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Photochemical Advanced Oxidation Processes for Water and Wastewater Treatment

To browse Academia. Skip to main content. By using our site, you agree to our collection of information through the use of cookies. To learn more, view our Privacy Policy. Log In Sign Up. Download Free PDF. Phan ThanhPhu. Download PDF. A short summary of this paper. In most cases, anthropogenically polluted water can be effectively treated by conventional methods, such as biological processes, adsorption on activated carbon or other materials, thermal oxidation, chlorination, ozonation, flocculationprecipitation, reverse osmosis RO , etc.

However, in some cases, conventional procedures are not adequate to reach the degree of purity required by international or local regulations or by the subsequent use of the effluent. In these cases, Advanced Oxidation Processes AOPs or Advanced Oxidation Technologies AOTs are efficient novel methods for water treatment that permit the total or partial elimination of compounds resistant to conventional treatments, reduction of toxicity or destruction of pathogen microorganisms.

Depending on the physicochemical process leading to the formation of these species, AOPs can be divided into nonphotochemical and photochemical processes. If light irradiation of low UV-visible fluence is provided, the second group would require less energy consumption and fewer amounts of chemicals than the second type of processes.

Thus, photochemical processes are at present more widely employed. Most common AOPs are listed in Table 1. Hydroxyl radicals formed in AOPs react principally via hydrogen abstraction eq. In every case, the process can lead to the total mineralization of the compound.

AOPs are developed and commercialized to a variable degree and are undergoing constant change as technological advances take place. This review will focus on the description and advances related with main PAOPs from last years ca. The article will include studies of combination of individual AOPs and examples of patents.

Previous revisions on the subject, including AOPs not cited here can be found, for example, in references [2][3][4][5][6][7][8][9][10][11][12][13][14]. However, if the contaminants can be directly photolyzed, this may improve the efficiency of the oxidative destruction process. Since the intensity of UV radiation decays exponentially towards the bulk of the solution, it is necessary to establish conditions of turbulent flow to renew continuously the solution surrounding the luminous source.

The UV fluence rate [15] varies with distance from the lamp and it is a function of the absorptive characteristics of the media through which the UV radiation passes.

Reflection, refraction, shadowing, and lamp characteristics influence also the radiant power distribution within a UV reactor [16]. In alkaline media, the photochemical process is more efficient since the concentration of the conjugate anion of hydrogen peroxide increases with pH eq. HOIn all cases, it is necessary to determine the optimal H 2 O 2 concentration, which will depend on the concentration and chemical nature of the pollutants in the effluent stream.

Consequently, treatability tests are needed to determine the right amount of H 2 O 2 and to validate the technology [11]. There are no mass transfer problems associated with gases, as in the case of ozone.

Since the needed amounts of the reagent are relatively low, the process is rather economical. In these cases, a large amount of H 2 O 2 is needed [11]. It allows to extend the earlier UV-C technology for disinfection for simultaneous treatment of chemical detoxification.

The method can be sensibly improved by combination with ultrasound or by pretreatment with ozone [11]. The first category of kinetic models is a rate expression derived from an empirically determined correlation. Some experimental data from the oxidation of several compounds was successfully correlated using the power law model, including in some cases the effect of the UV intensity on the oxidation rate.

The second type is a kinetic model based on reaction mechanism and known chemical and photochemical reactions. Recently [19], the decolorization of C. A design equation was used to predict the concentration of AO7 and the electrical energy per order E EO 2 [20] at different conditions.

A more ambitious approach was made by Alpert et al. The authors concluded that effective CFD models for AOPs should incorporate rigorous turbulence and fluence rate submodels, kinetic rate equations, and proper characterization of the background water matrix.

As soon as oxidation pathways for water contaminants are identified, a simulation model may become an important tool for the design and optimization of AOPs, and the model will allow evaluation of multiple design scenarios, including number of lamps, layout of reactors, and upstream hydraulic conditions.

Since the reaction mechanisms for additional emerging contaminants become available, especially quantification of specific byproduct formation, CFD should be considered as a tool for predicting the outcome of direct photolysis and advanced oxidation on environmentally important compounds.

This is why, in principle, ozonation is sensibly more efficient in alkaline media, presenting an optimum around pH 9 [11]. It must be highlighted that ozone final products are O 2 and H 2 O, making the method less toxic to other conventional treatments that use Cl 2 or chromic acid. Ozonation is a good pretreatment before a biological treatment, because complex organics are transformed into aldehydes, ketones or carboxylic acids, all easily biodegradable compounds.

Ozonation is also versatile to be combined with other conventional or AOPs. However, from the operational point of view, there are limitations associated with the gas-liquid ozone mass transfer [11,13]. Consequently, the process requires efficient reactor design in order to maximize the ozone mass transfer coefficient; increasing the interfacial area of contact the bubble size by using small size diffusers, ceramic membranes, etc.

In addition, increasing the retention time in the reactor by large bubble columns, or increasing the solubility of ozone by increasing the pressure to several atmospheres, may be effective. Addition of H 2 O 2 to the ozonation system enhances the oxidation capacity of the process through secondary reactions.

Hydrogen peroxide initiates O 3 decomposition by electron transfer. It was suggested that the acceleration of ozonation is due to the increase of ozone transfer in water by H 2 O 2. One of the principal fields of application of this treatment is in the degradation of pesticides [6].

It is also effective for the post-treatment of water previously treated with chlorine because it can decompose trihalomethanes or related compounds. When ozone is combined with UV irradiation, several processes take place. The efficiency is higher than that of O 3 or direct UV, because UV-B light nm can be used, avoiding the use of a quartz reactor.

This brings a possible way to increase ozone reactivity at a low cost. Copper II can be used in place of iron. The most frequent use of the photo-Fenton process has been the treatment of industrial waters and lixiviates. Nitroaromatics, polychlorinated phenols, herbicides 2,4,5trichlorophenoxyacetic 2,4,5-T , 2,4-dichlorophenoxyacetic acid 2,4-D and other pesticides have been successfully degraded [11].

Photo-Fenton processes can use sunlight instead of UV light with a minor decrease in the rate of degradation. According to Gogate and Pandit [14], this is a very important factor for the scale-up and commercial use of a PAOP, since the costs of treatments will be substantially lowered if sunlight is used.

The photo-Fenton process can take advantage of the presence of constituents of real effluents like iron or copper salts, avoiding an additional dosage, and oligocarboxylic acids such as oxalate or ethylenediaminetetraacetic acid EDTA , which form photochemically active iron III complexes and enhance the process.

Appropriate selection of the iron salts needs to be done, and use of oxalate ions as the counter-ions is recommended for the majority of the pollutants and reaction conditions [14]. The role of iron on the degradation of different organic compounds, differing in their structure aliphatic versus aromatic and iron complex formation capacity, by conventional and photo-Fenton processes was recently investigated by Hermosilla et al.

It has been seen that these chemical characteristics can affect the degree of treatment in terms of COD chemical oxygen demand and TOC total organic carbon removals. While aromatics exhibited a fast and pronounced reduction in the COD by conventional Fenton process, aliphatic compounds required the presence of UV light to enhance treatment results.

Many publications can be found in the literature on applications of Fenton and photo-Fenton processes and the revision will not be done in this article. Heterogeneous PhotocatalysisHeterogeneous photocatalysis is a very well known technology, valuable for purification and remediation of water and air.

Several excellent revisions exist on the subject, with different approaches see for example [5,[7][8][9][10]13,[27][28][29]. TiO 2 is so far the most useful semiconductor material for photocatalytic purposes, owing to its exceptional optical and electronic properties, chemical stability, non-toxicity and low cost. The energy bandgaps of the photocatalytic forms of TiO 2 , anatase and rutile, are 3. The most popular and photoactive commercial form of TiO 2 is produced by the German company Degussa now Evonik under the name P For Degussa P, the values of the edges of conduction and valence bands at pH 0 have been calculated as Photogenerated holes and electrons can recombine easily this being one of the most important drawbacks of the process for its application or migrate to the surface where they can react with donor D or acceptor A species Fig.

The energy level at the bottom of the conduction band is actually the reduction potential of photoelectrons and the energy level at the top of the valence band determines the oxidizing ability of photoholes, each value reflecting the ability of the system to promote reductions and oxidations. From a thermodynamic point of view, the couples present in the system can be photocatalyti-cally reduced by conduction band electrons if they have redox potentials more positive than the flatband potential 3 V fb of the conduction band, and can be oxidized by valence band holes if they have redox potentials more negative than the V fb of the valence band [12 and references therein].

Titanium dioxide is an excellent photocatalytic material useful for environmental applications [8]. In some cases, addition of a noble metal to the TiO 2 surface increases the photocatalytic activity, although the activity of the transformed photocatalyst depends largely on the target pollutant [27,32].

Solution pH affects HP due to its influence on the superficial electric charge on the semiconductor influencing the redox level of the charge carriers, i.

The addition of an oxidant to the system inhibits recombination of electrons and holes and the photocatalytic system can become more efficient. For example, in aerated suspensions, O 2 is adsorbed onto the TiO 2 surface, acting as an electron acceptor and leading to the formation of superoxide anions eq. As the following set of equations indicates, this cathodic pathway is an additional source of hydroxyl radicals and hydrogen peroxide is produced. Another important oxidant is H 2 O 2.

Besides the amount formed by eq. An additional serious limitation for TiO 2 technological applications is the requirement of UV light to promote chemical processes due to the wide semiconductor bandgap.

Attempts to extend the range of activity of TiO 2 to the visible have been made in various ways: a ion implantation, b use of coupled semiconductors like TiO 2 -CdS or ZnO-CdS photocatalysts; c substitution of non-metals like N, C, S, P or B for oxygen sites in the TiO 2 lattice; d attachment of suitable dyes [34 and references therein].

However, all these techniques present several drawbacks and the photoactivity of these modified semiconductors is still rather low for real application. Zerovalent Iron ZVI Zerovalent iron is an emergent material, increasingly used for the treatment of several pollutants, particularly chlorinated organics, nitroaromatics, nitrate, azo-dyes, toxic metal ions and arsenic in solution [35][36][37]. The technology is based on the use of iron in the elemental state and the material can be employed in various forms: microparticles powders , fillings, wires, nails, wool and, in recent times, nanoparticles.

The physicochemical processes taking place in this technology depend on pH, the nature of the pollutant and other factors. In some cases, a reducing process takes place but, depending on the conditions, the process is oxidative [36]. Several pollutants chlorinated aliphatics, Cr VI , etc. ZVI has several advantages compared to other materials: i it is cheap and widely available in many forms, ii it is simple and can be easily handled, iii the technology can be straightforwardly scalable, iv it can be improved by solar light.

ZVI reactions are rather slow, but the process can be notably accelerated using iron nanoparticles NZVI [36 and references therein].

The tiny particle size, the large surface area and the high density of reactive surface sites or surface sites of high intrinsic reactivity lead to a very high efficiency, and make these materials very attractive for remediation. Studies on UV irradiation, economically promissory because solar light can be used, were generally focused on As III oxidation. SORAS removes arsenic from water in polyethyleneterephtalate PET bottles by photo-Fenton processes taking place by addition of lemon juice citrate and solar light, for example in natural waters of Bangladesh.

Photochemical Advanced Oxidation Processes for Water and Wastewater Treatment

The suitability of Advanced Oxidation Processes AOPs for pollutant degradation was recognised in the early s and much research and development work has been undertaken to commercialise some of these processes. AOPs have shown great potential in treating pollutants at both low and high concentrations and have found applications as diverse as ground water treatment, municipal wastewater sludge destruction and VOCs control. Advanced Oxidation Processes for Water and Wastewater Treatment is an overview of the advanced oxidation processes currently used or proposed for the remediation of water, wastewater, odours and sludge. The book contains two opening chapters which present introductions to advanced oxidation processes and a background to UV photolysis, seven chapters focusing on individual advanced oxidation processes and, finally, three chapters concentrating on selected applications of advanced oxidation processes. Advanced Oxidation Processes for Water and Wastewater Treatment will be invaluable to readers interested in water and wastewater treatment processes, including professionals and suppliers, as well as students and academics studying in this area.

photochemical purification of water and air pdf

Semantic Scholar extracted view of "Thomas Oppenländer Photochemical Purification of Water and Air" by T. Oppenländer.


Thomas Oppenländer Photochemical Purification of Water and Air

Highlights include: Explores economical aspects in a special chapter Includes extensive list of more than references and a glossary of terms according to the IUPAC nomenclature Over detailed figures visualize photochemcal and photophysical phenomena throughout the book Invaluable to Environmental Chemists, Water Chemists and Process Engineers. Seneci, Pierfausto. Gottschalk, Christiane. Tidwell, Thomas T.

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Photochemical Purification of Water and Air (E-Book, PDF)

Not a MyNAP member yet? Register for a free account to start saving and receiving special member only perks. Ultraviolet UV irradiation is considered an emerging technology for public health protection even though it is an ageless process that was instrumental in bringing about life on Earth and was harnessed into a technology for human use in treating water in the late s Downes and Blunt, This paper will review why there is now such an emerging interest in UV, the basics of UV technology, why UV works, the use of UV for disinfection and oxidation of pollutants in water, and the frontiers of UV technologies. Since the s, there has been a growing understanding that chlorine application for disinfection of water has adverse effects in both natural waters and drinking water. In wastewater, chlorine was used to disinfect the sewage before it was discharged into natural water bodies. In drinking water, chlorine has been used for over years to disinfect water for potable uses.

Bookworm Books and publications hot off the press. See also www. While the treatment of water and exhaust gas using ultraviolet light offers both ecological and economic advantages, information on photo-initiated advanced oxidation technologies AOTs has been dispersed among various journals and proceedings until now. This authoritative and comprehensive handbook is the first to cover both the photochemical fundamentals and practical applications, including a description of advanced oxidation processes AOPs and process engineering of suitable photoreactors. The author presents various real-world examples, including economic aspects and uses the IUPAC recommendations for nomenclature in photochemistry.


Photochemical Purification of Water and Air: Advanced Oxidation Processes (​AOPs) - Principles, Reaction Mechanisms, Reactor Concepts [Oppenländer.


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These metrics are regularly updated to reflect usage leading up to the last few days. Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts. The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.

Enter your mobile number or email address below and we'll send you a link to download the free Kindle App. Then you can start reading Kindle books on your smartphone, tablet, or computer - no Kindle device required. To get the free app, enter your mobile phone number. While the treatment of water and exhaust gas using ultraviolet UV light offers both ecological and economic advantages, information on photo-initiated advanced oxidation technologies AOTs has been dispersed among various journals and proceedings until now. This authoritative and comprehensive handbook is the first to cover both the photochemical fundamentals and practical applications, including a description of advanced oxidation processes AOPs and process engineering of suitable photoreactors. The author presents various real-world examples, including economic aspects, while many references to current scientific literature facilitate access to current research topics relevant for water and air industries.

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После паузы, показавшейся ей вечностью, она прошептала: - Коммандер.

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