Desalination Treatment Research Articles

A Review of Renewable Energy Powered Seawater Desalination Treatment Process for Zero Waste

Freshwater resources have faced serious threats in recent decades, primarily due to rapid population growth and climate change. Seawater desalination has emerged as an essential process to ensure a sustainable supply of freshwater to meet the global demand for freshwater. However, this approach has some shortcomings, such as the disposal of brines containing high levels of contaminants creating environmental problems, and the energy-intensive nature of desalination, primarily powered by fossil fuels, which contribute to greenhouse gas emissions. Consequently, as a solution, the zero liquid discharge approach has been identified by the body of research to be one of the viable methods to solve these problems. Over 90% of freshwater and reusable salts could be recovered through this approach. Adopting renewable energy-powered systems could make zero-liquid discharge desalination plants operate in an entirely environmentally friendly and sustainable manner. This review explores the integration of renewable energy-powered systems for the optimisation of seawater desalination treatment processes for zero-waste and improved productivity. The review also examines technologies and strategies that improve the efficiency and sustainability of desalination systems. By analysing recent research, we provide insights into the advancements, challenges, and prospects for optimizing renewable energy-powered seawater desalination processes aimed at achieving zero waste.

Novel insights on the setting process, hardened properties, and durability of sustainable ultra-high-performance seawater sea sand concrete

Using seawater and sea sand to prepare concrete could effectively alleviate the shortage of freshwater and river sand resources and promote the sustainable development of concrete. However, the current research on the setting process, hardened properties, and sustainability of ultra-high-performance seawater sea sand concrete (UHPSSC) remain considerably limited. In this paper, the UHPSSC was designed to mitigate the autogenous shrinkage and enhance the sustainability, and the effect of seawater, untreated and desalinated sea sand on the setting process, mechanical properties, durability, and sustainability was explored by various tests. Results show that the abundant ions (e.g., Cl- and SO42-) in seawater and untreated sea sand promote the dissolution and nucleation of cement, accelerating the hydration process, and seawater provides a high pH hydration environment, which enhances the pozzolanic reaction activity of silica fume and fly ash. This leads to the enhanced flexural and compressive strengths at early age, reduced flowability, and increased autogenous shrinkage. Although the seawater and untreated sea sand considerably alleviate the natural raw materials consumption, the mechanical performance at 28 d and durability are reduced, thereby decreasing the sustainability index by 7.8 %. The desalination treatment of sea sand decelerates the hydration process of UHPSSC with untreated sea sand due to the lower ion content in desalinated sea sand. The application of desalinated sea sand mitigates the adverse impact of untreated sea sand on the workability, mechanical properties, and durability. However, this desalination process requires more energy and freshwater consumption, thereby decreasing sustainability index. The fly ash incorporation could improve the workability of UHPSSC, and decrease the autogenous shrinkage value by 17.9 %. Moreover, it mitigates the environmental effect without compromising the mechanical properties and durability, leading to an impressive 42.8 % improvement in sustainability. Durability assessment reveals that the prepared UHPSSC specimen maintains outstanding mechanical properties even after 360 d of exposure to severe marine environment, indicating its excellent durability. This paper provides novel insights for achieving a cleaner and more sustainable concrete production.

The green resource recovery process of a new type of selective bipolar membrane electrodialysis system for saline wastewater treatment

The selective electrodialysis with bipolar membrane (BMSED) is an advanced electro-membrane process that combines monovalent perm-selective ion exchange membrane and a bipolar membrane, and presented significant potential in high salinity wastewater treatment and reclamation. Herein, we accomplished an in-depth assessment of the external-integration and internal-integration systems for the treatment of high-salinity mining wastewater and seawater desalination concentrate brine. The issues surrounding their cycling performance during batch operation, their anti-fouling potential in the presence of Mg2+/Ca2+ ions, and its specific operational cost were thoroughly investigated. The results suggest that the internal integration system demonstrates suitable stability during long-term operation under batch (cycling) mode. Nevertheless, the membrane exhibited inorganic scaling due to co-ion leakage at high current density. A highly pure NaOH was obtained through an internal integration process at a cost of 0.68 $/kg, outperforming the external integration system (98.96 %, 1.85 $/kg). The findings presented in this study offer valuable insights for the industrial application of BMSED technology in managing high salinity wastewaters.

Experimental study on the scaling law of the heat exchange tube surface in the process of low-temperature single-effect distillation of high-mineralized mine water

High-mineralized mine water, due to its characteristics such as high mineralization degree, will have scaling phenomena on the surface of the heat exchange tube during the desalination treatment process, resulting in a reduction in the water production efficiency of the equipment and affecting the normal operation. To reduce the cost of water production and improve the service life of distillation equipment, this paper independently designs and builds a low-temperature single-effect distillation high-mineralized mine water experimental system to study the influence of operating parameters (temperature, spray density, concentration ratio, and system pressure) on the scaling law on the surface of the heat exchange tube. The distribution and characteristics of scale deposits on the surface of the heat exchange tube are analyzed through the growth rate and microscopic morphology of the scale deposit. The results indicate that the scaling on the surface of the titanium plate is mainly in the needle-like and rod-like morphology of CaCO3 aragonite, and a small amount of CaSO4 and calcite are generated with the increase of temperature. It was found that within the range of spray density from 0.0509 kg/(m·s) to 0.0625 kg/(m·s), concentration ratio from 2.3 to 2.7, and system pressure at 36.3 kPa, it is beneficial to the evaporation heat transfer of the heat exchange tube and the reduction of scaling generation. At the same time, it is found that the scaling of the first row of heat exchange tubes is mainly within the range of circumferential angle from 0 to 100 degrees, and the scaling of the second row and the third row of heat exchange tubes is mainly within the range of circumferential angle from 110 to 170 degrees. The research results of this paper provide support for the design and operation of the low-temperature multi-effect treatment system for mine water in engineering, promote the process of zero discharge of high-mineralized mine water in Xinjiang, China, and improve the resource utilization rate of high-mineralized mine water.

A Sustainable Water Resources Management Assessment Framework (SWRM-AF) for Arid and Semi-Arid Regions—Part 1: Developing the Conceptual Framework

The evaluation of water resources management practices is essential for water usage decisions in regions with limited water resources. The literature provides numerous assessment frameworks, but many ignore the unique characteristics and conditions of some special arid and semi-arid regions, such as the Gulf Cooperation Council (GCC) countries, which lack any permanent rivers or lakes. Thus, this study, the first in a two-part series, seeks to develop a conceptual Sustainable Water Resources Management Assessment Framework (SWRM-AF). General and particular criteria explain how components and indicators were identified. The conceptual SWRM-AF provided here has four components (environment, economy, society, and infrastructure) and 24 indicators. Almost every indicator has been selected from the literature and is briefly explained and justified. This research presents, possibly for the first time, clear and straightforward directions for evaluating each indicator in colour-coded tables. To create a more holistic framework for arid and semi-arid regions, social indicators like “intervention acceptability” and environmental indicators for assessing the impacts of desalination treatment plants have been added to form a unique framework applicable to such regions. Therefore, the components and indicators of conceptual SWRM-AF could work collectively to aid the process of decision-making. The next phase is validating this framework using a participatory approach.

PRELIMINARY CONSERVATION TREATMENT AND RECONSTRUCTION OF POTTERY ARTIFACTS EXCAVATED FROM TERRESTRIAL AND MARINE ENVIRONMENTS, LEPTIS, LIBYA

This paper presents a preliminary conservation treatment of four pottery fragments excavated at Leptis, Libya manufactured in varied shapes, sizes, and colours. Studied objects were unearthed as sherds from two different conditions. Determination of the deterioration rates and caused factors of the pottery objects was significant to take the correct decision for conservation treatment. Results demonstrate that marine environment was more deteriorate than sandy soil. This work aims to characterize the chemical structure of pottery objects in the original environment using functional analyses. Mechanical cleaning was the first aid and safe step of conservation procedures. Desalination treatment was used for the long-term stabilization of the excavated pottery; then, internal stresses was decreased. Immersion in distilled water was efficient for decreasing water-soluble salts as halite. Insoluble water-salts were removed mechanically and chemically using dilute hydrochloric acid. Colour and thickness of the potsherds were the clues for the classification for assembling using a PVAc/CN mixture (1:1). Completely reconstruction of the excavated sherds was undertaken for understanding the occupation of the objects, then they were preserved in the storage. After desalination and assembling, painted iron stands were prepared for displaying the treated objects.

Extraction of Soluble Salts and Iron Sulfides from the Wood of the “Huaguangjiao I” Shipwreck

Shipwreck wood often contains soluble salts and iron sulfides, which pose a threat to its stability. Therefore, desalination treatment must be carried out during protection. In this study, deionized water and ethylene diamine tetraacetic acid disodium salt (EDTA-2Na) solution were used to extract soluble salts and iron sulfides from the 511 wood components of the “Huaguangjiao I” shipwreck. The extraction lasted for 1120 days, during which extraction progress was monitored by measuring the electrical conductivity and iron content of the soaking solution. The results indicated that the extraction experiment reached its endpoint when the conductivity of the soaking solution was maintained at 80~100 μs/cm and the iron content was maintained at 8~15 mg/L. More than 143.35 kg of iron were extracted from the wood of the “Huaguangjiao I” shipwreck. After extraction, the content of soluble salt ions in the wood were less than 5 μg/g, with an iron content below 5%. The wood has returned to its original color and with a certain degree of degradation. “Huaguangjiao I” was the first large-scale marine shipwreck to complete the desalination treatment of all wooden components. This study provides guidance for the desalination treatment of large-scale wooden shipwrecks.

Innovative method for the brine treatment by electrokinetic principles integrated with solar photovoltaic plants

With the growing world population and industrial production, the demand for water has been continuously increasing. By 2030, it was estimated that 60.0 % of the world population will not have access to freshwater, which is about 2.50 % of the total global water. For this, a total of over 17,000 operational desalination plants have been constructed worldwide. However, the key barriers to expansion of the desalination treatments are the brine production and energy consumption. In fact, the brine production is 50.0 % higher than the freshwater, and its treatments could account for 5.0–33.0 % of total desalination cost. Here, a new theoretical approach for brine treatments integrated to solar photovoltaic plants (PVs) to supply renewable energy to the whole system has been proposed. This approach consists in combining electrokinetic and electrochemical phenomena to dilute the brine, by using an alkaline clay with high buffering power. This method substantially desalinates the brine to produce new treated seawater, using clean energy, optimizing energetic and management costs. Some hypotheses and secondary effects should validate the model, e.g., relatively high Ca2+ promotes the electro-migration; the Cl2 production reduces the Cl− concentrations; and the production of H2 can be used to store energy. A practical example for PVPs design is shown.

Development of crude oil desalination unit by using solar flat plate collectors

To date, two-thirds of the world's crude oil reservoirs need desalination treatment to remove the salt content of crude oil. Ensuring the quality of produced crude oil shows the critical need for desalting units. But, these plants are one of the high-energy consuming processes, especially in the indirect-fired heaters. In this concern, exergy analysis investigated the thermodynamic efficiency of the plant's equipment. Aspen Hysys, and Matlab software are used for simulating and calculating the integrated system based on solar flat plate collectors. Based on exergy analysis, the most inefficient equipment are the skimmer tank, and dual indirect fired heaters by 680, 262 and 216 kW, respectively. Regarding the high rate of exergy destruction in the indirect fired heaters, implementing solar flat plate collectors as alternative equipment that is economically affordable was considered. The desalination unit has significant potential for using solar flat plate collectors, as determined by key solar characteristics such as temperature, clearness index, and daylight length. Mathematical modeling shows that maximum solar irradiation was attained at altitude angle (31°). The economical optimal area was assessed based on the life cycle saving cost parameter. After obtaining the optimal area, it was found that using 52000 m2 of solar flat plate can supply a proper substitute for inefficient heaters. A comprehensive economic analysis of this proposed plan is based on effective indicators, such as purchase side costs, maintenance costs, and fuel inflation rate. The economic results show that the investment cost will be reimbursed 14 years after start-up. This optimum area can reduce CO2 emission of heaters up to 83 %.

Optimization of the design and operating parameters of a large-scale vacuum membrane distillation system to improve process performance

This study investigates the performance and optimal operating of a proposed large-scale vacuum membrane distillation (VMD) system with an external condenser for enhanced productivity and energy consumption. The VMD configuration reduces the resistance of vapor mass transfer across the membrane to increase its permeation rate. A comprehensive parametric analysis to evaluate the effects of various operational and design parameters of the MD module and the condenser unit has been performed. The optimized results were compared to the conventional direct-contact membrane distillation (DCMD) configuration. Results revealed that the feed temperature and flowrate have the most significant impacts on system productivity and energy consumption. Increasing the vacuum improves productivity, while increasing the membrane thickness decreases system productivity. Increasing the membrane pore diameter slightly enhances system productivity. Using smaller coil diameters for condenser and cooling the system using water at room temperature can minimize the energy consumption of the system. The proposed model outperforms the traditional DCMD unit of the same module design. The system can produce 388 L/h of freshwater, with a minimum SEC of 645 kWh/m3 at the optimum conditions. These findings demonstrate the potential of the vacuum membrane distillation process as a promising technology for water desalination treatment applications.

Investigating the Impact of Seawater Intrusion on the Operation Cost of Groundwater Supply in Island Aquifers

AbstractManaging fragile island freshwater resources requires identifying pumping strategies that trade off the financial cost of groundwater supply against controlling the seawater intrusion (SWI) associated with aquifer pumping. In this work, these tradeoffs are investigated through a sensitivity analysis conducted in the context of an optimization formulation of the groundwater management problem, which aims at minimizing the groundwater supply operation cost associated with groundwater pumping and desalination treatment, subject to constraints on SWI control, as quantified by the water table drawdown over the well (∆s), the reduction in freshwater volume (∆FV) in the aquifer, or the salt mass increase (∆SM) in the aquifer. This study focuses on a simplified two‐dimensional model of the San Salvador Island aquifer (Bahamas). Pumping strategies are characterized by the distance of the pumping system from the shoreline (WL), the abstraction screen depth (D) and overall pumping rate (Q), constituting the decision variables of the optimization problem. We investigate the impacts of pumping strategies on the operation cost, ∆s, ∆FV and ∆SM. Findings indicate increasing D or decreasing WL reduces ∆s, ∆FV and ∆SM, thus preserving the aquifer hydrogeologic stability, but also leads to extracting saltier groundwater, thus increasing the water treatment requirements, which have a strong impact on the overall groundwater supply cost. From a financial perspective, groundwater abstraction near the island center and at shallow depths seems the most convenient strategy. However, the analysis of the optimization constraints reveals that strategies where the pumping system approaches the island center tend to cause more severe SWI, highlighting the need to trade off groundwater supply cost against SWI control.

Water Management Adaptation to Climate Change in Mediterranean Semiarid Regions by Desalination and Photovoltaic Solar Energy, Spain

Integration of renewable energy sources and water production technologies is a must when facing water scarcity problems in semiarid regions, such as Mediterranean regions. The use of additional water resources and production methods, such as reclaimed water and, more specifically, desalinated water, means present and necessary water resources to introduce in the water balances to attend to water demands within a global warming and droughting scenario. These solutions have the inconvenience of energy/power needs and costs. However, the development of renewable energies like photovoltaic solar energy, with lower and lower costs and greater efficiency, makes these economically feasible facilities, reaching competitive production costs for marine or sea desalinated water by around 50% of reduction in energy costs and 20–30% of savings in final water production cost. This paper presents a practical project or action focused on the integration of renewable energies and new water resources by introducing a Photovoltaic Energy Plant (PVEP) as an energy source to feed a Seawater Desalination Treatment Plant (SWDTP). The PV facility is designed to cover all the energy demanded using the SWDTP during the day, and even studying the possibility of selling the energy production exceeds and injecting them into the energy supply network, covering the needs of buying energy needed during the high period where there is no photovoltaic energy production. Thus, savings related to energy costs and even incomes coming from energy sales mean an important reduction in operation costs or expenditures (OPEX), which makes economically feasible and sustainable the investment and the final price of water produced within the Mutxamel SWDTP. The final reduction cost in water desalination reaches 25% on average.

Pretty in pink? Complementary strategies for analysing pink biofilms on historical buildings

Salt-weathering is a deterioration mechanism affecting building materials that results from repetitive cycles of salt crystallisation-dissolution in the porous mineral network under changing environmental conditions, causing damage to surfaces. However, an additional biodeterioration phenomenon frequently associated with salt efflorescence is the appearance of coloured biofilms, comprising halotolerant/halophilic microorganisms, containing carotenoid pigments that cause pinkish patinas.In this work, two Austrian historical salt-weathered buildings showing pink biofilms, the St. Virgil's Chapel and the Charterhouse Mauerbach, were investigated. Substrate chemistry (salt concentration/composition) was analysed by ion chromatography and X-ray diffraction to correlate these parameters with the associated microorganisms. Microbiomes were analysed by sequencing full-length 16S rRNA amplicons using Nanopore technology.Data demonstrates that microbiomes are not only influenced by salt concentration, but also by its chemical composition. The chapel showed a high overall halite (NaCl) concentration, but the factor influencing the microbiome was the presence/absence of K+. The K+ areas showed a dominance of Aliifodinibius and Salinisphaera species, capable of tolerating high salt concentrations through the “salt-in” strategy by transporting K+ into cells. Conversely, areas without K+ showed a community shift towards Halomonas species, which favour the synthesis of compatible solutes for salt tolerance. In the charterhouse, the main salts were sulphates. In areas with low concentrations, Rubrobacter species dominated, while in areas with high concentrations, Haloechinothrix species did. Among archaea, Haloccoccus species were dominant in all samples, except at high sulphate concentrations, where Halalkalicoccus prevailed. Finally, the biological pigments visible in both buildings were analysed by Raman spectroscopy, showing the same spectra in all areas investigated, regardless of the building and the microbiomes, demonstrating the presence of carotenoids in the pink biofilms.Comprehensive information on the factors affecting the microbiome associated with salt-weathered buildings should provide the basis for selecting the most appropriate desalination treatment to remove both salt efflorescence and associated biofilms.

Study of Micro-Samples from the Open-Air Rock Art Site of Cueva de la Vieja (Alpera, Albacete, Spain) for Assessing the Performance of a Desalination Treatment.

In this work, some micro-samples belonging to the open-air rock art site of Cueva de la Vieja (Alpera, Albacete, Spain) were analysed. These samples were collected after and before a desalination treatment was carried out, with the aim of removing a whitish layer of concretion that affected the painted panel. The diagnostic study was performed to study the conservation state of the panel, and to then confirm the effectiveness of the treatment. Micro energy dispersive X-ray fluorescence spectrometry, Raman spectroscopy, and X-ray diffraction were employed for the characterization of the degradation product as well as that of the mineral substrate and pigments. The micro-samples analysis demonstrated that the painted layer was settled on a dolomitic limestone with silicon aggregates and aluminosilicates as well as iron oxides. The whitish crust was composed by sulfate compounds such as gypsum (CaSO4·2H2O) with a minor amount of epsomite (MgSO4·7H2O). An extensive phenomenon of biological activity has been demonstrated since then in almost all of the samples that have been analysed, and the presence of calcium oxalates monohydrate (CaC2O4·H2O) and dehydrate (CaC2O4·2H2O) were found. The presence of both calcium oxalates probably favoured the conservation of the pictographs. In addition, some carotenoids pigments, scytonemin (C36H20N2O4), and astaxanthin (C40H52O4) were characterized both by Raman spectroscopy and by X-ray diffraction. Hematite was found as a pigment voluntarily used for the painting of the panels used in a mixture with hydroxyapatite and amorphous carbon. The results of the analyses of the samples taken after the cleaning treatment confirmed a substantial decrease in sulphate formation on the panel surface.

Reaction of Polyamide Membrane Model Monomers with Chlorine Dioxide: Kinetics, Pathways, and Implications.

Aromatic polyamide (PA) based membranes are widely used for reverse osmosis (RO), but they can be degraded by free chlorine used for controlling the biofouling prior to RO treatment. Kinetics and mechanisms for the reactions of PA membrane model monomers, i.e., benzanilide (BA), and acetanilide (AC), with chlorine dioxide (ClO2) were investigated in this study. Rate constants for the reactions of ClO2 with BA and AC at pH 8.3 and 21°C were determined to be (4.1±0.1)×10-1 M-1.24 s-1 and (6.0±0.1)×10-3 M-1 s-1, respectively. These reactions are base assisted with a strong pH dependence. The activation energies of BA and AC degradation by ClO2 were 123.7 and 81.0 kJ mol-1, respectively. This indicates a relatively strong temperature dependence in the studied temperature range of 21-35 °C. The presence of bromide and natural organic matter does not promote the degradation of model monomers by ClO2. BA was degraded by ClO2 via two pathways: (1) the attack on the anilide moiety with the formation of benzamide (major pathway) and (2) oxidative hydrolysis to benzoic acid (minor pathway). A kinetic model was developed to simulate the degradation of BA and formation of byproducts during ClO2 pretreatment, and simulations agree well with the experimental data. Half-lives of BA treated by ClO2 were 1-5 orders of magnitude longer than chlorine under typical seawater treatment conditions. These novel findings suggest the potential application of ClO2 for controlling biofouling ahead of RO treatment at desalination treatments.

Peroxymonosulfate assisted mechanochemical remediation of high concentration DDTs contaminated soil

DDTs (DDT and its metabolites) contaminated sites urgently need to be treated efficiently and greenly. In this study, a horizontal planetary mechanochemical method with co-milling additives was developed aiming at efficiently degrading high-concentration DDTs in historical contaminated soil (∼7500 mg/kg). Peroxymonosulfate (PMS) was firstly used to the mechanochemical degradation of DDTs in historical contaminated soil, with a degradation efficiency of over 95% after 1 h of milling under the optimal milling conditions (CR = 30:1, r = 500 rpm, R = 1:4). Mechanism study indicated that DDTs in soil were partially dechlorinated and mineralized. The main products formed might be chlorinated aliphatic hydrocarbons, which need further treatment by ball milling or other methods. Under the action of mechanical energy, PMS could oxidize DDTs in soil through non-radical way rather than common radical way. Then, a comprehensive assessment of this remediation method was conducted by analyzing the changes in soil properties and acute biotoxicity after ball milling. Although PMS had a great performance on the degradation of DDTs, especially p, p’-DDE, it would cause the acidification and salinization of soil. Therefore, further pH adjustment and desalination treatment were suggested to reduce the negative impacts. This work successfully presents a practical approach to mechanochemical remediation of DDTs contaminated sites.

Nanofiltration combined with membrane capacitive deionization for efficient classification and recovery salts from simulated coal chemical industrial wastewater

Achieving water reuse and salt resources recycling in high-salt wastewater from the coal chemical industry is crucial to the sustainable development. However, the current widely used RO (reverse osmosis)-NF (nanofiltration)-crystallizationprocess requires significant energy consumption in the step of heat-driven crystallization. Here, RO-NF-membrane capacitive deionization (MCDI) system was designed for classify and recover salt from high-salt wastewater of coal chemical industry. Sludge-derived biochar with high specific surface area and hierarchical structure was used as the electrode for MCDI. The MCDI cell can stabilize desalination of source water containing NaCl up to 300 mM, i.e., the total dissolved solids (TDS) of 18,000 mg·L−1, which can be applied to the desalination treatment after RO-NF salt separation. Based on the MCDI, a two-channel architecture was designed, in which a concentration channel was constructed between the electrode and the anion exchange membrane, while the desalination channel remains between the anion and cation exchange membrane. Continuous operation of desalination and concentration was achieved by exchanging the inlet and outlet of the concentration and desalination channels during the charging and discharging phases. This work demonstrates that the RO-NF-MCDI system could be a feasible method for classification and recovery salts from coal chemical industrial wastewater.

Monitoring and controlling the desalination plant using IoT

In this paper, the need for innovative technology and ways to accomplish optimized resource use and desalination treatment, which transforms saltwater into clean drinking water, has been underlined by rising water demands and a degrading environment. The Internet of Things (IoT) now permits to automate a variety of formerly moment and source of energy tasks. One of these is improving water treatment management. This research represents an IoT model for monitoring and controlling a desalination plant. This system monitors the water quality parameters like pH values, temperature, and dissolved oxygen parameters, which are helpful to assess water quality and identify fault parameters at the desalination plant. Here, separate sensors are involved to gather the information and store it in the cloud. It also sends SMS notifications and warnings when it detects misfunctioning, and it regulates the gate valves. This is very needed to rectify the errors, prevent the system from failing, and reduce the maintenance costs as well. This proposed system is highly effective compared to others. According to experimental findings, the proposed technique extends the time by 1.0638%, 6.3829%, and 14.8936% compared to the RO, ED, and FACETS methods.

Simplistic determination of the membrane pore charge density in presence of mixture of electrolytes

Membrane pore charge density (Xd) is an effective but non-measurable parameter for determining the performance of low cut-off ultrafiltration (LCUF) and nanofiltration (NF) membranes. Xd along with the physicochemical properties of the solution determines the membrane zeta potential. These properties include the solution pH, ionic strength as well as the ratio and nature of electrolytes in the solution. Hence, with the prior knowledge of the solution physicochemical properties and the zeta potential, determination of Xd is possible. In this study, the effect of binary mixture of electrolytes, i.e., NaCl/Na2SO4 on the membrane zeta potential was investigated for different solution pH (3–9) as well as the total salt concentration (2–10 g L−1). An empirical correlation between Xd and the other experimentally measurable parameters was developed. Salt rejection experiments were carried out with the above mentioned combinations of pH and total salt concentration along with different weight ratios of NaCl/Na2SO4 namely, 100:0, 90:10, 70:30, 50:50 and 0:100 for six LCUF membranes. For PAN PDA/PEI 12 membrane, at pH 7 and 2 g L−1 of total salt concentration, the rejection of divalent anion (SO42−) was increased from 60% to 75.3%, for monovalent cation (Na+), it was increased from 33% to 41.2% with the concentration of Na2SO4. However, the corresponding rejection of monovalent anion (Cl−) was decreased from 33% to 16.1%. For each of the experimental condition, Xd obtained from the Donnan Steric Pore Model (DSPM) solution was correlated with the zeta potential (ζ) and weight fraction of divalent salt (r) as: Xd=a+br+cζ. The effect of the solution pH and ionic strength is included in the membrane zeta potential. The correlation was successfully tested for the commercial membranes in predictive mode. The empirical correlation proposed in this paper acts as a useful tool to determine Xd for amine based LCUF membranes. This helps to predict the membrane performance for real life desalination treatment without performing a series of rejection experiments.

Foaming and interfacial properties of desalted duck egg white nanogels after weak enzymatical hydrolyzation

Abstract Gel-assisted desalination is an efficient way of desalting salted duck egg whites, but results in severe loss of egg white functional properties, especially foaming properties. Here, slightly enzymatical hydrolyzation was used as a promising method to improve the interfacial properties of desalted duck egg white nanogels (DEWN). After partial hydrolysis (ranging from 2.27% to 4.22%), the foaming capability (FC) of the mixture could reach more than 200%, much higher than that of unhydrolyzed DEWN (about 30%). After separated examination, such improve FC was dominantly attributed to the supernatant, which also impacted enhanced foaming stability (FS). The adsorption of the supernatant and the resulting surface rheological measurements exhibited that the extension of the hydrolysis time can increase the diffusion and adsorption rate to the interface, performing high elasticity. Specially, the Lissajous curves displayed that the samples with short enzymolysis time first appeared asymmetric shape, indicating that extending enzymolysis time could improve the elasticity of the interface, which contributed to the improvement in foaming properties. As in a wide range of pH values, the FC and FS of the supernatant performed well, especially exhibited excellent FS at pH 5.0. In general, pepsin hydrolysis treatment, as an oversimplified and green modification strategy could significantly improve the foaming performance of DEWN, and solve the problem of loss in its foamability of salted duck egg whites obtained after desalination treatment. • Solid-state desalination method is an efficient and simple method for desalting salted egg whites. • Pepsin hydrolysates of desalted egg white microgels exhibited excellent foamability and foam stability. • The interfacial behavior of the enzymatic hydrolyzate was analyzed by combining nonlinear interface expansion rheology and Lissajous curve.