Decomposition of dissolved ozone in the presence of activated carbon: An experimental study

ABSTRACr In aqueous solutions molecular ozone (O-3) decomposes rapidly into secondary radical or Ionic species such as (OH.,O-3,O-2,...). This decomposition is enhanced by many factors, essentially the pH, the temperature, and the organic or inorganic compounds in the solution. The aim of this work is to study the effect of the addition of granular activated carbon on the rate of ozone decomposition in aqueous solutions containing promoter (P) and inhibitor (Q) mixtures. The activated carbon used is laboratory produced from olive stones. We found that the rate of decomposition of ozone in these conditions is described by a pseudo-first-order kinetic: r(O3) = k'(DeltaO3)[O-3]. Experimental results show that adding 15 mg/L of the olive stones activated carbon (OSAC) enhances the rate constant of the P and Q controlled chain depletion by about a factor of two. We found that the decomposition increases linearly with the solid concentration (W): k'Delta(O3) = 0.0001W + 0.0017 and that the kinetics are enhanced when the activated carbon specific area increases. We also conclude that the preozonation of the OSAC has no effect on its activity. We note that the temperature has a significant effect on the ozone decomposition rate even in the presence of OSAC. The value of the activation energy in the presence of the OSAC is lower than that obtained in homogeneous decomposition.