Influence of initial dissolved oxygen concentration on Fenton's reagent degradation

Influence of a reagents addition strategy on the Fenton oxidation of rhodamine B: control of the competitive reaction of ·OH

Microlevel competitive reactions of ·OH could be regulated by applying a macrolevel addition strategy of the Fenton reagents.

Application of response surface methodology in the optimization of photocatalytic removal of environmental pollutants using nanocatalysts

Response surface methodology is a widely used technique for modelling and optimization of the photocatalytic treatment processes of water and wastewater. This methodology not only estimates linear, interaction and quadratic effects of the factors on the response, but also provides a prediction model for the response at the range of the variables studied and the optimum conditions to achieve the highest performance. The present paper reviews the results of application of this innovative methodology in modelling and optimization of the photocatalytic treatment processes. Different experimental designs including 3k factorial, Doehlert, Box-Behnken and central composite designs have been developed to describe the treatment processes of dyeing effluents, pharmaceutical agents and hazardous phenolic compounds. The results showed that response surface methodology can describe the behaviour of complex reaction systems, such as photocatalytic processes, in the range of experimental conditions adopted. Optimization based on response surface methodology can also estimate the conditions of the photocatalytic processes to achieve the highest performance.

Optimization of the mineralization of a mixture of phenolic pollutants under a ferrioxalate-induced solar photo-Fenton process

The mineralization of solutions containing a mixture of three phenolic compounds, gallic, p-coumaric and protocatechuic acids, in a ferrioxalate-induced solar photo-Fenton process was investigated. The reactions were carried out in a pilot plant consisting of a compound parabolic collector (CPC) solar reactor. An optimization study was performed combining a multivariate experimental design and neuronal networks that included the following variables: pH, temperature, solar power, air flow and initial concentrations of H(2)O(2), Fe(II) and oxalic acid. Under optimal conditions, total elimination of the original compounds and 94% TOC removal of the mixture were achieved in 5 and 194 min, respectively. pH and initial concentrations of H(2)O(2) and Fe(II) were the most significant factors affecting the mixture mineralization. The molar correlation between consumed hydrogen peroxide and removed TOC was always between 1 and 3. A detailed analysis of the reaction was presented. The values of the pseudo-first-order mineralization kinetic rate constant, k(TOC), increased as initial Fe(II) and H(2)O(2) concentrations and temperature increased. The optimum pH value also slightly increased with greater Fe(II) and hydrogen peroxide concentrations but decreased when temperature increased. OH and O(2)(-) radicals were the main oxidative intermediate species in the process, although singlet oxygen ((1)O(2)) also played a role in the mineralization reaction.

Fenton degradation of tetrachloroethene and hexachloroethane in Fe(II) catalyzed systems

The degradation of tetrachlorothene (PCE) and hexachloroethane (HCA) using Fe(II) and Fe(II)-citrate at different H(2)O(2) concentrations was studied to clarify the role of oxidation and reduction pathways in Fenton chemistry. The interactions between oxidative and reductive radicals, and the cyclic nature of the Fe(II)-Fe(III) ions make for a complex system that displays a suppression or enhancement of PCE or HCA degradation as the experimental conditions are varied. PCE degradation decreased, while HCA degradation increased, for larger H(2)O(2) concentration. The degradations of PCE and HCA were lower in vials where they were individually present compared to vials with the PCE-HCA mixture. Using Fe(II)-citrate instead of Fe(II) resulted in slower PCE and insignificant HCA degradation. These observations indicate that degradation efficiency losses arise from interactions between the oxidant and reductant radical moieties, and that the production of reduction radicals is only significant when the hydroxyl radical (OH) production is rapid.