Enhanced surface activation of ground tire rubber via the radiolysis of water for effective rubber recycling.

In this study, we examined the chemical changes occurring in ground tire rubber (GTR) and on its surface as a result of gamma irradiation in water, with low doses of 5, 10, 15, 20, 25, and 30 kGy. To better distinguish the changes the radiation caused in the GTR and the surface activation of the GTR caused by the irradiated water, we also performed radiation treatments in an inert atmosphere. We mixed the treated GTRs with fresh rubber, and after vulcanization, investigated the mechanical properties and conducted dose optimization.

Oxidation and mineralization rates of harmful organic chemicals in hydroxyl radical induced reactions.

In most of advanced oxidation processes (AOPs) used to destroy harmful organic chemicals in water/wastewater hydroxyl radical (OH) reactions oxidize (increasing the oxygen/carbon ratio in the molecules) and mineralize (transforming them to inorganic molecules, HO, CO, etc.) these contaminants. In this paper, we used the radiolysis of water to produce OH and characterised the rate of oxidation and mineralization by the dose dependences of the Chemical Oxygen Demand (COD) and Total Organic Carbon (TOC) content values.

Changes in the behavior of Staphylococcus aureus strains in the presence of oxacillin under the effect of gamma radiation.

Staphylococcus aureus (S. aureus) as a major pathogen is implicated in a wide range of foodborne and hospital-acquired infections, its methicillin resistant variants contribute to the spread of β-lactam antibiotic resistance. It is essentially important to destroy these pathogens, their resistance genes and the antibiotics in wastewaters.

Rate constants for the reactions of chloride monoxide radical (ClO) and organic molecules of environmental interest.

ClO plays a key role in the UV/chlorine process besides Cl, Cl2 - , and OH. In many experiments, ClO proved to be the main reactant that destroyed the organic pollutants in advanced oxidation process. About 200 rate constants of ClO reactions were collected from the literature, grouped together according to the chemical structure, and the molecular structure dependencies were evaluated.

Rate constants of chlorine atom reactions with organic molecules in aqueous solutions, an overview.

Rate constants of chlorine atom (Cl) reactions (k) determined using a large variation of experimental methods, including transient measurements, steady-state and computation techniques, were collected from the literature and were discussed together with the reaction mechanisms. The k values are generally in the 10-10 mol dm s range when the basic reaction between the Cl and the target molecule is H-atom abstraction. When Cl addition to double bonds dominates the interaction, the k values are in the 1 × 10-2 × 10 mol dm s range.

Elimination of oxacillin, its toxicity and antibacterial activity by using ionizing radiation.

The chemical changes caused by electron beam and γ irradiations and the biochemical characteristics of degradation products of a frequently used antibiotic oxacillin were investigated and compared with those of cloxacillin by applying pulse radiolysis, chemical and biochemical oxygen demand, total organic carbon content, oxygen uptake rate, toxicity and antibacterial activity measurements. Oxacillin was found to be non-toxic, but poorly biodegradable by the mixed microbial population of the activated sludge of a wastewater treatment plant. Therefore, it can significantly contribute to the spread of β-lactam antibiotic resistant bacteria.

Treatment of pharmaceutical wastewater by ionizing radiation: Removal of antibiotics, antimicrobial resistance genes and antimicrobial activity.

In present study, the treatment of real pharmaceutical wastewater from an erythromycin (ERY) production factory by gamma irradiation was investigated. Results showed that a variety of antimicrobial resistance genes (ARGs), involving MLSB, tet, bla, multidrug, sul, MGEs and van genes and plentiful 9 bacterial phyla were identified in the raw wastewater. In addition to ERY, sulfamethoxazole (SMX) and tetracycline (TC) were also identified with the concentration of 3 order of magnitude lower than ERY.

Rate constants of dichloride radical anion reactions with molecules of environmental interest in aqueous solution: a review.

Natural waters, water droplets in the air at coastal regions and wastewaters usually contain chloride ions (Cl) in relatively high concentrations in the milimolar range. In the reactions of highly oxidizing radicals (e.g.

Antibiotics in a wastewater matrix at environmentally relevant concentrations affect coexisting resistant/sensitive bacterial cultures with profound impact on advanced oxidation treatment.

Antibiotic resistance containment strategies at wastewater treatment plants need to be supported by a firm knowledge on the behavior of resistant bacteria within a diverse microbial population in the presence of trace amount of antibiotics. In this study via investigating the population dynamics of resistant/sensitive Staphylococcus aureus co-cultures in several model wastewater matrix systems, valuable insights were obtained into the effect of trace amount of antibiotics (piperacillin and erythromycin) on bacteria, and into the suitability of advanced oxidation treatment (electron beam irradiation) as a remediation measure. It appears that environmentally relevant concentration levels of the antibiotic present in a wastewater matrix leads to a shift in the population in favor of the sensitive subtype, presumably on account of triggering protective biochemical processes in the resistant mutant, which confer no selective advantage since the sensitive strain remains unaffected in this concentration range.

Occurrence and fate of antibiotics, antibiotic resistant genes (ARGs) and antibiotic resistant bacteria (ARB) in municipal wastewater treatment plant: An overview.

The occurrence and fate of antibiotics and antibiotic resistant genes (ARGs) and antibiotic resistant bacteria (ARB) in Municipal Wastewater Treatment Plants (WWTPs) worldwide were reviewed. The prevalence of antibiotics in WWTPs among different periods (1999-2009 and 2010-2019) and geographical areas (Europe, America, Asia and Africa) was summarized, analyzed and evaluated. The classes of macrolides (clarithromycin, erythromycin/erythromycin-HO, azithromycin, roxithromycin), sulfonamides (sulfamethoxazole), trimethoprim, quinolones (ofloxacin, ciprofloxacin, norfloxacin) and tetracyclines (tetracycline) were the antibiotics most frequently detected, while bla (bla, bla), sul (sul1, sul2), tet (tetO, tetQ, tetW) and ermB genes were the ARGs commonly reported in WWTPs.

Rate constants of carbonate radical anion reactions with molecules of environmental interest in aqueous solution: A review.

The rate constants of carbonate radical anion (CO) reaction with organic molecules, mainly of environmental interest, were collected from the literature and structure effects were discussed together with methods of rate constant determination and reaction mechanisms. These rate constants are essential for modelling chemical processes taking place with participation of reactive radicals in the environment determining the persistence of certain toxic compounds. The rate constants span over a very wide range from 10 to 10 mol dm s, but, even the highest values are smaller by a factor of 2-5 as the diffusion controlled limit.

Rate constants of sulfate radical anion reactions with organic molecules: A review.

The rate constants of sulfate radical anion reaction (k) with about 230 organic molecules of environmental interest are tabulated and discussed, together with both the methods of rate constant determinations and the reaction mechanisms. k's were collected from the original publications. The highest values in the ∼10 M s range are published for aromatic molecules.

Radiolysis of sulfonamide antibiotics in aqueous solution: Degradation efficiency and assessment of antibacterial activity, toxicity and biodegradability of products.

Numerous studies have been published on the radiolysis of sulfonamide antibiotic solutions but little effort has been made to monitor the biological properties of degradation products. A complex approach should also clarify the changes in antibacterial activity and biodegradability, besides the usual screening of toxicity. To fill this gap, the ionizing radiation induced degradation of four sulfonamide antibiotics was investigated in dilute aqueous solutions, with emphasis on the biological assessment of decomposition products.

Applicability evaluation of advanced processes for elimination of neurophysiological activity of antidepressant fluoxetine.

Presence of the antidepressant fluoxetine in different water bodies has raised significant concerns due to its detrimental effects on non-targeted organisms, especially on fish. When seeking for an appropriate technology able to remove fluoxetine residue from a complex water matrix, special attention needs to be paid to the elimination of the neurophysiological activity that eventually lies behind the noxious effects of the parent compound. Our aim was to probe the applicability of advanced oxidation techniques for this purpose using in situ generated free radical system based on OH-initiated peroxyl radical-mediated processes.

Synthesis of carboxymethylcellulose/starch superabsorbent hydrogels by gamma-irradiation.

Background: Superabsorbent hydrogels show a large potential in a wide array of applications due to their unique properties. Carboxymethylcellulose (CMC) is a commercially available water-soluble cellulose derivative of major interest in the hydrogel synthesis. High-energy irradiation allows the chemical crosslinking without the use of crosslinking agents, while the introduction of other natural or synthetic polymers offers a convenient way to modify the gels.

Synthesis and characterization of superabsorbent hydrogels based on hydroxyethylcellulose and acrylic acid.

Hydroxyethylcellulose (HEC)/acrylic acid (AAc) copolymer gels with superabsorbent properties were synthesized from aqueous solutions by radiation-initiated crosslinking. The effect of the acrylic acid content on gel properties was determined at different synthesis conditions. The partial replacement of the cellulose derivative with acrylic acid improved the gelation, leading to higher gel fraction and lower water uptake even in very low concentrations (1-5%).

On the complex OH/O-induced free radical chemistry of arylalkylamines with special emphasis on the contribution of the alkylamine side chain.

A full account of the OH-induced free radical chemistry of an arylalkylamine is given taking all the possible reaction pathways quantitatively into consideration. Such knowledge is indispensable when the alkylamine side chain plays a crucial role in biological activity. The fundamental reactions are investigated on the model compound N-methyl-3-phenypropylamine (MPPA), and extended to its biologically active analog, to the antidepressant fluoxetine (FLX).

Radiation Induced Degradation of Organic Pollutants in Waters and Wastewaters.

In water treatment by ionizing radiation, and also in other advanced oxidation processes, the main goal is to destroy, or at least to deactivate harmful water contaminants: pharmaceutical compounds, pesticides, surfactants, health-care products, etc. The chemical transformations are mainly initiated by hydroxyl radicals, and the reactions of the formed carbon centered radicals with dissolved oxygen basically determine the rate of oxidation. The concentration of the target compounds is generally very low as compared to the concentration of such natural 'impurities' as chloride and carbonate/bicarbonate ions or the dissolved humic substances (generally referred to as dissolved organic carbon), which consume the majority of the hydroxyl radicals.

Change in hydrophilicity of penicillins during advanced oxidation by radiolytically generated OH compromises the elimination of selective pressure on bacterial strains.

Advanced oxidation processes are promising technologies for removal of antibiotic residues from wastewater in terms of their high efficacy. However, recent studies have reported the remaining antibacterial activity of the products at early-stages of treatment. The present study investigates the effect of such products of model β-lactams (amoxicillin, ampicillin, cloxacillin) on bacteria introducing structure-based, and biological approaches involving Gram-positive and Gram-negative bacterial strains.

One-Electron Reduction of Penicillins in Relation to the Oxidative Stress Phenomenon.

Certain bactericidal antibiotics target mitochondrial components and, due to the leakage of electrons from the electron transport chain, one-electron reduction might occur that can lead to intermediates passing the electron to suitable acceptors. This study aimed at investigating the one-electron reduction mechanism of selected penicillin derivatives using pulse radiolysis techniques. Penicillins can accommodate the electron on each of their carbonyl carbon.

Drugs with susceptible sites for free radical induced oxidative transformations: the case of a penicillin.

Penicillins, as bactericidal antibiotics, have been widely used to treat infections for several decades. Their structure contains both aromatic and thioether moieties susceptible to free radical oxidation. The (•)OH induced oxidation mechanism of amoxicillin was investigated by pulse radiolysis techniques and by final product analysis performed after steady-state γ-irradiation.

Ionizing radiation induced degradation of diuron in dilute aqueous solution.

Background: Cutting edge technologies based on Advanced Oxidation Processes (AOP) are under development for the elimination of highly persistent organic molecules (like pesticides) from water matrices. Among them, ionizing radiation treatment represents a promising technology that requires no additives and can be easily adapted to an industrial scale. In these processes several reactive species are produced, mainly powerful oxidizing radicals inducing the degradation.

Analytical approaches to the OH radical induced degradation of sulfonamide antibiotics in dilute aqueous solutions.

By combining a large variety of analytical techniques this study aimed at elaborating methods to follow up the degradation of sulfonamides in an advanced oxidation process (AOP): irradiation with ionizing radiation in dilute aqueous solution. In this process, besides other radicals, hydroxyl radicals are produced. As pulse radiolysis experiments show the basic initial reaction is hydroxyl radical addition to the benzene ring, forming cyclohexadienyl radical intermediates.

Hydroxyl radical-induced degradation of fenuron in pulse and gamma radiolysis: kinetics and product analysis.

Radiolytic reactions of phenylureas were studied in detail with fenuron model compound in dilute aqueous solutions using pulse radiolysis for detection of the intermediates, gamma radiolysis with UV-Vis and HPLC-MS techniques for analysis of the final products. The kinetics of oxidation was followed by COD, TOC and toxicity measurements. During radiolysis of aerated solutions hydroxyl radical ((•)OH), eaq (-), H(•) and O2 (•-)/HO2 (•) reactive intermediates are produced, the degradation of solute takes place practically entirely through (•)OH reactions.