Degradation In Seawater Research Articles

Coordination dependent photocatalytic peroxymonosulfate activation on biomass derived Fe single atom catalysts for atrazine degradation

Challenges associated with uncontrollable metal coordination structures in biomass-derived single-atom catalysts (SACs) and their intricate impacts on photocatalytic peroxymonosulfate (PMS) activation pose significant hurdles for the application of photo-Fenton technology towards wastewater treatment. Herein, we employed a co-pyrolysis strategy using Enteromorpha prolifera (E. prolifera) to synthesize Fe SACs with varying Fe–NX coordination, i.e., Fe–N5 and Fe–N6. Fe–N6-based SAC achieved over 80% atrazine (ATZ) degradation in 15 min, with a degradation rate of 0.13 min−1, representing 2.6-fold improvement over SAC with Fe–N5 structure. Experimental and simulation results revealed that Fe–N6 active sites acted as electron donors, enhancing the delocalization of π-electrons and improving photocatalytic PMS activation. This SAC also exhibited high selectivity for 1O2 degradation pathway and impressive ATZ degradation in seawater, with notable chlorine resistance, underscoring its potential in environmental pollutant remediation. This work unveils the catalyst structure-photocatalytic PMS activation performance relationship, offering avenue for developing more sustainable and efficient biomass-derived SACs for wastewater treatment.

Enhanced degradation of sulfonamides by copper and cuprous oxides activated ferrate (VI) synergistically: Mechanism and applicability

Sulfonamides are extensively utilized for their affordability and effectiveness, leading to their significant accumulation in the environment, and posing a potential threat to human health. In this study, we introduced a novel system utilizing copper and cuprous oxides (CuxO) to activate ferrate (Ⅵ) (Fe (Ⅵ)) for the degradation of sulfamethazine (SMT), achieving a reaction rate 15 times higher than using Fe (Ⅵ) alone. Various experiments have shown that the primary active species in the CuxO/Fe (Ⅵ) system were Fe (V) and Fe (Ⅳ), predominantly formed via the redox interaction between Cu (I) and Fe (Ⅵ). Additionally, this system exhibited remarkable degradation efficiency even in seawater, with negligeable disruption from surrounding substances. This research developed a novel strategy for Fe (Ⅵ) activation, offering a promising approach for sulfonamide degradation in seawater.

Evaluation of phenanthrene degradation in seawater by an isolated bacterial consortium from the Gulf of Mexico

Evaluation of phenanthrene degradation in seawater by an isolated bacterial consortium from the Gulf of Mexico

Photodegradation of bisphenol A (BPA) in coastal aquaculture waters: Influencing factors, products, and pathways

Bisphenol A (BPA), an endocrine-disrupting contaminant, is ubiquitous in the environment due to its presence in plastics, wastewater, and agricultural runoff. This study investigated the photodegradation behavior of BPA in coastal aquaculture waters near Qingdao, China. Lower salinity promoted BPA photodegradation, while higher salinity has an inhibitory effect, suggesting slower degradation in seawater compared to ultrapure water. Triplet-excited dissolved organic matter (3DOM*) was identified as the primary mediator of BPA degradation, with additional contributions from hydroxyl radicals (•OH), singlet oxygen (1O2), and halogen radicals (HRS). Alepocephalidae aquaculture water exhibited the fastest degradation rate, likely due to its high DOM and nitrate/nitrite (NO3−/NO2−) content, which are sources of 3DOM* and •OH. A positive correlation existed between NO3−/NO2− concentration and the BPA degradation rate. Ultra-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF-MS) analysis identified the primary BPA photodegradation products, formed mainly through oxidative degradation, hydroxyl substitution, nitration, and chlorination pathways. Elucidating these photodegradation mechanisms provides valuable insights into the environmental fate and potential ecological risks of BPA in aquaculture environments. This knowledge can inform strategies for marine environmental protection and the development of sustainable practices.

Quantifying the impact: Are coastal areas impoverished by marine pollution?

We propose a methodological framework to assess the causal impact of Harmful Algal Bloom (HAB) events on economic indicators at a territorial level, with special consideration for spatial effects. Using the Mar Menor region in Spain as a case study, we empirically apply our framework. Our findings indicate a significantly negative causal effect of marine pollution resulting from HAB events on income per capita at the census section level. We observe that this effect is exacerbated by spatial interactions among neighboring census sections adjacent to those directly affected by seawater degradation. These results underscore the importance of implementing effective environmental regulations to mitigate seawater pollution and proactive measures to safeguard the well-being of local populations. Our research provides valuable insights for future studies in similar coastal regions.

Construction of 2D/3D black g-C3N4/BiOI S-scheme heterojunction for boosted photothermal-assisted photocatalytic tetracycline degradation in seawater

Utilization of semiconductor photocatalyst to degrade broad-spectrum antibiotics (tetracycline, TC) in seawater to solve environmental pollution and human health problems has become a research hotspot in recent years. In this work, 2D/3D black g-C3N4/BiOI S-scheme heterojunction was constructed by loading 2D black g-C3N4 (CN-B) nanosheets onto 3D spherical bismuth oxyiodide (BiOI) surface by solvothermal method to improve TC degradation efficiency. The TC (30 mg/L) photodegradation efficiency of the optimal 10 % CN-B/BiOI sample was up to 93 % after 60 min visible light irradiation, which was significantly higher than that of pure CN-B and BiOI. Remarkably, the 2D/3D heterojunction formed between CN-B and BiOI can not only effectively improve the light absorption and separation efficiency of carriers, but also the photothermal effect of CN-B increases the reaction temperature, thereby promoting the photothermal-assisted photocatalytic degradation activity. This work provides a promising strategy and systematic method for the design of photocatalytic system for photothermal-assisted degradation antibiotic contaminants in seawater.

Study on the onset mechanism of bio-blister degradation of polyolefin by diatom attachment in seawater

It is essential to develop a mechanism for lowering the molecular weight of polyolefins to achieve biodegradation in seawater. In this study, a polypropylene/polylactic acid blend sample was first subjected to photodegradation pretreatment, and it was confirmed that in pure water, the acid generated promotes the polypropylene degradation (autoxidation), while in alkaline seawater, the promotion was inhibited by a neutralization reaction. In the autoxidation of polyolefins in alkaline seawater, aqueous Cl− was also the inhibitor. However, we found that autoxidation could be initiated even in seawater by lowering the pH and using dissociation of ClOH (called blister degradation). The blister degradation mechanism enabled autoxidation, even in seawater, by taking advantage of the ability of diatoms to secrete transparent exopolymer particles (TEP) to prevent direct contact between the surface layer of polyolefins and alkaline seawater. We named blister degradation in seawater with diatoms as bio-blister degradation and confirmed its manifestation using linear low-density polyethylene (LLDPE)/starch samples by SEM, IR, DSC and GPC analysis.

Basalt fibre degradation in seawater and consequences for long term composite reinforcement

Basalt fibres are increasingly employed as reinforcements in marine composites, but their behaviour in natural marine environments is underexplored. This study investigates basalt fibre ageing in renewed natural seawater at 15 °C and 40 °C. After one month in seawater at 15 °C and 40 °C, tensile strength dropped, stabilizing at approximately −40% and −60%, respectively. This rapid initial property decline, followed by slower degradation, is attributed to an altered surface layer on the fibres. Initially causing significant property loss, this layer then plays a protective role, preserving the fibre core. The impact on basalt/epoxy composites exposed to 7.5 years of seawater was less severe, with a 20% loss at 40 °C, demonstrating the protective function of the matrix. This study suggests that basalt fibres undergo rapid, then stable, property degradation in water, but remain suitable for use as epoxy matrix composite reinforcements, thanks to the protective role of the resin.

New modifications of PBAT by a small amount of oxalic acid: Fast crystallization and enhanced degradation in all natural environments

Biodegradable plastics are often mistakenly thought to be capable of degrading in any environment, but their slow degradation rate in the natural environment is still unsatisfactory. We synthetized a novel series of poly(butylene oxalate-co-adipate-co-terephthalate) (PBOAT) with unchanged melting point (135 °C), high elastic modulus (140 - 219 MPa) and elongation at break (478 - 769%). Fast isothermal crystallization with a semi-crystallization time < 20 s was demonstrated by the PBOAT. In N2 and air atmospheres, the PBOAT maintained the Td,5% higher than 329 °C. They also had good thermal stability at melt processing temperature for more than 20 min. PBOAT exhibited faster hydrolysis and seawater degradation, even under natural soil burial without light, but still kept stable under low humidity conditions during the storage and the shelf-life. Moreover, the hydrolysis mechanisms were clarified based on Fukui function analysis and DFT calculation, indicating that the hydrolysis of PBOAT would be more straightforward. The mechanism of soil burial is also elucidated through detailed characterization of the structure changes. The PBOAT offered a fresh approach to the development of high-performing, naturally degradable materials.

Evaluating the photochemical reactivity of disinfection byproducts formed during seawater desalination processes

Reverse osmosis (RO) is widely used for seawater desalination but pre-chlorination of intake water produces halogenated disinfection byproducts (DBPs). The fate and environmental impacts associated with the discharge of DBP-containing RO brine wastewater are unknown. Therefore, to evaluate if photochemistry plays a role in DBP degradation in seawater, we collected samples at a desalination plant, which were desalted and concentrated using two-inline solid phase extraction (SPE) techniques combining reverse-phase polymeric (PPL) and weak anion exchange (WAX) resins. Both filtered water samples and SPE samples (extracts reconstituted in open ocean seawater) were exposed to simulated sunlight in a custom-built flow-through system. Optical property analysis during irradiation experiments did not provide distinguishing features between intake water and RO reject water (brine). Extractable organic bromine (organoBr) concentrations were low in intake water samples (7.8 μg Br L−1) and did not change significantly due to irradiation. OrganoBr concentrations in laboratory-chlorinated raw water were much higher (135 μg Br L−1) and on average decreased by 42 % after 24 h irradiation. However, while organoBr concentrations were highest in RO reject water (473 μg Br L−1), changes in organoBr concentrations in PPL SPE samples after 24 h irradiation were variable, ranging from a 1–46 % loss. Furthermore, most bromine-containing molecular ions identified by high resolution mass spectrometry that were present in RO reject water before irradiation were also found after both 24 h and 50 h exposures. Although only one RO reject water sample was tested in this study, results highlight that hundreds of yet to be identified brominated DBPs in RO reject water could be resistant to photodegradation or phototransform into existing DBPs in the environment. Future work examining the biolability of DBPs in RO reject water, as well as the interplay between photochemical and biological DBP cycling, is warranted.

Photo-Degradation Mechanism and Pathway for Tetracycline in Simulated Seawater Under Irradiation of Visible Light

To explore the mechanism and pathway for pollutant degradation in seawater by heterogeneous photocatalysts, the degradation of tetracycline (TC) in pure water and simulated seawater with different mesoporous TiO2 under the excitation of visible light was first investigated; then the effect of different salt ions on the photocatalytic degradation process was clarified. Combined with radical trapping experiments, electron spin resonance (ESR) spectroscopy, and intermediate product analysis, the main active species for photodegrading pollutants and the pathway of TC degradation in simulated seawater were investigated. The results showed that the photodegradation for TC in simulated seawater was significantly inhibited. Compared with the TC photodegradation in pure water, the reaction rate of the chiral mesoporous TiO2 photocatalyst for TC was reduced by approximately 70%, whereas the achiral mesoporous TiO2 photocatalyst could hardly degrade TC in seawater. Anions in simulated seawater had little effect on photodegradation, but Mg2+ and Ca2+ ions significantly inhibited the TC photodegradation process. Whether in water or simulated seawater, the active species generated by the catalyst after excitation by visible light were mainly holes, and each salt ion did not inhibit the generation of active species; thus, the degradation pathway both in simulated seawater and in water was the same. However, Mg2+ and Ca2+ would be enriched around the highly electronegative atoms in TC molecules, hindering the attack of holes to highly electronegative atoms in TC molecules, thereby inhibiting the photocatalytic degradation efficiency.

Degradation of polyethylene terephthalate (PET) and polypropylene (PP) plastics in seawater

The world's marine litter consists mainly of plastic, and 99% of it does not float on the surface of the sea but on the seabed. The plastic carbon footprint necessarily includes the extraction or manufacture of raw materials, the conversion process, the distribution of products, the consumption of specific types of products and the disposal of the final product, as all these stages release carbon into the atmosphere. This work, inspired by marine microplastics and investigates how plastic waste is degraded and transformed in high-pressure, low-temperature seawater, this paper investigates the corrosion of polyethylene terephthalate (PET) and polypropylene (PP) plastics in seawater at high-pressure, using artificial seawater temperatures to simulate ocean temperatures of approximately 4 ​°C and time settings of 1 day–7 days. The results show that increasing the time enhances the degradation of the plastics and that changing the pressure has little effect on the degradation effect. Understanding its degradation in seawater can help us to better treat plastic waste and thus reduce the carbon footprint of the disposal process.

Comparison of properties of wood-plastic composites based on alternate degradation in seawater and acid rain

To investigate the change of the service performance of wood-plastic composites degraded by sea water and acid rain, three types of wood-plastic composite materials were prepared with sorghum straw reinforced with high-density polyethylene (SS/HDPE), polypropylene (SS/PP), and polyvinyl chloride (SS/PVC). Under the extreme alternate degradation conditions simulated by seawater (salinity 3.5%, temperature 55 °C) and acid rain (pH 2.5, temperature 55 °C), the effects on the mechanical and wear properties and the chemical structures of the composites were determined. The exposure to the alternate sea water and acid rain deteriorated the fiber/matrix bonding quality of the composites; the mechanical and wear properties decreased accordingly. Before and after degradation, the three composites were sorted in descending order of the mechanical and wear properties as follows: SS/PVC composites &gt; SS/PP composites &gt; SS/HDPE composites. Sorghum straw /PVC had the best resistance to degradation and sorghum straw /HDPE composite had the least resistance. The matrix molecular chains of the SS/HDPE under the conditions of exposure were broken after 12 days.

Abiotic Long-Term Simulation of Microplastic Weathering Pathways under Different Aqueous Conditions.

Microplastics (MPs) are one of the most abundant and widespread anthropogenic pollutants worldwide. In addition to the global spread and threats of plastic to native species by carrying toxic substances, its slow degradation rate and resulting long retention time in the environment constitute a problem that is still poorly understood. In this study, five of the most manufactured plastic types were weathered under simulated beach conditions for 18 months in freshwater, brackish water, and seawater. Those included polyethylene (PE), polypropylene (PP), polystyrene (PS), polyethylene terephthalate (PET), and polyvinyl chloride (PVC). PP was the first polymer type that fragmented after 9 months of weathering and influenced the pH of the surrounding water. Molecular surface changes were detected for all polymers, just after the first week. Hydroxyl bonds were one of the first groups incorporated into the polymers, weakening 2-3 weeks later. Carbonyl groups were also measured early, but with significantly different developments with time between the polymer types. Differences in degradation rates were proven between the water media, with the fastest degradation in seawater compared to brackish water and freshwater for PE and PP. These results are consistent with previous findings on MPs aged under environmental conditions and provide initial long-term observations of MP degradation pathways under simulated environmental conditions. These findings are valuable for assessing the fate and hazards of MPs in aquatic systems.

Products of Bisphenol A Degradation Induce Cytotoxicity in Human Erythrocytes (In Vitro).

The aim of this work has been to study the possible degradation path of BPA under the Fenton reaction, namely to determine the energetically favorable intermediate products and to compare the cytotoxicity of BPA and its intermediate products of degradation. The DFT calculations of the Gibbs free energy at M06-2X/6-311G(d,p) level of theory showed that the formation of hydroquinone was the most energetically favorable path in a water environment. To explore the cytotoxicity the erythrocytes were incubated with BPA and three intermediate products of its degradation, i.e., phenol, hydroquinone and 4-isopropylphenol, in the concentrations 5-200 μg/mL, for 1, 4 and 24 h. BPA induced the strongest hemolytic changes in erythrocytes, followed by hydroquinone, phenol and 4-isopropylphenol. In the presence of hydroquinone, the highest level of RONS was observed, whereas BPA had the weakest effect on RONS generation. In addition, hydroquinone decreased the level of GSH the most. Generally, our results suggest that a preferable BPA degradation path under a Fenton reaction should be controlled in order to avoid the formation of hydroquinone. This is applicable to the degradation of BPA during waste water treatment and during chemical degradation in sea water.

Influence of Different Environments and Temperatures on the Photo-Oxidation Behaviour of the Polypropylene.

The photo-oxidation of polypropylene at two different temperatures and in three different environments-air, distilled water and sea water-has been followed as a function of the irradiation time. The photo-oxidation kinetic is dramatically dependent on the amount of oxygen available for the oxidation reactions and on the temperature. While the photo-oxidation is very fast in air, the degradation is much slower in the two aqueous media. The degradation in sea water is slightly slower than in distilled water. In all cases, the degradation kinetic increases remarkably with the temperature. This behavior has been attributed to the lower oxygen availability for the oxidation reactions of the polymers. The light difference of the degradation kinetic between the two aqueous media depends on the small difference of the oxygen concentration at the test temperatures of 40 and 70 °C. At the latter temperature, the difference between the degradation kinetic in distilled water and sea water is still less important because increasing the temperature decreases the solubility of the oxygen, and it tends to became very similar in both samples of water.

Evaluation of plastic packaging waste degradation in seawater and simulated solar radiation by spectroscopic techniques

The goal of this study was to evaluate the degradation of plastic packaging waste in seawater and under simulated solar radiation by different spectroscopic techniques in view of their potential recycling. Selected packaging products made of polypropylene (PP), high-density polyethylene (HDPE) and polystyrene (PS) were weathered in a Solar Box for 4 cycles of 504 h each (21 days), for a total of 2016 h (84 days). At each aging cycle, digital images of the polymer samples were acquired to investigate surface changes in terms of cracking and fragmentation. Furthermore, color measurements were carried out by reflectance spectrophotometry in the visible range (VIS: 400–700 nm). Finally, hyperspectral imaging (HSI) in the shortwave infrared region (SWIR: 1000–2500 nm) coupled with chemometric techniques was applied to monitor the aging process in terms of reflectance spectral variations and to evaluate the possibility of predicting the polymer aging time.The results showed that plastic packaging samples are characterized by different degradation behaviors, such as surface alteration (i.e. fractures, grooves and deep cracks), color variation (i.e. yellowing and discoloration) and fragmentation and microplastic formation, corresponding to changes in reflectance and chemical bonds vibrations. The degradation phenomena are influenced by both thickness and polymer type, being more evident for PP and PS samples rather than for HDPE ones.Concerning the results based on SWIR-HSI, principal component analysis (PCA) highlighted the spectral variation of polymers occurring during the artificial aging process through the different clustering in the score plot. Furthermore, good correlations were obtained between polymer spectral signature and aging time applying Support Vector Machines (SVM) prediction model. The use of the proposed spectroscopic techniques, as well as the development of predictive models based on HSI, contributes to understand the behavior of polymers when exposed to marine environment. This approach represents a promising tool for the definition of the degradation status of polymers and for the selection of marine plastics characterized by a level of degradation compatible with their recycling, fully in line with the principles of circular and sustainable economy.

Jatobá (Hymenaea stigonocarpa) pulp films: Properties, antioxidant potential and biodegradability

This study aimed to use jatobá pulp in the production of biodegradable and active films for food packaging. The films were obtained by the casting technique, through a factorial experimental design (23), analyzing concentration of jatobá pulp, glycerol, and temperature. Increasing the jatobá concentration to the maximum studied level (+1) resulted in a 4-fold increase in tensile strength than the lowest level and 1.7-fold greater elongation. The differential scanning calorimetry and contact angle results indicated that the temperature of 80 °C favored the formation of films with interesting mechanical properties of 0.81 MPa of tensile strength and 55 % of elongation, and barrier properties that reduced the water vapor permeability in 28.8 %, without affecting the stability of phenolic compounds and antioxidant activity. In addition, the films showed fast degradation in seawater, soil and beach sand, being completely degraded in 7 days.

GFRP bar-reinforced seawater sea-sand concrete beam under the combined influence of seawater exposure and sustained load: Durability and degradation mechanism

This paper presents an experimental study on the durability of the seawater sea-sand concrete (SWSSC) beam reinforced with glass fiber-reinforced polymer (GFRP) bars under the combined influence of seawater exposure and sustained load. The effects of exposure duration (90, 180, and 270 days) and sustained load level (25 % and 40 % of ultimate load) on the beam’s durability were investigated. The results indicated that the combined influence of seawater exposure and sustained load had little effect on the initial stiffness of the load vs mid-span deflection curve, but it influenced the second stiffness of the curve. The ultimate load improved slightly with the increased sustained load level in the early time due to the further hydration of SWSSC and the water swelling of bars. Then it was reduced with the exposure duration and sustained load level. The degradation mechanism of the GFRP bar-reinforced SWSSC beam under the combined influence of seawater exposure and sustained load was revealed: the composite action loss of SWSSC and GFRP bar is chiefly responsible for the beam degradation in seawater; the internal stress induced by the sustained load could facilitate the development of the existing damages and accelerate the beam degradation.

Enhanced seawater degradation through copolymerization with diglycolic acid: Synthesis, microstructure, degradation mechanism and modification for antibacterial packaging

Marine plastic pollution is a worldwide challenge making new progress in the field of degradable polymers necessary. However, it is difficult for commercial biodegradable polymers, such as polylactide (PLA), to realize rapid degradation in seawater by simply blending modification. Here, we prepared a novel series of poly(butylene diglycolate/terephthalate) (PBDT) copolymers by introducing diglycolic acid into PBT. The proposed polyesters can serve as an eco-friendly substitute for existing packaging materials. The mechanical property of PBDTs, with high tensile strength (>23.4 MPa) and elastic modulus (95–610 MPa), had advantages compared with commercial degradable polymers. The hydrophilicity is enhanced with ether bonds of butylene diglycolate (BD) segments. And the hydrolysis of copolymers was accelerated in seawater, showing 16% weight loss after 30 days. Moreover, PBDTs with BD segments ≥ 20% performed great degradability in Phosphate Buffered Saline and enzymatic solution. And their degradation mechanism was monitored through various tests such as 1H NMR, SEM and GPC. With a small number of antibacterial agents, such as 8% mass fraction of chitosan nanoparticles (CHNPs) or 1.0% of Ag@AgCl, PBDT composites could obtain good antibacterial ability for Gram-negative Escherichia coli without sacrificing the thermal, mechanical properties of the parent PBDT50. This work provides insights and direction for the development of seawater degradable polymers and thereby is able to relieve additional marine pollution in the future.