Catalytic Ozonation Of Methylene Blue In The Presence Of Activated Carbon Or Modified CNTs

This study choosed methylene blue which frequently used in printing and dyeing industry as a model compound of synthetic macromolecular organic matter. Ozone is used to catalyze the degradation of MB. The effect of pH value, radical scavenger, granulate activated carbon, carbon nanotubes and carbon nanotubes combined with zero-valent iron was investigated.The degradation process follows stable pseudo first order kinetics while sufficient ozone provides upper mass transfer driving force. The pH value could change the constant reaction rate on a large scale. Dissolved ozone molecules decompose to hydroxyl radical to promote the reaction process at alkalinity solutions. GAC plays the role as adsorbent, catalyst and buffer agent in the system. Experiments show that the enhancement of GAC casting to reaction is limited, the optimum dosing is9g/L. The addition of GAC is in favour of stable pH value and low ozone comsumption. The study conjectured the possible mechanism of reaction which shows that ozone combined with activated carbon has good effect on degrading macromolecular organic matter under optimum conditions.CNTs(Fe0) was prepared by impregnation method. The Energy dispersive X-Ray spectroscopy shows its content of zero valent iron is3.70%. It is used to compare with CNTs at different pH. System containing CNTs(Fe0) gets the highest decolorization rate at acidic solutions, and the second highest one at alkaline pH. The TOC removal is also the highest when the pH value is3.0. It shows that CNTs(Fe0) prepared by impregnation method is feasible to use in the degration process of MB. According to the catalytic performance at different pH, we conjecture the possible mechanism of the system containing CNTs(Fe0).Fe0-CNTs was prepared by electrophoresis method. Its catalytic performance reaches the high-point when the electrophoresis time is3min. The TOC removal of system containing Fe0-CNTs is65%when the pH value is3.0. The iron ion concentration shows that Fe0-CNTs participates actively in the reaction at acidic pH. The system containing Fe0-CNTs also shows good effect on the degradation process of MB at alkaline pH. The decolorizing effect decreases when the tertiary butanol is added to the system, which illustrates that the enhancement from Fe0-CNTs is the enhancement of the generate of hydroxyl radicals.