Multivariate optimization of solar photo-Fenton process for chemical oxygen demand removal in landfill leachate treatment

ABSTRACT

This research aimed to optimize the solar photo-Fenton process in landfill leachate treatment. Central Composite Rotatable Design associated with the Response Surface Methodology was applied to investigate three operational factors: reagents ratio [H₂O₂]/[FeSO₄.7H₂O], H₂O₂ factor and initial pH, in order to maximize the organic matter removal, in terms of chemical oxygen demand (COD). According to the results, high COD reduction was obtained in three hours of solar photocatalysis (70.97 to 84.74%). Based on the analysis of variance (ANOVA), the response variable can be described by a quadratic model, with a high coefficient of determination, R²=0.9894. The analysis of response surfaces indicated that the optimum conditions were: initial pH range between 2.5 and 3.5, with a peak at 2.79, and reagents ratio range from 6 to the maximum level studied (7.36). Hydrogen peroxide concentration was calculated from the H₂O₂ factor, reaching the critical point at 143.77% of the stoichiometric amount of H₂O₂ needed for the complete oxidation of organic matter, that is, 11,751.05 mg H₂O₂.L^-1 to stabilize a COD of 3,845.55 mg O₂.L^-1.

Keywords:
homogeneous photocatalysis; central composite rotatable design; response surface methodology; landfill leachates