Presence Of Organic Contaminants Research Articles

Superoxide radicals mediated by high-spin Fe catalysis for organic wastewater treatment

Water resources are indispensable basic resources and important environmental carriers; the presence of organic contaminants in wastewater poses considerable risks to the health of both humans and ecosystems. Although the Fenton-like reactions using H2O2 as the oxidant to destroy organic pollutants are attractive, there are still challenges in improving reaction activity under neutral or even alkaline conditions. Herein, we designed a H2O2 activation pathway with O2•- as the main active species and elucidated that the spin interaction between Fe sites and coordinated O atoms effectively promotes the generation of the key intermediate Fe-*OOH. Furthermore, we successfully captured and analyzed the Fe-*OOH intermediate by in situ Raman spectroscopy. When applying FBOB to a continuous-flow reactor, CIP removal efficiency remained at around 90% within 600 min of continuous operation, achieving excellent efficiency, stability, and pH tolerance in removing pollutants.

Structural investigation, photoluminescence, and antibacterial properties of purified palygorskite impregnated with α-Ag2WO4 microcrystals

The presence of organic contaminants in aquatic environments, such as antibiotics, induces the proliferation of resistant pathogens, giving rise to the need to develop new materials with antimicrobial action. Therefore, in this work, we report new results to purified Palygorskite (P-Pal) clay with a surface impregnated with alpha-silver tungstate (α-Ag2WO4) microcrystals abbreviated as AWO, and its structural, photoluminescence (PL) and antibacterial investigation for inactivation of gram-negative (Escherichia coli) and gram-positive (Staphylococcus aureus) bacterial strains at concentrations of P-Pal/x%/AWO from x = 4–32%. X-ray diffraction patterns, Rietveld refinement data, and Fourier transform infrared spectroscopy confirmed that the P-Pal is composed of two crystal phases (Mg2.074Al1.026) (Si4O10.48)2(OH)2(H2O)10.68 with an orthorhombic structure and α-SiO2 with a rhombohedral structure; already the AWO microcrystals are single-phase with an orthorhombic structure and their vibrational modes. Ultraviolet–visible spectroscopy shows an increase in the Egap values for mixed systems compared to the isolated materials, indicating a synergistic interaction between the energy levels of both materials. Field emission scanning electron microscopy images display the presence of several elongated fibers and hexagonal crystals in the P-Pal clay and rod-like AWO microcrystals. In contrast, P-Pal clay/AWO microcrystals exhibit the presence of all three crystal shapes. Photoluminescence spectra show a high emission for the P-Pal clay/4% AWO microcrystals, indicating a better energy band gap synergistic. Finally, the microbiological tests show that as the proportion of AWO crystals on the P-Pal clay surface increases, there is a rise in antibacterial activity.

A CFD Analysis of the Desalination Performance of Ceramic-Based Hollow Fiber Membranes in Direct Contact Membrane Distillation

In this numerical study, the performance of ceramic-based mullite hollow fiber (HF) membranes in a direct contact membrane distillation (DCMD) process was evaluated. Three types of membranes were tested: (i) hydrophobic membrane C8-HFM, (ii) rod-like omniphobic membrane (C8-RL/TiO2), and (iii) flower-like omniphobic membrane (C8-FL/TiO2). The CFD model was developed and validated with experimental results, which were performed over a 500 min period. The initial mass flux of C8-HFM was 30% and 9% higher than that of C8-FL/TiO2 and C8-RL/TiO2, respectively. However, the flower-like omniphobic membrane C8-FL/TiO2 had the lowest drop in flux, around 11%, while the rod-like omniphobic membrane C8-RL/TiO2 had a 15% reduction, both better than the 23% reduction in the hydrophobic membrane C8-HFM over the 500 min. The study also analyzed the impact of fouling by examining the variation in mass transfer coefficient (MTC) over time. The results indicated that the ceramic-based mullite HF membranes with TiO2 flowers and rods demonstrated a high resistance to fouling compared to C8-HFM. The modified membranes could find applications in the desalination and handling of seawater samples containing organic contaminants. The CFD model’s versatility can be utilized beyond the current investigation’s scope, offering a valuable tool for efficient membrane development solutions, particularly for challenges such as the presence of organic contaminants in seawater.

Preventive geochemical barriers during transport construction

The article discusses the possibility of using chlorite crushed stone as part of geochemical barriers in transport construction. It has been shown that during the construction of railways and during their operation, the main pollutants are petroleum products and heavy metal ions. To substantiate and study the neutralizing properties of chlorite crushed stone, infrared spectroscopy, ionomer, atomic absorption spectrometry and the gravimetric method for determining petroleum products were used. Research has shown that chlorite crushed stone is a quartz-albite-chlorite shale with a small inclusion of carbon; its physical and mechanical characteristics are not inferior to granite crushed stone. The oil capacity of chlorite crushed stone depends on the concentration of petroleum products in the model solution and ranges from 0.03 to 0.5 g/g. Chlorite crushed stone has a capacity towards nickel, iron and cadmium ions, while their simultaneous presence in the model solution does not have selectivity towards these ions. It has been proven that when the capacity of chlorite crushed stone is fully realized in relation to one of the heavy metal ions, it is not washed out and replaced by another metal ion (for example, nickel and iron ions). It has been proven that the presence of organic contaminants in the model solution does not significantly affect the capacity of chlorite crushed stone for heavy metal ions. It has been shown that chlorite crushed stone, due to its physical, physical-mechanical and chemical properties, can be used in geochemical barriers to protect the environment from pollution.

Development of superhydrophobic ceramic membrane decorated with flake-like structure by two-step synthesis for seawater desalination by membrane distillation

BackgroundDeveloping durable superhydrophobic ceramic membranes capable of withstanding harsh operating conditions and maintaining their properties over an extended period poses a challenge due to the limited robustness and stability of superhydrophobic membranes. MethodsIn this study, a two-step technique, previously unreported, was successfully used to prepare superhydrophobic mullite-based kaolinite (MK) and stainless steel (SS) composite hollow fibre membranes (HFMs). The surface roughening step was attained through the hydrothermal treatment of copper oxide nanoparticles (CuO) at different reaction times (2- 5 h) on the MK-SS HFM surface. The fluorinating process was achieved using 1H, 1H, 2H, 2H perfluorooctyltriethoxysilane (C8, 97%) through a dip-coating technique. A seawater desalination experiment by a membrane distillation (MD) system evaluated the performance of MK-SS HFM for 500 min. Significant findingsThe results revealed that the MK-SS/4 h HFM, characterized by its flake-like structure, exhibited optimal superhydrophobic behavior. It displayed contact angles (CAs) of 155.9° for water, 144° for water/ethanol, 129° for palm oil, and 112° for engine oil, with a liquid entry pressure (LEP) of 5.2 bar Furthermore, the membrane performance was tested in a direct contact membrane distillation (DCMD) at 70 °C using a solution that simulated real seawater conditions, including sodium chloride (NaCl) at 35 g/L, sodium sulfate (Na2SO4) at 1.2 g/L, sodium carbonate (Na2CO3) at 1 g/L, and humic acid at 8 mg/L. Remarkably, a rejection rate of about 99.91% and a permeate flux of 24.3 L/(m².h) were achieved. Despite the presence of organic contaminants and various salts, this superhydrophobic HFM, prepared using a two-step technique, exhibited higher contact angles, rejection rates, and permeate flux than other superhydrophobic HFMs reported in the literature due to its superior superhydrophobic and antiwetting properties. This robust superhydrophobic membrane holds promise for developing effective superhydrophobic HFMs that can be applied in various real MD applications.

Development of Janus membranes with asymmetric wettability for desalination of impaired seawater by direct contact membrane distillation

Membrane distillation (MD) is an emerging technology for direct seawater desalination. The widely employed hydrophobic membranes are susceptible to pore wetting/ fouling in the presence of organic contaminants in seawater. Here, we demonstrate a facile method of preparing Janus membranes with hydrophilic/hydrophobic faces having excellent anti-fouling and anti-wetting properties. The hydrophobic substrate is a PVDF-co-HFP membrane incorporating fluoroalkylsilane (FAS) grafted hydrophobic MIL-53(Al)- a form of metal organic framework (h-MIL-53(Al)), and the hydrophilic coating is prepared by the direct deposition of polydopamine (PDA) (top layer). The optimum membrane exhibited a stable flux of 11 L/m2h and permeate conductivity ∼10 µS/cm for up to 60 h of seawater desalination. The anti-wetting property of the Janus membrane was demonstrated from the stable performance when challenging the membrane with impaired seawater containing low surface tension compounds such as sodium dodecyl sulphate (SDS) and propylene glycol (PG), and oil (hexadecane). The prepared membrane exhibited wetting resistance of 45 h and 18 h when feed was seawater containing 0.3 mM SDS and 3 wt% PG, respectively. The membrane displayed excellent resistance to fouling for desalination from SDS-stabilized hexadecane (500 ppm)/seawater feeds for up to 50 h (5 cycles). The membrane fabricated in this study holds the potential for seawater desalination.

Robust omniphobic ceramic hollow fibre membrane with leaf-like copper oxide hierarchical structure by membrane distillation

Omniphobic membranes have recently shown promising performance in water desalination using MD due to their ability to repel all liquid drop types and keep the membrane surface dry. This study successfully modified the surface of robust hydrophilic mullite-stainless steel hollow fibre membranes (M-SS HFMs) to omniphobic properties. The omniphobic layer was achieved through surface grafting with copper oxide (CuO) rough layer by a hydrothermal technique at different hydrothermal reaction times of 1, 2, 3, 4 and 5 h, followed by fluorination step using 1H,1H,2H,2H-perfluorode-cyltriethoxysilane (C8, 97 %). Next, the omniphobic membranes were characterized in terms of membrane morphology, roughness, mechanical strength, pore size/distribution, liquid entry pressure, contact angle and fouling accumulation. The prepared omniphobic M-SS HFMs were also tested through the DCMD system at 80 °C using a feed solution containing 35 g/L of NaCl and 10 mg/L of humic acid as a foulant agent. The results indicated that M-SS HFMs subjected to a 4 h hydrothermal reaction time, resulting in a leaf-like surface structure, exhibited superior characteristics compared to other omniphobic HFMs reported in the literature that used titania (SiO2), zinc oxide (ZnO), and cobalt (Co3O4) as roughing material. These superior features included higher roughness of 0.798 μm, liquid entry pressure of 5.40 bar, and enhanced liquid repellence and contact angles towards DI water of 167°, olive oil of 152°, and ethanol of 145°. Additionally, the M-SS HFMs at 4 h hydrothermal demonstrated remarkable performance in terms of rejection performance (99.99 %) and vapour flux stability of about 29 kg/m2.h in DCMD operations, surpassing the performance of omniphobic HFMs fabricated using mullite-ball clay, mullite-kaolinite, and alumina (Al2O3). Notably, no fouling/wetting on the membrane surface and elements leaching was observed throughout the MD operation. These findings highlight the potential of this omniphobic HFM for seawater desalination using DCMD systems, even in the presence of organic contaminants.

DOM accumulation in the hyporheic zone promotes geogenic Fe mobility: A laboratory column study

Hyporheic zone (HZ) systems have a natural purification capacity, and they are commonly used to provide high quality drinking water. However, the presence of organic contaminants in HZ systems in anaerobic environments causes the aquifer sediments to release metals (e.g., Fe) at levels above drinking water standards, which affects the quality of groundwater. In this study, the effects of typical organic pollutants (dissolved organic matter (DOM)) on Fe release from anaerobic HZ sediments were investigated. Ultraviolet fluorescence spectroscopy, three-dimensional excitation-emission matrix fluorescence spectroscopy, excitation–emission matrix spectroscopy coupled with parallel factor analysis and Illumina MiSeq high-throughput sequencing were used to determine the effects of the system conditions on Fe release from HZ sediments. Compared with the control conditions (low traffic and low DOM as a baseline), the Fe release capacity was enhanced by 26.7 % and 64.4 % at low flow rate (85.8 m/d) and high organic matter concentration (1200 mg/L), which was consistent with the residence-time effect. The transport of heavy metals under different system conditions varied with the influent organic composition. The influent organic matter composition and fluorescence parameters (the humification index, biological index and fluorescence index) were closely related to the release of the Fe effluent, while these factors had less influence on Mn and As. From 16S rRNA analysis of the aquifer media at different depths at the end of the experiment, under low flow rate and high influent concentration conditions, reduction of Fe minerals by Proteobacteria, Actinobacteriota, Bacillus, and Acidobacteria promoted the release of Fe. These functional microbes play an active role in the Fe biogeochemical cycle in addition to reducing Fe minerals to promote Fe release. In summary, this study reveals the effects of the flow rate and influent DOM concentration on the release and biogeochemistry of Fe in the HZ. The results presented herein will contribute to a better understanding of the release and transport of common groundwater contaminants in the HZ and other groundwater recharge environments.

Metal oxide encapsulated by 3D graphene oxide creates a nanocomposite with enhanced organic adsorption in aqueous solution.

The presence of organic contaminants (OCs) in aquatic systems is a threat to ecological and human health. Adsorption by graphene-based adsorbent is a promising technique for OC removal and we previously fabricated crumpled graphene balls (CGBs), via a novel nano-spray drying technique, which show robust adsorptive performance. Yet, since CGBs contain non-accessible surface area due to 2D graphene stacking, the goal of this research was to investigate the efficacy of maximizing the accessible CGB surface by synthesizing a nanocomposite composed of metal oxide nanoparticles encapsulated by crumpled graphene oxide (MGC). The metal oxides reduce graphene oxide stacking, expand the internal adsorptive surface area, and boost the adsorptive capacity of the MGC. MGC (fumed SiO2 or SiO2) exhibit an enhanced Langmuir adsorption capacity (qm, normalized by the % carbon) for an OC model, methylene blue (MB), achieving improvements of 60-86% compared to CGB, 3-4 fold compared to powder activated carbon (PAC) and 6-7 fold compared to granular activated carbon (GAC). MGCs display rapid adsorption reaching equilibrium after 9-12min of contact and remaining stable in wastewater effluent /surface water. A cost-efficiency comparison reveals MGCs achieve one ton of MB removal at similar or lower material costs than that of PAC/GAC.

Quantitative Estimation of COD Values from an Array of Metal Nanoparticle Modified Electrodes and Artificial Neural Networks

Water quality monitoring has become critical in modern societies in multiple areas and at different stages. In this regard, chemical oxygen demand (COD) has become a key index in water testing, as it readily allows the determination of its overall quality and the presence of organic contaminants. However, conventional COD determination presents several drawbacks in view of the use of toxic reagents and possible interferences. The electrochemical determination of COD can be an alternative with many advantages, especially if using an array of sensors. Herein, the use of an electronic tongue (ET) for the estimation of COD was explored. The proposed ET was formed by an array of five voltammetric electrodes modified with different metal nanoparticles. An artificial neural network (ANN) model was built based on the responses of the array towards glucose and glycine as standards. This model was then used with real and spiked water samples, and the results compared to the electrochemical calibration and the commercial COD colorimetric methods. While the COD values of the real samples were low and outside the range of the ANN model, a satisfactory prediction for the spiked samples was achieved, showing a good agreement with the reference colorimetric method, that was better than the performance of the conventional electrochemical calibration method.

Presence of novel and legacy flame retardants and other pollutants in an e-waste site in China and associated risks

Electrical and Electronic Equipment (EEE) residues and their management have been widely identified as potential sources of plasticizers and flame retardants to the environment, especially in non-formal e-waste facilities. This study evaluates the distribution, partitioning and environmental and human impact of organophosphate esters (OPEs), legacy polychlorinated biphenyls (PCBs), polybromodiphenyl ethers (PBDEs) and organochlorine pesticides (OCPs) in the e-waste recycling area of Baihe Tang village, in the Qingyuan county, Guangdong province, China. A plastic debris lump accumulated in a small pond during years was identified as the main source of pollution with ∑pollutants of 8400 μg/g dw, being OPEs the main contaminants detected, followed by PBDEs. This lump produced the contamination of water, sediments, soils and hen eggs in the surrounding area at high concentrations. Plastic-water and water-sediment partitioning coefficients explained the migration of OPEs to the water body and accumulation in sediments, with a strong dependence according to the KOW. Triphenyl phosphate (TPhP), tricresyl phosphate (TCPs) and high chlorination degree PCBs produced a risk in soils and sediments, considering the lowest predicted no effect concentration, while the presence of PCBs and PBDEs in free range hen eggs exceeded the acceptable daily intake. OCPs were detected at low concentrations in all samples. The presence of organic contaminants in e-waste facilities worldwide is discussed to highlight the need for a strict control of EEE management to minimize environmental and human risks.

Photoreactive Coating Material as an Effective and Durable Antimicrobial Composite in Reducing Bacterial Load on Surfaces in Livestock.

Titanium dioxide (TiO2) is a well-known photocatalytic compound that can be used to effectively reduce the presence of pathogens in human and animal hospitals via ROS release. The aim of this study was to investigate the efficacy of a polymer-based composite layer containing TiO2 and zinc oxide (ZnO) against Escherichia coli (E. coli) of animal origin. We showed that the photocatalyst coating caused a significant (p < 0.001) reduction in pathogen numbers compared to the control with an average reduction of 94% over 30 min. We used six light sources of different wattages (4 W, 7 W, 9 W, 12 W, 18 W, 36 W) at six distances (35 cm, 100 cm, 150 cm, 200 cm, 250 cm, 300 cm). Samples (n = 2160) were taken in the 36 settings and showed no significant difference in efficacy between light intensity and distance. We also investigated the influence of organic contaminant that resulted in lower activity as well as the effect of a water jet and a high-pressure device on the antibacterial activity. We found that the latter completely removed the coating from the surface, which significantly (p < 0.0001) reduced its antibacterial potential. As a conclusion, light intensity and distance does not reduce the efficacy of the polymer, but the presence of organic contaminants does.

Passive Sampling of Organic Contaminants as a Novel Approach to Monitor Seawater Quality in Aquarium Ocean Tanks

The determination of trace pollutants in seawater is challenging, and sampling is a crucial step in the entire analytical process. Passive samplers combine in situ sampling and preconcentration, thus limiting the tedious treatment steps of the conventional sampling methods. Their use to monitor water quality in confined marine environment could bring several advantages. In this work, the presence of organic contaminants at trace and ultra-trace levels was assessed in the Genoa Aquarium supply-and-treated water using Polar Organic Integrative Samplers (POCIS). Both untargeted gas chromatography-mass spectrometry and targeted liquid chromatography-tandem mass spectrometry were employed. The untargeted approach showed the presence of hydrocarbons, diphenyl sulfone and 2,4-di-tert-butyl-phenol. Only hydrocarbons were detected in all the samples. Nineteen emerging contaminants, belonging to different classes (pharmaceuticals, UV-filters, hormones and perfluorinated compounds), were selected for the target analysis. Thirteen analytes were detected, mainly in supply water, even though the majority of them were below the quantitation limit. It is worthy to note that two of the detected UV-filters had never been reported in seawater using the POCIS samplers. The comparison of the analytes detected in supply and treated water indicated a good performance of the Aquarium water treatment system in the abatement of seawater contaminants.

Development of Ultra performance Liquid Chromatography (UPLC) method for the Separation of Alfuzosin Hydrochloride and its organic impurities

For assessing alfuzosin hydrochloride in the presence of organic contaminants and degradants by forced breakdown products, a novel, quick, precise, sensitive, specific, and stability-indicating reverse-phase (RP-UPLC) approach was established. Acquity BEH C18 (50 × 2.1 mm,1.7), BEH C8 (50 × 2.1 mm,1.7), Acquity CSH C18 (50 × 2.1 mm,1.8), and Acquity BEH C18 (100 × 2.1 mm,1.7) are among the rapid liquid chromatography columns that have been investigated. Low and neutral pH buffers were also used. Furthermore, the best chromatographic separation was achieved with a Waters Acquity HSS T3 C18, 100 mm × 2.1 mm, particle size 1.8, UV detection at As a mobile phase carrier, (acetonitrile, tetrahydrofuran) is used. The final technique conditions enable excellent impurity separation, which can be used to analyse the stability of alfuzosin hydrochloride commercial samples as well as for quality control throughout production. The gradient time was about 6.5 min, and the re-equilibration time was roughly 1.5 min, allowing for more than 100 samples each day to be analysed. Aside from that, the pH sensitive analytical approach addressed in both the US and European Pharmacopoeias was explored.

A systematic study on the effect of coating type and surface preparation on the wettability of Si-Bronze brazing filler material on GI and GA-coated DP600

Zn-coated advanced high strength steels are popular in the automotive industry due to their excellent combination of mechanical strength and ductility as well as superior corrosion resistance provided by the Zn-coating – with hot-dip galvanized and galvannealed coatings being the most popular. Gas metal arc brazing technology is a non-fusion joining method, proposed as an alternative to the gas metal arc welding process due to several advantages: The arc-brazing process delivers significantly lower heat input to the substrate, which minimizes the Zn-coating burn-off leading to higher corrosion protection for the joined parts, and reduces the HAZ softening phenomenon which affects the mechanical integrity of the substrate, while at the same time reduces welding defects such as porosity and blowholes. The strength of an arc-brazed joint depends on the spreading of the molten filler material over the joint to create a bond between the parts as the molten braze solidifies. Existing literature on the subject suggests that heat input is the main driving factor controlling the wettability of the molten braze material with the type of shielding gas used also having an effect. However, the influence of different types of Zn-coatings and their respective surface condition (i.e., clean, or unclean) on the wettability of Cu-based molten braze materials during arc-brazing has not been investigated. The present work investigates the effect of surface morphology of galvanized and galvannealed DP600 steel in the as-received and plasma cleaned conditions on the wettability of molten Si-Bronze (CuSi3Mn1) brazing filler material in the bead-on-plate configuration. The findings of this work clearly demonstrate that the type of coating and its surface condition has a significant effect on the spreading of the molten filler material and on the growth of the intermetallic compound layer at the joint interface and therefore, should be taken into consideration as a factor that can impact the efficacy of an arc-brazed joint. • Evaluating surface morphology of different Zn-coatings to calculate their surface free energy. • Establishing a clear link between the surface roughness of Zn-coated steels on the wettability of molten Si-Bronze filler material. • The study shows that the wettability of the molten filler material is also affected by the presence of organic contaminants on the coating surface. • This work shows the relevance of surface morphology in controlling the wetting length of weld brazed joints. • The thickness of the intermetallic compound layer at the braze interface can be controlled by using oxygen plasma cleaning.

Characterisation of the chemo-mechanical behaviour of clays polluted by BTEX: a case study of benzene

In chemo-mechanical coupling of clays, chemical phenomena are likely to have a stronger influence on the mechanical behaviour and mechanical actions can modify the chemical behaviour. The understanding of these different phenomena, taking into account the coupled mechanisms, is essential in the context of the problem of the durability of structures and works built on polluted sites. Thus, the laboratory characterisation of the chemo-mechanical behaviour of a clay contaminated by light hydrocarbon pollutant (BTEX: benzene) was carried out. First in the absence of pollutants, i.e., by the presence of water only, then under the influence of the pollutant, all in two stages: with no external stress, then under imposed external stress. This study presents an experimental protocol based on a series of uniaxial consolidation tests, specific oedometric tests and direct shear strength, this tests performed under controlled saturation conditions and in the presence of organic contamination by benzene. All results confirm the influence of pollutants in different concentrations on the mechanical behaviour of the soil. They show a strong increase in compressibility and a significant increase in swelling, the soil becomes more cohesive, low friction and less elastic. Furthermore, the results show that external load forces play a major role in modifying the behaviour of clay.

Kinetics of Bacterial Inactivation by Peroxynitric Acid in the Presence of Organic Contaminants.

Low-temperature atmospheric-pressure plasma has been studied for disinfection purposes. When plasma is exposed to water, reactive oxygen and nitrogen species are generated and preserved in the water fraction (plasma-treated water [PTW]), which consequently exhibits bactericidal activity. At low temperatures, one of the bactericidal components of PTW is peroxynitric acid (PNA). Importantly, PNA can also be synthesized by chemical reaction, without exposure to plasma. In this study, we evaluated the bactericidal properties of PNA based on reaction kinetics in comparison with other disinfectants. The analysis, based on dose-dependent effects, showed that PNA exhibited about 1 and 10 times the bactericidal activity of hypochlorous acid (HOCl) and peracetic acid, respectively. In addition, we evaluated the influence of organic contaminants on the bactericidal effects of PNA and HOCl. The bactericidal potential of both disinfectants was reduced by bovine serum albumin (BSA); however, PNA showed about 30-times-higher resistance against BSA inhibition than HOCl. Analysis of the dose-dependent effects of PNA revealed that the inhibition of bactericidal effect was caused by its consumption. Further experiments using model substrates containing particular amino acid residues (Met, Cys, Lys, and Leu) suggested that the bacterial inactivation by PNA is less affected by BSA due to the low reactivity and narrow reactivity spectrum of PNA for amino acid residues. Overall, our results suggest that PNA has a great disinfection potential, especially in the presence of organic contaminants (e.g., on the surface of the human body and on medical instruments contaminated with biological fluids).IMPORTANCE A good disinfectant for the human body should have various properties, such as strong bactericidal activity, harmlessness to living tissues, and resistance against biological fluids (or other organic contaminants). Peroxynitric acid (PNA) showed a bactericidal effect that was several tens up to several hundred times higher per unit of molarity than that of sodium hypochlorite and peracetic acid, which are used as general disinfectants for medical equipment. Moreover, the high resistance of PNA to organic load was confirmed, indicating that PNA will inactivate bacteria effectively even on contaminated surfaces, such as used medical devices or the human body surface. Therefore, we propose that PNA can be used as a strong disinfectant for the human body.

Organic wastewater treatment by a single-atom catalyst and electrolytically produced H2O2.

The presence of organic contaminants in wastewater poses considerable risks to the health of both humans and ecosystems. Although advanced oxidation processes that rely on highly reactive radicals to destroy organic contaminants are appealing treatment options, substantial energy and chemical inputs limit their practical applications. Here we demonstrate that Cu single atoms incorporated in graphitic carbon nitride can catalytically activate H2O2 to generate hydroxyl radicals at pH 7.0 without energy input, and show robust stability within a filtration device. We further design an electrolysis reactor for the on-site generation of H2O2 from air, water and renewable energy. Coupling the single-atom catalytic filter and the H2O2 electrolytic generator in tandem delivers a wastewater treatment system. These findings provide a promising path toward reducing the energy and chemical demands of advanced oxidation processes, as well as enabling their implementation in remote areas and isolated communities.

EVALUACIÓN DE LA CALIDAD DEL AGUA Y DE LA RIBERA EN DOS CUENCAS TRIBUTARIAS DEL RÍO TUXCACUESCO, JALISCO, MÉXICO

It has been documented that in Mexico 80% of aquatic ecosystems, including water bodies such as rivers, are under some degree of contamination. It has been detected that the main pollutants are organic matter, nutrients (nitrogen and phosphorous) and microorganisms (faecal coliforms). Addressing this problem is of vital importance for the conservation of aquatic ecosystems and for improving the quality of life of the inhabitants of the surroundings. In this sense the lack information on the quality status of aquatic ecosystems in the Tuxcacuesco river basin, in the satate of Jalisco, is very scarce and non-existent for its tributary basins. Therefore, in the present study the objective was to infer the quality of the aquatic ecosystems of two tributary basins (Tonaya and Apulco) of the Tuxcacuesco river, in Jalisco, Mexico, by using two indices. The first an index of biotic integrity based on the presence or absence of families of aquatic macroinvertebrates, and the second an index to assess the ecological status and quality of riverbanks, the riverbank quality index (RQI). Two samplings were carried out at four sites, in the month of October 2015 (end of the rainy season) and February of the year 2016 (beginning of the dry season), in which aquatic macroinvertebrates were collected and the RQI index was applied. In addition, physical and chemical parameters (pH, electrical conductivity and flow rate) were evaluated and the total nitrogen content was determinated in each site. By means of a canonical correspondence analysis, it was evidenced that the flow and the electrical conductivity are the environmental variables that have the greater relation with the order of the families of macroinvertebrates found. In general, the ecological status of the banks is poor in the two tributary basins, and the nitrogen content in the waters exceeds the permissible limits for potable use and agricultural irrigation. Regarding the application of the biotic integrity index, it was found that in most of the sites there is the presence of organic contamination.

Contaminated marine sediment stabilization/solidification treatment with cement/lime: leaching behaviour investigation.

Among ex situ remediation technologies, stabilization/solidification (S/S) provides for the addition of a binder to dredged materials in order to chemically immobilise the contaminants and improve mechanical behaviour of sediments. The simplest form of treatment is obtained by the addition of Portland cement or lime (calcium oxide), although other additives such as adsorbents may be added. Nevertheless, the success of the S/S treatment may be affected by the contaminants present or by the salt content in the water. In this study, experimental laboratory investigation was carried out on sediments carefully collected from the Mar Piccolo of Taranto in Southern Italy, contaminated by heavy metals, polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs); the goal was to explore the effectiveness of S/S treatment by using Portland cement/lime as binders, monitoring over time (28days) the leaching of the different mixtures of treated sediment. It is noted that the Mar Piccolo of Taranto is one of the sites of national interest subject to remediation by the Italian government. Once taken within the first meter under the sea floor by a team of experienced divers, the samples were stored at a controlled temperature, characterised in terms of grain size and physical-chemical characteristics and treated by S/S laboratory tests. The results indicate that the addition of binders increased the pH of the mixtures with a consequent leachability of different metals. The mobility of the metals appeared to be governed also by the curing time. The performance of the mixtures in terms of immobilised metals was influenced by the presence of organic contaminants (e.g. organic matter, PAHs and PCBs). As a lesson, high organic matter and fine-grained particles can negatively affect the effectiveness of the S/S treatment in terms of metal immobilisation.