Immobilized titanium dioxide/powdered activated carbon system for the photocatalytic adsorptive removal of phenol

Titanium dioxide (TiO2) and powdered activated carbon (PAC) were fabricated via a layer by layer arrangement on a glass plate using a dip-coating technique for the photocatalytic-adsorptive removal of phenol. Thinner TiO2 layer coated on PAC sub-layer has larger surface area and better phenol removal than the thicker TiO2 layer. The system obeyed the Langmuir isotherm model, which exhibited a homogeneous and monolayer adsorption with a maximum capacity of 27.8 mg g(-1). The intra-particle diffusion was the rate-limiting step as the linear plot crossed the origin, while the adsorption was unfavorable at elevated temperature. Under light irradiation, the TiO2/PAC system removed phenol two-times more effectively than the TiO2 monolayer due to the synergistic effect of photocatalysis by TiO2 top layer and adsorption by PAC sub-layer. The COD removal of phenol was rapid for 10mg L-1 of concentration and under solar light irradiation. It was shown that the PAC sub-layer plays a significant role in the total removal of phenol by providing the adsorption sites and slowing down the recombination rate of charge carriers to improve the TiO2 photocatalytic oxidation performance.