Presence Of Scavengers Research Articles

Determination of Superoxide Radical Scavenging Activity and Total Antioxidant Capacity by Modified DMPD Method

Among the reactive oxygen species, Superoxide radicals can produce dangerous species that cause lipid peroxidation. Therefore, the determination and scavenging of superoxide radicals is critical. Our study is based on the interaction of the superoxide radical produced from the β-Nicotinamide adenine dinucleotide reduced disodium salt hydrate and phenazine methosulfate (NADH-PMS) system with N, N-dimethyl-p-phenylenediamine dihydrochloride (DMPD) to form the pink colored DMPD-quinone (DMPDQ) radical. In the presence of scavengers with superoxide radical scavenging activity (antioxidants, herbal teas) the color intensity decreases due to reduced DMPDQ radical production. The absorbance of the colored reference solution and the sample solution containing the radical scavenger was measured at 552 nm. The difference in absorbance (ΔA) between the reference solution and the sample solution was found. ΔA is proportional to the scavenger concentration. In the study, the superoxide radical scavenging effect of trolox (TR) and different AOXs was investigated. The superoxide radical scavenging effect of three different herbal tea infusion solutions was measured with this method. From the graph drawn between herbal tea concentrations and percentage inhibition values, 50% inhibition (EC50) values of herbal teas were found. EC50 method values were compared with the EC50 values of the nitroblue tetrazolium (NBT) and the 2,2'-azino-bis(3-etilbenzotiyazolin-6-sülfonik asit (ABTS) method. In addition, ABTS, cupric reducing antioxidant capacity (CUPRAC), and this study total antioxidant capacity (TAC) values of herbal tea infusions were calculated and compared.

Electroplating wastewater treatment containing heavy metals and COD using batch and once through continuous electro-oxidation process

ABSTRACT The rapidly growing electroplating industry has led to the discharge of large amounts of wastewater containing heavy metals and organic acids. Innovative techniques are required for the efficient and effective treatment of such effluents. The present work explored electroplating wastewater treatment through new TiO2-NTs/GO/SnO2 electrodes by electro-oxidation (EO) in batch and once-through continuous system. A new electrode with excellent oxidation ability was successfully fabricated by introducing a SnO2 outer layer through a simple anodization method. Moreover, a response surface methodology (RSM)-Box-Behnken design (BBD) model was used to optimize the responses. The effects of operating conditions, i.e. pH (3–9), current (0.1–0.9 A), and time (30–180 min), on the efficiency of the process were investigated. With optimum conditions, 97.1% Cu, 95.7% Zn, 91.2% COD degradation, and 7.32 kWh/m3 energy consumption were achieved. A once-through continuous setup working at a flow rate of 5–20 mL/min was performed under optimal conditions. The electrodes remained durable even after 50 cycles. The contribution of several reactive species to the EO was examined in the presence of scavengers. Moreover, according to a toxicity study, EO can detoxify electroplating effluents. Hence, this EO process, which is low-cost and highly efficient, can be applied to the treatment of electroplating wastewater.

Modelling ozone disinfection of secondary effluents in presence of scavengers and metal catalyst: Synergistic effect and regrowth

The variation in the matrix composition can lead to the use of inadequate oxidant dose and disturb a correct ozone treatment. The aim of this study was to model the ozone disinfection process of secondary effluents in presence of carbonate and nitrate using metal ozonation catalysts. The biological indicator used was the Escherichia coli. The ROH,O3 concept was applied to quantify and compare the E. coli inactivation by the radical pathway. The metals Fe and Zn caused a significative improvement on ROH values (p < 0.05) even in the presence of the •OH radical scavengers (carbonate and nitrate). The modelling results based on ROH values demonstrate that E. coli inactivation can be predicted satisfactory (R2 > 0.94–0.99), being a useful tool for the generalized prediction of disinfection by ozone. The presence of metals inhibited significantly bacterial regrowth (p < 0.05) even in the scavengers presence.

Photocatalytic Applications of SnO2 and Ag2O-Decorated SnO2 Coatings on Cement Paste

Recently, the production of new photocatalytic materials has attracted considerable attention as a promising strategy to mitigate anthropogenic environmental degradation. In this study, cement paste composites (water/cement ratio = 0.5) were prepared using a coating based on nanoparticles of SnO2 (SnO2/cement paste) and SnO2 decorated with Ag2O (Ag2O-decorated SnO2/cement paste) for photocatalytic applications. These coatings were prepared in this study by using the hydrothermal method as the strategy. Thus, photocatalyst efficiency was evaluated through the degradation of methylene blue (MB) and methyl red (MR) as cationic and anionic dyes, respectively, and the simultaneous degradation of MB/MR (1:1 v/v) dyes. Moreover, the photocatalytic mechanism was investigated in the presence of scavengers. Notably, an increase in pH in the range of 2–6 resulted in selective degradation of the MB/MR dye mixtures. Overall, the photocatalytic performance of these materials provides a novel platform technology focused on advanced civil engineering applications, which consequently facilitates the mitigation of various environmental problems.

Unlocking the synergistic potential of peanut shell derived activated carbon-doped TiO2 for highly efficient photocatalytic removal of organic dye under visible light irradiation

The goal of this study was to examine the photocatalytic performance of peanut shell-derived activated carbon (AC) doped TiO2 materials (AC@TiO2) for the treatment of wastewater through degradation of Rhodamine B (RhB) dye. The synthesized materials underwent thorough characterization using XRD, SEM, EDX, UV–Visible spectroscopy, PL spectroscopy, and FTIR spectroscopy to assess their crystallinity, surface morphology, bandgap energy, and functional groups. 2% AC@TiO2 exhibited exceptional photocatalytic performance with a maximum degradation efficiency of 89.9% and a high-rate constant (k) value of 0.0401 min−1, attributed to increased surface area and reduced bandgap. The reaction rate increased with temperature up to 35 °C, but then declined. 2% AC@TiO2 exhibited high degradation efficiency and reusability for six cycles. The optimal pH for maximum efficiency was 7.4. Higher initial dye concentration and the presence of scavengers (BA, OA, Cl) reduced degradation efficiency. These photocatalysts proved highly effective for dye degradation in wastewater treatment.

Dodecahedron CsPbBr3 Perovskite Nanocrystals Enable Facile Harvesting of Hot Electrons and Holes

This Letter reports the facile harvesting of hot carriers (HCs) in a composite of 12-faceted dodecahedron CsPbBr3 nanocrystal (NC) and a scavenger molecule. We recorded ∼3.3 × 1011 s-1 HC cooling rate in NC when excited with ∼1.4 times the band gap energy (Eg), increasing to >3 × 1012 s-1 in the presence of scavengers at high concentration due to the HC extractions. Since the observed intrinsic charge transfer rate (∼1.7 × 1012 s-1) in our NC-scavenger complex is about an order of magnitude higher than the HC cooling rate (∼3.3 × 1011 s-1), carriers are harvested before their cooling. Further, a fluorescence correlation spectroscopy study reveals NC tends to form a quasi-stable complex with a scavenger molecule, ensuring charge transfer completed (τct ≈ 0.6 ps) much before the complex breaks apart (>600 μs). The overall results of our study highlight the promise shown by 12-faceted NCs and their implications in modern applications, including hot carrier solar cells.

Modeling of scavenging systems in water radiolysis with Geant4-DNA

PurposeThis paper presents the capabilities of the Geant4-DNA Monte Carlo toolkit to simulate water radiolysis with scavengers using the step-by-step (SBS) or the independent reaction times (IRT) methods. It features two examples of application areas: (1) computing the escape yield of H2O2 following a 60Co γ-irradiation and (2) computing the oxygen depletion in water irradiated with 1 MeV electrons. MethodsTo ease the implementation of the chemical stage in Geant4-DNA, we developed a user interface that helps define the chemical reactions and set the concentration of scavengers. The first application area example required two computational steps to perform water radiolysis using NO2- and NO3- as scavengers and a 60Co irradiation. The oxygen depletion computation technique for the second application area example consisted of simulating track segments of 1 MeV electrons and determining the radio-induced loss and gain of oxygen molecules. ResultsThe production of H2O2 under variable scavenging levels is consistent with the literature; the mean relative difference between the SBS and IRT methods is 7.2 % ± 0.5 %. For the oxygen depletion 1 µs post-irradiation, the mean relative difference between both methods is equal to 9.8 % ± 0.3 %. The results in the microsecond scale depend on the initial partial pressure of oxygen in water. In addition, the computed oxygen depletions agree well with the literature. ConclusionsThe Geant4-DNA toolkit makes it possible to simulate water radiolysis in the presence of scavengers. This feature offers perspectives in radiobiology, with the possibility of simulating cell-relevant scavenging mechanisms.

Rapid and facile synthesis of Z-scheme ZnO/g-C3N4 heterostructure as efficient visible light-driven photocatalysts for dye degradation and hydrogen evolution reaction

The coupling of two-different semiconductors which are photocatalytically active is gaining popularity in recent years because the heterojunction can decrease the rate of recombination of photoexcited electron-hole pairs and enhance the photocatalytic activity. In the current work, ZnO/g-C3N4 heterojunction hybrids have been generated by simple solution mixing of the dispersed ZnO and graphitic carbon nitride (g-C3N4) nanoparticles. The ZnO/g-C3N4 composite under visible light exhibits 91.5% degradation of the methylene blue (MB) dye in 120 min and also demonstrated excellent cyclic stability. Mechanistic studies and dye degradation experiments carried out in the presence of scavengers (ascorbic acid, potassium dichromate and ammonium oxalate) revealed that the generated superoxide radical (O2•‒) and hydroxyl radicals play a crucial role in MB dye degradation using ZnO/g-C3N4 as a photocatalyst. Further, the ZnO/g-C3N4 composite exhibits improved hydrogen evolution reaction (HER) activity (1358 μmol g-1 h-1) compared to the pristine ZnO nanoparticles (545 μmol g-1 h-1) and g-C3N4 (238 μmol g-1 h-1). The superior HER activity of the hybrid is ascribed to the increased charge-transfer rate owing to the better interfacial contact between the heterocomponents. Secondly, the nanoparticle nature of ZnO and g-C3N4 heterocomponents provides more exposed edge sites and thereby gives significant photocatalytic activity.

Dynamics and optimal harvesting of prey–predator in a polluted environment in the presence of scavenger and pollution control

This paper is concerned with the dynamics and optimal harvesting of a prey–predator system in a polluted environment in the presence of scavengers and pollution control. Toxicants, released from external sources and the dead bodies of prey and predators, pollute the environment, which affects the growth of both prey and predators, resulting in a decline in the economic revenue from harvest. We assume that scavengers reduce pollution by consuming dead bodies. Further, we consider pollution reduction through depollution efforts as an alternative to enhancing revenue. We propose and analyze a prey–predator–pollutant model and study the optimal harvesting problem. We investigate the persistence of the ecosystem, and we solve the optimal harvest problem using Pontryagin’s maximum principle. The results indicate that uncontrolled prey harvesting and a high rate of pollution drive the system toward the extinction of both species. A moderate amount of pollution and the reasonable harvest efforts allow the system to persist. The optimal harvest strategy highlights that investing in pollution reduction enhances the persistence of the system as well as economic revenue. Numerical examples demonstrate the significant outcomes of the study.

Novel C-dots/titanate nanotubular hybrid materials with enhanced optical and photocatalytic properties

Advanced nanomaterials with enhanced optical and photocatalytic properties for the photodegradation of organic pollutants, in particular pharmaceuticals and personal care products (PPCPs), were successfully prepared by a swift one-pot synthesis. Nanostructured materials were synthesized through an integrated hydrothermal procedure which generates titanate nanotubes (TNTs) with different carbon dots (C-dots) contents, from an amorphous titanium oxide-based source and cork industry wastewaters (CIWW) as carbon source. Their structural, microstructural, morphological, and optical properties were studied by XRD, TEM, XPS, UV-Vis diffuse reflectance and photoluminescence spectroscopies. As aimed, the hybrid C-dots/TNT nanomaterials extend their light absorption towards the red, in comparison to pristine TNT, prompting them for a more efficient use of light in photocatalysis by widening the TNT energy uptake range. The decrease of bandgap energy with increasing sample’s C-dots content seems to be originated from energy intermediate states formed within the TNTs’ forbidden band resulting from Ti−O−C bonds established between the TNTs and the C-dots that form tails of states.The as-synthesized C-dots/TNT samples were tested in the photodegradation of caffeine as a pollutant model for PPCPs. Rewarding results were obtained, with the hybrid C-dots/TNT nanomaterials showing significant enhanced photocatalytic ability toward caffeine degradation in comparison to pristine TNTs. Photocatalysis assays in the presence of scavengers and/or in the absence of oxygen were also performed aiming to characterize the most reactive species formed during the semiconductor photo-activation process and thus assessing to possible reactive pathways underpinning the photocatalytic activity of the hybrid C-dots/TNT nanomaterials.

Fabrication and photocatalytic evaluation of functionalized chitosan decorated vanadium pentoxide nano-adsorbents for water remediation

The narrow bandgap and rapid interconversion of the oxidation states of vanadium in vanadium pentoxide makes it an extensively used photocatalyst for the degradation of organic pollutant but inadequate response towards visible spectrum and low quantum yield limits its activity. Here, functionalized chitosan decorated vanadium pentoxide nano-adsorbents are fabricated that exhibited significant sensitivity to visible light absorption and shows more efficient quantum yield by the transformation of absorbed light into radiated light. Further, they were used in the photodegradation of methylene blue under natural conditions. The characterization results demonstrated the presence of chitosan and its derivatives over the surface of nanoparticles. Decorated vanadium pentoxide nano-adsorbents exhibited enhanced surface area and better catalytic properties which increases the photodegradation by lowering the recombination rate of charge and hole. Among the decorated nano-adsorbents, chitosan-anisaldehyde decorated vanadium pentoxide (CHVD3) possessed wedge-shaped pore that favoured the photocatalytic degradation of methylene blue followed by others synthesized nanoparticles. The degradation rate constant and half life time for CHVD3 were 3.84 × 10−3 min−1 and 18.07 min respectively. Major species responsible for the degradation and the mechanism has been elucidated by taking into consideration the degradation process in absence and presence of various scavengers. The degradation performance of CHVD3 was severely affected, reducing from 92% to 36% in the presence of the scavenger, where *O2− act as a major active species in degradation process.

Degradation of phenol using Fe(II)-activated CaO2: effect of ball-milled activated carbon (ACBM) addition

In-situ chemical oxidation (ISCO) based on peroxide activation is one of the most promising technologies for removing organic contaminants from natural groundwater (NGW). However, use of the most common form of hydrogen peroxide (H2O2) is limited owing to its significantly rapid reaction rate and heat generation. Therefore, in the present study, the activation of calcium peroxide (CaO2), a slow H2O2 releasing agent, by Fe(II) was proposed (CaO2/Fe(II)), and the phenol degradation mechanisms and feasibility of NGW remediation were investigated. The optimum molar ratio of [phenol]/[CaO2]/[Fe(II)] (phenol = 0.5 mM) was 1/10/10, resulting in 87.0–92.5% phenol removal within 120 min under a broad initial pH range of 3–9. HCO3−, PO43−, and humic acid significantly inhibited degradation, whereas the effects of Cl−, NO3−, and SO42− were negligible. Reactive oxygen species (ROS) were identified based on the results of phenol degradation in the presence of scavengers and electron spin resonance (ESR) spectroscopy, which demonstrated that 1O2 played the dominant role, supported by •OH, in CaO2/Fe(II). Phenol removal in NGW (67.81%) was less than that in distilled and deionized water (DIW, 92.5%) at a [phenol]/[CaO2]/[Fe(II)] ratio of 1/10/10. However, phenol removal was significantly improved (∼100%) by increasing the CaO2 and Fe(II) doses to 1/20/20–40. Furthermore, when 125–250 mg L−1 of ball-milled activated carbon (ACBM) was added (CaO2/Fe(II)-ACBM), phenol removal was enhanced from 67.81% to 90.94–100% in the NGW. CaO2/Fe(II)-ACBM exhibited higher total organic carbon (TOC) removal than CaO2/Fe(II). In addition, no notable by-products were detected using CaO2/Fe(II)-ACBM, whereas the polymerisation products of hydroxylated and/or ring-cleaved compounds, that is, aconitic acid, gallocatechin, and 10-hydroxyaloin, were found in the reaction with CaO2/Fe(II). These results strongly suggest that CaO2/Fe(II)-ACBM is highly promising for groundwater remediation, minimizing degradation byproducts and the adverse effects caused by the NGW components.

Abstract LB066: Targeting low density lipoprotein receptors in the pancreatic adenocarcinoma

Abstract Introduction: Pancreatic ductal adenocarcinoma (PDAC) is a highly aggressive malignancy with a poor 5-year overall survival rate at all stages of disease (7-10%). The immunohistochemistry of pancreatic cancer tissue has shown a significantly higher level of positive LDLR (low-density lipoprotein receptor) staining in primary tumors compared to the normal adjacent pancreas. LDLR is overexpressed in the epithelial pancreatic adenocarcinoma, irrespectively of tumor size, stage, and aggressiveness. The objective of this study was to determine the LDLR-targeting properties of 68Ga-labeled peptide conjugate, 68Ga-RMX-VH, in pancreatic adenocarcinoma cell lines. Methods: RMX-VH peptide conjugate (25-50μg) was labeled with 68Ga (50-100mCi, ITM Germany) in mild conditions in the presence of scavenger, sodium ascorbate (8mg/ml). The cellular uptake and competition studies of the radiotracer (15μCi/well) were completed in multiple pancreatic adenocarcinoma cell lines and in vivo in PDAC xenografts generated in athymic nude mice. The PET/CT images were acquired using a G4 PET/X-ray camera (Sofie Biosciences; 10min/scan) at 1h, 2h post-injection. This study determined in vivo and in vitro time-dependent accumulation of this agent in LDLR-overexpressing pancreatic adenocarcinoma cells. Results: 68Ga-RMX-VH was synthesized with higher than 95% radiochemical purity. The radiotracer was incubated in pancreatic adenocarcinoma cell lines for 1h and has shown the highest uptake in HPAF-II (6.7%ID/mg) and BxPC-3 (5.3 %ID/mg) and MiaPaCa2 (4.75 %ID/mg), respectively. Western blot showed a variable level of LDLR overexpression in human pancreatic cancer cells. The microPET imaging studies confirmed rapid accumulation and retention of radiotracer in the tumor (1.18 %ID/g) and elimination through kidneys (4.5 %ID/g) and bladder (SUV ratio of tumor to kidneys: 0.21). These results correlate with previously reported retention of the agent in Pk4a pancreatic adenocarcinoma. Conclusions: RMX-VH has the potential to evaluate the role of LDL receptors in pancreatic adenocarcinoma. We have initiated the exploratory clinical study of this agent in LDLR-overexpressing solid tumors, including pancreatic adenocarcinoma. Citation Format: Leo Flores, Xuewei Qu, Cedric Malicet, Pascaline Lecorche, Ebrahim Delpassand, Jamal Temsamani, Izabela Tworowska. Targeting low density lipoprotein receptors in the pancreatic adenocarcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr LB066.

Investigation of the Degradation Behavior of Cyclophosphamide by Catalytic Ozonation Based on Mg(OH)2

Metal hydroxides, owing to their catalytic active sites for the decomposition of O3 to Reactive Oxygen Species (ROS), have been adapted for catalytic ozonation of micropollutants in wastewater. In this study, commercial Mg (OH)2 was used for the degradation of cyclophosphamide (CYP) by ozone. The crystal phase was confirmed by X-ray powder Diffraction (XRD). Percent degradation of 10 ppm CYP after 30 min by O3 and Mg (OH)2/O3 was 56 and 93, respectively, suggesting enhanced decomposition of O3 to ROS by the catalyst. The presence of ROS was further confirmed using pCBA as a probe, which showed that the concentration of ROS was eight times higher in the presence of Mg (OH)2/O3 than O3 alone. Catalytic ozonation experiments in the presence of scavengers showed that OH· radicals play a significant role in the degradation of CYP. The catalyst was found to be reusable for at least three cycles without significant loss in degradation efficiency. To study the compatibility of Mg (OH)2 for wastewater treatment applications, synthetic effluent was spiked with CYP and subjected to ozonation by Mg(OH)2/O3. The TOC of CYP before and after the treatment showed that Mg (OH)2/O3 not only degrades CYP but also mineralizes to a certain extent unlike O3 alone.

Hybrid Biochar/Ceria Nanomaterials: Synthesis, Characterization and Activity Assessment for the Persulfate-Induced Degradation of Antibiotic Sulfamethoxazole.

Biochar from spent malt rootlets was employed as the template to synthesize hybrid biochar-ceria materials through a wet impregnation method. The materials were tested for the activation of persulfate (SPS) and subsequent degradation of sulfamethoxazole (SMX), a representative antibiotic, in various matrices. Different calcination temperatures in the range 300–500 °C were employed and the resulting materials were characterized by means of N2 adsorption and potentiometric mass titration as well as TGA, XRD, SEM, FTIR, DRS, and Raman spectroscopy. Calcination temperature affects the biochar content and the physicochemical properties of the hybrid materials, which were tested for the degradation of 500 μg L−1 SMX with SPS (in the range 200–500 mg L−1) in various matrices including ultrapure water (UPW), bottled water, wastewater, and UPW spiked with bicarbonate, chloride, or humic acid. Materials calcined at 300–350 °C, with a surface area of ca. 120 m2 g−1, were the most active, yielding ca. 65% SMX degradation after 120 min of reaction in UPW; materials calcined at higher temperatures as well as bare biochar were less active. Degradation decreased with increasing matrix complexity due to the interactions amongst the surface, the contaminant, and the oxidant. Experiments in the presence of scavengers (i.e., methanol, t-butanol, and sodium azide) revealed that sulfate and hydroxyl radicals as well as singlet oxygen were the main oxidative species.

Social Life of Scavengers in The Sukawinatan Landfill in Palembang, Indonesia

Scavengers is one of the marginal communities in urban areas, including in Palembang City. The presence of scavengers in this city is illegal, because it is considered to interfere with the activities of the management, which is authorized to manage waste at the Sukawinatan Landfill, Palembang. This case study research is concerned to discern at the social life, threats and opportunities of the scavenger community in Sukawinatan Landfill. This study is conducted to determine strategic steps for improving the scavengers' life in the future. This study is carried out qualitatively. Therefore, in-depth interviews, observation and documentation are used as a way of collecting data. In-depth interviews were conducted to scavengers, informal leader and also the stakeholders. Data is analyzed through reduction, data presentation and making conclusion process. The results of the study indicate that the physical environment of the scavenger community is bad. Meanwhile, according to the in-depth interview and literatures review, some aspects of the social life of scavengers, actually worsen their quality of life, such as: drugs and low education. Nevertheless, there is hope that can be maximized to improve the quality of life of this community, such as: communality and kinship. The description of the scavenger social life can be used as a basis in formulating appropriate interventions for improving the quality of life in this scavenger community.

Pd single-atom decorated CdS nanocatalyst for highly efficient overall water splitting under simulated solar light

Solar-induced overall water splitting to produce hydrogen is inspiring towards energy sustainability, but it is also formidable due to its limited efficiency seriously hindering its scale up for practical application. CdS is an important transition metal sulfide with low-work-function. However, its photostability is often deteriorated due to photocorrosion influence. To overcome this issue, single-atom Pd was employed here to decorate CdS to form a CdS-Pd nanocatalyst through a simple and controllable photoinduced reduction strategy. The synergetic semiconductor (CdS)-metal (Pd) interaction promotes the fast bulk-to-surface electron migration, thereby the resultant CdS-Pd (3.83‰) nanocatalyst shows considerable structural stability and dramatically improved solar-induced HER activity in overall water splitting, about 110-fold higher than that of pristine CdS. Meanwhile, high apparent quantum yields (AQYs) of 4.47%/1.81% and 33.92%/27.49% were respectively achieved with this decorated nanocatalyst under the light of 420 nm/500 nm in absence and presence of scavenger, demonstrating the high-efficiency under broadband light illumination. Density functional theory (DFT) calculation supports that the easy formation of H* intermediates on the decorated nanocatalyst due to low energy barriers accounts for the internal promoted mechanism for hydrogen production. This study provides important insight to gain stable CdS-based photocatalysts for high-efficient hydrogen production by overall water splitting.

Quantification of reactive species generated in pulsed electrical discharge plasma reactor and its application for 17α-ethinylestradiol degradation in different water matrices

The degradation of a synthetic female hormone, a typical endocrine disruptor i.e., 17α-ethinylestradiol (EE2), in water was studied using pulsed electrical discharge plasma reactor with multiple pin-plate electrode configuration at atmospheric pressure and room temperature. Various liquid phase reactive oxygen species generated in the system were also quantified to understand the scenario in depth. The effect of different operating parameters such as initial concentration of EE2, solution pH, presence of scavenger, purging of air and reactor overhead gases, different water matrices, humic acid (HA) and different ions on the removal kinetics of the reactor was probed in detail. The complete removal of EE2 was achieved in 15 sec of treatment time at concentration of 100 µg L-1 and the corresponding electrical energy per order and direct electricity cost were 2.43 kWh m−3 and ~ 0.16 US$ m−3, respectively. The plausible degradation pathways of EE2 in the reactor have also been proposed through the identification of intermediates. Further, algal acute toxicity test of all the treated samples revealed complete removal of toxicity. Thus, these findings demonstrated the promise of non-thermal pulsed plasma technology for degradation of EE2 at environmentally relevant concentrations.

TOPAS-nBio validation for simulating water radiolysis and DNA damage under low-LET irradiation

The chemical stage of the Monte Carlo track-structure simulation code Geant4-DNA has been revised and validated. The root-mean-square (RMS) empirical parameter that dictates the displacement of water molecules after an ionization and excitation event in Geant4-DNA has been shortened to better fit experimental data. The pre-defined dissociation channels and branching ratios were not modified, but the reaction rate coefficients for simulating the chemical stage of water radiolysis were updated. The evaluation of Geant4-DNA was accomplished with TOPAS-nBio. For that, we compared predicted time-dependent G values in pure liquid water for ·OH, e– aq, and H2 with published experimental data. For H2O2 and H·, simulation of added scavengers at different concentrations resulted in better agreement with measurements. In addition, DNA geometry information was integrated with chemistry simulation in TOPAS-nBio to realize reactions between radiolytic chemical species and DNA. This was used in the estimation of the yield of single-strand breaks (SSB) induced by 137Cs γ-ray radiolysis of supercoiled pUC18 plasmids dissolved in aerated solutions containing DMSO. The efficiency of SSB induction by reaction between radiolytic species and DNA used in the simulation was chosen to provide the best agreement with published measurements. An RMS displacement of 1.24 nm provided agreement with measured data within experimental uncertainties for time-dependent G values and under the presence of scavengers. SSB efficiencies of 24% and 0.5% for ·OH and H·, respectively, led to an overall agreement of TOPAS-nBio results within experimental uncertainties. The efficiencies obtained agreed with values obtained with published non-homogeneous kinetic model and step-by-step Monte Carlo simulations but disagreed by 12% with published direct measurements. Improvement of the spatial resolution of the DNA damage model might mitigate such disagreement. In conclusion, with these improvements, Geant4-DNA/TOPAS-nBio provides a fast, accurate, and user-friendly tool for simulating DNA damage under low linear energy transfer irradiation.

Insights into remediation of acid cracked intensive real olive mill wastewater by electro-Fenton process in the presence of per-sulphate

ABSTRACT Olive mill wastewaters (OMW) have complicated pollutants that are hard to treat as it contains high concentrations of refractory and toxic compounds, which is looking for practicable and economical treatment options. In this work, the remediation of OMW was conducted using the electro-Fenton process (EFP) with iron electrodes in the presence of per-sulphate (PS) to chemical oxygen demand (COD) and total phenol (TP) reduction after acid cracking step. The system performance were COD, Colour, and TP per cent removal while initial pH, voltage, reaction time, H2O2 dosage, electrical conductivity (EC) and dosage of PS were independent variables. Acid cracking of wastewater in pH 2.5 was used to reduce disturbing parameters to provide suitable condition for reaction. Acid cracking leads to mean removal of turbidity, COD, TP, colour up to 80%, 18%, 17% and 30%, respectively. It was found that parameters such as H2O2, pH, reaction time, voltage and EC in an optimum value increase the process efficiency. The optimum condition by EFP was obtained at a pH 2, H2O2 0.2 M, voltage 10 V and conductivity of 11,000 µS/cm for removing over 70% of COD and TP at 60 min. However, after adding low concentration of PS there was not any enhance in the efficiency of COD and TP due to plenty presence of scavengers in OMW. It could be concluded that the remediation of pretreated OMW with acid cracking using EFP may be considered as reliable pretreatment method with further modifications.