Degradation of cyanobacteria toxin by advanced oxidation processes

Advanced oxidation processes (AOPs) using O-3, H2O2, O-3/H2O2, O-3/Fe(II), and Fenton treatment were investigated for the degradation of aqueous solutions of cyanobacteria. The effects of concentration of reactants, temperature, and pH on toxins degradation were monitored and the reaction kinetics was assessed. O-3 alone or combined with either H2O2 or Fe(H) were efficient treatment for toxins elimination. A higher toxin oxidation tendency was observed with Fenton reaction; total toxins degradation (MC-LR and MC-RR) was achieved in only 60 s. The ozonation treatment was successfully described by second-order kinetics model, with a first-order with respect to the concentration of either ozone or toxin. At 20 degrees C, with initial concentration of MC-LR of 1 mg/L, the overall second-order reaction rate constant ranged from 6.79 x 10(4) to 3.49 x 10(3) M-1 s(-1) as the solution pH increased from 2 to 11. The reaction kinetics of the other AOPs (O-3/H2O2, O-3/Fe(II), and Fenton), were fitted to pseudo first-order kinetics. A rapid reaction was observed to took place at higher initial concentrations of O-3, H2O2 and Fe(II), and higher temperatures. At pH 3, initial concentration of toxin of 1 mg/L, the pseudo first-order rate constant, achieved by Fenton process, was in order of 8.76 +/- 0.7 s(-1). (c) 2007 Published by Elsevier B.V.