Calcinated kaolin supported nanoscale zero-valent iron (K-nZVI) was synthesized and used for the
removal of tetrad azo-group dye-Direct Fast Black G (DFBG) from aqueous solution. The results
demonstrated that after reacting for 10 min with an initial concentration of DFBG 100 mg L1 (pH 9.49),
78.60% of DFBG was removed using K-nZVI, while only 41.39% and 12.56% of DFBG were removed using
nZVI and kaolin, respectively. K-nZVI with a mass ratio of nZVI nanoparticles versus kaolin at 1:1 was
found to have a high degree of reactivity. Furthermore, scanning electron microscopy (SEM) confirmed
that nZVI was better dispersed when kaolin was present. XRD patterns indicated that iron oxides were
formed after reaction. Fourier transforms infrared spectra (FTIR) and UV–visible demonstrated that the
peak in the visible light region of DFBG was degraded and new bands were observed. Kinetics studies
showed that the degradation of DFBG fitted well to the pseudo first-order model. The degradation of
DFBG by K-nZVI was based on its adsorption onto kaolin and iron oxides, and subsequently reduction
using nZVI was proposed. A significant outcome emerged in that 99.84% of DFBG in wastewater was
removed using K-nZVI after reacting for 60 min