Fenton chemistry encompasses reactions of hydrogen peroxide in the presence of iron to generate highly reactive species such as the hydroxyl radical and possibly others. In this review, the complex mechanisms of Fenton and Fenton-like reactions and the important factors influencing these reactions, from both a fundamental and practical perspective, in applications to water and soil treatment, are discussed. The review covers modified versions including the photoassisted Fenton reaction, use of chelated iron, electro-Fenton reactions, and Fenton reactions using heterogeneous catalysts. Sections are devoted to nonclassical pathways, by-products, kinetics and process modeling, experimental design methodology, soil and aquifer treatment, use of Fenton in combination with other advanced oxidation processes or biodegradation, economic comparison with other advanced oxidation processes, and case studies.

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Advanced Oxidation Processes for Organic Contaminant Destruction Based on the Fenton Reaction and Related Chemistry

2.2. Fenton’s Chemistry 6575 2.2.1. Origins 6575 2.2.2. Fenton Process 6575 2.3. Photo-Fenton Process 6577 3. H2O2 Electrogeneration for Water Treatment 6577 3.1. Fundamentals 6578 3.2. Cathode Materials 6579 3.3. Divided Cells 6580 3.4. Undivided Cells 6583 4. Electro-Fenton (EF) Process 6585 4.1. Origins 6585 4.2. Fundamentals of EF for Water Remediation 6586 4.2.1. Cell Configuration 6586 4.2.2. Cathodic Fe2+ Regeneration 6586 4.2.3. Anodic Generation of Heterogeneous Hydroxyl Radical 6587

Electro-Fenton process and related electrochemical technologies based on Fenton's reaction chemistry

Advanced oxidation processes (AOPs) constitute important, promising, efficient, and environmental-friendly methods developed to principally remove persistent organic pollutants (POPs) from waters and wastewaters. Generally, AOPs are based on the in situ generation of a powerful oxidizing agent, such as hydroxyl radicals (•OH), obtained at a sufficient concentration to effectively decontaminate waters. This critical review presents a precise and overall description of the recent literature (period 1990–2012) concerning the main types of AOPs, based on chemical, photochemical, sonochemical, and electrochemical reactions. The principles, performances, advantages, drawbacks, and applications of these AOPs to the degradation and destruction of POPs in aquatic media and to the treatment of waters and waste waters have been reported and compared.

Advanced Oxidation Processes in Water/Wastewater Treatment: Principles and Applications. A Review

Advanced oxidation processes (AOPs), defined as those technologies that utilize the hydroxyl radical (·OH) for oxidation, have received increasing attention in the research and development of wastewater treatment technologies in the last decades. These processes have been applied successfully for the removal or degradation of toxic pollutants or used as pretreatment to convert recalcitrant pollutants into biodegradable compounds that can then be treated by conventional biological methods. The efficacy of AOPs depends on the generation of reactive free radicals, the most important of which is the hydroxyl radical (·OH). The authors summarize the formation reactions of ·OH and the mechanisms of pollutants degradation. They cover six types of advanced oxidation processes, including radiation, photolysis and photocatalysis, sonolysis, electrochemical oxidation technologies, Fenton-based reactions, and ozone-based processes. Controversial issues in pollutants degradation mechanism were discussed. They review t...

Advanced Oxidation Processes for Wastewater Treatment: Formation of Hydroxyl Radical and Application

The application of strong electric fields in water and organic liquids has been studied for several years, because of its importance in electrical transmission processes and its practical applications in biology, chemistry, and electrochemistry. More recently, liquid-phase electrical discharge reactors have been investigated, and are being developed, for many environmental applications, including drinking water and wastewater treatment, as well as, potentially, for environmentally benign chemical processes. This paper reviews the current status of research on the application of high-voltage electrical discharges for promoting chemical reactions in the aqueous phase, with particular emphasis on applications to water cleaning.

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Electrohydraulic Discharge and Nonthermal Plasma for Water Treatment

The effects of column dimensions, gas velocity and the properties of liquid and solid particles on the gas holdup eG and the volumetric liquid-phase mass transfer coefficient kLa in the solid-suspended bubble column of liquid-solid batch operation were studied experimentally. The presence of suspended solid particles in the bubble column reduces values of eG and kLa, and their reduction by an addition of solid particles to the column is high in the transition regime and low in the heterogeneous flow regime. Based on these observations, empirical equations for eG in transition flow and in heterogeneous flow, and an empirical equation for kLa a applicable to the above two flow regimes are proposed.

Gas holdup and volumetric liquid-phase mass transfer coefficient in solid-suspended bubble columns

A novel process of an oxidative degradation of aqueous phenol effluent with hydrogen peroxide produced by electroreduction of oxygen dissolved in the effluent was studied. Effects of operational conditions such as pH, cathode potential, ferrous ion concentration and phenol concentration on the degradation rate of phenol were clarified. Phenol was successively degraded to carbon dioxide at pH 3 with higher efficiency rather than the other pH''s. The COD current efficiency at pH 3 was higher than that for the anodic oxidation process of phenol and was more than 60% for complete degradation in the range of 260-2600 ppm of initial COD.

Oxidative degradation of aqueous phenol effluent with electrogenerated fenton''s reagent

The gas holdup e and the volumetric liquid-phase mass transfer coefficient kLa were studied experimentally in a bubble column with a draught tube and with gas dispersion into the tube. From experimental observation e increases with increasing gas velocity and frothing ability of liquid, while the other properties of the liquid and the column dimensions have a minor effect on e. kLa increases with gas velocity, column diameter, frothing ability of liquid and diffusivity of the dissolved gas, and decreases with increase in (Di/Do). Other dimensions of the column have a minor effect on kLa. Based on these observations, empirical equations for e and kLa are proposed which are applicable to columns with diameters of 0.1-0.3 m. At the same gas velocity, kLa in this column is larger than that in the bubble column and smaller than that in the column with a draught tube and with gas dispersion into the annulus for a liquid with frothing ability.

Gas holdup and volumetric liquid-phase mass transfer coefficient in bubble column with draught tube and with gas dispersion into annulus

The effects of surfactants and antifoam agent on the gas holdup e, the liquid-phase mass transfer coefficient kL and the volumetric liquid-phase mass transfer coefficient kLa in a bubble column were studied experimentally. An addition of surfactants such as n-alcohols to water increases e and decreases kL, and an addition of antifoam agent to water decreases e, kL and kLa. However, the degree of reduction of kL value by an addition of surfactant to water is lower for bubble swarms in a bubble column than that for a single bubble in stagnant liquid. Based on these observations, the previous model for estimating kL of a single bubble in aqueous solutions of surface-active substance is modified so as to be applicable to the estimation of kL for bubble swarms in a bubble column.

Effects of surface-active substances on gas holdup and gas-liquid mass transfer in bubble column

The effects of column dimensions, gas velocity and properties of the liquid and the solid particles on the gas holdup eG and the volumetric liquid-phase mass transfer coefficient kLa in a solid suspended bubble column with a draught tube and a conical bottom were studied experimentally in a liquid-solid batch operation. The presence of suspended solid particles in the column reduces the values of eG and kLa, and their reduction due to the addition of solid particles to the column increases with increasing solid concentration and terminal velocity of a single particle. Based on these observations, empirical equations for eG and kLa are proposed which are applicable to columns with diameter of 0.1-0.3 m.

Kozo Koide

Papers

Gas holdup and volumetric liquid-phase mass transfer coefficient in solid-suspended bubble columns

Oxidative degradation of aqueous phenol effluent with electrogenerated fenton''s reagent

Gas holdup and volumetric liquid-phase mass transfer coefficient in bubble column with draught tube and with gas dispersion into annulus

Effects of surface-active substances on gas holdup and gas-liquid mass transfer in bubble column

Gas holdup and volumetric liquid-phase mass transfer coefficient in solid-suspended bubble column with draught tube