Kinetics of the atrazine degradation process using H₂O₂-UVC

This work is concerned with the intrinsic reaction kinetic of the degradation of atrazine (ATZ) using H₂O₂-UVC. Experimental runs were carried out in annular photoreactor. The initial concentration of ATZ was 2.2 × 10⁻² mol m⁻³ while the H₂O₂-ATZ molar ratio range was 0–578 mol H₂O₂ mol⁻¹ ATZ. The ATZ molecules are decomposed by means of free-radical attack (95.2%) and direct photolysis (4.8%). There is an optimal H₂O₂/ATZ molar ratio (R_OP = 347 H₂O₂ mol⁻¹ ATZ) which maximizes the initial degradation rate and conversion at 300 s at 83% and 77%, respectively. The process is economically feasible as the values of the energy requirement, energy and H₂O₂ costs at R_OP are 0.14 KWh m⁻³ order⁻¹, US$0.02 kWh⁻¹ m⁻³ and US$1.0 m⁻³, respectively. The kinetic model proposed is based on Lea's reaction scheme for the H₂O₂ direct photolysis, the hypothesis that unknown ATZ sub-products that absorb UVC radiation are generated, and the local volumetric rate of photon absorption. The radiation transport equation was solved and the linear spherical source emission model was used to represent the lamp emission. Intrinsic reaction kinetic parameters were estimated and the model was validated. The model predicted the data in a range of 90 to 98%.