For photocatalytic process, prior to irradiation, the TCF was
placed in a solution in 1000 mL of photocatalytic reactor. The solution
was illuminated by a 10 W germicide lamp with a nominal
wavelength range of 254 nm located at the centre of the reactor. Air
was bubbled through the reaction solution to ensure a constant
supply of nitrogen gas and to give agitation effect to achieve an
equilibrium state of Cr(VI) and TCF. The dark adsorption was conducted
until it reached equilibrium and, then, a lampwas turned on
to illuminate the TCF for 180 min. The Cr(VI) solution was agitated
thoroughly by the magnetic stirrer. The 1.0 mL of the sample after
illumination was syringed out for Cr(VI) analysis using a 1.5-
diphenylcarbarzide (BDH) colorimetric method (Zhou et al.,
1993). The Cr(VI) determination was measured at the absorbance
at 540 nm in acid solution with a PerkinElmer Lambda 20 UVevis
spectrometer. The residual Cr(VI) concentration in the aqueous
solution was plotted as a function of time. The observed rate constant
(kobs) from each experimental condition was calculated. All
experiments in the adsorption and photocatalytic reactions were
duplicated.