Removal of methanol from pulp and paper mills using combined activated carbon adsorption and photocatalytic regeneration

Methanol is one of the major hazardous air pollutants emitted from chemical pulp mills. Its collection and treatment is required by the Maximum Achievable Control Technology portion of the 1998 Cluster Rule. The objective of this study is to investigate the technical feasibility of combined adsorption and photocatalytic regeneration for the removal and destruction of methanol. To facilitate the regeneration, activated carbon (AC) was coated with commercially available photocatalyst by a spray desiccation method. Laboratory-scale experiments were conducted in a fixed-bed reactor equipped with an 8 W black light UV lamp (peak wavelength at 365 nm) at the center. The photocatalyst loaded onto AC had no significant impact on the adsorption capacity of the carbon. High humidity was found to greatly reduce the material's capacity in the adsorption and simultaneous adsorption and photocatalytic oxidation of methanol. The photocatalytic regeneration process is limited by the desorption of the adsorbate. Increasing desorption rate by using purge air greatly increased the regeneration capacity. When the desorption rate was greater than the photocatalytic oxidation rate, however, part of the methanol was directly desorbed without degradation.