Abstract:
Hexavalent chromium (Cr (VI)) contamination of surface and groundwater has become a major environmental
concern owing to the diverse applications of Cr(VI)) in several industries. In the current study kaolinite-supported
and size-controlled Fe/Al oxide(oxyhydroxide) nanocomposites (Kaolinite@Fe/Al nanocomposites) were
synthesized for efficient removal of Cr(VI) from aqueous solution. Scanning Electron Microscopy (SEM) and
Transmission Electron Microscopy (TEM) analysis of the nanocomposites revealed that the nanocomposites
were uniformly dispersed, with an average particle size of ~ 25 nm. Batch adsorption studies were carried out
to study the effect of (Kaolinite@Fe/Al nanocomposites) on the removal of chromium (VI) from 100 mg/L Cr(VI)
contaminated water over a wide pH range (3–10) at various adsorbent dosages. The result demonstrated that
the nanocomposites’ adsorption efficiency increased with increasing adsorbent dosage. When the
Kaolinite@Fe/Al nanocomposites dosage was increased from 1.0 to 3.0 g/L, the Cr(VI) removal percentage
increased from 65.4 % to ∼99.0 %. This is due to the greater surface area and availability of more adsorption
sites at higher dosages of the adsorbent. There was a significant removal of Cr(VI) in the pH range 3–6 reaching
up to 99.0% Cr(VI) removal, however, removal efficiency decreased drastically beyond pH 6. Chromium (VI)
exists as CrO4
2−, HCrO4
− and Cr2O7
2− oxyanionic species while the surface of the adsorbent becomes highly
protonated, owing to the variable surface charge imparted by Al/Fe oxides/hydroxides favouring remarkable
uptake of Cr(VI) in the anionic form. The experimental data fitted Langmuir adsorption model well with a
maximum adsorption capacity of 70.71 mg/g. The results of the study demonstrate that Kaolinite@Fe/Al
nanocomposites may have a promising potential for remediation of Cr(VI) contaminated wastewater and
industrial effluents.
