Initial Seawater Research Articles

Ecosystem changes after Early Cretaceous seawater intrusion into the proto-South Atlantic Ocean

The early evolution of the South Atlantic Ocean following the Cretaceous break-up of Gondwana is extensively recorded in rift basins along the conjugate margins of Africa and Brazil. For the Brazil side, divergent views of the source and pathway of the initial seawater incursion persist due to a paucity of recognized transitional sequences that document marine transgressive deposits over the continental interior. To address this, we conducted a high-resolution sedimentological and geochemical study through a core in the Campos Basin that encompasses the key lithologic switch from lacustrine carbonate to marine evaporite settings. Steroid lipid biomarkers, derived from pelagophyte marine algae, make a striking appearance in concert with a pronounced negative shift of 87Sr/86Sr ratios and coincident with the appearance of anhydrite. Importantly, the sulfur-sequestered biomarkers reveal a dynamic system where redox-stratified and anoxic conditions were amplified along with a deepening chemocline through the marine transition.

Organoclay flocculation as a pathway to export carbon from the sea surface

Marine microorganisms play a critical role in regulating atmospheric CO2 concentration via the biological carbon pump. Deposition of continental mineral dust on the sea surface increases carbon sequestration but the interaction between minerals and marine microorganisms is not well understood. We discovered that the interaction of clay minerals with dissolved organic matter and a γ-proteobacterium in seawater increases Transparent Exopolymer Particle (TEP) concentration, leading to organoclay floc formation. To explore this observation further, we conducted a microcosm experiment using surface seawater collected from the Spring 2023 phytoplankton bloom in the Gulf of Maine. Unfiltered (natural community) and filtered (200 μm and 3 μm) seawater was sprayed with clay (20 mg L− 1 and 60 mg L− 1) and incubated. All clay treatments led to a tenfold increase in TEP concentration. 16S rRNA gene amplicon sequence analyses of seawater and settled organoclay flocs showed the dominance of α-proteobacteria, γ-proteobacteria, and Bacteroidota. The initial seawater phytoplankton community was dominated by dinoflagellates followed by a haptophyte (Phaeocystis sp.) and diatoms. Following clay addition, dinoflagellate cell abundance declined sharply while diatom cell abundance increased. By analyzing organoclay flocs for 18S rRNA we confirmed that dinoflagellates were removed in the flocs. The clay amendment removed as much as 50% of phytoplankton organic carbon. We then explored the fate of organoclay flocs at the next trophic level by feeding clay and phytoplankton (Rhodomonas salina) to Calanus finmarchicus. The copepod ingested R. salina and organoclay flocs and egested denser fecal pellets with 1.8- to 3.6- fold higher sinking velocity compared to controls. Fecal pellet density enhancement could facilitate carbon sequestration through zooplankton diel vertical migration. These findings provide insights into how atmospheric dust-derived clay minerals interact with marine microorganisms to enhance the biological carbon pump, facilitating the burial of organic carbon at depths where it is less likely to exchange with the atmosphere.

Experimental and numerical investigation of the effect of air injection on seawater intrusion mitigation

Previous studies have proposed compressed air injection to mitigate seawater intrusion, as a substitute for a hydraulic barrier created using freshwater injection. However, the current understanding of this strategy is based almost entirely on numerical simulation, and therefore, there is a need to investigate the complex processes accompanying this method within a physical setting. This study used sand tank experiments to explore the influence of air injection on the behavior of saltwater within a coastal confined aquifer, extending previous experiments by accounting for freshwater-saltwater density differences. Numerical modeling of the experiments assisted in interpreting experimental observations and allowed for field-scale conditions to be assessed. Numerical models were well matched to experimental observations, which showed a 34 % reduction in saltwater volume and a retreat of the saltwater toe length from 59 cm to 40 cm following air injection. A hypothetical field-scale confined aquifer model indicated that the largest seaward shift in the seawater wedge toe is obtained when the air-injection well is above the initial seawater wedge toe. However, maximal reductions in the seawater volume within the aquifer were obtained from injecting air within the original wedge rather than landward of the toe. This study provides the first physical evidence (through laboratory experiments) that injecting compressed air can effectively mitigate seawater intrusion. We considered a period of one year for field-scale applications, which show that the extent of desaturation likely needs to be mitigated from prolonged application of the method. Initial guidance is developed for the selection of air-injection locations, at least under simplified conditions (e.g. homogeneous, uniform aquifer, etc.).

THE EFFECT OF VARIATION IN THE NUMBER OF SPRAYS AND DISCHARGE ON THE TECHNOLOGY SPRAY FOR EVAPORATION

Spray technology is an innovative salt production process technology that is able to increase seawater salinity and accelerate the salt production process. This study aims to determine the effect of variations in the amount of spray and discharge in spray technology on increasing seawater salinity. The experimental method was carried out by varying the spray and water discharge amount in spray technology according to the variables. This research has been successfully carried out to increase the salinity of synthetic seawater where to increase from the initial seawater salinity of 2.5 °Be to 24 °Be. It takes 16 hours taken in 3 days using the number of sprays as much as 5 sprays with a seawater flow rate of 0.2424 m³/hour in an evaporation pond of 15í—7 m. The use of the spray method proved effective in accelerating the rate of increase in salinity of synthetic seawater, which was tested to increase the salinity of synthetic seawater from 2.5 °Be to 12 °Be with an evaporation time in traditional methods of 15 days to only 11 hours. This can also happen because the temperature, humidity and wind speed were relatively stable when the research took place.

Interfacial Solar Evaporation: From Fundamental Research to Applications.

In the last decade, interfacial solar steam generation (ISSG), powered by natural sunlight garnered significant attention due to its great potential for low-cost and environmentally friendly clean water production in alignment with the global decarbonization efforts. This review aims to share the knowledge and engage with a broader readership about the current progress of ISSG technology and the facing challenges to promote further advancements toward practical applications. The first part of this review assesses the current strategies for enhancing the energy efficiency of ISSG systems, including optimizing light absorption, reducing energy losses, harvesting additional energy, and lowering evaporation enthalpy. Subsequently, the current challenges faced by ISSG technologies, notably salt accumulation and bio-fouling issues in practical applications, are elucidated and contemporary methods are discussed to overcome these challenges. In the end, potential applications of ISSG, ranging from initial seawater desalination and industrial wastewater purification to power generation, sterilization, soil remediation, and innovative concept of solar sea farm, are introduced, highlighting the promising potential of ISSG technology in contributing to sustainable and environmentally conscious practices. Based on the review and in-depth understanding of these aspects, the future research focuses are proposed to address potential issues in both fundamental research and practical applications.

Early Cretaceous marine incursions into South Atlantic rift basins originated from the south

The breakup of Gondwana resulted in sedimentary deposits recording lacustrine to marine environmental transitions in the South Atlantic rift basins during the Early Cretaceous. Currently, ambiguity pervades our understanding of the timing and orientation of the initial seawater incursion. Here we investigated hydrocarbon biomarkers in sediments from two drill cores off West Africa with stratigraphic coverage from the Berriasian-Barremian to Albian. Based on biomarkers that can distinguish non-marine from marine-influenced settings, initial seawater influx occurred through the southern entrance across the Rio Grande Rise-Walvis Ridge during the early Aptian stage. Transitional conditions prevailed during the Aptian stage as the seawater incursion induced microbial community and environmental reorganization until the Albian when fully marine conditions prevailed. Overall, results of this study are valuable in deciphering the final opening of the South Atlantic Ocean, fulfilling the global comparison of paleoenvironments, and facilitating future petroleum exploration along the South Atlantic conjugate margins.

The DIC carbon isotope evolutions during CO2 bubbling: Implications for ocean acidification laboratory culture

Ocean acidification increases pCO2 and decreases pH of seawater and its impact on marine organisms has emerged as a key research focus. In addition to directly measured variables such as growth or calcification rate, stable isotopic tracers such as carbon isotopes have also been used to more completely understand the physiological processes contributing to the response of organisms to ocean acidification. To simulate ocean acidification in laboratory cultures, direct bubbling of seawater with CO2 has been a preferred method because it adjusts pCO2 and pH without altering total alkalinity. Unfortunately, the carbon isotope equilibrium between seawater and CO2 gas has been largely ignored so far. Frequently, the dissolved inorganic carbon (DIC) in the initial seawater culture has a distinct 13C/12C ratio which is far from the equilibrium expected with the isotopic composition of the bubbled CO2. To evaluate the consequences of this type of experiment for isotopic work, we measured the carbon isotope evolutions in two chemostats during CO2 bubbling and composed a numerical model to simulate this process. The isotopic model can predict well the carbon isotope ratio of dissolved inorganic carbon evolutions during bubbling. With help of this model, the carbon isotope evolution during a batch and continuous culture can be traced dynamically improving the accuracy of fractionation results from laboratory culture. Our simulations show that, if not properly accounted for in experimental or sampling design, many typical culture configurations involving CO2 bubbling can lead to large errors in estimated carbon isotope fractionation between seawater and biomass or biominerals, consequently affecting interpretations and hampering comparisons among different experiments. Therefore, we describe the best practices on future studies working with isotope fingerprinting in the ocean acidification background.

Variability of sulfur isotopes and trace metals in pyrites from the upper oceanic crust of the South China Sea basin, implications for sulfur and trace metal cycling in subsurface

The circulation of seawater within the oceanic crust promotes cycling of metals and sulfur, as well as development of the subsurface biosphere. Characterization of the full spectrum of sulfide geochemistry in the altered oceanic crust is critical for a complete understanding of global cycling of sulfur and metals, while those in off-axis hydrothermal circulation have received less attention. This study applied a combination of in-situ sulfur isotopic and trace metal analyses to study the pyrite geochemical features in altered basalts of the South China Sea basin. This contribution unravels a detailed picture of the cycling of sulfur and metals in the subsurface. Such cycling is likely to be co-controlled by the hydrothermal and microbial activities when oceanic crusts transit from on-axis to off-axis hydrothermal systems.A total of five groups of pyrites associated with distinct mineral assemblages, morphologies, trace metal enrichment and sulfur isotopic values were observed in altered basalts. Pyrite disseminated (type 1) within the background hydrothermal alteration is characterized by δ34S values close to zero, with relative enrichment of trace metals (> 500 ppm), such as Ni, Co, and Cu. This type of pyrite is most likely to precipitate from upwelling high-temperature hydrothermal fluids when they ascended towards the seafloor. Sulfur was mainly derived from magmatic sulfides. Linear regression analyses of trace metal contents in disseminated pyrite show various strong positive correlations between trace metals reflecting a series of metal mobility processes, including incorporation into pyrite and leaching directly from sulfides or silicate minerals. Additionally, a population of pyrite has δ34S values ranging from +4 to +8 ‰ and low trace element contents, which reveals precipitation conditions where the ascending high-temperature hydrothermal fluids have mixed with significant amounts of seawater-sourced fluids. This group of pyrites is either formed by the replacement of silicates as patchy texture (type 2) or are exclusively associated with epidote‑carbonate veins (type 3). Furthermore, strongly positive δ34S signatures are observed within framboidal pyrite (type 4) (δ34S up to +57 ‰) and within overgrown euhedral pyrite (type 5) (δ34S up to +24 ‰). These unprecedented isotopically-heavy framboidal pyrite in modern oceanic crust presents a well-preserved organic matter framework, which is interpreted as a consequence of microbial sulfate reduction activities based on current observations. The extremely positive values of the sulfur isotopes could be produced by Rayleigh isotopic fractionation when ~77% sulfate (assumed with an initial seawater sulfate δ34S of 21%) is consumed by microorganisms in closed systems, in this case, the cavities in the altered basalt. The microorganisms meanwhile may enhance the sequestration of trace metals into pyrite, possibly through microbial metabolisms or detoxification processes. The positive δ34S values of overgrown euhedral pyrite (type 5) are interpreted to be mainly introduced by the involvement of seawater-derived sulfur or inherited from the framboidal pyrite.The various isotopic and elemental signatures in these five types of pyrites could be linked to either the hydrothermal or microbial processes occurring within the upper oceanic crust in the South China Sea basin. Both processes are critical to the metal and sulfur cycling in subsurface and should be considered jointly in future studies. Additionally, our results exemplify the potential roles of microorganisms, not only in accumulating trace metals in sulfides in the subsurface but also as a potential biosignature to reveal microbial activities in similar environments in the early Earth.

Copper mobilization via seawater-volcanic rock interactions: New experimental constraints for the formation of the iron oxide Cu-Au (IOCG) mineralization

The involvement of modified seawater and/or basinal brine in IOCG mineralization was documented by numerous geologic studies. Still, this process remains poorly understood. In this study, we reacted seawater with andesite and basalt, the most common arc volcanic rocks, at 150 and 240 °C and water vapor-saturated pressure to assess the Cu leaching capacity and fluid evolution due to the seawater-volcanic rock interactions. The experimental results show that Mg, Fe, Al, and SO42− in the modified seawater decreased significantly, accompanied by an increased Ca concentration. The fluid pH also decreased from 8.3 of the initial seawater to ∼7.5 and ∼7.0 after 150 and 240 °C experiments, respectively. The incongruent calcsilicate (e.g., plagioclase) dissolution and anhydrite precipitation were observed in the reacted rock samples. Thermodynamic modeling confirmed the trends of those concentration changes but predicted several alteration minerals that were not observed in the experiments. Our experiments show that Cu-leaching efficiency is much higher from the andesite than from the basalt, also higher at 240 °C than at 150 °C. The andesite contains more Cu than the basalt samples, and abundant Cu-rich (average 106 ppm) plagioclase-hosted silicate melt inclusions and Cu-bearing (average 59 ppm) groundmass are identified in the original andesite sample but not in the original basalt sample, which is considered to be the cause of the Cu-leaching differences between the two rock samples. The δ34S value of resultant fluids is dominated by seawater sulfate with a minor contribution of magmatic sulfur from the rock. Thermodynamic modeling combined with recent experimental studies show that deposition of Cu sulfides is the most effective when Cu-bearing fluids react with early-stage pyrite. Our results suggest that the seawater/(brine)-volcanic rock reactions at 150–250 °C can produce Cu-bearing fluids, which in turn can form IOCG deposits, and that Cu mineralization with sulfides zonation can result from replacement reactions between the Cu-bearing fluids and Fe-rich minerals in precursor iron ore bodies.

Numerical study on the hydrodynamic performance of a revetment breakwater in the South China Sea: A case study

The South China Sea (SCS) is an important channel for international trade and energy transportation of China, which is of great significance for strategic and economic development. To prevent the reclaimed reef islands in the SCS from wave scouring and impacting, a large number of revetment breakwaters have been constructed at the margins of those reclaimed artificial lands. It is of great engineering importance to evaluate the ability of those revetment breakwaters withstanding the impact of ocean waves. In this study, a series of hydrodynamic numerical simulations are carried out to study the performance of the revetment breakwaters built on the reclaimed reef islands in the SCS adopting the actual terrain and real size of structure. It is found that under the fortified wave condition, the peak value of wave impact imposed on the caisson can reach up to 43.5 kPa, and the peak rate of wave overtopping is 3 m3/s per meter. However, under the condition of extremely higher waves, the peak wave impact could reach 102.2 kPa, and the overtopping rate is 11.5 m3/s per meter. The significantly increased wave impact and wave overtopping are harmful to the stability of those revetment breakwaters and the ecological environment on the reclaimed reef islands. Meanwhile, the relationship between the wave height, wave period, the initial seawater level and the water level setup on reef flat, wave impact on the revetment breakwaters, water overtopping is parametrically studied. The results of this study should own some reference significance for the design, post-construction maintenance, and safety evaluation of the revetment breakwaters built on the reclaimed reef islands in the SCS.

Carbonized sawdust/barium titanate composite solar absorber for solar driven seawater desalination

A low cost and feasible fabrication of novel photothermal conversion material and solar absorber was widely studied for enhanced solar-to-vapor performance in solar driven vapor generation. In this work, a novel hybrid carbonized sawdust/barium titanate composite was fabricated by sol-gel method, where it was later incorporated with a cotton towel using a dip-coating process to produce a solar absorber. The solar driven seawater desalination setup was made up of i) solar absorber where heat was localized and the evaporation occurs, ii) thermal insulation using polystyrene foam and air gap to minimize the heat loss, and iii) water pathway for continuous supply of seawater to the solar absorber. Carbonized sawdust/barium titanate composite solar absorber was tested under direct solar radiation for about 2 h using seawater collected from the beach coast of Universiti Malaysia Sabah, where it was repeated three times to observe the stability of the solar absorber. The average efficiency of the carbonized sawdust/barium titanate composite solar absorber was about 72.04% with average evaporation rate of 1.32 kg/m2 h. Salinity of the clean water was significantly reduced about 99.8% from the initial seawater salinity at 29300 ppm to 50 ppm, and the pH value was observed at 7.40. The salinity and pH value of the generated clean water was within the safe water limit based on the World Health Organization (WHO) standard.

Microbial Community Dynamics during Biodegradation of Crude Oil and Its Response to Biostimulation in Svalbard Seawater at Low Temperature.

The development of oil exploration activities and an increase in shipping in Arctic areas have increased the risk of oil spills in this cold marine environment. The objective of this experimental study was to assess the effect of biostimulation on microbial community abundance, structure, dynamics, and metabolic potential for oil hydrocarbon degradation in oil-contaminated Arctic seawater. The combination of amplicon-based and shotgun sequencing, together with the integration of genome-resolved metagenomics and omics data, was applied to assess microbial community structure and metabolic properties in naphthenic crude oil-amended microcosms. The comparison of estimates for oil-degrading microbial taxa obtained with different sequencing and taxonomic assignment methods showed substantial discrepancies between applied methods. Consequently, the data acquired with different methods was integrated for the analysis of microbial community structure, and amended with quantitative PCR, producing a more objective description of microbial community dynamics and evaluation of the effect of biostimulation on particular microbial taxa. Implementing biostimulation of the seawater microbial community with the addition of nutrients resulted in substantially elevated prokaryotic community abundance (103-fold), a distinctly different bacterial community structure from that in the initial seawater, 1.3-fold elevation in the normalized abundance of hydrocarbon degradation genes, and 12% enhancement of crude oil biodegradation. The bacterial communities in biostimulated microcosms after four months of incubation were dominated by Gammaproteobacterial genera Pseudomonas, Marinomonas, and Oleispira, which were succeeded by Cycloclasticus and Paraperlucidibaca after eight months of incubation. The majority of 195 compiled good-quality metagenome-assembled genomes (MAGs) exhibited diverse hydrocarbon degradation gene profiles. The results reveal that biostimulation with nutrients promotes naphthenic oil degradation in Arctic seawater, but this strategy alone might not be sufficient to effectively achieve bioremediation goals within a reasonable timeframe.

Isolation of SAR11 Marine Bacteria from Cryopreserved Seawater.

While marine microorganisms are frequently studied in their natural environment, isolated strains are invaluable resources that can be used in controlled experiments to expand upon direct observations from natural systems. Here, we sought a means to enhance culture collections of SAR11 marine bacteria by testing the use of seawater cryopreserved with glycerol as an inoculum. Using a raw seawater sample collected from the tropical Pacific Ocean, a subsample was diluted in seawater growth medium to create 576 2-ml dilution cultures containing 5 cells each and incubated for a high-throughput culturing (HTC) experiment, while another portion was cryopreserved in 10% glycerol. After 10 months, a cryopreserved aliquot was thawed and used to create a second cultivation experiment of 480 2-ml cultures containing 5 cells each and 470 cultures containing 105 cells each. The raw seawater cultivation experiment resulted in the successful isolation of 54 monocultures and 29 mixed cultures, while cryopreserved seawater resulted in 59 monocultures and 29 mixed cultures. Combined, the cultures included 51 SAR11 isolates spanning 11 unique 16S rRNA gene amplicon sequence variants (ASVs) from the raw seawater inoculum and 74 SAR11 isolates spanning 13 unique ASVs from cryopreserved seawater. A vast majority (92%) of SAR11 isolates from the two HTC experiments were members of SAR11 subclade Ia, though subclades IIIa and Va were also recovered from cryopreserved seawater and subclade Ib was recovered from both. The four most abundant SAR11 subclade Ia ASVs found in the initial seawater environmental sample were isolated by both approaches.IMPORTANCE High-throughput dilution culture has proved to be a successful approach to bring some difficult-to-isolate planktonic microorganisms into culture, including the highly abundant SAR11 lineage of marine bacteria. While the long-term preservation of bacterial isolates by freezing them in the presence of cryoprotectants, such as glycerol, has been shown to be an effective method of storing viable cells over long time periods (i.e., years), to our knowledge it had not previously been tested for its efficacy in preserving raw seawater for later use as an inoculum for high-throughput cultivation experiments. We found that SAR11 and other abundant marine bacteria could be isolated from seawater that was previously cryopreserved for nearly 10 months at a rate of culturability similar to that of the same seawater used fresh, immediately after collection. Our findings (i) expand the potential of high-throughput cultivation experiments to include testing when immediate isolation experiments are impractical, (ii) allow for targeted isolation experiments from specific samples based on analyses such as microbial community structure, and (iii) enable cultivation experiments across a wide range of other conditions that would benefit from having source inocula available over extended periods of time.

Characterization and oil recovery enhancement by a polymeric nanogel combined with surfactant for sandstone reservoirs

The characterization and enhanced oil recovery mechanisms of a nanosized polymeric cross-linked gel are presented herein. A negatively charged nanogel was synthesized using a typical free radical suspension polymerization process by employing 2-acrylamido 2-methyl propane sulfonic acid monomer. The synthesized nanogel showed a narrow size distribution with one peak pointing to a predominant homogeneous droplet size. The charged nanogels were also able to adsorb at the oil–water interfaces to reduce interfacial tension and stabilize oil-in-water emulsions, which ultimately improved the recovered oil from hydrocarbon reservoirs. In addition, a fixed concentration of negatively charged surfactant (sodium dodecyl sulfate or SDS) was combined with different concentrations of the nanogel. The effect of the nanogels combined with surfactant on sandstone core plugs was examined by running a series of core flooding experiments using multiple flow patterns. The results show that combining nanogel and SDS was able to reduce the interfacial tension to a value of 6 Nm/m. The core flooding experiments suggest the ability of the nanogel, both alone and combined with SDS, to improve the oil recovery by a factor of 15% after initial seawater flooding.

Effects of methanol and acetone as mutual solvents on wettability alteration of carbonate reservoir rock and imbibition of carbonated seawater

The enhanced oil recovery (EOR) methods combination is a way to simultaneously utilize the mechanisms of the combined methods. Besides, in chemical water injection, additives controlling the mechanisms by their mutual interactions also exert other effects on the system, known as synergistic effects. In the current study, acetone and methanol mutual solvents were utilized to enrich carbonated water and their effects on the mechanisms of carbonate reservoir rock wettability alteration and oil production in the imbibition process have been investigated at different conditions of salinity, the ratio of solvent to water and pressure. Also, various boundary conditions and fracture effects were considered in the imbibition experiments. Imbibition fluid optimization was performed based on the contact angle tests and reservoir rock wettability alteration. Seawater was used as the base fluid at various initial and diluted concentrations. According to the results, the contact angle magnitude depends on the parameters of salinity, the volume percent of the mutual solvents and the pressure so that as the solvents volume and pressure increase and the salinity decreases, the contact angle decreases when carbon dioxide (CO2) is present but in absence of CO2, the contact angle decreases with increasing base fluid salinity. The lowest contact angle values for methanol and acetone solvents were recorded at 10.342 MPa, initial seawater salinity, 15% volumetric solvent, and a constant temperature 75 °C in absence of dissolved CO2 at 60.95° and 58.43°, respectively. The lowest contact angle values were obtained in the presence of dissolved CO2 for methanol and acetone solvents at 15% volumetric pressure at 10.342 MPa, salinity resulting from 20 times seawater dilution and at a temperature of 75 °C at 36.31° and 32.92°. Final oil production of 66.29%, 28.44%, 85.42% and 91.38% of primary oil saturation for the imbibition of carbonated water containing 15%Vol of methanol and final oil production of 70.32%, 32.10%, 90.60% and 94.09% of primary oil saturation for the imbibition of carbonated water containing 15%Vol acetone were obtained which were performed as one-dimensional co-current spontaneous imbibition (COCSI), one-dimensional counter-current spontaneous imbibition (COUCSI), multi-dimensional COUCSI and imbibition in the fractured plug, respectively.

Nutrient Supply to Seawater from Steelmaking Slag: The Coupled Effect of Gluconic Acid Usage and Slag Carbonation

Vanishing of seaweeds in coastal areas has become a serious environmental problem. Part of the reason is nutrient deficiency in seawater, especially iron. Steelmaking slag is probably one of the best nutrient suppliers in terms of cost and quantity. Utilizing steelmaking slag to fertilize coastal seaweeds may simultaneously address the two challenges of seaweed restoration and byproduct treatment. However, direct usage of slag from a basic oxygen furnace is not practical because of negative effects such as a sharp pH increase and magnesium loss. To address the disadvantages, this work investigated the leaching behavior of a practical steelmaking slag in an artificial seawater and clarified the coupled effect of gluconic acid usage and slag carbonation on aiding the nutrient supply. Slag carbonation prevents a drastic pH increase and Mg loss, while gluconic acid induces formation of stable chelated complexes. The combination of slag carbonation and gluconic acid usage results in significant improvements in the nutrient supply. By leaching the slag, the maximum concentration of Fe in seawater increases to 0.29 mg L−1, 193 times larger than the value in the initial seawater (1.5 μg L−1).

Experimental investigation on novel desalination system via gas hydrate

Freshwater scarcity has been troubling the high-quality development of many countries and regions, and seawater desalination is a vital source of freshwater. Recently, gas hydrate based desalination (GHBD) technology attracts much attention because of bringing no extra pollution to water. We developed a novel multifunctional desalination apparatus via gas hydrate with various operation modes and separation methods. In this study, the desalination characters under different separation modes were conducted using simulated seawater, and the hydrate-purging method with a desalination efficiency of more than 80% was selected to desalt the natural seawater sample. In addition, the purging method can greatly improve the desalination effects of both squeezed hydrate column and loose hydrates. The experimental results indicate that the removal efficiencies of different ions in the seawater were similar and their difference was related to the strength of ionic hydration. And above all, we designed and conducted a continuous desalination process including multiple injection, separation, washing and purging operations. The ultimate desalination efficiency using hydrate-purging method was over 80%, and the freshwater recovery was above 30% with 200 mL initial seawater in this study. The experimental proposal and results of this study are of great significance to the development of GHBD technology.

New configurations for sea water desalination system using Ranque-Hilsch vortex tubes

In this study, evaluation and performance investigation of new three different configurations, for sea water desalination system using two identical Ranque-Hilsch vortex tubes (RHVT) is carried out. The new technique for water desalination is developed using various series and parallel vortex tubes configurations, instead of single vortex tube integrated desalination system, two series RHVTs using the hot air stream of the first tube as the air source of the second one is called series hot vortex tubes (SHVT) configuration, another configuration was two series RHVTs using the cold air steam of the first tube as the air source of the second one, is called series cold vortex tubes (SCVT) configuration, the third one was two parallel RHVTs collecting both hot air steams of the two tubes from one side and collecting both cold air steams of the two tube from the other side, and is called parallel vortex tubes (PVT) configuration. The main study conclusions are deduced that, the desalinated water quantity reached about 79% of the initial sea water quantity for SHVT arrangement, otherwise, it was about only 70% for SCVT arrangement and 74% for PVT arrangement. Furthermore, the results of this work could help to adopt more efficient desalination systems based on using RHVTs, and the SHVT configuration can be strongly recommended for use in seawater desalination.

Orthogonal Experiment for Desalination Efficiency of Electromagnetic Desalination System

Electromagnetic desalination system is designed by coupling effect of electric field and magnetic field. By designing the L27 (313) orthogonal table as the experimental scheme, the electromagnetic desalination efficiency is used as the data of the range R analysis. The main and secondary factors influencing desalination efficiency are as follows: initial seawater concentration(F)>influent flow(G)>interaction of adsorption voltage(D) and magnetic field(E)> interaction of activated carbon pore size(A) and substrate material(B)>interaction of activated carbon pore size(A) and adsorption voltage(D)> adsorption voltage(D)>magnetic field(E)>number of electrodes(E)>substrate material(B)>activated carbon pore size(A).The best combination of seawater desalination is A2B2C1D3E3F1G2. The range R of factor F is 20.53, which indicates that the initial seawater concentration has a highly significant influence on the desalination effect of seawater.

Experimental investigation of a novel sea water desalination system using ranque-hilsch vortex tube

This study is experimentally targeting to develop an effective novel system to produce fresh water, by sea water desalination using vortex tube. The vortex tube used compressed air as a power source, and produced hot air stream from one end and cold air stream from the other, taking that advantage in water desalination technology, with low consumption of heating energy under vacuum condition. Using four modes of compressor operation, mode I of continuous operation, mode II of five minutes on then ten minutes off, mode III of ten minutes on then five minutes off and mode IV of ten minutes on then ten minutes off. The following results are obtained: the quantity of the desalinated water was, 26% of the initial sea water quantity for mode II, while for mode IV, it was about 34%, for mode III, it was about 51%, while the maximum desalinated water quantity of 68% is obtained at mode I. Finally, the total dissolved solids in the produced desalinated water were about 480 mg/l. Therefore, using Ranque-Hilsch vortex tube in sea water desalination is highly recommended to be used as an effective agent to initiate sea water evaporation and desalinated water condensation.