The stopped-flow spectrophotometric method was used to study the kinetics of the ozonation between dissolved ozone and p-nitroaniline in aqueous solutions of pH values varying from 2.1 to 6 at 298 K. It was found that four moles of ozone were required for conversion of each mole of p-nitroaniline in the aqueous solution containing a limited amount of dissolved ozone. The overall ozonation reaction of p-nitroaniline was of second order

but of first order for each reactant.The overall ozonation rate constant increased with solution pH value in the range of 2.1 to 6 investigated. As pH value increased from 2.1 to 6

the overall rate constant increased from 6.17×104(mol8226;L-1)-18226;s-1 to 1.55×106(mol8226;L-1)-18226;s-1 at 298 K. To validate its applicability

the absorption process was simulated as ozone absorption in p-nitroaniline solution in stirred-tank. The mass balance equations about absorption process for the complete mixing model were solved by utilizing the Matlab ODE program. The concentration of ozone and the concentration of p-nitroaniline during an absorption experiment were simulated. The simulated concentrations of p-nitroaniline agreed well with the measured concentrations up to 80% consumption of p-nitroaniline.