2.6 Photoinduced degradation of 2,4-D in presence of goethite, fluoride, and bicarbonate at natural concentrations by H2O2 addition. Factorial experimental design 22
The photoinduced experiments were carried out according to previous work reported by GutiƩrrez-Zapata et al, and following the methodology described in section 2.4. A factorial experimental design 22 was used to study the significant influence of two experimental factors: (A) F- and (B) HCO3- concentrations, evaluated in two levels low (-) and high (+) which are often found in natural well waters on the degradation of 2,4-D pesticide in presence of natural goethite concentrations (0.3 mg L-1; 0.2 mg L-1 of total iron) and H2O2 (10 mg L-1) at pH 6.9. The experimental matrix is presented in table 1 and additionally, control experiments such as dark reactions (Fenton), 2,4-D photolysis, and sunlight H2O2-photolysis were also performed. Results were analyzed by using variance analysis (ANOVA) and response surface plots obtained by STATGRAPHICS centurion XVI Software.