The Green Method in Water Management: Electron Beam Treatment

Decolorization and degradation of crystal violet dye by electron beam radiation: Performance, degradation pathways, and synergetic effect with peroxymonosulfate

Ionizing radiation (mainly including gamma ray and electron beam) technology provides a more efficient and ecological option for dye-containing wastewater treatment, which is supported by its successful achievements in industrial-scale applications. However, the degradation pathway of triphenylmethane dyes by radiation technology is still unclear. In this study, crystal violet (CV) was selected as representative cationic triphenylmethane dye, the decolorization and degradation performance by electron beam radiation technology was systematically evaluated. The results showed that CV can be efficiently decolorized and mineralized by radiation, and its degradation kinetics followed the first-order kinetic model. The effect of inorganic anions and chelating agents commonly existed in dye-containing wastewater on CV decolorization and total organic carbon (TOC) removal was explored. Quenching experiments, density functional theory (DFT) calculation and high performance liquid chromatography mass spectrometry (HPLC-MS) analysis were employed to reveal CV decolorization and degradation mechanism and pathway, which mainly included N-demethylation, triphenylmethane chromophore cleavage, ring-opening of aromatic products and further oxidation to carboxylic acid, and mineralization to CO2 and H2O. Additionally, electron beam radiation/PMS process was explored to decrease the absorbed dose required for decolorization and degradation, and the synergetic effect of radiation with PMS was elucidated. More importantly, the findings of this study would provide the support for treating actual dyeing wastewater by electron beam radiation technology.

Water Radiocatalysis for Selective Aqueous-Phase Methane Carboxylation with Carbon Dioxide into Acetic Acid at Room Temperature

Methane (CH4) carboxylation with carbon dioxide (CO2) into acetic acid (CH3COOH) is an ideal chemical reaction to utilize both greenhouse gases with 100% atom efficiency but remains a great challenge under mild conditions. Herein, we introduce a concept of water (H2O) radiocatalysis for efficient and selective aqueous-phase CH4 carboxylation with CO2 into CH3COOH at room temperature. H2O radiolysis occurs under γ-ray radiation to produce ·OH radicals and hydrated electrons that efficiently react with CH4 and CO2, respectively, to produce ·CH3 radicals and ·CO2- species facilely coupling to produce CH3COOH. CH3COOH selectivity as high as 96.9 and 96.6% calculated respectively from CH4 and CO2 and a CH3COOH production rate of as high as 121.9 μmol·h-1 are acquired. The water radiocatalysis driven by γ-rays is also applicable to selectively produce organic acids from other hydrocarbons and CO2.

Decolorization and degradation of various dyes and dye-containing wastewater treatment by electron beam radiation technology: An overview

The treatment of dye-containing wastewater generated from textile industries is still a challenge, and various technologies, including physical, chemical and biological ones have been used. In recent years, the ionizing radiation (usually including gamma ray generated by radionuclide, such as 60Co and 137Cs, and electron beam generated by electron accelerator) technology has received increasing attention for degrading refractory or toxic organic pollutants in wastewater because of its unique advantages, such as no chemical additives, fast reaction rate, strong degradation capacity, high efficiency, flexibility, controllability. Compared to the conventional wastewater treatment processes, ionizing radiation technology, as a disruptive wastewater treatment technology, is more efficient for the decolorization and degradation of dyes and the treatment of dye-containing wastewater. In this paper, the recent advances in the treatment of dye-containing wastewater by ionizing radiation, in particular by electron beam (EB) radiation were summarized and analyzed, focusing on the decolorization and degradation of various dyes. Firstly, the formation of various reactive species induced by radiation and their interactions with dye molecules, as well as the influencing factors on the removal efficiency of dyes were discussed. Secondly, the researches on the treating dye-containing wastewater by electron beam radiation technology were systematically reviewed. Then, the decolorization and degradation mechanisms by electron beam radiation were further discussed in detail. And the integrated processes that would contribute to the advancement of this technology in practical applications were examined. More importantly, the recent advances of electron beam radiation technology from laboratory to application were reviewed, especially successful operation of dye-containing wastewater treatment facilities in China. And eventually, current challenges, future research directions, and outlooks of electron beam radiation technology were proposed for further advancing this technology for the sustainable development of water resources.

Pretreatment of alkali/surfactant/polymer (ASP)-flooding produced wastewater by electron beam radiation to improve oil-water separation

The management of wastewater produced from alkali/surfactant/polymer (ASP) flooding, known for its considerable volume and high emulsion stability, poses a challenge in oilfields globally. This study has demonstrated that ionizing irradiation is a promising pretreatment method for ASP wastewater to improve oil-water separation. After a settling time of 1 h, approximately 69.5% of oil remained in the raw ASP wastewater, while only 20-29% of the oil persisted in the liquid phase following radiation at absorbed doses ranging from 0.1 to 5.0 kGy. A noticeable increase in the size of oil droplets and reduction in turbidity was observed after irradiation. Further analysis revealed that the combination of surfactant, sodium dodecyl sulfate (SDS) and alkali exhibits a synergistic impact, leading to a substantial reduction in interface tension of ASP wastewater. Notably, ionizing irradiation induces several key changes that are crucial for efficient demulsification. The transformation of the wastewater's rheological behavior from pseudoplastics to a Newtonian fluid accompanied by a reduction in viscosity, the increased interfacial tension at both liquid-air and liquid-oil interfaces, along with the degradation of organic components such as partly hydrolyzed polyacrylamide (HPAM) and SDS, all contribute to the coalescence and floatation of oil droplets.

Selective CO2 reduction to CH3OH over atomic dual-metal sites embedded in a metal-organic framework with high-energy radiation

The efficient use of renewable X/γ-rays or accelerated electrons for chemical transformation of CO2 and water to fuels holds promise for a carbon-neutral economy; however, such processes are challenging to implement and require the assistance of catalysts capable of sensitizing secondary electron scattering and providing active metal sites to bind intermediates. Here we show atomic Cu-Ni dual-metal sites embedded in a metal-organic framework enable efficient and selective CH3OH production (~98%) over multiple irradiated cycles. The usage of practical electron-beam irradiation (200 keV; 40 kGy min-1) with a cost-effective hydroxyl radical scavenger promotes CH3OH production rate to 0.27 mmol g-1 min-1. Moreover, time-resolved experiments with calculations reveal the direct generation of CO2•‒ radical anions via aqueous electrons attachment occurred on nanosecond timescale, and cascade hydrogenation steps. Our study highlights a radiolytic route to produce CH3OH with CO2 feedstock and introduces a desirable atomic structure to improve performance.

Applicability of Electron Beam Technology for the Degradation of Microcystin-LR in Surface Waters

Studies were performed to investigate the effects of surface water quality parameters on the degradation of microcystin-LR (MC-LR) using high-energy electron beam (eBeam) technology. Surface water samples were collected across different geographic locations in the United States. Water quality parameters including pH, alkalinity, TDS, and dissolved oxygen were measured in all samples. Degradation of MC-LR in all samples, regardless of parameter concentrations, was above 99%. The effect of natural organic matter (NOM) on MC-LR degradation was also investigated in the presence of fulvic acid. Similarly, the degradation efficiency of MC-LR exceeded 99% for all concentrations of fulvic acid at 5 kGy. This study suggests that surface water quality has a negligible effect on the degradation of MC-LR via eBeam treatment. The results indicate that eBeam technology is a promising technique for the treatment of water contaminated with microcystins.

Radiolytic Water Splitting Sensitized by Nanoscale Metal-Organic Frameworks

High-energy radiation that is compatible with renewable energy sources enables direct H₂ production from water for fuels; however, the challenge is to convert it as efficiently as possible, and the existing strategies have limited success. Herein, we report the use of Zr/Hf-based nanoscale UiO-66 metal-organic frameworks as highly effective and stable radiation sensitizers for purified and natural water splitting under γ-ray irradiation. Scavenging and pulse radiolysis experiments with Monte Carlo simulations show that the combination of 3D arrays of ultrasmall metal-oxo clusters and high porosity affords unprecedented effective scattering between secondary electrons and confined water, generating increased precursors of solvated electrons and excited states of water, which are the main species responsible for H₂ production enhancement. The use of a small quantity (<80 mmol/L) of UiO-66-Hf-OH can achieve a γ-rays-to-hydrogen conversion efficiency exceeding 10% that significantly outperforms Zr-/Hf-oxide nanoparticles and the existing radiolytic H₂ promoters. Our work highlights the feasibility and merit of MOF-assisted radiolytic water splitting and promises a competitive method for creating a green H₂ economy.

Investigation of Colored Film Indicators for the Assessment of the Occasional Radiation Exposure

Occupational radiation exposure monitoring is well-established in clinical or industrial environments with various different dosimeter systems. Despite the availability of many dosimetry methods and devices, a challenge with the occasional exposure registration, which may occur due to the spilling of radioactive materials or splitting of these materials in the environment, still exists, because not every individual will have an appropriate dosimeter at the time of the irradiation event. The aim of this work was to develop radiation-sensitive films—color-changing radiation indicators, which can be attached to or integrated in the textile. Polyvinyl alcohol (PVA)-based polymer hydrogels were used as a basis for fabrication of radiation indicator films. Several organic dyes (brilliant carmosine (BC), brilliant scarlet (BS), methylene red (MR), brilliant green (BG), brilliant blue (BB), methylene blue (MB) and xylenol orange (XiO)) were used as a coloring additives. Moreover, PVA films enriched with Ag nanoparticles (PVA-Ag) were investigated. In order to assess the radiation sensitivity of the produced films, experimental samples were irradiated in a linear accelerator with 6 MeV X-ray photons and the radiation sensitivity of irradiated films was evaluated using UV–Vis spectrophotometry method. The most sensitive were PVA-BB films indicating 0.4 Gy−1 sensitivity in low-dose (0–1 or 2 Gy) range. The sensitivity at higher doses was modest. These PVA-dye films were sensitive enough to detect doses up to 10 Gy and PVA-MR film indicated stable 33.3% decolorization after irradiation at this dose. It was found that the dose sensitivity of all PVA-Ag gel films varied from 0.068 to 0.11 Gy−1 and was dependent on the Ag additives concentration. Exchange of a small amount of water with ethanol or isopropanol caused the enhancement of radiation sensitivity in the films with the lowest AgNO3 concentration. Radiation-induced color change of AgPVA films varied between 30 and 40%. Performed research demonstrated the potential of colored hydrogel films in their applications as indicators for the assessment of the occasional radiation exposure.

Electron beam treatment for the removal of 1,4-dioxane in water and wastewater

Electron beam (e-beam) treatment uses accelerated electrons to form oxidizing and reducing radicals when applied to water without the use of external chemicals. In this study, electron beam treatment was used to degrade 1,4-dioxane in several water matrices. Removal improved in the progressively cleaner water matrices and removals as high as 94% to 99% were observed at a dose of 2.3 kGy in secondary effluent. 1,4-dioxane removal was confirmed to be primarily through hydroxyl radical oxidation. The calculated electrical energy per order was found to be 0.53, 0.26, and 0.08 kWh/m³/order for secondary effluent (Avg. total organic carbon (TOC) 9.25 mg/L), granular activated carbon effluent (TOC 3.46 mg/L), and ultrapure water, respectively, with a 70% generation and transfer efficiency applied.

Natural Radioactivity and Chemical Evolution on the Early Earth: Prebiotic Chemistry and Oxygenation

It is generally recognized that the evolution of the early Earth was affected by an external energy source: radiation from the early Sun. The hypothesis about the important role of natural radioactivity, as a source of internal energy in the evolution of the early Earth, is considered and substantiated in this work. The decay of the long-lived isotopes ²³²Th, ²³⁸U, ²³⁵U, and ⁴⁰K in the Global Ocean initiated the oxygenation of the hydro- and atmosphere, and the abiogenesis. The content of isotopes in the ocean and the kinetics of their decay, the values of the absorbed dose and dose rate, and the efficiency of sea water radiolysis, as a function of time, were calculated. The ocean served as both a "reservoir" that collected components of the early atmosphere and products of their transformations, and a "converter" in which further chemical reactions of these compounds took place. Radical mechanisms were proposed for the formation of simple amino acids, sugars, and nitrogen bases, i.e., the key structures of all living things, and also for the formation of oxygen. The calculation results confirm the possible important role of natural radioactivity in the evolution of terrestrial matter, and the emergence of life.

Treatment of hospital wastewater by electron beam technology: Removal of COD, pathogenic bacteria and viruses

The effective treatment of hospital sewage is crucial to human health and eco-environment, especially during the pandemic of COVID-19. In this study, a demonstration project of actual hospital sewage using electron beam technology was established as advanced treatment process during the outbreak of COVID-19 pandemic in Hubei, China in July 2020. The results indicated that electron beam radiation could effectively remove COD, pathogenic bacteria and viruses in hospital sewage. The continuous monitoring date showed that the effluent COD concentration after electron beam treatment was stably below 30 mg/L, and the concentration of fecal Escherichia coli was below 50 MPN/L, when the absorbed dose was 4 kGy. Electron beam radiation was also an effective method for inactivating viruses. Compared to the inactivation of fecal Escherichia coli, higher absorbed dose was required for the inactivation of virus. Absorbed dose had different effect on the removal of virus. When the absorbed dose ranged from 30 to 50 kGy, Hepatitis A virus (HAV) and Astrovirus (ASV) could be completely removed by electron beam treatment. For Rotavirus (RV) and Enterovirus (EV) virus, the removal efficiency firstly increased and then decreased. The maximum removal efficiency of RV and EV was 98.90% and 88.49%, respectively. For the Norovirus (NVLII) virus, the maximum removal efficiency was 81.58%. This study firstly reported the performance of electron beam in the removal of COD, fecal Escherichia coli and virus in the actual hospital sewage, which would provide useful information for the application of electron beam technology in the treatment of hospital sewage.

Inactivation of biohazards in healthcare wastewater by E-Beam and Gamma irradiation: a comparative study

The main objective of this study is to evaluate the effect of irradiation by Gamma rays and Electron Beam (E-Beam) on naturally occurring microorganisms shed in healthcare wastewater issued from multi-specialties hospital. We examined the susceptibility of naturally occurring total indicator bacteriophages towards Gamma rays and E-Beam irradiation to evaluate their appropriateness as viral indicators for healthcare wastewater quality control. Results showed that healthcare wastewater is a rich matrix containing bacteriophages surrogates of pathogenic waterborne viruses (4.5 Log10 PFU/100 mL for SOMCPH and 2.3 Log10 PFU/100 mL for FRNAPH), antibiotic resistant bacteria (Mean concentrations from 2.3 to 5.5 Log10 CFU/100 mL), molds and yeasts (2.7 Log10 CFU/100 mL), and spores of Clostridium perfringens (Mean concentration of 3.3 Log10 CFU/100 mL). After E-Beam irradiation, naturally occurring bacteria in healthcare wastewater showed lower resistance patterns (D10 values ranging between 0.21 ± 0.005 and 0.59 ± 0.005) compared to those obtained after Gamma irradiation (D10 values ranging between 0.25 ± 0.015 and 0.70 ± 0.0001). Spores of Clostridium perfringens were the most resistant assayed microbes either after E-Beam (D10 values of 3.74 ± 0.005) or Gamma irradiation (D10 values of 4.77 ± 0.025) of collected samples. According to inactivation patterns, a dose of 10 kGy was sufficient for a complete inactivation of spores. Bacteriophages isolated from healthcare wastewater showed the same resistance patterns as those previously obtained in urban treated sewage and were inactivated using higher doses than waterborne bacteria (D10 values of SOMCPH 1.46 ± 0.057; D10 values of FRNAPH 1.03 ± 0.057). Their resistance to irradiation treatment in such complex matrix corroborates their use to survey the viral quality of healthcare wastewater before their discharge in the urban sanitation network. D10 value analysis showed that bacteria and bacteriophages inactivation by E-Beam irradiation required lower doses than those required for their inactivation using Gamma rays. According to inactivation patterns, a dose of 7 kGy was sufficient for total inactivation of both pathogenic bacteria and viruses. Thus, E-Beam irradiation seems to be an efficient physical pre-treatment process for healthcare wastewater treatment prior to its discharge in urban sanitation system to ensure compliance with environmental standards and protect public health.

The performance and pathway of benzothiazole degradation by electron beam irradiation

Benzothiazole (BTH) is a typical refractory heterocyclic compound that can be used as a photosensitive material in organic synthesis and conditional plant resource research. The extensive use of BTH has led to high BTH concentrations in natural environment, such as in tap water and urine, which tend to inhibit animal hormone synthesis and induce genotoxicity. Traditional wastewater treatment processes cannot effectively remove BTH. Therefore, we aimed to use the electron beam method, an emerging method for pollutant degradation, to degrade BTH in water. Experiments showed that BTH can be effectively degraded (up to 90%) when the electron beam reaches 5 kGy and irradiation conformed perfectly to the pseudo first-order kinetics model. Experimental results showed that acidic conditions are more favorable for electron beam degradation of BTH, while the degradation of most other inorganic ions is inhibited (except SO₄^2-). Hydroxyl radicals (•OH) was confirmed to play a major role in degradation by the experiment, and the mineralization rate was greatly increased by the addition of H₂O₂ and K₂S₂O₈. In addition, our experimental and theoretical calculations showed that the degradation of BTH occurred mainly through the opening of the benzene ring. Theoretical calculations showed that the toxicity of BTH decreased significantly after electron beam degradation, making it an effective way to degrade BTH.

Impact of gamma-irradiation on the degradation and mineralization of hydroxychloroquine aqueous solutions

In this work, the effect of gamma irradiation emitted by Cobalt 60 source has been investigated for the degradation of hydroxychloroquine (HCQ). The monitoring of the gamma irradiation treatment of HCQ aqueous solutions was followed by UV-visible, chemical oxygen demand, total organic carbon (TOC) and LC/MS analyses. Effects of several important parameters such as concentration, dose rate and pH on the degradation efficiency were studied then evaluated. Achieved results showed that % TOC removal efficiency of 98.5 was obtained after 8 kGy absorbed dose which warrants HCQ mineralization. The process was found to be more efficient when the initial pollutant concentration was low, with higher dose rate and at neutral pH. Furthermore, HCQ degradation kinetic study revealed a pseudo-first-order kinetic. Additionally, based on by-products identified by LC/MS, a degradation mechanistic schema mediated through hydroxyl radicals generated by water radiolysis has been proposed. Finally, in order to check the potential industrial application viability the energy consuming was evaluated.

Removal of Per- and Polyfluoroalkyl Substances by Electron Beam and Plasma Irradiation: A Mini-Review

The global prevalence and environmental risks of per- and polyfluoroalkyl substances (PFASs) have caused increasing concern regarding their strategic elimination from aqueous environments. It has recently been recognized that advanced oxidation–reduction technologies (AO/RTs) exhibit superior removal performance for these ubiquitous pollutants. However, the detailed mechanisms and product risks have not been well summarized and systematically deciphered. In this mini-review article, the basic operating principles of two typical AO/RTs (electron beam and plasma irradiation) and their reported applications in the abatement of PFASs are described in detail. It is noteworthy that these reductive treatments induced remarkable defluorination efficiency of PFOA and PFOS with the generation of short-chain congeners in water. The reaction mechanisms mainly included desulfonization, decarboxylation, H/F exchange, radical cyclization, and stepwise losses of CF2 groups. Unexpectedly, partial degradation products manifested high potential in triggering acute and chronic aquatic toxicity, genotoxicity, and developmental toxicity. Additionally, high or even increased resistance to biodegradability was observed for multiple products relative to the parent chemicals. Taken together, both electron beam and plasma irradiation hold great promise in remediating PFAS-contaminated water and wastewater, while the secondary ecological risks should be taken into account during practical applications.

Degradation of chloroaniline in chemical wastewater by ionizing radiation technology: Degradation mechanism and toxicity evaluation

Chloroaniline is a typical organic pollutant in chemical wastewater, which cannot be effectively removed in conventional wastewater treatment processes. In this study, ionizing radiation was used as advanced treatment process to degrade 2-chloroaniline (2-CA). The results showed that 10 mg/l of 2-CA could be completely degraded at 1 kGy. The required dose for completely degrading 2-CA by radiation increased when its initial concentration increased. Solution pH affected 2-CA degradation by changing the radiation-chemical yield of reactive species. Chloride ions (10 and 100 mM) had not obvious influence on 2-CA degradation. Hydrogen radicals, hydrated electrons and hydroxyl radicals, all contributed to the degradation of 2-CA, but with different degradation mechanisms. Hydrogen radicals and hydrated electrons could initiate reductive dechlorination of 2-CA, while hydroxyl radicals can degrade 2-CA by hydroxylation. 6-amino-1,4-cyclohexadiene and chlorobenzene were the main intermediate products of 2-CA degradation in the hydrogen radicals or hydrated electrons dominant process; while o-hydroxyaniline and nitroso-chlorobenzene were the main intermediate products in the hydroxyl radicals dominant process. The solution toxicity after radiation treatment varied with the initial concentration of 2-CA and the absorbed dose. In the actual chemical wastewater, 2-CA can be effectively removed by radiation, even in the presence of high concentration of chloride ions (about 2800 mg/l). The solution toxicity of actual wastewater decreased with the increase of adsorbed dose. This study provided an insight into the 2-CA degradation by radiation, and demonstrated that radiation could be an alternative option for the treatment of chloroaniline-containing chemical wastewater.

Degradation of anticorrosive agent benzotriazole by electron beam irradiation: Mechanisms, degradation pathway and toxicological analysis

Benzotriazole (BTA), which is extensively served as household and engineering agent, is one of the emerging and persistent contaminants. Despite the spirit to remove BTA is willing, the traditional wastewater treatments are weak. Therefore, the degradation of BTA via electron beam was systematically explored in this study. It turned out that after 5.0 kGy irradiation, even 87.5 mg L^-1 BTA could be completely removed, and the irradiation conformed perfectly to the pseudo first-order kinetics model. The effects of solution pH, inorganic anions (CO₃^2-, HCO₃^-, NO₃^-, NO₂^-, SO₄^2-, SO₃^2-, Cl^-), and gas atmosphere were all explored. And results indicated that oxidative hydroxyl radicals played critical role in BTA irradiation. Additionally, presence of H₂O₂ and K₂S₂O₈ promoted significantly not only degradation extent but also mineralization efficiency of BTA due to they both augmented the generation of oxidative free radicals. Moreover, by combining theoretical calculations with experimental results, it could be inferred that degradation of BTA was mainly carried out by the benzene ring-opening. Further toxicity evaluation proved that as irradiation proceeded, the toxicity alleviated. Taken together, there were various indications that BTA could be effectively eliminated by electron beam irradiation in aquatic environments.