Actual Seawater Research Articles

Nanofiltration range desalination by high flux graphene oxide impregnated ultrafiltration hollow fiber mixed matrix membrane

In this work, a novel graphene oxide impregnated ultrafiltration grade hollow fiber membrane was prepared having capability of salt rejection in the range of nanofiltration. Sodium sulfate showed higher rejection (40%–50%) than the other salts, magnesium sulfate and sodium chloride. Charge-charge interaction is the major salt retention mechanism. Optimum operating conditions were identified as 55 kPa transmembrane pressure drop and 5 L/h cross-flow rate. Increasing the solution pH from 5 to 9 augmented the rejection of sodium sulfate from 43% to 51% at relatively high permeate flux 0.25 L/m2.h.kPa. In case of filtration of actual sea water, the permeate flux is lowered to 0.20 L/m2.h.kPa due to presence of other fouling agents. Rejection of total dissolved solids was 30% for seawater. Beyond 11 h (breakthrough time) the rejection decreases due to screening of charge effects of the membrane surface. Pretreatment by activated carbon delayed the breakthrough time to 14 h and improved permeate flux 0.22 L/m2.h.kPa. Thus, ultrafiltration grade hollow fiber mixed matrix membrane offers equivalent salt rejection of nanofiltration membrane at a much higher throughput.

An energy-saving “nanofiltration/electrodialysis with polarity reversal (NF/EDR)” integrated membrane process for seawater desalination. Part III. Optimization of the energy consumption in a demonstration operation

For the proposed energy-saving “nanofiltration/electrodialysis with polarity reversal (NF/EDR)” integrated membrane process for seawater desalination, studies on the NF process and the optimization of the ED process have been previously conducted. Based on the obtained results, a multi-stage, multi-passage ED process is presented in this manuscript to realize the optimization of energy consumption. In addition, the integration between NF and EDR processes at a pilot scale was accomplished, in which actual seawater was the feed water and >1200 h of demonstrative operation was implemented. During the NF process, 15 NF90-4040 elements with high desalination capacity were applied. During the EDR process, the membrane stack consisted of three stages with six passages were utilized, in which 250 cell pairs were included with unequal pairs of membranes for each stage. From the first to the third stage, there were 100, 80, and 70 membrane pairs, respectively. In addition, the energy-saving process was achieved by thinning the thickness of the electrode chamber to 2 mm and filling the electrode chambers with mixed ion exchange resin at an appropriate volume ratio. Furthermore, the voltage and the current for each stage can be independently controlled. The results show that the total desalination rate of the integrated process can be 99.26%, the system energy consumption is <2.15 kWh/(m3 produced water), which is significantly lower than that of SWRO, suggesting that the proposed integrated membrane process is an efficient and economically feasible seawater desalination system.

Flexible Fire-Resistant Photothermal Paper Comprising Ultralong Hydroxyapatite Nanowires and Carbon Nanotubes for Solar Energy-Driven Water Purification.

Efficient utilization of abundant solar energy for clean water generation is considered a sustainable and environment friendly approach to mitigate the global water crisis. For this purpose, this study reports a flexible fire-resistant photothermal paper by combining carbon nanotubes (CNTs) and fire-resistant inorganic paper based on ultralong hydroxyapatite nanowires (HNs) for efficient solar energy-driven water steam generation and water purification. Benefiting from the structural characteristics of the HN/CNT photothermal paper, the black CNT surface layer exhibits a high light absorbability and photothermal conversion capability, the HN-based inorganic paper acts as a thermal insulator with a high temperature stability, low thermal conductivity, and interconnected porous structure. By combining these advantages, high water evaporation efficiencies of 83.2% at 1 kW m-2 and 92.8% at 10 kW m-2 are achieved. In addition, the HN/CNT photothermal paper has a stable water evaporation capability during recycling and long-time usage. The promising potential of the HN/CNT photothermal paper for efficient production of drinkable water from both actual seawater and simulative wastewater samples containing heavy metal ions, dyes, and bacteria is also demonstrated. The highly flexible HN/CNT photothermal paper is promising for application in highly efficient solar energy-driven seawater desalination and wastewater purification.

Fabrication of ZnO/rGO/PPy heterostructure for electrochemical detection of mercury ion

The sensitive online detection technique for heavy metal ions present in ocean, while effectively eliminating the interference of other chemicals, has been lacking at the present time. We found that the interfacial barrier of ZnO/rGO/PPy heterostructure had powerful physical effects on electrochemistry, and the Schottky barrier driven electrochemical detection was further developed. As based on the interfacial physical barrier, it could avoid the existing problem of the traditional electrochemical sensing mechanism and apply in more interfering environment. The sensitive detection of trace mercury ion (Hg2+) in actual seawater was achieved by employing the ZnO/rGO/PPy heterostructure. The interfacial barrier effect provides a chance to develop sensors used in more interfering environment.

Temperature and Composition Dependence of Sea Spray Aerosol Production

AbstractA discrepancy between laboratory and field‐derived parameterizations for the dependence of sea spray aerosol (SSA) particle number concentrations (Np) and size distributions on water temperature (Tw) exists. Here we address this discrepancy by quantifying the Tw dependence of SSA production over the range −2–25 °C for laboratory‐generated particles using a marine aerosol reference tank (MART), a miniature MART (miniMART), and a plunging jet. Four water types were considered: NaCl water, reef salt (RS) water, filtered and autoclaved reef salt (FARS), and filtered but not autoclaved seawater (NASW). For NaCl, RS, and FARS water the Np exhibited a moderate, monotonic increase with Tw for all generation methods (sensitivity of 2.1–4.1%/°C). This contrasts with some previous laboratory studies but is consistent with parameterizations derived from ambient observations. The reconciliation of laboratory results with these parameterizations supports their use in global models. The Tw sensitivity also increased with particle size in the submicron size range. This indicates the fraction of primary SSA that can act as cloud condensation nuclei has a different sensitivity to Tw than the total particle number. The particle production for actual seawater (NASW) differed from the other water types, exhibiting complex, irreproducible behavior with no clear Tw dependence due most likely to biologically or physically driven temporal evolution of seawater composition. This suggests that variability in seawater composition may have as large an impact as temperature on actual SSA production. These observations provide new constraints and context for understanding the dependence of SSA production on water temperature and composition.

An electrochemical method based on OCP fluctuations for anti-corrosion alloy composition optimization

Purpose An electrochemical method based on the open circuit potential (OCP) fluctuations was put forward. It can be used to optimize the alloy compositions for improving the corrosion resistance of rust layer. Design/methodology/approach The potential trends and potential fluctuations of carbon steels in seawater were separated by Hodrick–Prescott filter. The Spearman correlation coefficient and max information coefficient were used to explore the correlation of alloy compositions and potential fluctuations. Findings After long-term immersion, potential fluctuation resistance (PFR) can be used to characterize the corrosion resistance of metals and its rust layers. In the 1,500 to 2,500 h exposure period, Fe, C and S compositions have strong negative correlations, whereas PFR and P composition have weak negative correlations. Mn, Cu and Ti alloy compositions help the rust layer of carbon steels have higher PFRs. These elements that exhibit higher PFRs in this period have been confirmed to have the effect on improving the corrosion resistance of rust layer. Originality/value A new computing method for alloy composition optimization of carbon steels based on the OCP fluctuations was put forward. This method combines electrochemical monitoring with the long-term actual seawater environmental tests of various carbon steels.

Rapid removal of radioactive cesium by polyacrylonitrile nanofibers containing Prussian blue

After the Fukushima Daiichi Nuclear Power Plant disaster in Japan in 2011, the demand drastically increased for efficient technology for the removal of radioactive cesium. Prussian blue (PB) nanoparticles have shown excellent adsorption ability toward Cs. In this study, we synthesized PB nanoparticles incorporated polyacrylonitrile nanofiber (PB/PAN). PB/PAN has the porous structure of nanofibers, with diameters of several hundred nanometers. PB nanoparticles can be incorporated successfully into the PAN matrix without any change to their intrinsic crystallinity and structure. The mesoporous structure of PB/PAN and the incorporation of PB nanoparticles led to an increase in the Brunauer–Emmett–Teller surface area and pore volume. In addition, PB/PAN exhibited excellent wettability with water. With simple filtering for the removal of radioactive cesium, PB/PAN showed high removal efficiency (87 ± 3%) within 10 s for 10 mL of 137Cs solution (1000 Bq L−1). In addition, the 137Cs removal by PB/PAN showed high removal efficiency (70 ± 2%, after 1 h), even in the actual seawater medium (1000 Bq L−1 of 137Cs). Therefore, PB-incorporated PAN nanofibers can be considered useful in the practical application of Cs removal from radioactive wastewater.

Effects of magnesium and potassium sulfates on oil recovery by water flooding

Conventional water flooding has been applied successfully worldwide using sea water and/or formation brine. Two processes are proposed to improve oil recovery by water flooding such as; lowering water salinity as LoSal (300 to 5,000ppm) and changing concentration of cations and/or anions as designer water.This experimental study investigates combined effects of concentration of magnesium and potassium sulfates with consideration of sodium chloride salinity on oil recovery by water flooding. To achieve the objectives of the study, nine flood experiments were conducted using actual sea water and synthetic water injected through actual sandstone reservoir cores. Three experiments were achieved using actual Egyptian sea waters of Al-Obayied, Balteam and Abo Rudies to investigate the combined effect of magnesium and potassium sulfate concentration on oil recovery. Three experiments were conducted to study the combined effect of Magnesium sulfate and sodium chloride contents on oil recovery. In addition, three other experiments were carried out to investigate the effect of potassium chloride concentrations associated with sodium chloride salinity (higher than the 5000ppm stated for low salinity process) on oil recovery.The results revealed that sea water of higher content of magnesium sulfate and potassium sulfate increases the oil recovery by water flooding. In addition, the increase of concentration of magnesium sulfate with lower sodium chloride increases the oil recovery by designer water injected containing sodium chloride. It is also concluded that the increase of potassium sulfate increases the oil recovery. The increment in oil recovery by increase of magnesium, and/or potassium sulfate is attributed to wettability alteration to more water-wet, higher pH condition and also to the decrease in sodium chloride associated in the same water injected.The application of the attained results will have real importance in designing the concentration of magnesium and/or potassium concentration of the designer water injected with consideration of sodium chloride salinity of the reservoir.

Simulation of Typhoon-Induced Storm Tides and Wind Waves for the Northeastern Coast of Taiwan Using a Tide–Surge–Wave Coupled Model

The storm tide is a combination of the astronomical tide and storm surge, which is the actual sea water level leading to flooding in low-lying coastal areas. A full coupled modeling system (Semi-implicit Eulerian-Lagrangian Finite-Element model coupled with Wind Wave Model II, SELFE-WWM-II) for simulating the interaction of tide, surge and waves based on an unstructured grid is applied to simulate the storm tide and wind waves for the northeastern coast of Taiwan. The coupled model was driven by the astronomical tide and consisted of main eight tidal constituents and the meteorological forcings (air pressure and wind stress) of typhoons. SELFE computes the depth-averaged current and water surface elevation passed to WWM-II, while WWM-II passes the radiation stress to SELFE by solving the wave action equation. Hindcasts of wind waves and storm tides for five typhoon events were developed to validate the coupled model. The detailed comparisons generally show good agreement between the simulations and measurements. The contributions of surge induced by wave and meteorological forcings to the storm tide were investigated for Typhoon Soudelor (2015) at three tide gauge stations. The results reveal that the surge contributed by wave radiation stress was 0.55 m at Suao Port due to the giant offshore wind wave (exceeding 16.0 m) caused by Typhoon Soudelor (2015) and the steep sea-bottom slope. The air pressure resulted in a 0.6 m surge at Hualien Port because of an inverted barometer effect. The wind stress effect was only slightly significant at Keelung Port, contributing 0.22 m to the storm tide. We conclude that wind waves should not be neglected when modeling typhoon-induced storm tides, especially in regions with steep sea-bottom slopes. In addition, accurate tidal and meteorological forces are also required for storm tide modeling.

Rocking Chair Desalination Battery Based on Prussian Blue Electrodes.

The demand for fresh water has been increasing, caused by the growing population and industrialization throughout the world. In this study, we report a capacitive-based desalination system using Prussian blue materials in a rocking chair desalination battery, which is composed of sodium nickel hexacyanoferrate (NaNiHCF) and sodium iron HCF (NaFeHCF) electrodes. In this system, ions are removed not only by charging steps but also by discharging steps, and it is possible to treat actual seawater with this system because the Prussian blue material has a high charge capacity with a reversible reaction of alkaline cations. Here, we demonstrate a rocking chair desalination battery to desalt seawater, and the results show that this system has a high desalination capacity (59.9 mg/g) with efficient energy consumption (0.34 Wh/L for 40% Na ion removal efficiency).

Development of adsorption and solidification process for decontamination of Cs-contaminated radioactive water in Fukushima through silica-based AMP hybrid adsorbent

Abstract Developing highly efficient cesium (Cs) adsorbent and a stable solidification method for Cs is vital for the advancement of the decontamination system for Fukushima Daiichi Nuclear Power Plant. A novel porous silica loaded with ammonium molybdophosphate (AMP/SiO 2 ) was prepared through impregnation/precipitation/freeze-drying method. The composite with 32.4 wt% AMP loading amount had superior large 254.2 A pore width and 72.2 m 2 /g surface area. The 137 Cs removal efficiency in actual seawater was 97.1% within 30 min, indicating that AMP/SiO 2 effectively treated contaminant water with low-level concentration of Cs even in the presence of highly concentrated competing ions. The AMP/SiO 2 adsorption of 137 Cs in seawater conformed well with Redlich-Peterson model. The ion exchange ratio of Cs + and NH 4 + in AMP was estimated to be 71% from the equivalent of Cs 2 NH 4 MP. Pyrogenetic AMP/SiO 2 -adsorbed Cs (Cs-AMP/SiO 2 ) was decomposed above 400 °C sintering temperature, and Cs immobilization (%) decreased from 100% to 40% after sintering at 1200 °C; porous silica support matrix had no immobility for Cs. In contrast, adding natural mordenite (NM) can depress the volatilization of Cs, resulting to the steady immobilization ratio of Cs at nearly 100% for the sintered products. The crystal phase immobilizing Cs was identified as Cs 4 Al 4 Si 20 O 48 through X-ray diffractometry. The Cs leachability from the sintered products was less than 0.1% even at 90 °C in distilled water and 0.1 M sodium chloride.

Direct extraction of U(VI) from alkaline solution and seawater via anion exchange by metal-organic framework

Directly extracting uranium from alkaline solution and seawater through an effective and economical method is still a challenging task. In this work, we for the first time propose a method of anionic exchange, based on a cationic MOF (metal-organic framework) adsorbent, namely Co-SLUG-35, to directly extract U(VI) from alkaline solution and seawater (South China Sea). The U(VI) adsorption experiments indicates that the EDS2− anions in Co-SLUG-35 can be completely replaced by U(VI) ions in an anionic manner, leading to an adsorption capability of 118mg/g from alkaline U(VI) solution and excellent extraction efficiency of 1.05mg/g from 1L actual seawater in the concentration of 5.35ppb. Most importantly, unlike other MOFs where degassing is primarily needed, however the use of present MOF need not any pretreatment. Moreover, ultrahigh selectivity towards U(VI) ions even over CrO42− and Cl− ions is also observed in Co-SLUG-35, suggesting its superior potential in extraction of uranium from seawater.

Characteristics of Double Layered TiO2 Anode Assembling to Marine Microbial Fuel Cell

We have been investigating the electrochemical characteristics of the marine microbial fuel cell (MMFC) composed of biofilm covered stainless steel cathode and titanium dioxide anode in actual seawater. In the past study, the double layered TiO2 electrode showed a superior photocatalytic property as an intermediate layer plays a role of accelerating electron transfer. This intermediate layer also behaves as a protective barrier which suppresses the substrate corrosion against the cyclic light irradiation. The present work attempted to analyze the Rutile / Anatase double layered TiO2 electrode characteristics by means of electrochemical impedance spectroscopy (EIS) to improve the electrode performance when TiO2 double layered anode is assembled to the MMFC.

Differences in the viability of murine norovirus in different aquatic locations

Norovirus is detected from shellfish and environmental water more frequently in winter than in other seasons. However, there is no report regarding its viability in actual seawater in situ. We investigated the viability of murine norovirus strain 1 (MNV-1), a surrogate for human norovirus, in 2 types of aquatic locations, a seawater pool carrying oceanic water and inner bay carrying brackish water. Sterilized seawater was inoculated with MNV-1 and enclosed in dialysis tubes, which were placed at the 2 locations. MNV-1 exhibited higher level of viability in brackish than in oceanic water. Factors that influenced the viability of MNV-1 included salt concentration as well as temperature of the seawater. Therefore, based on our findings, coastal brackish water that is routinely used for harvesting or cleaning seafood at fishing ports may promote the viability of norovirus.

An approach to determination of phenolic compounds in seawater using SPME-GC-MS based on SWCNTs coating

Phenolic compounds have become one kind of the important pollutants of the marine environment. Single-walled Carbon nanotubes, as one-dimensional nano materials, have light weight and perfect hexagonal structure of connections, with many unusual mechanical, chemical and electrical properties. In recent years, with the research of carbon nanotubes and other nano materials, the application prospect is also constantly discussed. In this paper, homemade single-walled carbon nanotubes (SWCNTs) coating was used for establishing an analytical approach to the determination of five kinds of phenolic compounds in seawater using SPME-GC-MS. Optimal conditions: After saturation was conducted with NaCl, and pH was adjusted to 2.0 with H2SO4, the extract was immersed in a water bath at 40°C for GC-MS determination through 40-min agitating extraction at 500 rmin−1 and 3-min desorption at 280°C. The liniearities ranged between 0.01-100 μg L−1, and the determination limits ranged between 1.5-10 ng L−1. The relative standard deviation (RSD, n = 5) was less than 6.5%. For the phenolic compounds obtained from the spiked recovery test for actual seawater samples, the rates of recovery were 87.5%-101.7%, and the RSDs were less than 8.8%, which met the requirements of determination. Due to its simplicity, high efficiency and low consumption, this approach is suitable for the analysis of trace amounts of phenolic compounds in marine waters.

Polymer-Supported Bifunctional Amidoximes for the Sorption of Uranium from Seawater

Bifunctional amidoxime fibers are synthesized from commercially available polyacrylonitrile as sorbents for the recovery of U(VI) from seawater. The purpose of introducing a second ligand is to enhance the affinity of the amidoxime (AO) ligand via two possible mechanisms: by acting directly upon the AO to increase its ability to ion exchange or providing additional coordination sites to the uranyl ion. Amines are chosen as the second ligand since they have a high affinity for U(VI) at ppm levels from synthetic seawater. Diethylenetriamine (DETA) is utilized as the amine because it is sufficiently flexible to interact with AO and able to bind metal ions. Along with AO and AO-DETA fibers, the primary NH2 moieties were modified with phosphonic acid ligands (AO-phon-DETA). All fibers have high affinities (>99% sorption) for the uranyl ion when initially present at 0.90 ppm in synthetic seawater. When contacted with actual seawater at the Pacific Northwest National Laboratory for 20.8 days, the loadings for th...

Aquifer vulnerability and seawater intrusion risk using GALDIT, GQISWI and GIS: case of a coastal aquifer in Tunisia

Due to increase in population and agricultural activities, the Sfax coastal aquifer is under tremendous stress and seawater intrusion becomes a serious concern. This situation needs an assessment of aquifer vulnerability and seawater intrusion risk. A new approach for vulnerability mapping using GALDIT, groundwater quality index for seawater intrusion (GQISWI), geostatistics, the Ghyben–Herzberg model and GIS was developed. The model is used to determine the trend of groundwater contamination by seawater intrusion in the coastal aquifer in Sfax basin (Tunisia). Vulnerability assessment method is recognized through assessing weight and ratings of the GALDIT relevant parameter. A second vulnerability map was realized based upon the groundwater quality index for seawater intrusion integrating the water quality parameters for delineating seawater intrusion in the aquifer. The validation of GQISWI and GALDIT vulnerability maps was undertaken through comparison of areas of high Jones Ratio, chloride and TDS concentration and their relative vulnerability index. The Ghyben–Herzberg model has been used to predict the actual seawater intrusion extend and evaluate the freshwater–saltwater dynamics. The results reveal that the coastal area is currently undergoing seawater intrusion and its northern part is the most affected one by this contamination.

Misleading reconstruction of seawater intrusion via integral depth sampling

Summary Saltwater intrusion in coastal aquifers is an urgent issue for the actual and future groundwater supply and a detailed characterization of groundwater quality with depth is a fundamental prerequisite to correctly distinguish salinization processes. In this study, interpolated Cl− maps of the Po River delta coastal aquifer (Italy), gained with Integrated Depth Sampling (IDS) and Multi-Level Sampling (MLS) techniques, are compared. The data set used to build up the IDS and MLS interpolated Cl− maps come from numerous monitoring campaigns on surface and ground waters, covering the time frame from 2010 to 2014. The IDS interpolated Cl− map recalls the phenomenon of actual seawater intrusion, with Cl− concentration never exceeding that of seawater and the absence of hypersaline groundwater all over the study area. On the contrary, in the MLS interpolated Cl− maps the lower portion of the unconfined aquifer presents hypersaline groundwater making it necessary to consider salinization processes other than actual seawater intrusion, like upward flux from a saline aquitard. Results demonstrate the obligation of using MLS in reconstructing a reliable representation of the distribution of salinity, especially in areas where the density contrast between fresh and saline groundwater is large. Implications of the reported field case are not limited to the local situation but have a wider significance, since the IDS technique is often employed in saltwater intrusion monitoring even in recent works, with detrimental effect on the sustainable water resource management of coastal aquifers.

Determination of strontium-90 from direct separation of yttrium-90 by solid phase extraction using DGA Resin for seawater monitoring

It is important for public safety to monitor strontium-90 in aquatic environments in the vicinity of nuclear related facilities. Strontium-90 concentrations in seawater exceeding the background level have been observed in accidents of nuclear facilities. However, the analytical procedure for measuring strontium-90 in seawater is highly demanding. Here we show a simple and high throughput analytical technique for the determination of strontium-90 in seawater samples using a direct yttrium-90 separation. The DGA Resin is used to determine the abundance of strontium-90 by detecting yttrium-90 decay (beta-emission) in secular equilibrium. The DGA Resin can selectively collect yttrium-90 and remove naturally occurring radionuclides such as 40K, 210Pb, 214Bi, 238U, and 232Th and anthropogenic radionuclides such as 140Ba, and 140La. Through a sample separation procedure, a high chemical yield of yttrium-90 was achieved at 95.5±2.3%. The result of IAEA-443 certified seawater analysis (107.7±3.4mBqkg−1) was in good agreement with the certified value (110±5mBqkg−1). By developed method, we can finish analyzing 8 samples per day after achieving secular equilibrium, which is a reasonably fast throughput in actual seawater monitoring. By processing 3L of seawater sample and applying a counting time of 20h, minimum detectable activity can be as low as 1.5mBqkg−1, which could be applied to monitoring for the contaminated marine environment. Reproducibility was found to be 3.4% according to 10 independent analyses of natural seawater samples from the vicinity of the Fukushima Daiichi Nuclear Power Plant in September 2013.

Energy Efficiency Enhancement Potential of the Heat Pump Unit in a Seawater Source Heat Pump District Heating System

Seawater source heat pump district heating system is a renewable energy utilization system as it can utilize the sensible heat energy contained in the seawater. The energy efficiency of the system is always the main concern for the system researchers. So a field measurement with an emphasis on the energy efficiency of an actual seawater source heat pump district heating system was conducted, and the energy efficiency enhancement potential of the heat pump unit was analyzed and evaluated. The measurement showed that the heat pump units consumed the largest part of energy consumption of the whole system, and the coefficient of heating performance (COP) of the seawater source heat pump units was quite low especially during the coldest measurement period which was only 2.43. In the light of the concept of Thermodynamic Perfectibility, the energy efficiency enhancement potential of the heat pump unit was carefully analyzed and calculated. And the results showed that there is about an average of 24.2% energy efficiency enhancement potential of the heat pump units in this project.