Titanium dioxide photocatalysis for the pulp and paper industry wastewater treatment

Abstract

This paper provides an in depth discussion on the titanium dioxide photocatalysis for the treatment of pulp and paper industry wastewater. The mechanism behind TiO 2 photocatalysis, various reaction variables and application of TiO 2 photocatalysis for the remediation of pulp and paper mill wastewater are discussed. TiO2 photocatalysis can cause rapid and complete degradation of nearly all electron rich organic compounds. It involves in situ generation of very reactive non-selective oxidizing species i.e. OH- radicals. Some laboratory experiments were performed to study the effect of catalyst dose and reaction time on the photodegradation efficiency. Paper mill wastewater was treated with UV/TiO 2 process at pH 7 in a slurry type of reactor under artificial UV light. The catalyst dose (0.25 to 1.50 g/L) and reaction time (0.50 to 8.0 h) were varied for studying their effect on the degradation efficiency. The degradation efficiency was measured in terms of percent reduction in COD and colour of the wastewater. Up to 0.75 g/L of TiO 2 the degradation efficiency increased but beyond this it decreased. The degradation rate during the first hour of treatment was very fast. After 4 h of treatment the degradation efficiency became more or less constant and there was no significant increase. The optimum results were obtained at a TiO 2 dose of 0.75 g/L and reaction time of 4 h.