Utilization of tannery wastewater as a source of Cr doped into TiO2 for improving its activity under visible light in the Congo red degradation

The use of the Cr contained in tannery wastewater as a dopant for improving TiO2
activity under visible light has been studied systematically in the present paper. The
doping was conducted by reacting titanium tetra-isopropoxide (TTIP) as TiO2
precursor
and Cr-containing tannery wastewater through the sol–gel method. The concentration
of Cr in the wastewater was varied giving mole ratio of TiO2
to Cr as
1:0.25, 1:0.5, and 1:1. The Cr-doped TiO2
photocatalysts obtained were characterized
by UV/Vis diffuse reflectance, Fourier Transform infrared, X-ray diffraction,
X-ray fluoresence, and Scanning electron microscopy machines. The effect of the Cr
doping on the TiO2
activity under visible light was evaluated through Congo red dye
photodegradation by batch experiment. The results reveal that Cr doping on TiO2
has successfully proceeded which can reduce the gap energy shifting into the visible
region, and further enhance TiO2
activity under visible light. The interesting result
is also found that doping TiO2
with Cr by the mole ratio of TiO2
to Cr = 1:1, has
converted TiO2
into CrTi2O5
crystal that also shows a photocatalyst character. The
most effective degradation of 10 mg/L Congo red in 50 mL solution which is about
98%, can be obtained by applying 20 mg of TiO2-
Cr(1:0.5) photocatalyst weight,
solution pH at 5 in 60 min. It is clearly inferred that the toxic Cr in the leather tannery
wastewater can be utilized to form a more valuable material, preventing environmental
pollution by Congo red dye.