nontoxic trivalent chromium (Cr(III)), was synthesized,
characterized and tested for adsorption of Cr(VI). Zero valent iron (Fe0
) nanoparticles
were synthesized by reduction of Ferrous Sulphate (FeSO4.7H2O) in the presence of
polyphenol extracted from Eucalyptus Camaldulensis leaves. The synthesized particles
were identified as iron nanoparticles using UV visible spectrophotometer. X-ray
Diffraction (XRD) was used to determine the crystallinity of synthesized nano zero valent
iron (nZVI) particles, hence, the formed polyphenol based iron nanoparticles have no
crystalline structure. FT-IR spectra revealed the existence of -OH stretching vibration of
polyphenols and Fe-O bond formation in the prepared nanomaterials. The batch
adsorption experiments for the removal of hexavalent chromium has been conducted
using nZVI-TS dosage, initial concentrations of Cr(VI), solution pH and contact time as
parameters and the process was significantly affected by these parameters. The highest
removal efficiency obtained was 99.79%. Langmuir isotherm model was better to fit to
the experimental data and favored adsorption process. Response Surface Methodology
using Central Composite Design was applied to analyze statistical experimental analysis
for the data obtained from laboratory experiments and its optimal condition was
identified. The optimal conditions selected using design tool were nZVI-TS dosage of
0.972 g/100 ml, initial Cr(VI) concentration of 21.034 mg/1000 ml, pH of 4.166, and
contact time of 6.99 min providing predicted value of 99.984% removal efficiency
