carlos a. martínez-huitle 6. a review on arrangement … · 1centro de investigación y desarrollo...

Research Signpost

37/661 (2), Fort P.O.

Trivandrum-695 023

Kerala, India

Evaluation of Electrochemical Reactors as a New Way to Environmental Protection, 2014: 97-137 ISBN: 978-81-308-0549-8 Editors: Juan M. Peralta-Hernández, Manuel A. Rodrigo-Rodrigo and

Carlos A. Martínez-Huitle

6. A review on arrangement and reactors for

Fenton-based water treatment processes

Jennifer A. Bañuelos, F. J. Rodríguez, J. Manríquez, E. Bustos, A. Rodríguez and Luis A. Godínez1

1Centro de Investigación y Desarrollo Tecnológico en Electroquímica. Parque Tecnológico Qro Sanfandila, P.O. Box 76703, Pedro Escobedo, Querétaro, México

Abstract. A review on different arrangements and reactor designs

for Advanced Oxidation Processes based on the use of the Fenton

reagent is presented. The review focuses on reports that include

publications and patents dealing with water contaminated with

different recalcitrant pollutants. The work includes a brief

introduction that deals with the basics of the Fenton reagent use for

the oxidation of pollutants of water effluents, followed by a set of

sections in which some of the reports and patents of the different

forms in which the Fenton reagent is employed for water treatment

processes are presented. In this way, this review includes a section

dealing with processes in which the components of the Fenton

reagent is administered by means of H2O2 and Fe salts addition, in

which it is photo-assisted with UV light and in which it is electro-

generated in-situ and photo-assisted taking advantage of the

electrochemical reduction of dissolved oxygen on a carbonaceous

cathode.

Correspondence/Reprint request: Dr. Luis Arturo Godínez Mora-Tovar, Centro de Investigación y Desarrollo

Tecnológico en Electroquímica, 52(442)2116006 Querétaro, México

E-mail: [email protected]

Jennifer A. Bañuelos et al. 98

Introduction

Organic pollutants such as dyes, pigments, benzenes, alcohols, amines,

ethers and chlorinated aromatic derivatives are toxic and dangerous to the

environment. These pollutants, which are frequently present in wastewater

discharged from industrial operations, must be removed to environmentally

safe levels [1]. Biological and chemical removal of these organic compounds

is often difficult.

In recent years, advanced oxidation processes (AOPs) have been the

most promising methods for treating these residues. These processes are

defined as treatments that generate hydroxyl radicals in an aqueous medium

to promote the oxidation of pollutants through their high oxidizing power

(E°=2.8 eV) [2-4]. Among the AOPs are: ozonation (O3), the combination of

ozonation with ultraviolet irradiation (O3/UV), the combination in the

presence of TiO2 (O3/UV/ TiO2), Fenton reaction and electrocoagulation

[5-9]. However, many studies have demonstrated that methods based on

hydrogen peroxide to produce hydroxyl radicals, like the Fenton reaction,

are the most effective for treating wastewater [10-13]. The Fenton reaction

was discovered by H. J. H. Fenton in 1884. In the Fenton process hydroxyl

radicals are generated by the reaction between ferrous ions and hydrogen

peroxide, as shown in equations:

Pignatello and Sun [14] demonstrated that ferric ions in a Fenton system

can be reoxidized to form ferrous ions and hydroxyl radicals. These

hydroxyl radicals were considered to be the primary oxidizing species

involved in the Fenton reaction. The rate of the oxidation reaction depends

on pH, the reaction conditions and the concentration of free hydroxyl

radicals. Despite the high oxidative efficiency of Fenton’s reagent, its

application is limited by problems related to the storage and shipment of

concentrated hydrogen peroxide and the production of Fe3+

sludge.

Moreover, it is very important to control the quantity of ionic iron in order to

prevent contamination of the solution by an excess of this species [11].

There are several variations of Fenton's reagent including: photo-assisted

Fenton, electro-Fenton and photo-assisted electro-Fenton processes, which

are described below.

A review on arrangement and reactors for Fenton-based water treatment processes 99

Photo-assisted Fenton

The photo-assisted Fenton process occurs in homogenous phase by the

addition of UV light to Fenton’s reagent. This method has been widely

studied since the 1990’s and is viewed as an effective alternative to

biological wastewater treatment processes [15-17]. A solution containing

Fe2+

or Fe3+

ions and H2O2 is irradiated by UV light. The decomposition of

hydrogen peroxide in acidic media is catalyzed by oxidizing Fe2+

to Fe3+

,

which is later photo-reduced back to Fe2+

by photons. UV radiation results

not only in the formation of additional ●OH radicals, but also in the

regeneration of the iron species as shown in the following reactions:

However, in both the Fenton process and the photo-assisted Fenton

reaction, the Fe sludge which remains is a huge disadvantage because Fe

ions must be removed from the water. In addition, the use of UV light

increases costs, so both of these processes have limited industrial application

[2-18].

Electro-Fenton process

Applying electrical current between two suitable electrodes in water

produces a primary chemical reaction, generating hydroxyl radicals which

oxidizes organic matter:

As shown by equation, the system efficiency may be improved by adding

Fe (II), and this process is called electro-Fenton. The electro-Fenton process

involves in-situ generation of hydrogen peroxide under acidic conditions by

the 2e- reduction of dissolved oxygen. A fundamental requirement is high

H2O2 production at the cathodes. These electrodes are carbon based

materials—for example: graphite [19-20], reticulated vitreous carbon [21],

nitrogen functionalized carbon nanotube [22], carbon sponge [23], activated

carbon fiber [24] or granular activated carbon [25] and gas diffusion

electrodes [26]. Additionally, since electricity is a clean energy source and

does not use harmful reagents, this method is considered to be

environmentaly friendly.


Photoelectro-Fenton and photo-assisted electro-Fenton process

As previously mentioned, UV irradiation produces additional hydroxyl

radicals by reduction of ferric ions. Both processes in combination

generate a greater amount of ●OH, resulting in higher degradation

efficiency and faster regeneration of Fe2+

[2]:

This combined process is called photoelectro-Fenton (PEF), but its

application for water treatment is limited by the costly electrical energy

requirements. A more economic technique is to combine UV light with

electro-Fenton in the so-called photo-assisted electro-Fenton (PA–EF)

process. In this technique, the electro-Fenton process is applied only for

the time needed to convert most pollutants into intermediates. Many recent

studies of the environmental application for the PEF and PA-EF process

have investigated their efficacy in removing herbicides [27], dyes [28] and

organics [29, 30].

In general, the recovery of industrial effluents containing low levels of

organic substances by conventional treatments is not economically viable.

This has fueled interest in the development of new, more effective and

economically viable methods for pollution control and prevention. Of the

AOPs that have been proposed so far, the Fenton reaction with all its

variants and modifications, appears to be the most promising for practical

industrial applications. The remainder of this chapter focuses on

fundamental design details and experimental conditions of Fenton-like

reactors. This information is essential for the proper use and control of this

relatively new alternative techonology for the degradation of organic

pollutants. This chapter also explores recent patents for pollutant removal

employing Fenton-like processes.

1. Arrangements and reactors

There are several reactor types, and many factors affect the design of

Fenton's reagent, photo-assisted Fenton, electro-Fenton and photo-assisted

electro-Fenton reactors used by researchers. Some important design

considerations for these reactors are discussed below.


1.1. Fenton’s reagent

The simplest Fenton process requires an acidic medium, because low pH

favors Fenton oxidation. There are two ways to control acidity. One is to

adjust the initial pH of the solution. The other is to control pH throughout the

process by adding sulfuric acid or sodium hydroxide. Another important

factor is the form of the Fenton reagents that are added to the system.

Typically, the pH is first adjusted to prevent formation of iron

oxyhydroxides. Then iron salt, commonly ferrous sulfate, is added and

finally, H2O2 is slowly introduced.

Typically these reactors are operated in batch mode, but recently a

fluidized-bed reactor type (FBR) was employed with a Fenton system. Fig. 1

shows the system used by Chia-Chi Su et al. [31]. The FBR is a cylindrical

vessel consisting of outlet, inlet and recirculation sections. The FBR had a

working volume of 1.45 L and was operated in recirculation mode by

adjusting internal circulation at 50% bed expansion. The ferrous solution

was added continuously, and the H2O2 solution was added to the reactor all

at once. Then monoethalamine (MEA) and phosphate solutions were added

in two stages in order to start the removal. The pH was monitored and

controlled at 3±0.2. The results showed that Fe2+

concentration was an

important factor for MEA and chemical oxygen demand removal. The best

conditions for MEA removal was 3 mM Fe2+

and 50 mM H2O2 at pH 3

which gave a removal efficiency of 76 %.

Figure 1. Schematic diagram of fluidized-bed Fenton reactor.


As previously mentioned disadvantages of the Fenton process are that the

pH must be relatively acidic and removing the sludge that forms at the end

of the process. In order to avoid this, much work has been focused on

incorporating a heterogeneous Fenton process, which consists of placing iron

ions on a support such as carbon, resin or Nafion. T.L.P. Dantas et al. [32]

added different dosages of solids (Fe2O3/carbon) to a 400 mL reactor of

textile wastewater. They concluded that these solids had the advantage of

being effective at pH 3.0 while consuming less H2O2 than the homogenous

Fenton process.

The Fenton process has also been investigated for its performance in

reducing dyes from waste water. For example, K. Swaminathan et al. [33]

investigated the decolorization and degradation of Red M5B and Blue MR in

a closed 1 L reactor. They reported that the optimum conditions for

maximum degradation were pH 3.0, Fe2+

concentration of 10-25 mg/l, a

H2O2 dose of 400-500 mg/l and 120 min of contact time with the

contaminated solution. For Red M5B, a COD removal of 0.78 and for Blue

MR a COD removal of 0.82 were achieved.

Table 1 presents some illustrative works for the degradation of

pollutants by the Fenton process. In addition to these studies, Fenton’s

reagent has been effectively used for chlorobenzene in a 500 mL reactor

[34], p-chlorephenol with a volume of 4 L [35], p-hidroxypheny acetic acid

used a reactor of 0.5 L [36], p-hydroxybenzoic acid containing in a 1.1 L

reactor [37] and a 1L reactor made up of borosilicate glass with simulated

dyebath wastewater obtained 80.8% TOC removal for an initial TOC loading

of 200 mg/L [38].

Fenton’s chemistry is not a universal solution, since there are many

chemicals that are refractory towards Fenton’s reagent such as some

chlorophenols. Benitez et al. For instance, studied different types in a 350

mL reactor. And Fenton oxidation was not found to be effective in

degradation. Only 4 chlorophenol showed 55% removal after 80 min of

treatment [39]. The importance of Fenton’s reagent as an oxidation system

cannot be underestimated, and the oxidation degree can be substantially

increased when used in combination with other treatments or techniques. For

example, as shown in Table 2, researchers have shown that a combined

process to treat different types of pollutants is a better option for the use for

Fenton’s reagent.

Table 2 shows some of the most important patents published from 1999

to 2012, illustrating that fenton reactors are increasingly being used at an

industrial level.


Table 1. Typical reactor conditions for using Fenton oxidation to treat wastewater.

Reference Year Pollutant Experimental Conditions % Removal

[40] 1996 Landfill leachate 2130, 200, 294 (mgL-1

) of

initial COD, H2O2 and iron

ions respectively.

70


) of


ions respectively.

50

[41] 1997 Effluent containing poly-

vinyl alcohol and two

dyes as Blue

G and Black B

1500, 1000, 200 (mgL-1

) of


ions respectively.

80


) of


ions respectively.

63


) of initial

COD, H2O2 and iron ions

respectively.

72

[44] 1999 alkylbenzene sulfonate and linear alkylbenzene

sulfonate

10, 60, 90 (mgL-1

) of initial COD, H2O2 and iron ions

respectively.

95

[45] 1999 Effluent containing

different compositions of

surfactants

1000, 2000, 3290 (mgL-1

) of


ions respectively.

49


) of

initial COD, H2O2 and iron ions respectively.

45


) of


ions respectively.

70


) of


ions respectively.

69


) of initial COD, H2O2 and iron

ions respectively.

45


)

of initial COD, H2O2 and iron

ions respectively.

60


)

of initial COD, H2O2 and iron ions respectively.

79


) of


ions respectively.

80


Table 2. Patents for the use of Fenton reactor to treatment.


Table 2. Continued


Table 2. Continued

1.2. Photo-assisted Fenton

The Photo-assisted Fenton process adds UV radiation to the system,

producing more hydroxyl free radicals. Many comparative studies between

Fenton and photo-assisted Fenton have been done and the biggest difference

is in the TOC removal rate and not in the color removal rate, when the

pollutants are dyes. Although various reactor geometries have been used, the

most popular is a cylindrical reactor with UV-lamps in the center. Soo-

Myung Kim and Alfons Vogelpohl [65], tested two types of reactors. The

first was a 1.6 L glass reactor with an external loop operated in batch mode.


A medium-pressure Hg lamp was located in the center, surrounded by a

cooling pipe made of quartz glass. Fig. 2 shows the second system used for

the degradation of organic pollutants. This reactor operated in continuous

mode, the UV reactor was connected to the jet-loop reactor by a PVC tube

and the volumes were 1.0 and 3.9 L respectively. The system also used a

medium pressure Hg lamp (type EQ 1023 Z4). The results indicated that

H2O2 should be added at a molar ratio of H2O2:COD = 1: 1, and aeration of

the wastewater was recommended to improve degradation rate.

Figure 3 shows another photo-reactor with a typical configuration. In the

center there is a 150-watt medium-pressure UV lamp inside a quartz sleeve.

The reactor was made of Pyrex glass with a capacity of 2 L. The reactor was

surrounded by a water cooling jacket to maintain constant temperature.

Under optimum conditions, the amount of COD removal from municipal

solid waste landfill leachate was 83.2%. In addition, the optimum pH was 3

and the optimum contact time was 120 minutes. This study also tested the

Fenton process which achieved only 69.6% COD removal in 150 minutes

[66].

Figure 2. Schematic diagram of the pilot unit.


Figure 3. Schematic diagram of the typical photo-reactor.

An early example of industrial-scale application of the photo-assisted

Fenton process was the decontamination of 500 L batches from industrial

wastewater containing 3,4 xylidine. This was done in a tubular

photochemical reactor fitted with a 10 kW medium pressure mercury lamp.

The lamp was positioned in the axis of the reactor and the reactor was

connected to a 3000 L reservoir tank open to air.

The solution with pH 3.0 was aerated and circulated. H2O2 was

continuously introduced into the photochemical reactor and the solution

was irradiated for 3 h. The final results showed that the light-enhanced

Fenton procedure is one of the only methods that can process large

volumes of industrial waste water [67].

Other researchers [68] used a different configuration called Heber

multilamp photo-reactor model HMLMP 88 shown in Fig. 4. Unlike

previous reactors, this model consists of eight medium pressure Mercury

vapor lamps (8 W) set in parallel and emitting at 365 nm wavelength. The

reaction chamber has specially designed reflectors made of highly polished

aluminum, a built-in cooling fan at the bottom and a magnetic stirrer in the

center. An open 50 ml borosilicate glass tube, 40 cm tall and 20 mm in

diameter, was used as the reaction vessel with a total light exposure length

of 330 mm. They determined that the optimal conditions were 20 mmol

H2O2 and 0.1 mmol Fe2+

for the decolorization of Reactive orange 4.


Figure 4. Schematic diagram of the Heber multilamp photo-reactor.

Like the Fenton process, photo-assisted Fenton has been studied as a

heterogeneous process using a strongly acidic ion exchange resin as a

catalyst placed in a cylindrical reactor with two UV lamps (8 W 254 nm) in

the center. To suspend the resin, compressed air was bubbled up from the

bottom. The capacity of the reactor was 1.8 L. The start of the reaction was

defined as the time when the UV light was turned on and H2O2 was added to

the photo-reactor [69].

Photo-assisted Fenton reactors have also been used to regenerate

adsorbent material like activated carbon. An annular photochemical reactor

was employed with 80 W pressure mercury UV lamp as the light source. It

was placed in jacketed quartz well, immersed in a borosilicate vessel and

connected to the activated carbon column and a stirred Pyrex tank. A volume

of 2 L was circulated through the reactor and the column. After two cycles,

56% of activated carbon adsorption capacity was recovered [70].

It should be emphasized that light is almost always the limiting reagent

in photochemical reactions, and photo-Fenton reactions are often conducted

in reactors in which the solution is recirculated through the photo-reactor

from an external reservoir. Table 3 presents some of the photo-reactors

employed for the degradation of pollutants, and Table 4 shows the latest

patents that have been reported. Despite significant advances in the last

decade, widespread application of photochemical technology for treatment

and decontamination of industrial residues and wastewater is still not a

reality. Engineers and chemists need to work together to solve the most

important problems that limit greater industrial application. Optimization

strategies must be applied to the design of large scale reactors to reduce

economic and energy costs.


Table 3. Typical photo-assisted Fenton reactor approaches used for wastewater

treatment.


Table 3. Continued


Table 4. Patents for the use of photo-assisted Fenton reactor to treatment.


Table 4. Continued


1.3. Electro-Fenton

Numerous electrochemical methods for wastewater treatment have been

studied, such as oxidative processes, electrodeposition, direct reduction and

especially the electro-Fenton process. It is well known that an

electrochemical reactor could be scaled to an industrial level for

decontaminating wastewater at a cost comparable with other methods.

However, the process must be specified with parameters like current density,

voltage, reaction kinetics and efficiency. Some work has been done

analyzing different electrolytic cell configurations.

Fig. 5 shows some of these reactors. For example, the design used by

Zhou et al. (Fig. 5a) [86] for removing methyl red consists of a saturated

calomel electrode (SCE), a platinum electrode and a graphite fabrication

electrode as reference, counter and cathode electrodes respectively. The

distance between the working electrode and counter electrode was 3 cm and

the capacity of the electrolytic cell was 100 mL. Oxygen was sparged and

FeSO4 was added to the solution. This system of divided three-electrode

electrochemical cell degraded 80% of the initial 100 mg/L dye concentration

in 20 min.

A bubble reactor designed by Rosales et al. (Fig. 5b) [87] used a glass

cylinder with a working volume of 0.675 L and operated in batch mode with

total reflux or in continuous mode. Two electrode bars were connected to a

direct current power supply. The cathode and anode bars were placed 30mm

and 270mm above the bottom of the cell, respectively. The distance between

the electrodes was fixed at 240.4 mm. Steel or graphite bars were employed.

Continuous saturation of air at atmospheric pressure was ensured by

bubbling compressed air near the cathode at about 1 L min−1

and iron was

added. They concluded that the continuous bubble Electro-Fenton reactor

could operate without problems, and that attaining high decoloration

percentages depended on the residence time.

Another electro-Fenton reactor configuration is shown in the Fig. 5c [88].

The two compartment reactor was used to degrade Rhodamine B. The anode

(Pt flakes) and cathode (Pt flakes) were placed in compartment 1 and only a

cathode was placed in compartment 2. Agar was used to connect the

compartments. Micro bubbles of H2 and O2 were generated in compartment 1

by water electrolysis. The cathode in compartment 2 was used as a bypass to

accumulate OH− and to neutralize the low pH effluent from compartment 1.

The maximum concentration of H2O2 was 53.1 mg/L within 120 min at pH 2

and a current of 100 mA.

The electrochemical reactor in Fig. 5d was operated in a continuous

flow by Hui Zhang et al. [89] for degradation of mature landfill leachate. This


1, magnetic stirrer; 2, platinum wire; 3, saturated calomel electrode (SCE); 1, power supply; 2, air compressor; 3, cathode; 4, anode,

4, gas diffusion electrode; 5,gas flowmeter; 6, CHI600B; 7, oxygen tank. 5, control unit; 6, pumps; and 7, reflux (only in batch

conditions).

1, hydrogen peroxide storage tank; 2, ferrous iron storage tank; 3, leachate storage tank; 4, electrolytic cell; 5, DC power supply; 6,

tubing pump; 7, magnetic stirrer; 8, electrode.

5a

5c

5b

5d

Figure 5. Schematic diagram for the different electro-Fenton reactor.

rectangular electrolytic reactor was made of 12 × 10 × 16.5 cm Plexiglas with

a working volume 800 mL. Two 15 × 10 cm mesh anodes (Ti/RuO2–IrO2–

SnO2–TiO2) and three Ti mesh cathodes of the same dimensions were

alternately positioned perpendicular and parallel to each other. Electro-Fenton

experiments were conducted at a constant current of 1 A using a direct current

power supply. They reported that the most favorable operation conditions were

an initial pH of 3, inter-electrode gap of 2 cm, H2O2 to Fe2+

molar ratio of 6,

hydrogen peroxide concentration of one theoretical dosage and hydraulic

retention time of 40 min. The electro-Fenton process was used successfully in many other reactor

types to degrade different pollutants. Details are provided in Table 5, and the

only two patents that we found are shown in Table 6.


Table 5. Typical electro-Fenton reactor used to wastewater treatment.


Table 5. Continued


Table 5. Continued

Table 6. Patents for the use of electro-Fenton reactor to treatment.


It is very clear that electro-Fenton reactors are a very powerful tool for

wastewater treatment. However, there is still much to do to bring these

reactors up to an industrial scale, because this process depends on Fe2+

and

H2O2 concentration, pH, feed mode and oxygen sparging rate, temperature,

applied current density, distance between the electrodes, nature of the

supporting electrolyte and type of pollutant. Overall, however, the E-Fenton

process is a promising technology for treating industrial wastewater.

1.4. Photoelectro-Fenton and photo-assisted electro-Fenton

The electro-Fenton process has been further improved by using UV to

further enhance its efficiency by destroying Fe3+

complexes to degrade

products like oxalic acid. This new technology, called Photoelectro-Fenton

(PEF), was applied to the treatment of landfill leachate by Ahmet Altin [102]

using the reactor shown in Fig. 6. This 1L reactor was made of quartz glass

and equipped with a magnetic stirrer. Two pairs of cast iron anode and

cathode electrodes (4.0 cm×5.0 cm×0.4 cm) were positioned approximately

1.0 cm apart from each other. Ultraviolet (UV) radiation was provided by

two low-pressure UV lamps, with an intensity of 253.7 nm 1.4Wm−2

. The

initial H2O2 concentration was 2000 mg L−1

and a 3A constant DC current

were applied to the electrodes. It can be used to the treat wastewater heavily

polluted with organic compounds that are not readily biodegradable.

Nevertheless, as in many other studies, they concluded that its commercial

usage was limited by the high operating costs due to the high concentrations

of H2O2 which it needed.

Figure 6. Schematic diagram used for photo electro-Fenton process.


One important modification some researchers made to this process was to

use sunlight as the source of UV light, avoiding the high cost of using lamps.

Juan Casado et al. [103] did a pilot scale mineralization of organic acids by

electro-Fenton process using sunlight. The pilot flow reactor shown in Fig. 7

was previously used for aniline degradation by Electro-Fenton and peroxi-

coagulation processes by Brillas and Casado [104]. The electrochemical cell

was an undivided filter-press containing two 100 cm2 square electrodes in

contact with the solution and separated 5mm by a turbulence promoter. Two

oxygen diffusion cathodes made of 0.35 mm thick carbon cloth were used.

O2 was supplied from a cylinder to a gas chamber in contact with the

cathode, and a platinized titanium (Ti/Pt) mesh was used as the anode. After

electrochemical treatment, the samples were exposed to sunlight in a glass

crystallizing dishes of 19 cm diameter. After 30–50min almost complete

mineralization was achieved without any additional cost.

There are many studies comparing this process to the one above. Table 7

summarizes these comparisons. In general, it is quite evident that all the

researchers obtained higher removal efficiencies in less time with the PEF

and PA-EF processes. However, because of the high costs of these methods,

scaling to industrial level remains a major challenge.

Figure 7. Schematic diagram of pilot flow reactor used for aniline degradation.


Table 7. Typical PEF and PA-EF reactors used to treat wastewater.


Table 7. Continued


Table 7. Continued

1.5. Additional reactor types

In recent years, several research groups have studied electro-Fenton-based

processes in which carbonaceous substrates were used to cathodically generate

H2O2 by means of reduction of dissolved oxygen. Complementary to

electrochemical synthesis of peroxide, iron supported on various materials

(heterogeneous process) has been incorporated in the reactor to promote the

presence of the Fenton mixture in the solution, thus avoiding the use of

dissolved Fe salts. Shuan Liu et al. [113] studied the degradation of

tetracycline by photo-electro-Fenton oxidation with a Fe3O4–graphite cathode.

Comparisons of tetracycline degradation by electro-Fenton, UV irradiation and

photo-electro-Fenton processes were investigated. Their results showed that

the degradation efficiency was: photo-electro-Fenton > electro-Fenton > UV

irradiation. They also found that the Fe3O4–graphite cathode was stable and

could be reused without catalytic decrease.

Yujing Wang et al. [114] proposed a novel electrosorption enhanced

electro-Fenton (ES-EF) method for wastewater treatment. They grew mixed-

valence iron oxide on bulk activated carbon aerogel (FeOx/ACA) as a


bifunctional integrated cathode for ES-EF process to purify wastewater. This

new cathode functioned at neutral pH and removed 93% of TOC in 150 min.

A similar cathode with the Fe3O4@Fe2O3/activated carbon aerogel (ACA) was

used by Hongying Zhao et al. [115]. It degraded imidacloprid with high

catalytic efficiency over a wide range of pH from 3 to 9. This system removed

up to 90% of imidacloprid and TOC. A heterogeneous system promises to be a feasible and effective

technological alternative for water treatment, and some of these processes are

being patented. One patent relates to a system that conducts the Fenton’s

reaction by a photo-electro-chemical-catalytic effect and a method for

obtaining free radicals (●OH) and regenerating supported iron (Fe(II)), where

the residual iron intends to comply with the standard established for the

presence of said metal in potable water. In this way, the method generates the

free radicals (●OH) required to degrade organic matter like pesticides,

insecticides, dyes and other harmful compounds dissolved in residual water.

By providing more free radicals (●OH) in the same dissolution volume,

degradation of organic matter, discoloration and removal of total organic

carbon are all accelerated. The free radicals (●OH) are generated by hydrogen

peroxide (H2O2) in situ in a Fenton reactor, using supported iron in ionic

exchange resins of low desorption level, as well as photo assisted processes

and an anode coated with a nano-crystalline semiconductor [116].

In order to avoid electrolyte leakage and gas bubbles in electro-Fenton

reactors that use a gas diffusion cathode, Yangming Lei et al. [117] developed

a trickle bed cathode by coating a layer of carbon black and

polytetrafluoroethylene (C-PTFE) on graphite chips instead of carbon cloth.

As shown in Fig. 8, the electrochemical trickle bed reactor consists

of a Ti/PbO2 anode, a porous nylon diaphragm, a cathode frame containing

1. Cell body, 2. Gasket, 3. Ti/PbO2anode, 4. Gasket ring, 5. Nylon diaphragm, 6. Cathode frame

for loading graphite chips and 7. Ni plate.

Figure 8. Schematic diagram of trickle bed reactor assembly.


C-PTFE-coated graphite chips, and a nickel cathode plate. Three sealing

gasket rings with empty parts (60 mm × 50 mm) are placed between each of

those components. The cathode frame has two couplings that serve as a fluid

feed and an outlet. The active dimensions of the cathode with the C-PTFE-

coated graphite chips are 60 × 50 × 14 mm (width, height, thickness). In the

reactor assembled by the trickle bed cathode, H2O2 was generated with a

current of 0.3 A and a current efficiency of 60%. This performance was

attributed to the fine distribution of electrolyte and air, as well as the effective

oxygen transfer from the gas phase to the electrolyte–cathode interface.

The reactor shown in the Fig. 9 was used by J.M. Peralta-Hernández

[118]. They prepared Nanocrystalline semiconductor electrodes (NSE) by

depositing a thin film of a paste made of 6 g of colloidal TiO2 mixed with

10mL of a pH 3 HNO3 solution. This paste was spread evenly on the outer

surface of a hollow glass tube, 1.0cm outer diameter and 12cm long.

Electrochemical and photo-electrochemical generation of H2O2 was studied

using an experimental recycle annular tube reactor. They discovered that under

UV radiation of the semiconductor anode, the electrochemical oxidation rate

increased substantially compared to the same processes carried out in the dark.

Finally, it should be mentioned that dynamically regulating the Electro-

Fenton process remains difficult. However, this is critical for reducing

operating costs and enhancing process performance. To address this,

Ruey-Fang Yu et al. [119] studied the potential of on-line monitoring of

Oxidation Reduction Potential (ORP) and Dissolved Oxygen (DO) as key

parameters for controlling the E-Fenton process in treating textile wastewater.

Figure 9. Schematic diagram of the photo-electrochemical reactor.


Figure 10. Schematic diagram of the electro-Fenton reactor.

Their results showed that the DO and ORP profiles have high correlation with

the variations in H2O2, Fe+2

and Fe+3

, which can help identify over-dosing of

H2O2. They concluded that monitoring DO and ORP has high potential to

effectively control the E-Fenton process and could result in chemical cost

savings. This type of electro-Fenton reactor and the correlating monitoring and

control units is shown in the Fig. 10. It is a laboratory-scale batch type Electro-

Fenton reactor with 2 L of capacity, an anode of a titanium (Ti) rod coated

with IrO2/Ta2O5 (DSA). One ORP probe with the Ag/AgCl electrode, one DO

meter, and one pH probe were installed in the Electro-Fenton reactor for on-

line monitoring of the ORP/DO/pH variations during Fenton oxidation. A

mechanical mixer was installed in the bottom of reactor to provide sufficient

mixing. Two mix tanks were used for storing the prepared Fenton doses of

FeSO4 (20,000 mg/L of Fe+2

) and H2O2 (20,000 mg/L). All probes/meters and

dosing pumps were connected to a PC computer.

2. Conclusions

Of the current advanced oxidation processes, the Fenton-like reaction

process is the most promising for practical industrial application on a moderate

scale. The most popular reactor type for industrial use is the Fenton-batch

reactor, but higher removal efficiencies are usually obtained from a combined

process. For the reactors that use UV light, it is most common to place the

lamps at the center of the reactor and to use a water cooling jacket to maintain


constant temperature. Divided double-electrode electrochemical cells and

divided three-electrode electrochemical cells are the most common electro-

Fenton reactors. These are used mainly with carbon cathodes and iron anodes

installed in parallel. Other electrode materials such as platinum and boron-

doped diamond (BDD) are frequently used as the anode for the degradation of

pollutants in electro-Fenton system. Areas that need additional study include:

the role of temperature, H2O2 dosage, and iron’s effect on the Fenton’s reagent,

as well as new strategies to improve efficiency and reduce costs. Finally

reactor design must be improved in order to optimize conditions so that the

process can be used at an efficient, effective and profitable industrial scale.

References

1. R.S. Ramalho, Tratamiento de aguas residuales, in, Ed. Reverté España, 1996.

2. J.M. Peralta-Hernández, Mejía, S., Godínez, L.A., Meas-Vong, Y.,, Fenton and

Electrochemical Approaches for Water Purification Technologies., in, In: Palomar,

M. (Ed.), Applications of Analytical Chemistry in Environmental Research.,

Research Signpost, Trivandrum, Kerala, India, 2005.

3.

6570.

4. C.A. Martínez-Huitle, E. Brillas, Applied Catalysis B: Environmental, 87 (2009)

105.

5. P.C. Chiang, Y.W. Ko, C.H. Liang, E.E. Chang, Chemosphere, 39 (1999) 55.

6. G.R. Peyton, W.H. Glaze, Environ Sci Technol, 22 (1988) 761.

7. P. Pichat, L. Cermenati, A. Albini, D. Mas, H. Delprat, C. Guillard, Res Chem

Intermed, 26 (2000) 161.

8. S. Meriç, D. Kaptan, T. Ölmez, Chemosphere, 54 (2004) 435.

9. M.Y.A. Mollah, P. Morkovsky, J.A.G. Gomes, M. Kesmez, J. Parga, D.L. Cocke,

J Hazard Mater, 114 (2004) 199.

10. C.P. Huang, C. Dong, Z. Tang, Waste Management, 13 (1993) 361.

11. C.A. Murray, S.A. Parsons, Chemosphere, 54 (2004) 1017.

12. I. Sirés, E. Guivarch, N. Oturan, M.A. Oturan, Chemosphere, 72 (2008) 592.

13. E. Brillas, M.Á. Baños, J.A. Garrido, Electrochim Acta, 48 (2003) 1697.

14. J.J. Pignatello, Y. Sun, Water Res, 29 (1995) 1837.

15. B.C. Faust, J. Hoigné, Atmospheric Environment. Part A. General Topics, 24

(1990) 79.

16. N.H. Ince, G. Tezcanh, Water Sci Technol, 40 (1999) 183.

17. S.-F. Kang, C.-H. Liao, H.-P. Hung, J Hazard Mater, 65 (1999) 317.

18. R. Bauer, G. Waldner, H. Fallmann, S. Hager, M. Klare, T. Krutzler, S. Malato, P.

Maletzky, Catal Today, 53 (1999) 131.

19. Z. Qiang, J.-H. Chang, C.-P. Huang, Water Res, 36 (2002) 85.

20. J.S. Do, C.P. Chen, J Electrochem Soc, 140 (1993) 1632.

21. A. Alverez-Gallegos, D. Pletcher, Electrochim Acta, 44 (1999) 2483.

22. X. Zhang, J. Fu, Y. Zhang, L. Lei, Sep Purif Technol, 64 (2008) 116.


23. A. Özcan, Y. Şahin, A. Savaş Koparal, M.A. Oturan, J Electroanal Chem, 616

(2008) 71.

24. C.-T. Wang, W.-L. Chou, M.-H. Chung, Y.-M. Kuo, Desalination, 253 (2010) 129.

25. J.A. Bañuelos, F.J. Rodríguez, J. Manríquez Rocha, E. Bustos, A. Rodríguez, J.C.

Cruz, L.G. Arriaga, L.A. Godínez, Environ Sci Technol, 47 (2013) 7927.

26. A. El-Ghenymy, R.M. Rodríguez, C. Arias, F. Centellas, J.A. Garrido, P.L. Cabot,

E. Brillas, J Electroanal Chem, 701 (2013) 7.

27. B. Boye, M.M. Dieng, E. Brillas, Environ Sci Technol, 36 (2002) 3030.

28. C. Flox, S. Ammar, C. Arias, E. Brillas, A.V. Vargas-Zavala, R. Abdelhedi,

Applied Catalysis B: Environmental, 67 (2006) 93.

29. B. Boye, E. Brillas, A. Buso, G. Farnia, C. Flox, M. Giomo, G. Sandonà,

Electrochim Acta, 52 (2006) 256.

30. M.L.L.-V. Andrés Déctor-Espinoza1, Eruviel Flandes-Alemán, Jesús Cárdenas-

Mijangos, María del Carmen Cuevas-Díaz, Arnulfo Terán-López, José Abel

Paredes, Carlota Ruiz-Juárez, Leticia Montoya-Herrera, Comparison of two

methods of advanced oxidation for industrial waste water treatment with organic

compounds, in: third international congress of sciences, arts, technology, and

humanities, Coatzacoalcos, Veracruz, México, 2009.

31. C.-C. Su, C.-M. Chen, J. Anotai, M.-C. Lu, Chem Eng J (Lausanne), 222 (2013)

128.

32. T.L.P. Dantas, V.P. Mendonça, H.J. José, A.E. Rodrigues, R.F.P.M. Moreira,

Chem Eng J (Lausanne), 118 (2006) 77.

33. K. Swaminathan, S. Sandhya, A. Carmalin Sophia, K. Pachhade, Y.V.

Subrahmanyam, Chemosphere, 50 (2003) 619.

34. D.L. Sedlak, A.W. Andren, Environ Sci Technol, 25 (1991) 777.

35. B.G. Kwon, D.S. Lee, N. Kang, J. Yoon, Water Res, 33 (1999) 2110.

36. F.J. Benitez, J.L. Acero, F.J. Real, F.J. Rubio, A.I. Leal, Water Res, 35 (2001)

1338.

37. F.J. Rivas, F.J. Beltrán, J. Frades, P. Buxeda, Water Res, 35 (2001) 387.

38. I. Arslan, I.A. Balcioglu, Color Technol, 117 (2001) 38.

39. F.J. Benitez, J. Beltran-Heredia, J.L. Acero, F.J. Rubio, J Chem Technol

Biotechnol, 76 (2001) 312.

40. S.H. Gau, F.S. Chang, Water Sci Technol, 34 (1996) 455.

41. S.H. Lin, C.C. Lo, Water Res, 31 (1997) 2050.

42. J.-H. Bae, S.-K. Kim, H.-S. Chang, Water Sci Technol, 36 (1997) 341.

43. U. Welander, T. Henrysson, Environ Technol, 19 (1998) 591.

44. S.H. Lin, c.M. Lin, H.G. Leu, Water Res, 33 (1999) 1735.

45. M. Kitis, C.D. Adams, G.T. Daigger, Water Res, 33 (1999) 2561.

46. Y.W. Kang, K.-Y. Hwang, Water Res, 34 (2000) 2786.

47. I. Lau, P. Wang, H. Fang, Journal of Environmental Engineering, 127 (2001) 666.

48. J.S. Kim, Kim, H.Y., Won, C.H., Kim, J.G.,, J Chin Inst Chem Eng, 32 (2001)

425.

49. A. Lopez, M. Pagano, A. Volpe, A. Claudio Di Pinto, Chemosphere, 54 (2004)

1005.

50. A. Pala, G. Erden, Environ Eng Sci, 21 (2004) 549.


51. F.J. Rivas, F. Beltrán, F. Carvalho, B. Acedo, O. Gimeno, J Hazard Mater, 116

(2004) 95.

52. M.G.P. Kong, Cheol Hwi Park, Chil Rim Park, Mi Gyeong Yoo, Hui Chan.,

Process for treating leachate of landfill. , in: L. DAEWOO CO. (Ed.), korea, 1999.

53. J.J.K. Jo, Mi Hwa Kim, Yeong Gyu Lee, Hyeon Jun Lee, Jong Hyeon Pak, Tae Ju

Park, Jae Hong Park, Yu Ri., Automatic controlling apparatus of fenton oxidation

for preprocessing chemical wastewater and its apparatus and its method., in: J.J.P.

JO, TAE JU (Ed.), korea, 2000.

54. Y.u.L. Kim, Ui Sin Park, Chil Rim Park, Mi Gyeong Yoo, Hui Chan, Treatment

equipment of leachate containing high concentration organic matter and ammonia

nitrogen, in: L. DAEWOO CO. (Ed.), korea, 2000.

55. J.Y.J. Jung, Yun Cheol Lee, Sang Min Shin, Jeong Hun Son, Dae Hui, Advanced

wastewater treatment system for livestock wastewater, in: K.I.O.S.A.

TECHNOLOGY (Ed.), korea, 2002.

56. K.D.K. Lee, Byeong Yong Park, Jeong Je Jeong, Jae Beom Song, Joo Hoon Kim,

Yoon Jeong Jin, Soo Young Jeong, Hyeon La Gwak, Mi Jong Jo, Chang Woo

Kweon, Tae Hyeok. , Fenton-zeolite wastewater treatment system for primarily

removing contaminants by chemical coagulation and precipitation and increasing

removal efficiency of contaminants by fenton oxidation process and zeolite

adsorption process., in: CHOLLABUK-DO (Ed.), korea, 2004.

57. D.H. Lee, Method and apparatus for treating high concentration organic

wastewater using fe2o3 or/and fe3o4 as an iron oxide reaction catalyst, in: D.H.

LEE (Ed.), korea, 2005.

58. L.M. José, Method, devices and reagents which are used for wastewater treatment,

in: S.A. FMC FORET (Ed.), United States, 2005.

59. J.Y.L. Kim, Ho Seong Hong, Sin Pyo Bae, Jong Bok Park, Jong Sang, Wastewater

treatment method and apparatus for effectively reducing 1,4-dioxane, in: S.I.

INCORPORATION (Ed.), Korea, 2006.

60. B.K.S. Son, Yoo Duk, Process for effectively treating waste water containing

1,4-dioxane classified as a carcinogenic substance, in: L. SUNIL INVATEC CO.

(Ed.), Korea, 2007.

61. D.K.K. Kang, Seok Tae Kim, Jin Kil Han, Chul Woo Jo, Jung Gee, Treatment

process and equipment of steam generator chemical cleaning wastewater contained

chelate chemicals and radioactive materials using the low-temperature catalyst

oxidation/reduction technique, in: L. korea electric power corporation vitzrotech

co. (Ed.), Korea, 2009.

62. H.M. Choi, System for recycling mixing components in casting process, capable of

separating mixing components, in: h.m. company (Ed.), Korea, 2009.

63. J.E.L. Min, Sung Jae Lee, Bong Hee Nam, Kee Young Park, Jae Woo An, Sang

Woo, Portable leachate purifying system capable of treating leachate from a

livestock buried place based on flocculent and Fenton oxidation and filtering the

treated leachate, in: L. halla engineering&industrial development co. (Ed.), United

States, 2012.

64. M.B. Gad-El Joshua, Shitzer Boaz, Enhanced advanced oxidation procedure, in:

A.S. LTD (Ed.), United States, 2012.


65. S.-M. Kim, A. Vogelpohl, Chem Eng Technol, 21 (1998) 187.

66. M. Zazouli, Z. Yousefi, A. Eslami, M. Ardebilian, Iranian Journal of

Environmental Health Science & Engineering, 9 (2012) 3.

67. E. Oliveros, O. Legrini, M. Hohl, T. Müller, A.M. Braun, Chemical Engineering

and Processing: Process Intensification, 36 (1997) 397.

68. M. Muruganandham, M. Swaminathan, Dyes Pigm, 63 (2004) 315.

69. J. Feng, X. Hu, P.L. Yue, Chem Eng J (Lausanne), 100 (2004) 159.

70. C.n.T. Muranaka, C. Julcour, A.-M. Wilhelm, H. Delmas, C.A.O. Nascimento, Ind

Eng Chem Res, 49 (2009) 989.

71. S.-M. Kim, S.-U. Geissen, A. Vogelpohl, Water Sci Technol, 35 (1997) 239.

72. I.W.C. Lau, Wang, P., Chiu, S.S.T., Fang, H.H.P., Journal of Environmental

Sciences, 14 (2002) 388.

73. J. Feng, X. Hu, P.L. Yue, H.Y. Zhu, G.Q. Lu, Water Res, 37 (2003) 3776.

74. M. Neamtu, A. Yediler, I. Siminiceanu, A. Kettrup, Journal of Photochemistry and

Photobiology A: Chemistry, 161 (2003) 87.

75. M.S. Lucas, J.A. Peres, Dyes Pigm, 71 (2006) 236.

76. A. Riga, K. Soutsas, K. Ntampegliotis, V. Karayannis, G. Papapolymerou,

Desalination, 211 (2007) 72.

77. C.-H. Wu, Dyes Pigm, 77 (2008) 24.

78. K.S. Jung, Wastewater treatment system causing simultaneously electrolysis and

photo oxidation reaction, in: K.S. JUNG (Ed.), Korea, 2001.

79. G.P.K. Jang, Jun Hong Oh, Se Heon Song, Seok Ryong, Method for treating

wastewater from desulfurization facilities using photo Fenton oxidation process,

in: L. HYUNDAI HEAVY INDUSTRIES CO. (Ed.), Korea, 2003.

80. J.L. Cho, Method for treating non-biodegradable wastewater using photo-Fenton

oxidation mechanism by mixing collected wastewater with Fenton's reagent and

passing the wastewater through a uv ray irradiation region to perform photo-

Fenton reaction while circulating wastewater containing Fenton's reagent, in: H.M.

COMPANY (Ed.), Korea, 2005.

81. K.N. Yeon, High grade oxidation reactor apparatus, especially related to an

assembly of Fenton oxidation reactor and photo-Fenton reactor, in: L. KUNYANG

ENGINEERING CONSULTANTS & ARCHITECTS CO. (Ed.), Korea, 2006.

82. Y.C.K. Park, Tea Kwan Lee, Sung Gi, Chemical wastewater treatment apparatus

using combination of photolysis oxidation process and Fenton oxidation process,

in: L. SOLAR TECH CO. (Ed.), Korea, 2006.

83. C.J.L. Lee, Byoung Ho Kim, Sung Hyuk Han, Suk Won, Apparatus for treating

wastewater by multiplex oxidation, comprising a raw water pressurizing pump, a

Fenton solution supplying equipment, a reactor and an ozone gas supplying

equipment, and method for treating wastewater using the same, in: L. MICHIGAN

TECHNOLOGY CO. (Ed.), Korea, 2007.

84. K.J.H. Moon Il Shick, Apparatus for treating wastewater containing aromatic

carboxylic acid using complex advanced oxidation process, comprising an ozone

reactor, an ozone and hydrogen peroxide reactor, an uv tubular reactor, and a

catchment tank., in: I.-A.C.C.O.S.N. UNIVERSITY (Ed.), Korea, 2008.


85. D.K.K. Kim, Hae Wook Cho, Chong Joo Hong, Un Pyo Kang, Hyun Jin,

Apparatus and method for treatment of high concentration organic wastewater

without leaving sludge by degrading organic matters highly efficiently using

thermophilic microorganisms, performing solid-liquid separation and

concentration, and degrading recalcitrant organic matters, in: L. SUNIL

ENGINEERING CO. (Ed.), Korea, 2008.

86. M. Zhou, Q. Yu, L. Lei, G. Barton, Sep Purif Technol, 57 (2007) 380.

87. E. Rosales, M. Pazos, M.A. Longo, M.A. Sanromán, Chem Eng J (Lausanne), 155

(2009) 62.

88. S. Yuan, Y. Fan, Y. Zhang, M. Tong, P. Liao, Environ Sci Technol, 45 (2011)

8514.

89. H. Zhang, X. Ran, X. Wu, J Hazard Mater, 241–242 (2012) 259.

90. U. Kurt, O. Apaydin, M.T. Gonullu, J Hazard Mater, 143 (2007) 33.

91. H. Zhang, C. Fei, D. Zhang, F. Tang, J Hazard Mater, 145 (2007) 227.

92. Y. Yavuz, Sep Purif Technol, 53 (2007) 135.

93. D. Prabhakaran, T. Kannadasan, C.A. Basha, International Journal of

Environmental Science & Technology, 6 (2009) 491.

94. B.R. Babu, K.S. Meera, P. Venkatesan, D. Sunandha, Water, Air, Soil Pollut, 211

(2010) 203.

95. Y. Yavuz, A.S. Koparal, Ü.B. Öğütveren, Desalination, 258 (2010) 201.

96. P. Ghosh, A.N. Samanta, S. Ray, Desalination, 266 (2011) 213.

97. M.M. Ghoneim, H.S. El-Desoky, N.M. Zidan, Desalination, 274 (2011) 22.

98. L. Zhou, M. Zhou, C. Zhang, Y. Jiang, Z. Bi, J. Yang, Chem Eng J (Lausanne),

233 (2013) 185.

99. W. Cheng, M. Yang, Y. Xie, B. Liang, Z. Fang, E.P. Tsang, Chem Eng J

(Lausanne), 220 (2013) 214.

100. S.B.W. NA, SEONG SU, method for treating wastewater using electrolysis in: L.

KUM SUNG E & C CO. (Ed.), Korea, 2002.

101. V. KI, Apparatus and method for treatment of harmful wastewater by injecting fe2+

ions into influent, thereby performing electro-fenton oxidation by an electrode

plate part in: V. KI (Ed.), Korea, 2006.

102. A. Altin, Sep Purif Technol, 61 (2008) 391.

103. J. Casado, J. Fornaguera, M.I. Galán, Water Res, 40 (2006) 2511.

104. E. Brillas, J. Casado, Chemosphere, 47 (2002) 241.

105. W.-P. Ting, M.-C. Lu, Y.-H. Huang, J Hazard Mater, 156 (2008) 421.

106. E. Isarain-Chávez, R.M. Rodríguez, P.L. Cabot, F. Centellas, C. Arias, J.A.

Garrido, E. Brillas, Water Res, 45 (2011) 4119.

107. S. Garcia-Segura, A. El-Ghenymy, F. Centellas, R.M. Rodríguez, C. Arias, J.A.

Garrido, P.L. Cabot, E. Brillas, J Electroanal Chem, 681 (2012) 36.

108. A. El-Ghenymy, S. Garcia-Segura, R.M. Rodríguez, E. Brillas, M.S. El Begrani,

B.A. Abdelouahid, J Hazard Mater, 221–222 (2012) 288.

109. A. Babuponnusami, K. Muthukumar, Chem Eng J (Lausanne), 183 (2012) 1.

110. A. El-Ghenymy, N. Oturan, M.A. Oturan, J.A. Garrido, P.L. Cabot, F. Centellas,

R.M. Rodríguez, E. Brillas, Chem Eng J (Lausanne), 234 (2013) 115.


111. A. El-Ghenymy, P.L. Cabot, F. Centellas, J.A. Garrido, R.M. Rodríguez, C. Arias,

E. Brillas, Chemosphere, 91 (2013) 1324.

112. M.D.G. de Luna, J.I. Colades, C.-C. Su, M.-C. Lu, Chem Eng J (Lausanne), 232

(2013) 418.

113. S. Liu, X.-r. Zhao, H.-y. Sun, R.-p. Li, Y.-f. Fang, Y.-p. Huang, Chem Eng J

(Lausanne), 231 (2013) 441.

114. Y. Wang, H. Zhao, S. Chai, Y. Wang, G. Zhao, D. Li, Chem Eng J (Lausanne),

223 (2013) 524.

115. H. Zhao, Y. Wang, Y. Wang, T. Cao, G. Zhao, Applied Catalysis B:

Environmental, 125 (2012) 120.

116. L.A.G. Mora-tovar, F.J.R. Valadez, J.M.P. Hernández, J.R. Coutiño, K.E.

Escalante, system for performed the fentons reaction by a photo-electrochemical-

catalytic effect, method for obtaining free radicals (°oh) and regeneration of

supported iron (fe(ii)) in: s.c. centro de investigación y desarrollo tecnológico en

electroquímica (Ed.), México, 2011.

117. Y. Lei, H. Liu, Z. Shen, W. Wang, J Hazard Mater, 261 (2013) 570.

118. J.M. Peralta-Hernández, Y. Meas-Vong, F.J. Rodríguez, T.W. Chapman, M.I.

Maldonado, L.A. Godínez, Water Res, 40 (2006) 1754.

119. R.-F. Yu, C.-H. Lin, H.-W. Chen, W.-P. Cheng, M.-C. Kao, Chem Eng J

(Lausanne), 218 (2013) 341.

.

carlos a. martínez-huitle 6. a review on arrangement … · 1centro de investigación y desarrollo...

Documents