Profile of aromatic intermediates of titanium dioxide mediated degradation of phenol

Abstract

Photocatalysis is green technology for the degradation of recalcitrant organic compounds in water, and have found success in the removal of several water pollutants. Degradation of pollutants is often accompanied by their conversion into other compounds some of which are sometimes feared to be more environmentally harmful than the parent compound. This study profiles aromatic intermediates formed during photocatalytic degradation of phenol in a batch system. Catechol, hydroquinone and resorcinol were identified as the major aromatic degradation intermediates. Maximum concentrations of intermediates obtained is in the order catechol>resorcinol>hydroquinone with all three produced within the first two minutes of phenol degradation. Resorcinol attained steady state concentration of 3.73 mg/L after 2 minutes of phenol photocatalysis with no appreciable change in its concentrations until all phenol is degraded suggesting that production of resorcinol proceeds at approximately the same rate as its removal from solution. Catechol formed rapidly attaining maximum concentration of 7.00 – 7.11 mg/L; after 6 minutes at a rate of 0.764 – 0.868 mg/L/min; decreasing thereafter at rates of 0.241 – 0.348 mg/L/min. Maximum concentration of 0.96 – 1.66 mg/L; of hydroquinone was obtained then decreases steadily until all phenol is degraded. Complete mineralisation of phenol and intermediates was achieved under optimum reaction conditions.