Radiolytic Treatment Research Articles

The Green Method in Water Management: Electron Beam Treatment.

During the prebiotic era, radiolytic transformations in the oceans played a key role in purifying water from toxic impurities and, thus, played a role in the formation of the aquatic environment of our planet, making it suitable for the emergence of life. Today, the planet again faces the challenge of how to provide people with clean water. Therefore, it is reasonable to look back at past historical stages and again consider the possibility of neutralizing pollutants in water by means of radiolysis, which has already been tested by time. Modern radiolytic treatments can be much faster and safer thanks to the advent of powerful electron accelerators and high-rate electron beam treatment (ELT) of water and wastewater. Radiolytic treatment of water using accelerated electrons corresponds to the essence of advanced oxidative technologies and green chemistry. The ELT of water instantly generates a high concentration of short-lived radicals that can quickly neutralize and decompose chemical and bacterial pollutants. Due to the ability of accelerated electrons to penetrate into a substance, ELT provides the decomposition of both dissolved and suspended pollutants. The cleaning effect of ELT is due to the ability to inactivate toxic and chromophore functional groups, transform impurities into an easily removable form, damage the DNA of microorganisms and their spore forms, and increase the biodegradability of organic impurities. The use of ELT in water treatment provides significant savings in chemical reagents, thereby improving quality and reducing the number of cleaning steps. The compactness, high degree of automation of the equipment used, energy efficiency, high productivity, and excellent compatibility with traditional water treatment methods are important advantages of ELT. Unlike conventional chemicals, the excess radicals generated in the ELT process are converted back to water and hydrogen; thus, the chemical and corrosive activity of water does not increase. Equipping research institutes with electron accelerators, developing cheaper accelerators, and granting government support for pilot projects are key conditions for introducing ELT into water treatment practice.

Can radiation chemistry supply a highly efficient AO(R)P process for organics removal from drinking and waste water? A review.

The increasing role of chemistry in industrial production and its direct and indirect impacts in everyday life create the need for continuous search and efficiency improvement of new methods for decomposition/removal of different classes of waterborne anthropogenic pollutants. This review paper addresses a highly promising class of water treatment solutions, aimed at tackling the pressing problem of emerging contaminants in natural and drinking waters and wastewater discharges. Radiation processing, a technology originating from radiation chemistry studies, has shown encouraging results in the treatment of (mainly) organic water pollution. Radiation ("high energy") processing is an additive-free technology using short-lived reactive species formed by the radiolysis of water, both oxidative and reducing, to carry out decomposition of organic pollutants. The paper illustrates the basic principles of radiolytic treatment of organic pollutants in water and wastewaters and specifically of one of its most practical implementations (electron beam processing). Application examples, highlighting the technology's strong points and operational conditions are described, and a discussion on the possible future of this technology follows.

Radiolysis of carbamazepine aqueous solution using electron beam irradiation combining with hydrogen peroxide: Efficiency and mechanism

Herein, ionizing radiolytic treatment for CBZ in the absence of and in the presence of H2O2 was both studied. Although use of electron beam irradiation alone could efficiently decompose CBZ, combination with H2O2 could further promote degradation efficiency and mineralization level of CBZ. In the present study, the best degradation efficiency of CBZ was obtained in solution with 10mM H2O2, where the dose constant was 2.63kGy−1; while the highest mineralization level (41% TOC removal) was achieved in solution with 50mM H2O2. Five carboxylic acids and twelve organic transformation products (TPs) were identified and determined during the irradiation processes. On the basis of the tendency of TPs, possible transformation mechanisms of CBZ with the combinative processes of electron beam and H2O2 were proposed. It was found some mutagenic and carcinogenic transformation compounds, such as acridine (ACIN) could be promptly decomposed in the presence of H2O2.

Radiolytic Treatment of the Next-Generation Caustic-Side Solvent Extraction (NGS) Solvent and its Effect on the NGS Process

It is shown in this work that the solvent used in the Next Generation Caustic-Side Solvent Extraction (NGS) process can withstand a radiation dose well in excess of the dose it would receive in multiple years of treating legacy salt waste at the US Department of Energy Savannah River Site. The solvent was subjected to a maximum of 50 kGy of gamma radiation while in dynamic contact with each of the aqueous phases of the current NGS process, namely SRS−15 (a highly caustic waste simulant), sodium hydroxide scrub solution (0.025 M), and boric acid strip solution (0.01 M). Bench-top testing of irradiated solvent confirmed that irradiation has inconsequential impact on the extraction, scrubbing, and stripping performance of the solvent up to 13 times the estimated 0.73 kGy/y annual absorbed dose. Stripping performance is the most sensitive step to radiation, deteriorating more due to buildup of p-sec-butylphenol (SBP) and possibly other proton-ionizable products than to degradation of the guanidine suppressor, as shown by chemical analyses.

Role of eaq−, [rad]OH and H[rad] in radiolytic degradation of atrazine: A kinetic and mechanistic approach

The degradation of atrazine was investigated in aqueous solution by gamma-ray irradiation. 8.11μM initial atrazine concentration could be completely removed in N2 saturated solution by applying 3500Gy radiation dose at a dose rate of 296Gyh−1. Significant removal of atrazine (i.e., 39.4%) was observed at an absorbed dose of 1184Gy in air saturated solution and the removal efficiency was promoted to 50.5 and 65.4% in the presence of N2O and N2 gases, respectively. The relative contributions of hydrated electron, hydroxyl radical and hydrogen radical toward atrazine degradation were determined as ratio of observed dose constant (kobs) and found to be 5: 3: 1 for keaq−: kOH: kH, respectively. The degradation efficiency of atrazine was 69.5, 55.6 and 37.3% at pH 12.1, 1.7 and 5.7, respectively. A degradation mechanism was proposed based on the identified degradation by-products by gas chromatography–mass spectrometry. Taking the relative contributions of oxidative and reductive species to atrazine degradation into account, reductive pathway proved to be a better approach for the radiolytic treatment of atrazine contaminated water.

Gamma radiolysis of ceftriaxone sodium for water treatment: assessments of the activity

As large quantities of antibiotics have been misused in human and veterinary medicine, many different classes of antibiotics with low concentration have been detected in the environmental water. This existence may cause severe ecosystem alterations. Ceftriaxone sodium was employed as the targeted antibiotic to evaluate gamma radiolysis of antibiotics based on the primary elimination test and activity assay. The decomposition percentage of ceftriaxone sodium (20 microg/ml) in purified water increases with increasing doses and reaches 98% under 5 kGy of gamma radiation. The residual activity after gamma radiation does not follow the corresponding decomposition percentage of ceftriaxone sodium. Liquid chromatography and mass spectrometry (LC-MS) was subsequently employed to analyze possible structures of radiolytic products relating to the activity. Different degrees of the residual activity may attribute to different cleavage pathways of ceftriaxone sodium produced by radiation with different doses. The results indicate that the radiolytic treatment is a highly-effective means for degradation of ceftriaxone sodium, and the activity status of ceftriaxone sodium after primary elimination should be taken into consideration for selecting a degrading dose. Three kGy is the appropriate dose for radiolysis of ceftriaxone sodium in purified water.

Decomposition and mineralization of cefaclor by ionizing radiation: Kinetics and effects of the radical scavengers

There has been recent growing interest in the presence of antibiotics in different environmental sectors. One considerable concern is the potential development of antibiotic-resistant bacteria in the environment, even at low concentrations. Cefaclor, one of the β-lactam antibiotics, is widely used as an antibiotic. Kinetic studies were conducted to evaluate the decomposition and mineralization of cefaclor using gamma radiation. Cefaclor, 30mg/l, was completely degraded with 1000Gy of gamma radiation. At a concentration of 30mg/l, the removal efficiency, represented by the G-value, decreased with increasing accumulated radiation dose. Batch kinetic experiments with initial aqueous concentrations of 8.9, 13.3, 20.0 and 30.0mg/l showed the decomposition of cefaclor using gamma radiation followed a pseudo first-order reaction, and the dose constant increased with lower initial concentrations. At a given radiation dose, the G-values increased with higher initial cefaclor concentrations. The experimental results using methanol and thiourea as radical scavengers indicated that OH radicals were more closely associated with the radiolytic decomposition of cefaclor than other radicals, such as eaq- or H. The radical scavenger effects were tested under O2 and N2O saturations for the enhancement of the TOC percentage removal efficiencies in the radiolytic decomposition of cefaclor. Under O2 saturation, 90% TOC removal was observed with 100000Gy. Oxygen is well known to play a considerable role in the degradation of organic substances with effective chain reaction pathways. According to the effective radical reactions, the enhanced TOC percentage removal efficiencies might be based on the fast conversion reactions of eaq- and H with O2 into oxidizing radicals, such as O2- and HO2, respectively. 100% TOC removal was obtained with N2O gas at 20000Gy, as reducing radicals, such as eaq- and H, are scavenged by N2O and converted into OH radicals, which have strong oxidative properties. The results of this study showed that gamma irradiation was very effective for the removal of cefaclor in aqueous solution. The use of O2 or N2O, with radiation, shows promise as effective radical scavengers for enhancing the TOC or COD removal efficiencies in pharmaceutical wastewaters containing antibiotics. However, the biological toxicity and interactions between various chemicals during the radiolytic treatment, as well as treatments under conditions more representative of real wastewater will require further studies.

Diverse copper clusters confined in microporous nanocrystals

A selective formation of copper clusters in zeolite nanoparticles with GIS type structure is demonstrated. The size and the shape of the metal clusters are depending on the amount of copper incorporated in the small pores of the GIS crystalline structure and on their aperture. Different kinetics of reduction of the metal cations to clusters is observed under controlled radiolytic treatment of suspensions with constrained nanosized GIS particles. The solvated electrons produced in the bulk water under gamma radiolysis migrate into the GIS nanocrystals and subsequently reduce Cu II to Cu I starting from the external surface layers and progressing towards the center of the particles; this results in the coexistence of both Cu II cations and Cu 0 atoms. In the samples with low copper content, the formation of Cu I species is not observed, which is associated with the confinement of copper into the small zeolite pores preventing the reaction between Cu 2+ and Cu n 0. The copper loading of the nanocrystals, the conditions of radiolytic treatment and the features of the framework type crystalline structure determine the development of the reduction process resulting in selective formation of Cu I or Cu 0 species in the GIS nanocrystals.

Radiolytic decomposition of multi-class surfactants and their biotransformation products in sewage treatment plant effluents

Electron beam irradiation (EBI), as one of the most efficient advanced oxidation processes, was applied to the treatment of sewage treatment plant (STP) effluent, with the objective of evaluating the effectiveness of radiolytic decomposition of multi-class surfactants. Target compounds, included several high-volume surfactant groups, such as alkylphenol ethoxylates (APEOs) and their biotransformation products, linear alkylbenzene sulfonates (LAS), alkyl sulfates (AS), alkylether sulfates (AES), coconut diethanol amides (CDEA), alcohol ethoxylates (AEO) and polyethylene glycols (PEGs). EBI treatment of STP effluent (total concentration of APEO-derived compounds 265 μg l −1, being APE 2C the most abundant by-degradation products) resulted in efficient decomposition of all alkylphenolic compounds; elimination of 94% longer ethoxy chain nonylphenol ethoxylates (NPEO, n EO = 3–15) was obtained when 3 kGy were applied. Slightly less efficient decomposition of short ethoxy chain oligomers (NPEO 1 and NPEO 2) was observed, resulting in disappearance of about 80% of the initially present compounds. LC-MS analysis of treated wastewater suggested that the mechanism of EBI degradation of APEOs is a combination of two parallel pathways: a progressive shortening and oxidation of the ethoxy chain, which resulted in a formation of short ethoxy chain oligomers and APECs and central fission that resulted in formation of PEGs. Decomposition of APECs at 1 kGy initially yielded APs, which were subsequently eliminated applying higher radiation doses. With a radiation dose of 2 kGy about 95% of NPE 1C and 97% of NPE 2C were decomposed. Similar elimination rates were obtained for octylphenolic compounds. Radiolytic treatment applied was also very effective in removing PEGs formed as by-products from APEO degradation, as well as in decomposing other surfactants, such as linear LAS, AS and AES.

Method To Simultaneously Improve PCB Radiolysis Rates in Transformer Oil and To Close the Chlorine Mass Balance

The addition of alkaline 2-propanol to isooctane and transformer oil solutions of PCBs was found to increase the rate of PCB dechlorination by γ-radiolysis. Simultaneously, it facilitates the closure of the chlorine mass balance. The chlorine liberated from PCBs irradiated in alkaline 2-propanol-spiked solutions precipitated as an inorganic salt in a stoichiometric amount. This was demonstrated for an individual PCB congener (PCB 155) in isooctane and for Aroclor 1260 in transformer oil. Radiolysis rates are reported in terms of dose constants, d (kGy-1), the exponential rate constant for PCB decomposition with respect to absorbed dose. These are the highest decomposition rates yet reported for the radiolytic treatment of PCB-contaminated transformer oil.

Radiation processing of sewage and sludge. A review

This paper describes the potential of using ionizing radiation to disinfect sewage and sludge, as well as the possibilities of recycling natural resources and their by-products. Presented here is a brief review on the development of radiolytic treatment of wastewaters with electron beam accelerators or 60Co gamma sources to eliminate organic and biological contaminants from liquid and solid wastes. Suitable radiation doses are suggested for each particular case.

Radiolytic treatment of dioxin contaminated soils

Recent work in our laboratory has demonstrated that γ-radiolysis is a feasible method by which 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) can be converted to products of negligible toxicity. In the presence of 25% water, 2.5% non-ionic surfactant and at a dose of 800 kGy greater than 98% destruction was achieved in a standard soil artificially contaminated with 100 ppb TCDD. By-product analysis has illustrated that the destruction occurs via step-wise reductive dechlorination producing a suite of lesser chlorinated dioxins. These results in combination with scavenger studies, target theory calculations and yields indicate that direct radiation effects account for the major route of destruction. Radiolysis has also been conducted on a real soil contaminated with TCDD and other chlorinated aromatic compounds verifying the results of model studies. Based on the data of these experiments some designs of batch gamma systems are considered and a discussion of estimated capital and operating costs associated with γ-radiolysis is presented. Given the high costs of the alternatives (i.e. incineration), radiolysis appears to be not only technically feasible, but it may also be economically competitive.

Influence of ionizing radiation on the fatty acid composition of herring fillets

The effect of γ-irradiation (absorbed dose: 50 kGy, dose-rate: 2.9 kGy h ) on the distribution of fatty acid components in herring fillets has been examined using high-resolution gas chromatographic methods. Radiolytic treatment at 0°C and exclusion of atmospheric oxygen caused no significant decrease in the relative amounts of the constituent saturated, monounsaturated and polyunsaturated fatty acid components. Specifically, eicosapentaenoic acid (20:5) and docosahexaenoic acid (22:6), which are of particularly physiological interest were not affected by γ-rays, even after additional storage of the irradiated material at 0°C for 4 weeks. Irradiation of oil extracted from herring fillets or of herring oil/water emulsions under aerobic conditions, however, destroyed eicosapentaenoic acid and docosahexaenoic acid significantly. The loss of radio-resistance—as compared to the radiation-induced processes in the fillets—is explained by the absence of proteins, which effectively protect the lipid components from radiolytic decomposition. It is concluded that the commercial radiation processing of herring at the recommended dose levels (1–2 kGy) should not reduce the content of unsaturated fatty acid components.