Seawater Solutions Research Articles

Highly Efficient Porous Glass Solar Water Evaporator

AbstractThe global water crisis, exacerbated by excessive use and pollution, has resulted in energy scarcity and threats. Solar desalination provides a sustainable fix, with researchers developing photothermal materials and designs to improve efficiency and sustainability. Glass materials, with their exceptional chemical stability, are suitable for extreme desalination in acidic and alkaline conditions. In this work, we have developed a porous glass evaporator (PGE) with exceptional water evaporation efficiency, achieved through a novel fabrication method that blends glass powders with soluble salts to create structure with continuous pores. The evaporator's microstructure comprises micrometer‐scale pores that form interconnected porous channels, facilitating efficient water transport and preventing salt deposition. Under one sun irradiation, the PGE exhibits superior solar evaporation performance in pure water, achieving a rate of 2.21 kg m−2 h−1, with an evaporation efficiency of 98%. In more complex media, such as seawater and methylene blue solution, the PGE also displays excellent evaporation capabilities, reaching rates of 2.08 and 2.47 kg m−2 h−1, respectively. Even after sustained alternation between acidic and alkaline treatments, the PGE retains an impressive evaporation rate of over 2.0 kg m−2 h−1, coupled with structural robustness, making it a promising candidate for practical applications in extreme environments.

Electrospun Membranes of Hydrophobic Polyimide and NH2‐UiO‐66 Nanocomposite for Desalination

Hydrophobic nanofiber composite membranes comprising polyimide and metal–organic frameworks are developed for desalination via direct contact membrane distillation (DCMD). Our study demonstrates the synthesis of hydrophobic polyimides with trifluoromethyl groups, along with superhydrophobic UiO‐66 (hMOF) prepared by phenylsilane modification on the metal‐oxo nodes. These components are then combined to create nanofiber membranes with improved hydrophobicity, ensuring long‐term stability while preserving a high water flux. Integration of hMOF into the polymer matrix further increases membrane hydrophobic properties and provides additional pathways for vapor transport during MD. The resulting nanofiber composite membranes containing 20 wt% of hMOFs (PI‐1‐hMOF‐20) were able to desalinate hypersaline feed solution of up to 17 wt% NaCl solution, conditions that are beyond the capability of reverse osmosis systems. These membranes demonstrated a water flux of 68.1 kg m−2 h−1 with a rejection rate of 99.98% for a simulated seawater solution of 3.5 wt% NaCl at 70 °C, while maintaining consistent desalination performance for 250 h.

All-solid-state electrochemical marine sensors based on Na3V2(PO4)3@Na4Zr2Si3O12 solid-state reference electrodes

In this study, Na4Zr2Si3O12 (NZS) solid electrolyte was prepared using an elevated-temperature solid-state method. After heating under supercritical conditions (i.e., 400 °C and 40 MPa), the structure and performance stability of the as-fabricated NZS solid electrolyte were evaluated applying scanning electron microscopy (SEM), X-ray diffraction (XRD), and electrochemical impedance spectroscopy (EIS). A new all-solid-state reference electrode, combining Na3V2(PO4)3(NVP) with NZS (NVP@NZS), was developed, and its electrochemical properties were investigated. The prepared reference electrode demonstrated steady potential in both simulated seawater and buffer solutions across a range of pH values and different salt solutions. The reference electrode, integrated with an Ir/IrO2 working electrode, was used to construct an all-solid-state potentiometric pH sensor. This sensor demonstrated a strong linear related response when measuring the pH of both aqueous solutions and simulated seawater samples. Additionally, an ion sensor based on anodic stripping voltammetry, constructed with the assembled solid-state reference electrode, a platinum counter electrode, and a gold-mercury working electrode, was utilized to measure Cu2+ and S2− ions in both aqueous solutions and simulated seawater samples. These all-solid-state electrochemical sensors, incorporating the NVP@NZS solid-state reference electrode, demonstrated a small detection threshold, excellent linear correlation (R2 > 0.99), and a broad detection range, making them well-suited for chemical analysis in challenging marine environments.

Nanoarchitectonics of Nickel Nitride‐V2CTX Mxene: An Efficient Bifunctional Catalyst for Alkaline Water/Seawater Applications

AbstractSeawater, being the most plentiful natural water source worldwide, is a highly abundant and cost‐efficient medium for producing hydrogen by alkaline water electrolysis. However, the advancement of seawater electrolysis is hindered by notable impediments caused by chloride corrosion at the anode and the simultaneous chlorine evolution process. Only a limited number of non‐noble electrocatalysts demonstrate noteworthy bifunctional catalytic efficacy and long‐term durability. In this regard, Nickel Nitride tailored V2CTX Mxene nanostructures is reported as a bifunctional catalyst for overall water/seawater applications. The optimized sample Ni3N@3000‐V2CTx exhibits low overpotential values of 90 and 300 mV in acidic and alkaline + seawater solutions respectively at 10 mA cm−2 for hydrogen evolution reaction. Similarly, this catalyst shows 70 and 240 mV overpotential values in alkaline water and alkaline + seawater solutions respectively at the same current density for oxygen evolution reaction. Synergetic effects of Multiple Vanadium and Nickel valency along with compelling nitrogen bonds creates elevated density of exposed functional sites for electrocatalytic activity. Furthermore, the notable electrochemical active surface area and mass activity suggest an enhanced and significant presence of abundant active sites. Additionally, the high stability and significantly decreased charge transfer resistance expedited the overall water/seawater‐splitting reaction rate.

Methallylsulfonate Polymeric Antiscalants for Application in Thermal Desalination Processes.

Nine copolymers of acrylic acid and sodium methallyl sulfonate were tested as scale inhibitors in thermal desalination. The nine antiscalants covered molar masses between 2000 and 9500 g.mol-1 and concentrations of sulfonated monomer ranging between 10 and 30 mole percent. A pressure measurement and control (P-MAC) unit and a high-temperature pressurized vessel were used to measure the effectiveness of the scale inhibitors in seawater, concentrated seawater, and model solutions at 125 °C. The effectiveness of the novel copolymers was comparable to commercial antiscalant at times up to 15 min and improved at longer times. Molar mass was a more important determinant of effectiveness than degree of sulfonation, with the greatest mitigation of calcium sulfate precipitation observed for antiscalants of molar mass 2000 to 2500 g.mol-1 regardless of sulfonate content. Antiscalants of molar mass 4500 to 5000 g.mol-1 showed a higher threshold effect than antiscalants of molar mass 7000 to 9500 g.mol-1, with a 30% sulfonated polymer of molar mass 4500 g.mol-1 performing appreciably better than other polymers of a similar molar mass.

Cobalt Molybdenum Telluride as an Efficient Trifunctional Electrocatalyst for Seawater Splitting

A mixed-metal ternary chalcogenide, cobalt molybdenum telluride (CMT), has been identified as an efficient tri-functional electrocatalyst for seawater splitting, leading to enhanced oxygen evolution reaction (OER), hydrogen evolution reaction (HER), and oxygen reduction reaction (ORR). The CMT was synthesized by a single step hydrothermal technique. Detailed electrochemical studies of the CMT-modified electrodes showed that CMT has a promising performance for OER in the simulated seawater solutions, exhibiting a small overpotential of 385 mV at 20 mA cm−2, and superior catalyst durability for prolonged period of continuous oxygen evolution. Interestingly, while gas chromatography analysis confirmed the evolution of oxygen in an anodic chamber, it showed that there was no chlorine evolution from these electrodes in alkaline seawater, highlighting the novelty of this catalyst. CMT also displayed remarkable ORR activity in simulated seawater as indicated by its four-electron reduction pathway forming water as the dominant product. One of the primary challenges of seawater splitting is chlorine evolution from the oxidation of dissolved chloride salts. The CMT catalyst successfully and significantly lowers the water oxidation potential, thereby separating the chloride and water oxidation potentials by a larger margin. These results suggest that CMT can function as a highly active tri-functional electrocatalyst with significant stability, making it suitable for clean energy generation and environmental applications using seawater.

Research on smoke cleaning based on Mg(OH)2/NaClO2 seawater solution

Abstract Ship exhaust emissions contain a large amount of sulfur oxides and nitrogen oxides, which have attracted widespread attention from the international community for their pollution of the atmospheric environment. In order to reduce the emissions of these pollutants, the International Maritime Organization (IMO) and other national institutions have established strict emission standards and promoted the research and application of ship exhaust desulfurization and denitrification technology. Experimental and simulation analyses were conducted on the denitrification effect of Mg(OH)2/NaClO2 solution using a cyclic spray method. Simulation analysis was carried out using cyclic spraying. The experiment compared the reaction degree and reaction time of NO in NaClO2 seawater, NaClO2 water, and Mg(OH)2/NaClO2 marine solution. The experimental result is that in the process of cyclic spray, the removal rate of NO by these three solutions can reach 100%. The reaction time of NO is 71, 86, and 90 minutes, respectively. Under the same conditions, the simulation results showed that the reaction rate of NaClO2 water solution with NO was faster, followed by NaClO2 seawater solution. The reaction rate of Mg(OH)2/NaClO2 seawater solution with NO was the slowest of the three. When the pH value exceeds 7, it effectively inhibits the production of ClO2 gas by NaClO2. The removal rate of Mg(OH)2/NaClO2 seawater solution is directly proportional to the initial concentration of NaClO2. In addition, it could be seen from the simulation cloud diagram that the removal speed of NO in the spray reactor slows down as the concentration of NO increases.

Characterization of Ni-Cu multilayers deposition on low carbon steel substrate using electroplating technique

Abstract Low carbon steel is widely used in oil and gas applications. In this research, multilayers of Nickel (Ni) and Copper (Cu) were deposited on a low carbon steel substrate using the electroplating process (ELP). Initially, a layer of Ni was coated, followed by a layer of Cu. ELP was implemented using water bath containing (300 g/l) of NiSO4.6H2O, (30 g/l) of (NiCl2.6H2O), (40 g/l) of H3BO3 and (30 g/l) of (NaCN), (30 g/l) of (CuCN), (10 g/l) of (NaOH.6H2O). First bath parameters were temperature is (59 - 60 °C), current density in the range of (3-5 A/dcm2), voltage was holed at (8 V) for Ni, and temperature was between (50-51 °C), current density in the range of (1-2 A/dcm2), voltage was holed at (4 V), while the plating time (10 minutes) for both Ni and Cu. The results refer to Ni, Cu, and Ni & Cu ELP thicknesses 3, 4.77 and 6.75 μm respectively. Metallurgical tests were achieve including the micro hardness of ELP, Vickers micro hardness results showed improvement in hardness values compared, with steel substrate, and in the presence of Ni, Cu, Ni+Cu layers, 322, 581, 479, and 562 Hv respectively. The roughness was measured using surface roughness measurement device. The average surface roughness (Ra) depicted satisfying values as a result of Ni layer coating, which gave uniform surface distribution with Ra 0.363 μm. X-ray diffraction (XRD) test examinations serve as strong evidence for the presence of Ni and Cu in the internal and external finish layers, respectively. Corrosion examinations were carried out in seawater solution (3.5 g NaCl) the corrosion behavior tends to be more resistance, with layers of Ni, and Cu in sea water environment, which is considered an important criterion to increase the part life.

Fluorine-free superhydrophobic Ni/Mn-TiO2 composite coatings on carbon steel via one-step electrodeposition for enhanced durability and corrosion resistance

The application of superhydrophobic coatings on carbon steel (CS) surface represents an effective strategy for mitigating corrosion in these materials. This study presents the preparation of superhydrophobic Ni/Mn-TiO2 composite (SNMT) coatings on CS substrates through a facile one-step electrodeposition technique. The formation mechanism of SNMT coatings was meticulously analyzed under varying conditions of nanoparticle types and concentration levels. The inclusion of TiO2 nanoparticles, with an optimal additive concentration of 1 g, facilitated the formation of numerous low surface energy, cauliflower-like microstructures on CS interface. Surprisingly, the results indicate that SNMT coatings maintained commendable superhydrophobicity even post-exposure to superficial damages such as tape peeling, sandpaper wear, and knife-scratch, as evidenced by a static contact angle (CA) exceeding 158° and a sliding angle (SA) below 2°. Furthermore, the corrosion inhibition efficacy of SNMT coatings was quantitatively assessed via dynamic potential polarization curves in a simulated seawater environment. The results demonstrated that SNMT coatings exhibited excellent corrosion inhibition performance in simulated seawater solution, with a protection efficiency (PE) reaching 96.5%. In conclusion, superhydrophobic surfaces can effectively inhibit the penetration of corrosive liquids. The durability and robustness of such superhydrophobic surfaces advocate for their potential widespread application in enhancing the longevity and reliability of CS in corrosive environments.

NiP/Fe3P/MoP@NF nanoblocks as a bifunctional electrocatalyst for water splitting in alkaline seawater and urea solution

Compared with conventional electrolytic fresh water for hydrogen generation, electrolytic seawater for hydrogen production is more cost-effective, because seawater resources are rich, and fresh water resources are short. However, there are many impurity ions in seawater, especially chloride ions, which have great corrosion on the catalyst, so it is a major factor restricting the development of electrolytic seawater. In this study, a novel NiP/Fe3P/MoP@NF catalyst was made via conventional hydrothermal and phosphating method. Experimental results show that the overpotential of NiP/Fe3P/MoP@NF catalyst in the current density of 10 mA cm−2 is just 40 mV for hydrogen evolution reaction (HER) and the overpotential of NiP/Fe3P/MoP@NF catalyst in the same condition is 135 mV for oxygen evolution reaction (OER) in 1 M KOH and seawater solution. In electrolyte solution of 0.5 M urea and 1 M KOH, the overpotential of NiP/Fe3P/MoP@NF catalyst in the same current density of 10 mA cm−2 is 51 mV for HER. Furthermore, the whole alkaline seawater splitting requires an applied voltage of 1.66 V at current density of 10 mA cm−2. Experimental results show that the increased catalytic activity is assigned to the rapid electron transport rate, the exposure of more activity sites, and their synergistic catalysis. The density functional theory (DFT) can show that MoP has the best Gibbs free energy for hydrogen and electrical conductivity compared with NiP and Fe3P, thus enhancing the catalytic performance of NiP/Fe3P/MoP@NF. The paper proposes novel ideas concerning the exploration of catalysts in alkaline seawater and urea solution.

A Molecular Dynamics Study of the Influence of Low-Dosage Methanol on Hydrate Formation in Seawater and Pure Water Metastable Solutions of Methane

The behavior of low concentrations of methanol (0.5 and 1.0 wt% of water) as a promoter for hydrate formation in seawater or pure water metastable solutions of methane was investigated using the classical molecular dynamics method at moderate temperature and pressure. The influence of methanol on the dynamics of the re-arrangement of the hydrogen bond network in seawater and pure water solutions of methane was studied by calculating order parameters of the tetrahedral environment and intermolecular torsion angles for water molecules, as well as by calculating the number of hydrogen bonds, hydrate, and hydrate-like cavities. It was found that hydrate nucleation can be considered a collective process in which the rate of hydrate growth is faster in systems with low concentrations of methanol, and confident hydrate growth begins earlier in a metastable solution without sea salt with a small amount of methanol than in systems without methanol.

Regulating local atomic environment of Fe3O4 to promote anion exchange membrane based alkaline seawater electrolysis

Designing efficient and durable HER electrocatalysts for seawater splitting to resist the corrosive seawater is crucial for continuous seawater electrolysis technology. Herein, a self-supported Fe3O4 electrode with P doping and O vacancy (P-Fe3O4-x) was constructed as an efficient and stable HER catalyst under alkaline seawater. A set of characterization reveals that P doping and O vacancy can effectively regulate the local atomic environment of Fe3O4, optimizing the hydrogen adsorption/desorption of Fe site on P-Fe3O4-x. Moreover, the unique electron-rich local atomic environment of Fe site decreases the adsorption energy of Cl- at the Fe site, remarkably enhance the corrosion-resistance of P-Fe3O4-x. As expected, the obtained P-Fe3O4-x displays high activity (367 mV at 3 A cm−2) and outstanding 1000 h stability in alkaline seawater solution. Besides, the AEM electrolyzer using P-Fe3O4-x as cathode achieves seawater electrolysis of 1.0 A cm−2 at 1.97 V and operates stably for 100 h at the high current density of 1.0 A cm−2.

Boosting hydrogen adsorption via manipulating interfacial electronic structure of NiPx for enhanced alkaline seawater electrolysis

The development of transition metal phosphides (TMPs) electrocatalysts with appropriate binding strength towards intermediates and resistant to chlorine in alkaline seawater electrocatalysis remains a formidable challenge. Herein, an approach for manipulating electron redistribution in Ni2P/Ni5P4 treated by Co cationic doping engineering (denoted as Act-Co-NiPx) is proposed, exhibiting excellent catalytic activities and stability toward HER in alkaline seawater solution. First-principles calculations demonstrate that the Co doping can effectively adjust the electron redistribution of Ni2P/Ni5P4, resulting in a reduction in the hydrogen adsorption free energy for HER and an acceleration in the interfacial charge transfer. Furthermore, the enhanced Cl- adsorption energy avoids the toxicity of Cl- to the active sites in alkaline seawater splitting. Consequently, the resulting Act-Co-NiPx catalyst demonstrates remarkable HER performance with low overpotentials of 77 and 97 mV at a current density of 10 mA cm−2 in both 1.0 M KOH and 1.0 M KOH+Seasalt electrolytes. Furthermore, the seasalt electrolyzer assembled from Act-Co-NiPx achieves the low cell voltage of 1.63 V at 10 mA cm−2. This work demonstrates a feasible method for designing cost-effective and stable catalysts with excellent selectivity via regulating the electronic structure of TMPs for seawater electrolysis.

Effect of sulfidation and phosphidation on Fe doped Co LDH/nickel foam for efficient multifunctional water splitting electrodes, urea oxidation reaction, and seawater splitting: An experimental and computational study

In this work, the binder-free Fe-doped cobalt LDH/nickel foam (CoFe LDH/NF) electrode was prepared using the hydrothermal method. To achieve higher electrocatalyst activity of CoFe LDH/NF, sulfurization was conducted using the hydrothermal method, while the phosphidation was performed through a chemical vapor deposition (CVD) technique. The CoFeS/NF and CoFeP/NF electrodes exhibited significantly higher electrocatalytic activity than CoFe LDH/NF electrode. The CoFeP/NF electrode with a specific surface area of 6.8 m2 g−1 had lower overpotentials of 120 and 236 mV for hydrogen (HER) and oxygen (OER) evolution reactions, respectively. Additionally, the CoFeP/NF electrode exhibited a low potential of 1.32 V vs. RHE at a current density of 10 mA cm−2 for urea oxidation reaction (UOR). The CoFeP/NF electrode demonstrated low overpotentials of 224 and 273 mV in a seawater solution for HER and OER, respectively. The density functional theory (DFT) calculations confirmed the experimental results in which the CoFeP/NF material had promising electrocatalytic activity for renewable energy applications.

Assessing the Limit of CO2 Storage in Seawater as Bicarbonate-Enriched Solutions.

The dissolution of CO2 in seawater in the form of bicarbonate ions is an attractive alternative to storage in geological formations, on the condition that the storage is stable over long periods and does not harm the marine environment. In this work, we focus on the long-term chemical stability of CO2 absorbed in seawater as bicarbonate by monitoring the physico-chemical properties of the solutions (pH, dissolved inorganic carbon and alkalinity) in six different sets of experiments on both natural and artificial seawater lasting up to three months. The bicarbonate treatment of natural seawater consists of mixing it with pre-equilibrated solutions obtained from the reaction of CO2 and Ca(OH)2, with the same pH as natural seawater. This was achieved with a pilot plant working with tons of seawater, while small-scale laboratory experiments were carried out by adding sodium bicarbonate to artificial seawater solutions. If the increase in the overall carbon concentration in the final mixture does not exceed a critical threshold (about 1000-1500 μmol/L), the resulting bicarbonate-rich solutions are found to be stable for over three months.

Tribocorrosion of couplings in seawater environment: An investigation on the positive-negative role of synergy

Tribocorrosion is a recent paradigm of tribology defined as the combination of simultaneous mechanical and chemical wear of couplings. To date, this phenomenon is common in several engineering fields, such as the naval sector where marine equipment, offshore platforms and so on are clear examples. In this regard, the synergy between the mechanical and the chemical effects has a notable effect on the behavior of couplings in seawater environment. Nevertheless, the latter can act also as antagonistic factor. Hence, in this manuscript, an investigation was conducted on a tribosystem composed of an alumina sphere and a stainless-steel AISI 316 L flat, immersed in an artificial seawater solution of 3.8 % NaCl and a pH of 8.2. The analysis, carried out by a reciprocating tribometer equipped with a two/three-electrode potentiostat, was performed for different loads and frequency values, and their correlation with synergistic effects was investigated. The open-circuit potential, friction coefficient, tribocorrosive current and total wear were evaluated for different tribological conditions. It was found that the force and sliding velocity had a significant position in the synergistic response, passing from positive to negative mainly due to the protective action of oxide layer and lubrication behavior of corrosion products formed during the motion. Moreover, the current was modeled via two analytical laws discussed in literature, providing a good agreement with experimental data. Lastly, was provided the oxide thickness evolution formed on the samples surface and its relationship with total wear.

Investigating Cathode Dynamics in Realistic Desalination Reactors Using Operando High-Energy Synchrotron X-Ray Microscopy

Four billion people suffer from lack of clean water at least one month of the year.[1] This critical water shortage applies not only to the supply of potable water, but also to water for use in industrial, agricultural, and energy applications. While water resources like seawater are abundant, hardly any water resource is clean enough for direct use. Desalination provides a methodology to render unusable waters from such water resources fit for use. An innovative and particularly energy-efficient electrochemistry-based approach is the Desalination Battery (DB), which stores the energy input during desalination in chemical bonds between ions and faradaic electrode, allowing for its recovery during the salination process. DBs are at the forefront of the water-energy nexus[2]. While they are promising for seawater desalination (e.g., for seawater to brackish water conversion), practical implementation and their full potential still need to be unlocked. To this end, foundational understanding of the atomic- to electrode-scale physics/chemistry underlying functionality and degradation must be unraveled.Towards this end, we utilized our unique flow-by reactor setup to combine electrochemistry, conductivity, and temperature measurements with high-energy (75 keV) operando synchrotron X-ray diffraction (HEXRD) microscopy. Our investigation encompasses both the atomic and electrode levels, using a 3-electrodes setup with LiMn2O4 and Na0.44MnO2 as electrode active materials. As such, we were able to simulate a realistic electrode environment for operando measurements, as well as observe spatially resolved structural changes by scanning the beam across the electrodes surface. These phenomena are manifested through changes in unit cell parameters and the emergence of new phases during desalination cycles. Specifically, we tracked the changes in XRD patterns over the course of several desalination cycles in LiCl and NaCl solutions, as well as synthetic seawater and mixed solutions of LiCl/MgCl2. We were able to observe high selectivity of LiMn2O4 towards Li+, even in the highly concentrated synthetic seawater solutions, and could not observe the emergence of a new Mg+ rich phase down to potentials of 0 V vs. AgCl. Na0.44MnO2 exhibited good cycling behavior in synthetic seawater akin to pure NaCl solutions, and apart from the Na+ rich phase showed no signs of additional new phases, suggesting a highly selective nature towards Na+. Furthermore, we compared constant current and constant potential protocols and observed distinct differences in peak shift behavior. Ongoing analysis of the unit cell parameters and atomic positions allows us to allocate specific intercalation sites to specific potentials, providing foundational insight into the chemistry and physics underlying the selectivity of these materials.Literature:[1] M. M. Mekonnen, et al., Sci Adv 2016, 2, e1500323.[2] Q. Li, et al., Adv Sci (Weinh) 2020, 7, 2002213.

Performance of a Ship-Based Cupronickel Alloy in Exposure Conditions of Arabian Seawater-A Comparative Study.

Cupronickel-based alloys are widely known for their excellent resistance against aqueous corrosion, however, they can be susceptible to corrosion at accelerated rates and premature failure when exposed to a polluted or brackish seawater medium, even for short-term exposure durations. This unfamiliar corrosion behavior may be a result of the formation of an unprotected corrosion film during the early exposure durations. The paper investigates the corrosion phenomenon in cupronickel 90/10 alloy, by exposing the coupons in two different seawater compositions in the Arabian Sea region. Corrosion losses were investigated on the experimental coupons in a submerged position, for a maximum exposure duration of 150 days, using the conventional weight loss method and a new dimensional metrology-based measurement technique. Additionally, in this research the tubes of a marine heat exchanger having similar material that failed prematurely during operation in the Arabian Sea were also investigated for corrosion losses, followed by the characterization of the corrosion deposits using following analytical techniques: SEM, EDS, XRD and Raman Scattering. The experimental results showed significantly higher corrosion losses on coupons exposed to seawater site rich in pollutants and nutrients including dissolved inorganic nitrogenous compounds, compared to those subjected to a natural seawater solution in corrosion tanks maintained in a controlled environment.

Influence of calcined sediment inputs on the mechanical behavior of fiber-reinforced concrete in an aggressive environment

Dredged sediments and granite waste seriously threaten the environment and the oceans. In this work, we evaluated the Fergoug dam deposits as mineral materials for partially replacing Portland cement. The sediments were fired in a convection kiln at 450 degrees Celsius. This study aims to discover a sustainable cementitious material extracted from recycling residual sediments and granite, which can be an alternative to metakaolin (MK), usually used to reinforce cement compositions. Three concrete formations partially replaced Portland cement (CEM I 42.5 N). The first content was applied at 10% calcined sediment (CS), the second was 10% granite powder (GP), and the third was a mixture of 5% CS and 5% GP. Formations are detected and compared to vibrating concrete by placing them in aggressive media such as sulfuric acid and seawater solutions and evaluating their compressive strength and weight loss properties. SCCCSGP showed similar durability performance to the CV reference mix, including weight loss and electrical resistance. At the same time, using 10% CS gave good results regarding compressive strength and mass loss compared with using 10% GP alone. As for aggressive media, the results presented for the seawater solution were less aggressive than those of the sulfuric acid solution.

Polyethylene terephthalate (PET) microplastics as radionuclide (U-232) carriers: Surface alteration matters the most

Polyethylene terephthalate (PET) plastics find widespread use in various aspects of our daily lives but often end up in the environment as (micro)plastic waste. In this study, the adsorption efficiency of PET microplastics for U-232 has been investigated prior and after surface alteration (e.g. oxidation (PET-ox), MnO2-coating (PET/MnO2) and biofilm-formation (PET/Biofilm)) in the laboratory (at pH 4, 7 and 9) and seawater samples under ambient conditions and as a function of temperature. The results revealed a significant increase in the adsorption efficiency upon surface alteration, particularly after biofilm development on the MP's surface. Specifically, the Kd values evaluated for the adsorption of U-232 by PET, PET-ox, PET/MnO2 and PET/Biofilm are 12, 27, 73 and 363, respectively, at pH 7 and under ambient conditions. The significantly higher adsorption efficiency of the altered and particularly biofilm-coated PET, emphasizes the significance of surface alteration, which may occur under environmental conditions. In addition, according to the thermodynamic investigations the adsorption of U-232 by PET-MPs (both non-treated and modified), the adsorption is an endothermic and entropy-driven reaction. A similar behavior has been also observed using seawater solutions and assumes that surface alteration is expected to enhance the radionuclide, stability, mobility and bioavailability in environmental water systems.