Behavior In Seawater Research Articles

Eco-friendly corrosion inhibition and scale control in seawater using Foeniculum vulgare and Pimpinella anisum extracts with chemical compounds

This study investigated the corrosion inhibition and scale control properties of both natural extracts and chemical inhibitors for C25 galvanized steel sheets with an 85-μm thick zinc coating steel exposed to seawater. The inhibitors, including Foeniculum vulgare (AF-Sha), Pimpinella anisum (AF-Sim), M640, and Veo, underwent rigorous evaluation through techniques such as Tafel extrapolation, potentiodynamic polarization analysis, concentration factor scale, seawater analysis, X-ray diffraction (XRD), infrared spectroscopy (IR), and conductivity-temperature analysis. Notably, AF-Sha and AF-Sim exhibited outstanding corrosion prevention capabilities, achieving inhibitory efficiencies of 87% and 85%, respectively. Comparative analyses with chemical inhibitors, M640 and Veo, demonstrated promising performance, positioning natural inhibitors as environmentally friendly alternatives. Corrosion rates, inhibition efficiency, and concentration factor scale results provided insights into the inhibitory effectiveness of each compound, with Veo showing superior performance. The study also explored the antiscalant behavior of inhibitors, revealing their ability to prevent corrosion and scale formation. XRD analysis indicated the impact of inhibitors on the crystal structure of scales, while IR spectra provided insights into vibration properties. Conductivity and temperature analyses illustrated the inhibitors' role in reducing ion exchange and gypsum concentration in seawater. These findings suggest that the inhibitors offered robust protection for ferrous metal surfaces and hold significant potential for practical applications. Additionally, our weight loss investigation extends this understanding, demonstrating the practical applicability of corrosion inhibitors like AF-Sha and AF-Sim in real-world scenarios. The presented results contribute significantly to the understanding of galvanized steel corrosion behavior in seawater, offering valuable insights for corrosion engineering applications.

Monitoring and Evaluation of the Corrosion Behavior in Seawater of the Low-Alloy Steels BVDH36 and LRAH36.

The purpose of this study is to evaluate the corrosion resistance in natural seawater (Năvodari area) of two types of low-alloy carbon steels BVDH36 and LRAH36 by electrochemical methods. The electrochemical methods used were the evolution of the free potential (OCP), electrochemical impedance spectroscopy (EIS), polarization resistance (Rp) and corrosion rate (Vcorr), potentiodynamic polarization (PD), and cyclic voltammetry (CV). The studies were completed by ex situ characterization analyzes of the studied surfaces before and after corrosion such as: optical microscopy, scanning electron microscopy and X-ray diffraction analysis. The results of the study show us that the polarization resistance of the low-alloy carbon steel BVDH36 is higher compared to the polarization resistance of the low-alloy carbon steel LRAH36. It is also observed that with the increase in the immersion time of the samples in natural seawater, the polarization resistance of the BVDH36 alloy increases over time and finally decreases, and for the carbon steel LRAH36 the polarization resistance increases.

Broadening the coating applications of sustainable materials by reinforcing epoxidized corn oil with single-walled carbon nanotubes

In the global context of environmental awareness, the present research proposes a sustainable alternative to the widely used petroleum-based epoxy coatings. Epoxidized corn oil (ECO) was tested as potential matrix for advanced nanocomposite coating materials reinforced with 0.25 to 1 wt.% single-walled carbon nanotubes (SW) with carboxyl and amide functionalities. The elemental composition of the epoxy networks was monitored by XPS, showing the increase of O/C ratio to 0.387 when carboxyl-functionalized SW are added. To achieve sustainable composite materials, citric acid was used as curing agent, as a substitute for conventional counterparts. The influence of both surface functional groups and concentration of SW was evaluated through structural and thermo-mechanical analysis. The progressive increase of the DSC enthalpy for SW formulated systems indicates a possible pattern for specific interactions within the bio-based epoxy translated by adjusted activation energy. For 1% neat SW addition, the Ea values decreased to 46 kJ/mol in comparison with 53 kJ/mol calculated for neat epoxy. Furthermore, the -COOH groups from SW nanostructures exerted a strong influence over the mechanical performance of bio-epoxy networks, improving the crosslinking density with ~ 60% and twofold the storage modulus value. Accordingly, by gradual addition of SW-COOH filler within the ECO-based formulations, a very consistent behaviour in seawater was noted, with a 28% decreased value for the absorption degree.Graphical

Unipolar Solution Flow in Calcium-Organic Frameworks for Seawater-Evaporation-Induced Electricity Generation.

Seawater-flow- and -evaporation-induced electricity generation holds significant promise in advancing next-generation sustainable energy technologies. This method relies on the electrokinetic effect but faces substantial limitations when operating in a highly ion-concentrated environment, for example, natural seawater. We present herein a novel solution using calcium-based metal-organic frameworks (MOFs, C12H6Ca2O19·2H2O) for seawater-evaporation-induced electricity generation. Remarkably, Ca-MOFs show an open-circuit voltage of 0.4 V and a short-circuit current of 14 μA when immersed in seawater under natural conditions. Our experiments and simulations revealed that sodium (Na) ions selectively transport within sub-nanochannels of these synthetic superhydrophilic MOFs. This selective ion transport engenders a unipolar solution flow, which drives the electricity generation behavior in seawater. This work not only showcases an effective Ca-MOF for electricity generation through seawater flow/evaporation but also contributes significantly to our understanding of water-driven energy harvesting technologies and their potential applications beyond this specific context.

Photolysis characteristics and influencing factors of adenosine 5′-monophosphate in seawater

Environmental context Organophosphorus (OP) is bioavailable to phytoplankton with photolysis can play an important role in the process. The photolysis behaviour of an OP (adenosine 5′-monophosphate, AMP) in seawater was investigated, and AMP can release inorganic phosphate under environmentally relevant light conditions, indicating OP photodegradation might be important in the phosphorus biogeochemical cycle. The results are helpful to further understand the bioavailability and cycle of OP in marine environment. Rationale Organic phosphorus (OP) is a potential source of bioavailable phosphorus for phytoplankton through photolysis and other degradation processes. Therefore, OP photodegradation plays an important role in phosphorus biogeochemical cycle. Methodology Taking adenosine 5′-monophosphate (AMP) as a model OP, we investigated the photolysis behaviour in seawater and discussed the mechanism. The photolysis dynamics were studied based on the inorganic phosphorus production at appropriate time intervals, which was analysed by spectrophotometric molybdenum blue method. The effects of medium, light and radicals were investigated. Results It was found that AMP can release inorganic phosphate under photosynthetically active radiation and ultraviolet (UV) with UVB being the most reactive band. The degradation of AMP in seawater was lower than that in deionised water under the same conditions, and the fresh seawater was more beneficial than aged seawater. The kinetics could be described by a pseudo-first order equation. Fe3+ can promote the photolysis due to the generation of ·OH radicals, while within the range of this study, changes of Fe3+ content have no substantial effect on the promotion. The influence of ethanol and tetrahydrofuran as radical inhibitor showed evident inhabitation to the degradation, indicating that ·OH and 1O2 played an important role in the process, and ·OH seemed more important than 1O2. Discussion OP photodegradation is of importance in the phosphorus biogeochemical cycle. Varying properties of the medium and light can affect the OP transformation in seawater. The results are helpful to further understand the bioavailability and cycle of OP in the marine environment.

Early diagenetic mobilization of rare earth elements and implications for the Ce anomaly as a redox proxy

The Rare Earth Elements (REE) archived in carbonate rocks retain a wealth of information on paleo-seawater chemistry and local-regional redox conditions. However, interpretations are often ambiguous due to the potential for REE remobilization in marine environments. In this regard, many carbonate rocks that retain primary seawater isotopic signatures exhibit non-seawater-like REE patterns, implying either unusual REE behaviour in seawater or diagenetic overprinting of otherwise well-preserved rock samples. Here, we apply sequential leaching to constrain the possible effects of different REE-bearing phases on measured carbonate REE patterns in order to address this quandary. Our results show that the exchangeable phase contains negligible REE, but could be an important host phase for other elements such as Sr, Ba and K. The acidified hydroxylamine hydrochloride leach is shown here not only to dissolve Fe–Mn oxides but also phosphate minerals, which induces middle REE enrichment in corresponding leachates of dolostone samples in our study. The demonstrable Fe–Mn oxide phase in limestone samples is characterized by middle and/or light REE enrichment and positive Eu anomalies, which are attributed to hydrothermal processes and continuing exchange with marine fluids after initial precipitation. The non-seawater-like REE patterns observed in the carbonate phase of otherwise well-preserved limestones resemble those of the co-existing Fe–Mn oxide fraction, and are interpreted to reflect the dissolution of REE carrier phases during early diagenesis. This view is supported by fluid-rock interaction modelling, which shows how REE can be mobilized at relatively low fluid/rock ratios in shallow porewaters. Non-seawater-like REE patterns may therefore be caused by the incorporation of REE from shallow porewaters before final lithification due to an elevated flux of particulate REE carrier phases, e.g. Fe–Mn oxides and organic matter, to the seafloor. In spite of the sensitivity of carbonate REE patterns to early diagenetic exchange, the co-occurrence of non-seawater-like patterns with primary strontium and carbon isotope values suggests that REE should not be viewed as a general indicator for the preservation of other geochemical proxies. Importantly, Ce anomalies of the carbonate phase will also be affected by porewaters, masking primary seawater values. Our results favour a reevaluation of redox interpretations by taking into account REE patterns as a whole.

Adsorption of trimethoprim and sulfamethoxazole using residual carbon from coal gasification slag: Behavior, mechanism and cost-benefit analysis

The search for efficient adsorbents to mitigate the impact of antibiotic pollutants on marine ecosystems, food security and human health is a burgeoning field of research. Further, Trimethoprim (TMP) and sulfamethoxazole (SMX) are widely distributed in the marine environment and are difficult to degrade. In this research, we used gravity separation to enrich the residual carbon from the coal gasification coarse slag and used the resulting carbon-high product (GC) as a low-cost and high-efficiency adsorbent. TMP and SMX were investigated for their adsorption behavior in seawater using GC under varied conditions. The findings indicated that the adsorption capacities of TMP and SMX by GC were 5.0017 mg/g and 5.1391 mg/g, respectively. The equilibrium durations of TMP and SMX by GC were 21 min and 40 min, respectively. Various adsorption models were fitted to the adsorption behavior of two pollutants by GC. The results showed that the adsorption processes of the two pollutants were consistent with the Freundlich equation and the quasi-secondary kinetic model, suggesting that both pollutants were adsorbed on GC surface by both physical and chemical processes. GC more effectively adsorbed TMP than SMX under a competitive adsorption procedure. When we introduced molecular dynamics simulation into this research, the microscopic procedures of GC adsorbing two pollutants were investigated. The energy composition and hydrogen bond types in the adsorption process were quantified. Finally, we summarized the adsorption mechanism of GC adsorbing two pollutants. This work will pave the way for developing effective, low-cost and environmentally friendly novel materials for the adsorption and purification of antibiotic pollutants in the marine environment. This research can produce positive economic and environmental effects in the comprehensive utilization of coal gasification slag.

Self-powered (In,Ga)N-nanowire-based photodetector with fast response speed for under-seawater detection.

Due to the requirements of oceanography exploration and detection, self-powered photodetectors (PDs) with low-power consumption are essential for the next-generation optoelectronic applications. In this work, we successfully demonstrate a self-powered photoelectrochemical (PEC) PD in seawater based on the (In,Ga)N/GaN core-shell heterojunction nanowires. Compared to those of the PD in pure water, it is found that the upward and downward overshooting features of current can be the key reason contributing to the much faster response speed of the PD in seawater. Thanks to the enhanced response speed, the rise time of PD can be reduced more than 80%, and the fall time remains only 30% by applying in seawater instead of pure water. The key factors of generating these overshooting features should be the instantaneous temperature gradient, carrier accumulation and elimination on the semiconductor/electrolyte interfaces at the moments of light on and off. By the analysis of experimental results, the Na+ and Cl- ions are proposed to be the main factors affecting the PD behavior in seawater, which can enhance the conductivity and accelerate the oxidation-reduction reaction significantly. This work paves an effective way to develop the new self-powered PDs for the wide applications in under-seawater detection and communication.

Characterization of water masses around the southern Ryukyu Islands based on isotopic compositions

We investigated the water-mass structure on the Okinawa Trough and Pacific sides of the southern Ryukyu Island Arc (Yonaguni, Iriomote, and Ishigaki subareas) using the Nd isotope composition (143Nd/144Nd ratios; expressed as εNd values) of benthic foraminiferal tests in surface sediments, which reflect bottom-water composition, along with hydrogen and oxygen isotope compositions (δD and δ18O values, respectively) and physical properties (temperature and salinity) of seawater. The Okinawa Trough side has lower εNd values than the Pacific side due to continental/island material inputs characterized by relatively low εNd values. Moreover, within the Okinawa Trough, other processes control the Nd behavior of seawater and primarily affect the Yonaguni and Iriomote subareas, as follows. (1) Surface and subsurface waters are influenced by Taiwanese river discharge combined with temporospatial variations in oceanographic conditions including Kuroshio Current meandering. (2) Intermediate water is characterized by low εNd values (down to − 8.2), possibly attributable to sediment plumes and turbiditic fluxes. (3) The εNd values of bottom water indicate upwelling and vertical mixing, with composition therefore being similar to those of intermediate water. The εNd profiles are better defined on the Pacific side. High εNd values occur in surface and subsurface (< 300 m depth, potential density < 25.0 kg m−3) waters, and low values (down to − 7.0) occur in subsurface–core-intermediate water (400–600 m depth, 26–27 kg m−3). εNd values increase slightly to − 4.0 below 750 m depth and remain constant down to about 2000 m depth, below which deep water shows a slight decrease in εNd values. Intermediate and bottom/deep waters are distinguished from upper layers by their lower δD and δ18O values.

Rare earth element behaviour in seawater under the influence of organic matter cycling during a phytoplankton spring bloom – A mesocosm study

Rare earth elements (REEs) are used as powerful proxies for a variety of oceanic processes. The understanding of their biogeochemical behaviour in the marine environment is therefore essential. While the influence of OM-cycling on REE patterns in seawater is considered as insignificant, it has been shown that algae and bacteria provide good sorption surfaces for REEs and that components of the dissolved OM pool are able to complex REEs, thus potentially altering their behaviour. To investigate the impact of bio-associated processes on REEs in the bio-productive marine environment, we conducted an indoor mesocosm experiment that mimicked a phytoplankton spring bloom in the neritic coastal North Sea. The incubation period of 38 days covered two distinct phytoplankton bloom phases (diatoms followed by Phaeocystis sp.) and an interjacent bacterioplankton maximum. All dissolved REEs (dREEs) except samarium showed similar temporal concentration patterns, which were closely connected to the bloom succession. The concentration patterns were shaped by the ‘phytoplankton-shuttle’, which summarizes adsorption processes on phytoplankton-derived particulate OM (POM) and resulted in decreasing dREE concentrations alongside chlorophyll-a and POM maxima. The ‘heterotrophic-shuttle’ resulted in increasing dREE concentrations likely linked to heterotrophically mediated regeneration of POM and associated desorption processes. The effect of these processes on dREEs resulted in enhanced fractionation of light REEs (LREEs) relative to heavy REEs (HREEs) during adsorption processes and decreased fractionation as a result of desorption. At times of high dissolved organic carbon (DOC) concentrations, we observed a stabilization of especially dHREEs likely in organic complexes. To test the potential influence of DOC on dREEs, we used a PHREEQC model approach that revealed dREE complexation with components of the DOC pool and an increase in complexation with atomic mass of the REEs. That is, at high DOC concentrations OM-dREE complexation leads to an effective and preferential buffering of dHREE against adsorption. Our findings reveal that OM-cycling influences concentration patterns of dREEs via ad- and desorption processes as well as organic complexation with parts of the OM pool, suggesting these processes can have a significant impact on dREE concentrations in the natural marine environment under high OM conditions.

Corrosion behavior of a newly developed high strength aluminum alloy with high magnesium content under simulated seawater environment

AbstractAMg61 (Al‐6.2% Mg), a novel form of high‐strength, high‐magnesium‐content aluminum alloy, has been developed for specific maritime engineering in recent years, while its corrosion behavior in seawater is still unknown. Therefore, the corrosion behavior of AMg61 in the simulated seawater was investigated herein, using a weight‐loss test and different electrochemical measurements. In addition, corrosion morphology and chemical contents were characterized by metallography, scanning electron microscopy, and energy‐dispersive spectroscopy. The results demonstrated that intergranular corrosion and microcracks developed first in the second phase of AMg61, followed by pitting corrosion. The matrix of AMg61, on the other hand, exhibited a uniform and exfoliation corrosion. The corrosion rate gradually decreased over time.

Effect of the Surface Hydrophobicity–Morphology–Functionality of Nanoplastics on Their Homoaggregation in Seawater

The way nanoplastics aggregate in the environment is one of the key properties that control their final fate and impact on the environment. In the present work, to better predict their transportation pathways, nanoplastic homoaggregation was studied in saltwater to predict the behavior in seawater. We designed nanoplastic models that are free of additives with a chemical control of the surface to model surface weathering. The samples present a wide distribution of relevant surface properties such as functionality (ionizable carboxylic group, 0.10 to 1.7 mmol g–1), hydrophobicity (surface energy, 2.20 to 37.5 mJ m–2), surface morphology (smooth or “raspberry-textured),” zeta potential (−31 to −21 mV), and anisotropy in shape. The critical coagulation concentration (CCC) measurements demonstrate that spherical nanoparticles are more stable in seawater (CCC > 600 mmol L–1) than anisotropic nanoplastics (CCC ∼ 100 mmol L–1). The results highlight the importance of considering the surface properties and shape when assessing the behavior of nanoplastics in the environment.

Durability assessment of the oldest concrete structure in the Mediterranean coastline: The Ghazaouet harbour

The present article deals with the condition assessment and durability characterization of the oldest Algerian concrete structures exposed to the Mediterranean sea for around 100 years, taking as a study case the port of Ghazaouet, located in the extreme northwest of Algeria (province of Tlemcen). This study includes inspections of the condition of the harbour structures and in-situ tests conducted in atmospheric zone to characterise the mechanical characteristics of concrete (sclerometer rebound), and durability indicators determination as porosity (Mercury Intrusion Porosimetry) and chloride diffusion coefficient calculated with total and free chloride profiles.Diagnosis inspections on the port's concrete structures indicate localized damage with acceptable mechanical resistance. However, an increase in porosity with microstructure change was noted and extensive chloride penetration have been recorded. Finally, simulation analysis of the valuable data of diffusion coefficient (Da) and surface concentration (Cs), showed the great effect of the chlorides concentration at the surface on long-term exposure of concrete behaviour in seawater.

Detection of dynamic biofouling from adenosine triphosphate measurements in water concentrated from reverse osmosis desalination of seawater

The evaluation of fouling behavior, including biofouling, is crucial to increase efficiency in the reverse osmosis (RO) seawater desalination process (SDP). This paper reports on biofouling behavior in seawater in the SDP, detected by monitoring intracellular, extracellular, and total adenosine triphosphates (ATPs) in the cross-flow RO filtration system as bacterial activity tracers. The first-stage ultrafiltration (UF) treatment of raw seawater reduced the ATP range to approximately 25%, while the ATP concentration in seawater did not decrease significantly on average between the subsequent four stages until the RO membrane treatment. The results demonstrated temporal variation of ∆ATPs, the deference in ATPs between in RO concentrated water and in RO feed water, occurs randomly, as the membrane fouling index, evaluated from pressure measurements, increases to the level of fouling that requires cleaning. The significant increase in ∆ATPs despite a residence time of only approximately fifteen seconds over the RO module reflects bacteria cell detachment from biofilm. The large reduction in ∆ATPs reflects bacteria cell adhesion and biofilm growth on RO membrane surfaces. It is concluded that the temporal increase and decrease in ∆ATP in RO concentrated water capture the dynamic biofouling behavior and the formation process of biofilm on RO membrane surfaces.

Influence of Annealing Treatments on Welded CuNi Sheets on the Corrosion Behaviour in Sea Water

Due to their good corrosion resistance in seawater, tubes, rods, and forgings made from copper-nickel alloys (Cu-Ni) are widely used in ship building, offshore platforms, desalination plants, and numerous other applications. Welding is a major technology for joining this material. Since the microstructures of base material, weld seam, and heat affected zone may be quite different, the consequences with respect to corrosion must be considered. In this study the influence of microstructure on corrosion behaviour was investigated using welded test coupons of CuNi10Fe1.6 Mn, as-welded and after heat-treatment, by metallographic examination and electrochemical corrosion tests in synthetic seawater.

On the evolution of microstructure, texture and corrosion behavior of a hot-rolled and annealed AZ31 alloy

The microstructure and texture evolution of an AZ31 alloy were investigated after hot rolling and subsequent annealing using electron backscatter diffraction (EBSD). First, the alloy was hot-rolled at 350 °C up to low, medium and high strain (20, 50 and 85% of thickness reduction, respectively). The alloy samples where then annealed at 350 °C for 2, 10 and 60 min. The effect of strain level and annealing on corrosion behavior in seawater was also evaluated using electrochemical tests. At low strain, the microstructure was characterised by the absence of twinning, mainly due to the prior thermo-mechanical history of the as-received alloy. However, various modes of twinning were observed at medium strain. At high strain, the dynamic recrystallization process resulted in a microstructure with a typical basal texture. The results demonstrate that twins are responsible for the deviation of {0002} basal poles from normal towards the transversal direction. Annealing at 350 °C for up to 60 min led to normal grain growth in all the samples. In medium and highly strained samples, the deformation texture was retained, while the low strain sample underwent noticeable changes due to the absence of dynamic recrystallization. A synergetic effect of grain refinement and texture weakening was responsible for the alloy's enhanced corrosion resistance.

Gemini Surfactant as a Template Agent for the Synthesis of More Eco-Friendly Silica Nanocapsules

Silica mesoporous nanocapsules are a class of “smart” engineered nanomaterials (ENMs) applied in several fields. Recent studies have highlighted that they can exert deleterious effects into marine organisms, attributed to the use of the toxic cationic surfactant N-hexadecyl-N,N,N-trimethylammonium bromide (CTAB) during the synthesis of ENMs. The present study reports the successful synthesis and characterization of novel gemini surfactant-based silica nanocapsules. The gemini surfactant 1,4-bis-[N-(1-dodecyl)-N,N-dimethylammoniummethyl]benzene dibromide (QSB2-12) was chosen as a more environmentally-friendly replacement of CTAB. Nanocapsules were characterized by scanning electron microscopy (SEM), Fourier-transformed infrared spectroscopy (FTIR), dynamic light scattering (DLS), thermogravimetric analysis (TGA) and N2 adsorption-desorption isotherms. Short-term exposure effects of new ENMs were evaluated in four marine species (Nannochloropsis gaditana, Tetraselmis chuii and Phaeodactylum tricornutum) and the microcrustacean (Artemia salina). The replacement of the commercial cationic surfactant by the gemini surfactant does not change the structure nor the environmental behaviour in seawater of the newly synthesised silica nanocontainers. Additionally, it is demonstrated that using gemini surfactants can reduce the toxicity of novel silica nanocapsules towards the tested marine species. As a result, environmentally-friendly ENMs can be obtained based on a safe-by-design approach, thereby fitting the concept of Green Chemistry.

Impacts of Smart Waters on Calcite–Crude Oil Interactions Quantified by “Soft Tip” Atomic Force Microscopy (AFM) and Surface Complexation Modeling (SCM)

The interactions of calcite surface with crude oil are influenced by the ionic chemistry of the injection water in “smart water” flooding; however, the molecular evidence of their influences is missing in the current studies. To address this issue, we measured the calcite–oil interactions in four kinds of smart waters by driving a droplet of crude oil (“soft tip”) toward and away from the calcite surface using atomic force microscopy (AFM). The force behaviors showed that the calcite–oil interactions were repulsive in smart waters containing low concentrations of Ca2+ ions, such as seawater (SW) and seawater with one-fourth of Ca2+ concentration (SWCa), which have produced extremely weak adhesions and works of adhesion in these two brines. In contrast, the force curves showed “jump-in” behavior in seawater with four times increased SO42– concentration (SWSO) or Mg2+ concentration decreased to one-fourth (SWMg) compared to SW, which has produced extremely large adhesions and works of adhesion. The underlying reasons for calcite–oil interactions in response to different smart waters were investigated by the method of surface complexation modeling (SCM), which combined a charge-distribution multisite ion complexation (CD-MUSIC) model and a basic Stern model (BSM) to describe the complex electrochemical reactions of calcite, smart water, and crude oil. The adhesion energies were calculated based on the surface complexations, which showed good agreements with the AFM force results. The SCM results suggested that the weak calcite–oil interactions in SW and SWCa solutions can be attributed to the mitigation of cation (Ca2+) bridging interactions owing to a deficiency in surface Ca2+ ions. The strong calcite–oil interactions in SWSO and SWMg solutions are caused by a dramatic increase of cation (Ca2+) bridging interactions due to an excess of surface Ca2+ ions. Overall, the attractions of calcite surface with crude oil follow the order SWCa < SW ≪ SWMg < SWSO, which infers that the oil molecules may be easily displaced from the calcite surface with smart waters containing low concentrations of Ca2+ and SO42– ions but high concentrations of Mg2+ ions.

Ranking environmental degradation trends of plastic marine debris based on physical properties and molecular structure

As plastic marine debris continues to accumulate in the oceans, many important questions surround this global dilemma. In particular, how many descriptors would be necessary to model the degradation behavior of ocean plastics or understand if degradation is possible? Here, we report a data-driven approach to elucidate degradation trends of plastic debris by linking abiotic and biotic degradation behavior in seawater with physical properties and molecular structures. The results reveal a hierarchy of predictors to quantify surface erosion as well as combinations of features, like glass transition temperature and hydrophobicity, to classify ocean plastics into fast, medium, and slow degradation categories. Furthermore, to account for weathering and environmental factors, two equations model the influence of seawater temperature and mechanical forces.

Behaviour of seawater and sea sand concrete filled FRP square hollow sections

Abstract FRP tube could serve as formwork in new constructions and the square cross-section is convenient for connections. This paper presents an experimental and theoretical study on seawater sea sand concrete (SWSSC)-filled glass/carbon/basalt FRP square hollow section (SHS) stub columns and beams. FRP SHS includes fibres oriented in ±15°, ±40° and ±75° with respect to the longitudinal axis so that the hoop and axial strengths are comparable. Both unfilled FRP SHS and SWSSC-filled FRP SHS were tested under axial compressive, three-point or four-point bending loads. SWSSC-filled FRP columns failed by FRP rupture, whereas the failure mode for beams was the crushing of compressive flanges. In this paper, the stress-strain behaviour of columns and moment-strain curves of beams were discussed and compared to the corresponding SWSSC-filled stainless steel (SS) SHS specimens. It was found that existing stress-strain models, which were originally derived for rectangular concrete confined by FRP wrap, cannot precisely capture the stress-strain response of SWSSC-filled FRP columns. Existing models are improved to more accurately predict the ultimate axial strains and stress-strain relationship. A theoretical model is proposed to estimate the moment capacity of SWSSC-filled FRP beams with reasonable accuracy.