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Limiting quantum yield measurements for the disappearance of 1-propanol and propanal: an oxidative reaction study employing a TiO 2 based photoreactor

1993; NRC Research Press; Volume: 71; Issue: 12 Linguagem: Inglês

10.1139/v93-255

1480-3291

Giuseppe P. Lepore, Bhuvan C. Pant, Cooper H. Langford,

Advanced oxidation water treatment

Relative initial quantum yields [Formula: see text] for the disappearance of 1-propanol and propanal were estimated based on total light intensity entering the reaction vessels. Two types of photocatalytic reactor geometries were compared, a commercial prototype flow reactor with immobilized TiO 2 and a conventional reactor with TiO 2 dispersion. A maximum relative quantum yield, [Formula: see text], was extrapolated for pure propanol and propanal in both geometries. The high quantum yields were attributed to efficient competition of substrate oxidation with electron–hole recombination, at high surface coverage. Propanal was identified as the primary intermediate generated from 1-propanol in both reactor systems, but yields of propanal were systematically 10 times lower than 1-propanol loss, indicating that there was an effective pathway for propanal oxidation on the surface prior to desorption. The inhibition of 1-propanol reaction caused by accumulation of product arises because both reactant and product compete for active sites on the photocatalyst surface. These propositions were confirmed by introducing propanal into the feed. The relative quantum yields converge to unity for pure substrates, suggesting that they are true yields. That is to say, absorption by TiO 2 of light entering the reactor is efficient in these geometries.