Seawater Salt Research Articles

STUDY OF A NEW PASSIVE SOLAR DESALINATION DESIGN WITH A HEAT RECYCLING SYSTEM

This study presents a new and innovative suggestion to design a solar water desalination system by the direct passive method, with the aim of raising productivity by recycling the energy lost during the desalination process and raising the efficiency of condensation. In this study, the innovative design was evaluated to demonstrate its ability to increase the productivity of direct passive solar desalination while maintaining simplicity of installation and ease of operation. A prototype of the design was built to make a detailed study on the efficiency of the design and its ability to raise productivity under several different operational and climatic conditions in the city of Aden - Yemen, where several experiments were made to desalinate seawater taken from the city's coasts and the water of semi-salty wells in the city of Aden to compare the readings different. The results prove that the innovative design can raise productivity up to 80% higher than normal. The effect of pond water depth and salinity on productivity was studied. The results show that the higher the water depth in the evaporation basin, the higher the production capacity, and the higher the water salinity, the lower the production capacity of inactive direct solar desalination systems. This study also provides an assessment of the quality of the water produced by the innovative design by carrying out several chemical tests and making a comparison with the water quality before desalination to ensure that the design is capable of desalinating seawater or semi-salty well water to produce potable water. The results were confirmed for the quality of the produced water, which confirms the ability of the design to produce potable water in accordance with local and international standards, as the amount of total dissolved salts in sea water before desalination was 41340 mg/L and in well water 1300 mg/L, while after desalination by innovative design The total dissolved salts in treated sea water was 210 mg/L and in treated well water was 34 mg/L.

Changes in the salt concentration distribution in surface water (seawater) due to seawater recirculation in a porous medium under tidal fluctuations

Many studies have used numerical simulations and experiments to simulate saltwater intrusion in a nearshore aquifer. Thus, it is known that seawater recirculation occurs in a porous medium just below a sloping beach, and a saltwater wedge occurs in the medium below where the slope intersects the water level at low tide. This study investigated the salt distribution in the surface water when subterranean recirculation of seawater is occurring and there is a saltwater wedge in an underlying porous medium, along with the relationships between the seawater recirculation and the tidal amplitude and beach gradient. The salt distribution in a subterranean aquifer and in surface seawater where the shore sloped gently seaward with a constant slope of 1/10 or 1/5 under tidal amplitudes of 0.5, 1.0, or 2.0 m was numerically simulated by the ASGMF method, which couples water pressure and water flow in a porous medium with those in the overlying surface water and can simulate variable-density flows and the salt concentration distribution in both the porous medium and the surface water. The results showed that the recirculation of seawater depended on the tidal amplitude, being greater when the amplitude exceeded 1.0 m, but that it was unlikely to occur when the beach gradient was steep. Thus, the aspect ratio (width to depth) of the seawater recirculation decreased as the tidal amplitude increased above 1.0 m. Furthermore, the simulated surface water level was often lower than the tidal water level; thus, the surface water level was not consistent with the tidal water level imposed at the right boundary of the simulation domain but varied slightly under the influence of water flow in the surface water and gas flow in the atmosphere. The salt concentration in the surface water was not always the same as the seawater salt concentration because a thin freshwater layer and a brackish water layer of mixed freshwater and saltwater overlay the seawater.

Docosahexaenoic acid (DHA) production by Aurantiochytrium limacinum using cassava pulp hydrolysate as an alternative low-cost carbon source

Cost of nutrients is one of the major contributors to the production cost of docosahexaenoic acid (DHA) by thraustochytrids, and this remains the main challenge for economical and sustainable production of DHA. In the present study, cassava pulp (CP) was investigated as an alternative low-cost carbon source for DHA production by Aurantiochytrium limacinum SR21. Cultivation conditions, i.e., salinity level, type of nitrogen source, and concentrations of glucose and nitrogen sources, as well as pH, were optimized for cell growth. CP was enzymatically hydrolyzed, and used as the base medium, supplemented with artificial seawater salts, for DHA production under fed-batch cultivation. A. limacinum grew well at 18 g/L of NaCl (equivalent to 50% salinity level), and initial glucose concentration of 64 g/L, initial yeast extract concentration of 5 g/L, and pH 7.5 were optimum for cell growth. Fed-batch cultivation, with dissolved oxygen (DO) controlled at 10%, using CP-based medium as the carbon source gave a final cell dry mass of 26.3 ± 2.0 g/L, with 15.5 ± 0.1 g/L of lipid. DHA content in the lipid was 37.4 ± 1.5%, equivalent to 5.8 ± 0.3 g/L, and DHA productivity was 960 mg/(L·d). Medium-based economic analysis showed that an economic yield (EY) of this process was 0.86, which was higher than the 0.81 obtained using glucose as the substrate, assuming the same process and conditions. Overall, the results reveal that CP is a highly feasible feedstock for DHA production by A. limacinum SR21.

Grafted Groups’ Modification in the Main Chain of Polyfluorene‐Based Conjugated Polyelectrolytes to Greatly Boost Solar Hydrogen Production from Natural Seawater

Hydrogen represents an ideal fuel with environmental‐friendly properties and high energy density. It is attractive to directly produce clean hydrogen from inexhaustible solar energy and the most abundant seawater on the earth. Nevertheless, the search for highly efficient and stable photocatalysts remains a big challenge so far because of the dissolved salts in natural seawater, which may result in the decomposition of photocatalysts and undesirable side reactions. Herein, three polyfluorene‐based conjugated polyelectrolytes (CPEs) with different grafted groups in the polymer backbone for hydrogen production in natural seawater under solar light illumination are reported. The change in the grafted groups on the main chain of CPEs provides them very similar UV light absorption, but PFNH‐Br grafted with H group exhibits significantly improved charge transport and lower emission intensity compared with PFN‐Br (grafted with C8H17) and PFPABr (grafted with CH2CH2N(CH3)3Br). As a result, PFNH‐Br yield the highest hydrogen evolution rate (HER) of 1806 μmol h−1 g−1 without external cocatalysts under simulated solar light, while lower HERs of 356 and 225 μmol h−1 g−1 are found for PFN‐Br and PFPABr, respectively. This study shows that grafted group optimization is a powerful strategy to maximize the activity of polyfluorene‐based CPEs for direct photocatalytic seawater splitting.

Failure Analysis of Thermal Corrosion Cycling of EB-PVD YSZ Thermal Barrier Coatings Exposed to Molten NaCl

NaCl is the most abundant salt in seawater, thermal barrier coatings (TBCs) face the challenge of chloride salt hot corrosion in the marine environment. In this work, we focus on evaluating the thermal corrosion cycling of 9 wt.% Y2O3-ZrO2 (YSZ) exposed to NaCl molten salt. YSZ was prepared by electron beam–physical vapor deposition (EB-PVD). The result showed that the thermal cycling life of YSZ coating in the presence of NaCl molten salt was significantly shortened. The shortening of the service life of the coating can be ascribed to the collective effects of the thickening of thermal growth oxide and the degradation of the bond coating.

Modifications of Epitaxial Graphene on SiC for the Electrochemical Detection and Identification of Heavy Metal Salts in Seawater.

The electrochemical detection of heavy metal ions is reported using an inexpensive portable in-house built potentiostat and epitaxial graphene. Monolayer, hydrogen-intercalated quasi-freestanding bilayer, and multilayer epitaxial graphene were each tested as working electrodes before and after modification with an oxygen plasma etch to introduce oxygen chemical groups to the surface. The graphene samples were characterized using X-ray photoelectron spectroscopy, atomic force microscopy, Raman spectroscopy, and van der Pauw Hall measurements. Dose–response curves in seawater were evaluated with added trace levels of four heavy metal salts (CdCl2, CuSO4, HgCl2, and PbCl2), along with detection algorithms based on machine learning and library development for each form of graphene and its oxygen plasma modification. Oxygen plasma-modified, hydrogen-intercalated quasi-freestanding bilayer epitaxial graphene was found to perform best for correctly identifying heavy metals in seawater.

A Novel Approach for the Biological Desalination of Major Anions in Seawater Using Three Microalgal Species: A Kinetic Study

The global water shortage alert has been upgraded to a higher risk level. Consequently, a sustainable approach for ecofriendly, energy efficient water desalination is required for agricultural and municipal water reuse. In this study, an energy-efficient biological desalination process was used to treat chloride anions, which are the most abundant anion salt in seawater. Three algal species were studied: Scenedismus arcuatusa (S. arcuatusa), Chlorella vulgaris (C. vulgaris), and Spirulina maxima (Sp. maxima), under different operating conditions (saline concentrations, contact time, high light intensity, and CO2 supply), and two kinetic models were used. It was identified that under a high light intensity and CO2 supply, S. arcuatusa enhanced chloride removal from 32.42 to 48.93%; the daily bioaccumulation capacity (Qe), according to the kinetic models, was enhanced from 124 to 210 mg/g/day; and the net biomass production was enhanced from 0.02 to 0.740 g/L. The EDX analysis proved that salt bioaccumulation may be attributed to the replacement of Ca2+ and Mg2+ with Na+ and K+ through algal cells. The study’s findings provide promising data that can be used in the search for novel energy-efficient alternative ecofriendly desalination technologies based on algae biological systems with biomass byproducts that can be reused in a variety of ways.

A systematic construction of water-electricity cogeneration and thermal membrane coupling desalination technology using the waste heat in steel industry

The widespread use of fossil energy emits a large amount of carbon dioxide, leading to the greenhouse effect and global warming. The essence of reducing carbon emissions is to achieve higher-quality sustainable development. The recycling of waste heat in the iron and steel industry is of great significance to reducing carbon emissions. Aiming at the problem of insufficient utilization of gas in iron and steel industry and the development of seawater desalination industry, a water-electricity cogeneration and thermal membrane coupling technology is established. Low-temperature multi-effect distillation seawater desalination device is directly connected with steam turbine generator, which uses gas to generate electricity. After generating electricity, negative pressure exhaust at the end of steam turbine is used for seawater desalination. The thermal efficiency of the system is increased to over 80%, the waste heat is effectively utilized, and the carbon emission in the thermal desalination process is reduced. At the same time, the high-efficiency removal and resource utilization of salt in concentrated seawater are realized. The recovery ratio of freshwater is over 55%, the salt content of freshwater is below 500 mg/L, and the salt content of seawater concentrated by membrane method can reach 79,450 mg/L. A new comprehensive utilization and recycling system of seawater has been constructed to realize efficient recycling of energy resources and promote the development process of carbon emission reduction.

Study on Stress Corrosion Properties of 1Cr17Ni2 Stainless Steel

1Cr17Ni2 stainless steel is used in aviation, ships, machinery, and other fields. However, stress corrosion will lead to its strength reduction, thus failure. In this paper, we studied the stress corrosion resistance of 1Cr17Ni2 stainless steel bolts and nuts using fasteners’ stress corrosion test method and fasteners’ stress corrosion test method in a simulated environment with the accelerated stress corrosion test method of fasteners. The influence of seawater concentration, temperature, stress, test duration, and other parameters was fully considered during the test. The test results showed that 1Cr17Ni2 stainless steel would appear to stress corrosion crack under a specific corrosive environment, but the occurrence probability was not high. Therefore, in the complex seawater salt fog environment, the stress corrosion of 1Cr17Ni2 stainless steel cannot be ignored, which provides a practical reference for applying 1Cr17Ni2 stainless steel in a complex environment.

Slow Kinetics of Iron Binding to Marine Ligands in Seawater Measured by Isotope Exchange Liquid Chromatography-Inductively Coupled Plasma Mass Spectrometry.

Current understanding of dissolved iron (Fe) speciation in the ocean is based on two fundamentally different approaches: electrochemical methods that measure bulk properties of a heterogeneous ligand pool and liquid chromatography mass spectrometry methods that characterize ligands at a molecular level. Here, we describe a method for simultaneously determining Fe-ligand dissociation rate constants (kd) of suites of naturally occurring ligands in seawater by monitoring the exchange of ligand-bound 56Fe with 57Fe using liquid chromatography-inductively coupled mass spectrometry. Values of kd were determined for solutions of ferrichrome and ferrioxamine E. In seawater, the dissociation rate constant of ferrichrome (kd = 10 × 10-8 s-1) was greater than that of ferrioxamine E (kd = 3.6 × 10-8 s-1). The rates for both compounds were over twice as fast in seawater compared with pure water, suggesting that seawater salts accelerate dissociation. Isotope exchange experiments on organic extracts of natural seawater indicated that ligand-binding sites associated with chromatographically unresolved dissolved organic matter exchanged Fe more quickly (kd = 1.8 × 10-5 s-1) than amphibactin siderophores (kd = 2.15 × 10-6 s-1) and an unidentified siderophore with m/z 709 (kd = 9.6 × 10-6 s-1). These findings demonstrate that our approach can bridge molecular-level ligand identification with kinetic and thermodynamic metal-binding properties.

Coproduction xylo-oligosaccharides with low degree of polymerization and glucose from sugarcane bagasse by non-isothermal subcritical carbon dioxide assisted seawater autohydrolysis

High pretreatment temperature is necessary to obtain xylo-oligosaccharides (XOS) with low degree of polymerization (DP). However, traditional isothermal pretreatment for XOS production may increase the generation of xylose and furfural with the reaction time extending (10–100 min). In this study, non-isothermal subcritical CO2-assisted seawater autohydrolysis (NSCSA) firstly used seawater and CO2 for the coproduction of XOS with low DP and glucose. 51.44% XOS was obtained at 205 °C/5 MPa, and low-DP (2–4) XOS accounted for 79.13% of the total XOS. Furthermore, the specific surface area and total pore volume of the pretreated sugarcane bagasse (SCB) were 1.96 m2/g and 0.011 cm3/g, respectively, increased by 148% and 83% than that of nature SCB. Compared with subcritical CO2 pretreatment, NSCSA is an efficient method for the coproduction of XOS with low DP and glucose through inorganic salts in seawater and H2CO3 formed from CO2.

Local Photothermal Effect Enabling Ni3Bi2S2 Nanoarray Efficient Water Electrolysis at Large Current Density

AbstractIn terms of the large‐scale hydrogen production by water electrolysis, achieving the bifunctional electrocatalyst with high efficiency and stability at high current densities is of great significance but still remains a grand challenge. To address this issue, herein, one unique hybrid electrode is synthesized with the local photothermal effect (LPTE) by supporting the novel ternary nickel (Ni)bismuth (Bi)sulfur (S) nanosheet arrays onto nickel foam (Ni3Bi2S2@NF) via a one‐pot hydrothermal reaction. The combined experimental and theoretical observations reveal that owing to the intrinsic LPTE action of Bi, robust phase stability of Ni3Bi2S2 as well as the synergistic effect with hierarchical configuration, upon injecting the light, the as‐prepared Ni3Bi2S2 exhibits remarkably improved efficiency of 44% and 35% for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), respectively. Such enhanced values are also comparable to those performed in working media heated to 80 °C. In addition, the overall water splitting system by using Ni3Bi2S2@NF as bifunctional electrodes only delivers an ultralow voltage of 1.40 V at 10 mA cm−2 under LPTE, and can be stable more than 36 h at 500–1000 mA cm−2. More broadly, even worked at 0–5 °C, alkaline simulated seawater and high salt seawater, the electrodes still show apparent LPTE effect for improving catalytic efficiency.

Effect of Coral Aggregates of Blended Cement Concrete Subjected to Different Water Immersion Condition

The increasing use of concrete in construction has caused an increase in the need for resources for concrete mixtures and driving wide‐scale mining. One alternate material that can be used for aggregates replacement is coral. Coral aggregates (CA) have similar chemical characteristics to cement. The compressive strength and tensile splitting strength tests of concrete coral aggregates were performed based on the ASTM and ACI standards. This study aims are to investigate the usage of CA as a partial replacement of cement and fine aggregate to increase the strength of concrete at substitution percentages of 0, 5, 10, and 15%. Two different water submerged scenarios of distilled water and salt sea water immersion were applied. The concrete strength test was carried out after 28 days of curing time, with the specified concrete quality of 17 MPa. The results showed that immersion in distilled water has a higher concrete strength than immersion in sea water. The maximum compressive strength of concrete for distilled and sea water immersion is for 0% CA content of 18.47 and 14.89 MPa, respectively. Moreover, the highest value of the split tensile strength of concrete with distilled and sea water immersion is for CA substitution of 5% of 2.52 and 2.5 MPa, respectively. The addition of 5% coral aggregates to cement and fine sand is the optimum combination since it increases the maximum split tensile strength of concrete.

Impact of spatial and vertical distribution of air masses on PM10 chemical components at the Eastern Mediterranean – A seasonal approach

An upgraded three-dimensional (3D) version of the back-trajectory based Concentration Weighted Trajectory (CWT) model, segregating distinct vertical layers of atmospheric transport, was combined with two years of PM10 chemical composition measurements from the Finokalia superstation on the island of Crete, Greece, in the Eastern Mediterranean basin. Three altitudinal transport layers were studied: a) 0 m ≤ Layer 1 < 1000 m b) 1000 m ≤ Layer 2 < 2000 m c) 2000 m ≤ Layer 3, and the analysis was conducted separately for the cold (16 October – 15 April) and the warm (16 April – 15 October) periods. Mediterranean airflows in all layers enriched the concentrations of sea salt water soluble ions (Na+, Cl−, Mg2+ and K+) whilst during the warm period long-range northeastern airflows in layer 2 and layer 3 increased the levels of carbonaceous aerosols (OC and EC) and K+ due to intensive biomass burning in areas around the Black Sea. Peak concentrations of PM10-bound SO42− and NH4+ were associated with continental Northern airflows in layer 2 and layer 3, and were attributed to emissions in Northern Greece, Turkey, Balkan Peninsula and Eastern Europe. In addition, episodes of crustal constituents such as Ca2+, Mn, Al and Fe, were triggered by Saharan dust intrusions occurring mainly during cold period through all altitudinal layers. Moreover, the impact of heavy fuel oil combustion from shipping during warm period was reflected by maritime flows enhancing V concentrations, whilst a Saharan dust source for V was observed in all layers during cold period.

Interactive Effects of Drought and Saline Aerosol Stress on Morphological and Physiological Characteristics of Two Ornamental Shrub Species

Effects of drought and aerosol stresses were studied in a factorial experiment based on a Randomized Complete Design with triplicates on two ornamental shrubs. Treatments consisted of four levels of water container (40%, 30%, 20%, and 10% of water volumetric content of the substrate) and, after 30 days from experiment onset, three aerosol treatments (distilled water and 50% and 100% salt sea water concentrations). The trial was contextually replicated on two species: Callistemon citrinus (Curtis) Skeels and Viburnum tinus L. ‘Lucidum’. In both species, increasing drought stress negatively affected dry biomass, leaf area, net photosynthesis, chlorophyll a fluorescence, and relative water content. The added saline aerosol stress induced a further physiological water deficit in plants of both species, with more emphasis on Callistemon. The interaction between the two stress conditions was found to be additive for almost all the physiological parameters, resulting in enhanced damage on plants under stress combination. Total biomass, for effect of combined stresses, ranged from 120.1 to 86.4 g plant−1 in Callistemon and from 122.3 to 94.6 g plant−1 in Viburnum. The net photosynthesis in Callistemon declined by the 70% after 30 days in WC 10% and by the 45% and 53% in WC 20% and WC 10% respectively after 60 days. In Viburnum plants, since the first measurement (7 days), a decrease of net photosynthesis was observed for the more stressed treatments (WC 20% and WC 10%), by 57%. The overall data suggested that Viburnum was more tolerant compared the Callistemon under the experimental conditions studied.

Sea Water Intrusion Monitoring on the Sendangbiru of the Southern Malang Coastal Area based on Geoelectrical Resistivity Data

The study was conducted with the objective to distinguish the presence of seawater intrusion layer or salt-water aquifer distribution along the data acquisition line at the locations. Data acquisition was conducted by using the Wenner-Schumberger configuration of geoelectrical resistivity. From this research, 4 lines and 4 points of vertical electrical sounding (VES) data for every line were obtained with the distance between electrode a as 10m. Based on the data processing, obtained depth up to 120m with the smallest resistivity value is 0.02Ωm and the largest is 6764.52Ωm. To make the distribution of resistivity values along the path line of the study, cross sections were made until a depth of 120m. Based on the cross-section, the low resistivity value (less than 1.5 Ωm) that interpreted as a seawater intrusion layer or salt water aquifer distribution is located at varying depths. There are intrusions for the SB1 cross section, there is an intrusion at a depth of 6m-7m as far as 10m, at a depth of 6m-8m as far as 10m for the SB2 cross section and at a depth of 22m - 26m as far as 25m for the SB3 cross section.

Strength development mechanism of a marine binding material with red mud and seawater

This experiment works on red mud, blast furnace slag, desulfurized gypsum, fly ash, and seawater as raw materials to make a marine binding material. It is found that using seawater as mixing water in red mud based binding materials can promote the strength development comparing to using freshwater. The optimal ratio of red mud, blast furnace slag, cement, desulfurized gypsum, fly ash and externally polycarboxylate superplasticizer is 30%, 19%, 40%, 6%, 5% and 1.5%, respectively. Under the seawater to binder ratio of 0.33, the compressive strength of mortar specimen can reach 36.34 MPa, and the flexural strength can reach 11.32 MPa on the 28th day. Microstructural characterization results indicate that under the double stimulation of alkalinity from red mud and compound salts from seawater, more and more active ions of silicon and aluminum are released to form C-A-S-H gel and ettringite during the hydration of marine binding material. The micro-aggregate filling effect of red mud and hydration acceleration provided by the compound salts in seawater can improve pore structure of the hardened marine binding material. The utilization of red mud in this work can fulfill the green concept of development and avoid potential risk of environment pollution.

Mechanisms on Accelerating Hydration of Alite Mixed with Inorganic Salts in Seawater and Characteristics of Hydration Products

Mechanisms on Accelerating Hydration of Alite Mixed with Inorganic Salts in Seawater and Characteristics of Hydration Products

Enhancement of Emodin Production by Medium Optimization and KH2PO4 Supplementation in Submerged Fermentation of Marine-Derived Aspergillus favipes HN4-13.

Emodin is a widely distributed anthraquinone derivative with a variety of biological activities, one that can be efficiently produced by marine-derived fungus Aspergillus favipes HN4-13. However, its relatively low fermentation yield limits further development and pharmaceutical research work. In this study, Plaekett–Burman design and central composite design were adopted to optimize the fermentation conditions of A. favipes HN4-13. Optimal fermentation conditions in a 250-mL Erlenmeyer flask with 50 mL of medium were 59.3 g/L soluble starch, 10 g/L yeast extract paste, 30 g/L seawater salt, 1.04 g/L KH2PO4, 0.05 g/L MgSO4·7H2O, 0.01 g/L FeSO4·7H2O, seed culture 24 h, pH 5, inoculum size 18%, culture temperature 32 °C, and shaking at 160 rpm/min for 7 days. The production of emodin could achieve 132.40 ± 3.09 mg/L, with no significant difference from the predicted value (132.47 mg/L). Furthermore, KH2PO4 supplementation strategy was employed to regulate the mycelial morphology, upregulate the transcriptional level of biosynthesis gene cluster, and enhance emodin production (185.56 ± 4.39 mg/L).

Influence of physicochemical characteristics of feed solution on water permeability in forward osmosis desalination system

Many chemical species are involved in the feed solution (FS) in a forward osmosis (FO) process used for water/wastewater treatment and desalination. Chemicals and their molecular interactions in FS could have variable influences on water transfer and permeability, and consequently the overall performance of the FO process. This fundamental is important for understanding molecular transfer mechanisms in FO system, but has received a little attention. This preliminary study associated with its systematic investigations aimed to discover the impacts of physical and chemical properties (chemical composition, diffusivity, molar mass and charges) of FS on the water transfer characteristics and permeability in a FO desalination system. We evaluated the water flux in FS containing different salts in natural water and seawater. Our results revealed that water permeability can be significantly affected by the chemical constituents and molecular weights of FS. Water flux profiles follow an order of cations in FS: Na+ > K+ > Mg2+ > Ca2+, while high water flux reduction was found in K+ and NO3− FS. Solute diffusivity in FS was evidenced to play a crucial role in the water permeability. High water flux was determined in the FS with K+ and NO3− as which have the high diffusion coefficient. Experimental data showed that water flux could be affected by ionic mass and charge of solutes in FS as analysed by ratio of charge to molar mass (Z/M). Water flux reduction follows an increase of Z/M. This preliminary study raises insight to getting better understanding of molecular interactions in the chemically complex FS and their impact on the water transfer mechanisms in FO system.