Commercial herbicide degradation by solar corrosion Fenton processes of iron filaments in a continuous flow reactor and its computational fluid dynamics (CFD) simulation

Abstract Commercial solutions of paraquat (PQ) herbicide were treated by solar corrosion Fenton processes (SCF). A borosilicate reactor was packed with a coiled filament of annealed iron wire to different reactor volume/filament surface area ratios (Vt/Af). A cylindrical parabolic concentrator was designed to concentrate UV light. The response surface methodology was used to determine the optimal process conditions using a Box-Behnken design in the removal of PQ, COD, and TOC. The independent variables used in this study were: H2O2 concentration (500, 1500, and 2500 mg L-1), hydraulic retention time (HRT) (20, 30, and 40 min), and Vt/Af (3:1, 6:1 and 9:1 cm3: cm2). Solution pH was adjusted to 2.8. The optimal conditions for the removal of PQ were: 2248.7 mg L-1 of H2O2, an HTR of 28 min, and Vt/Af of 3.4:1. These yielded a 99.9% removal of PQ, 100% removal of COD, and 96.7% of TOC. Toxicity was 100% removed with 700 mg L-1 of H2O2. CFD indicated operating fluid velocity and turbulence contributed to maintaining an adequate Fe2 +.