Desalination Methods Research Articles

Theoretical and experimental study of a new freezing desalination system assisted by ultrasound

Compared with traditional seawater desalination methods, freezing desalination has gotten more attention for its advantages in reducing energy consumption and environmental protection. In this study, a new freezing desalination assisted by ultrasonic is proposed to improve desalination efficiency. A detailed freezing desalination model is established based on phase transition analysis and ultrasonic-assisted freezing theory. The experiment system is also developed to analyze the desalination process. The factors such as temperature, interface transformation and salinity in the process of droplet freezing under the action of ultrasound were analyzed and discussed. The result showed that the salinity of the droplet residual brine could decline to less than 2.4% when the initial salinity was 5% and droplet diameter was 2 mm after 1 min centrifugal treatment. After the treatment, the salinity of the existed ice-brine mixing was decreased below 0.2%. According to experiments and simulation analysis, the application of ultrasonic wave in freezing desalination can effectively increase the freezing speed of droplets and improve the efficiency of desalination. This study will contribute to the application of ultrasonic in the freezing desalination.

Investigation of effective parameters on brackish water desalination by flow-electrode capacitive deionization

Abstract Population growth and increasing global demand for freshwater have raised a serious challenge for the depleting sources of freshwater in the 21st century. Desalination technologies can be a reliable technique for providing freshwater. Capacitive deionization is one of the innovative desalination methods that has received increasing interest. Flow-electrode capacitive deionization (FCDI) (a new architecture of capacitive deionization) is one of the efficient, cost-effective, and environmentally friendly desalination methods for freshwater production. In this experimental research, the performance of an FCDI system was investigated and the influence of important parameters such as flow rate of flow-electrodes, electrolyte salt concentration of flow-electrodes, and initial feed water concentration will be assessed on the efficiency of desalination operation. In this study, the flow-electrodes operated in short-circuited closed-cycle operation (SCC) mode, and also the feed water operated similarly to the flow electrodes in closed cycle. Moreover, in all the experiments, the salt adsorption capacity (SAC) and salt removal efficiency (SRE) was calculated. Herein, by optimizing the above-mentioned parameters, the salt removal efficiency of 83% and a SAC value of 29.12 mg/gdry carbon were achieved in 5 hours.

Asymmetric Cellulose/Carbon Nanotubes Membrane with Interconnected Pores Fabricated by Droplet Method for Solar-Driven Interfacial Evaporation and Desalination.

Solar-driven interfacial water purification and desalination have attracted much attention in environmentally friendly water treatment field. The structure design of the photothermal materials is still a critical factor to improve the evaporation performance such as evaporation rate and energy conversion efficiency. Herein, an asymmetric cellulose/carbon nanotubes membrane was designed as the photothermal membrane via a modified droplet method. Under 1 sun irradiation, the evaporation rate and energy efficiency of pure water can reach up to 1.6 kg m−2 h−1 and 89%, respectively. Moreover, stable reusability and desalination performance made the cellulose/carbon nanotubes membrane a promising photothermal membrane which can be used for solar-driven desalination.

A review of nanofiber membranes for solar interface evaporation

The shortage of freshwater resources is a global problem while traditional desalination methods are energy consuming and inefficient. Recently, solar interface evaporation (SIE) has attracted more and more researchers' attention, due to its high efficiency, low cost and environmental friendliness. This article summarizes the latest development on the SIE materials based on nanofiber membranes. The mechanism, difficulties and solutions in the aspects of material preparation, light absorption, thermal management, water transportation and multi-functionalization are discussed in categories. The review is mainly focused on the evaporation efficiency, salt resistance performance, corrosion resistance and long-term stability of the SIE materials. Finally, the challenges and outlook of the nanofiber based SIE materials are proposed.

Water desalination by charged multilayer graphene membrane: A molecular dynamics simulation

Graphene, due to its unique excellent properties, is proposed as a developing method with high efficiency compared to classical water desalination methods. In this regard, charging the membrane is considered a promising and effective approach to enhance the performance of the graphene membrane. In this research, by using molecular dynamics simulations, the water desalination by charged multilayer graphene is evaluated and the influence of electric charge amount and geometric parameters, including the pore diameter and the interlayer distance, are investigated. According to the results, the multilayer nanoporous graphene with 16.35 Å pore diameter, in which the electric charge is distributed with the proper amount and particular arrangement on the carbon atoms on the periphery of the pores, shows a significant enhancement of 59.4% in the water flow rate and improves the salt rejection efficiency from 67.27% to the desired value of 94.54%, compared to the uncharged multilayer graphene with 12.6 Å pore diameter. Moreover, it is demonstrated that increasing the interlayer distance of the membrane diminishes the effect of electric charge on improving the water flux.

Designing salt transmission channel of solar-driven multistage desalination device for efficient and stable freshwater production from seawater

Solar-driven passive multistage distillation (MSD) device provides a new approach for environmentally friendly freshwater production. However, the MSD device easily forms salt crystals on the evaporation surface when treating brine, resulting in performance degradation. Here, we design an MSD device with an effective salt-resistant structure to enable rapid and automatic removal of high-concentration brine by a gravity drive. The structure was optimized by laboratory experiments and simulation. As a result, the stable freshwater production rate of the 4-stage device can reach 1.98 kg m−2 h−1 under a 1 kW m−2 light intensity. In particular, the MSD device can work stably at a high light intensity of 4 kW m−2 with an evaporation rate of 8.26 kg m−2 h−1, making its freshwater yield more than 1.7 times higher than that of a device without a salt-blocking structure. In summary, we explored a new method for salt removal in MSD devices, which is a meaningful method for long-term seawater desalination.

High efficiency desalination of wasted salted duck egg white and processing into food-grade pickering emulsion stabilizer

Salted duck egg white (SDEW) is difficult to convert into high-value products for the high salt content and unpleasant odor, which leads to the loss of high-quality protein resources. In this work, for the first time, the freeze-thaw treatment was used for protein desalination to achieve complete desalination of SDEW. After SDEW prepared into hydrogel by microwave-assisted hydrothermal (125 °C, 500 W) in only 12 min, repeated freeze-thaw treatments made the hydrogel porous at the molecular level from the inside, which accelerated the outward migration of salt, thereby increasing the desalination efficiency. After ultrasonic dispersion, completely desalted SDEW, as a food-grade Pickering emulsion stabilizer, can stabilize Pickering emulsion at a particle concentration of 0.5–3.0%, oil phase fraction of 0.20–0.80 and pH value of 3.0–11.0 for at least 28 days. Overall, the findings provide a novel, simple and efficient method for SDEW desalination, and confirm that desalted SDEW is a low-cost but efficient food-grade Pickering emulsion stabilizer, which extend the potential commercial applications for SDEW in food industry.

A novel layered activated carbon with rapid ion transport through chemical activation of chestnut inner shell for capacitive deionization

Capacitive deionization is a very promising method for future water desalination. However, desalination capacity and rate limit its wide application. In this study, a layered activated carbon with rapid ion transport was synthesized by carbonizing and activating chestnut inner shell with KOH. The effects of carbonization temperature and the ratio of KOH have been studied through structural characterization and electrochemical tests. All biochar showed lamellar structure and high specific surface area (>1000 m2 g−1), and the one obtained at 500 °C (CS500) exhibited the highest specific surface area (1943.2 m2 g−1) and more oxygen-containing functional groups. Correspondingly, CS500 brought excellent capacitance (127.2 F g−1, 5 mV s−1) and small internal resistance. Moreover, CS500 achieved a significant average salt adsorption rate of 5.7 mg g−1 min−1, with a high salt adsorption capacity of 17.7 mg g−1 and 21.0 mg g−1 in NaCl (0.5 g L−1) and CaCl2 (0.95 g L−1), respectively. Additionally, CS500 showed a preferential adsorption for Ca2+ in a mixed solution with Na+, suggesting its potential for hard water softening. Lastly, CS500 maintained high cycle stability (87.0%, 1.2 V) within 50 adsorption/desorption cycles. Thus, this work supports CS500 as a promising candidate for rapid desalination and large-scale application.

Engineering anti-scaling superhydrophobic membranes for photothermal membrane distillation

The emerging photothermal membrane distillation (PMD), which combines solar harvesting and heat localization, has the potential to address the water-energy nexus. However, PMD membrane scaling and its underlying mechanisms need in-depth examination. Herein, we describe a microsphere structured composite membrane (#PCNT-0.5) with simultaneous superior light-to-heat conversion and superhydrophobic properties, produced by electrospraying a polyvinylidene fluoride (PVDF)/polydimethylsiloxane (PDMS)/multi-walled carbon nanotubes (MWCNTs) hybrid solution on an electrospun PVDF nanofibrous substrate (#PVDF). The carbon-based material and a micro-rough structure endowed the membrane with high light absorptivity, heat recovery and vapor production. Meanwhile, it showed excellent wetting resistance with contact angles beyond 150° and 120° for deionized (DI) water and 40% v/v ethanol aqueous solutions. The robustness of the surface multifunctional coating of #PCNT-0.5 was confirmed by chemical erosions and physical treatments. The localized heating alleviated the temperature polarization, increased the permeation flux of the #PCNT-0.5 by ∼15% and reduced its specific thermal energy consumption. In addition, the modified #PCNT-0.5 exhibited better anti-scaling properties compared to #PVDF. The illumination slowed down the flux decline of #PCNT-0.5 and inhibited salt crystallization. The excellent anti-scaling properties of the illuminated #PCNT-0.5 are attributed to the inhibited bulk and heterogeneous crystallization, permission of slippage and accelerated dissolution-diffusion. This study demonstrates that PMD is a feasible and promising method for hypersaline wastewater desalination.

Desalination methods and their role in solving and managing the problem of salinization in Iraqi water resources

A rise in the demand for fresh water is due to population growth in desert areas where high-quality, low-salinity water is scarce has prompted a rapid development of desalination technology, which has demonstrated its ability to address as well as resolving the water shortages in many dry locations throughout the world. Despite the benefits that could be realized from desalination under the global water crisis, the majority of people, including those who work in the water sector, regard it as a novel technology due to its lack of application. Currently, Desalinated water is used by only 1% of the global total to meet their daily needs. Nonetheless, the United Nations predicts that by 2025, Water scarcity will afflict 14% of the world’s population. For the reasons indicated in this study, Iraqi water sources have undergone a quantitative and qualitative deterioration, resulting in a rise in salt concentrations.

Review on adsorption materials and system configurations of the adsorption desalination applications

Adsorption desalination is an emerging desalination technology with low energy consumption, which is based on the principle of desalination by using the adsorption and desorption characteristics of porous adsorbents for water vapor. Compared with the traditional distillation and membrane methods, adsorption desalination can use renewable energy sources such as solar energy, geothermal energy, or industrial low-grade waste heat as the driving heat source, and thus has the excellent characteristics of being green and pollution-free. However, as a newly developed desalination technology, there is relatively little theoretical and experimental research on adsorption desalination, and it is still at the stage of small-scale experiments. This paper firstly introduces the adsorption theory and circulation process to clarify the key elements of this desalination method. Further, based on the available results, the related researches are analyzed and summarized according to the critical elements of the adsorption desalination system, i.e., preparation of adsorbents, optimization of system configuration, cyclic operating conditions, and combination systems. Finally, the future directions to be focused on for future research prediction are discussed, which will be useful for related studies in this field.

Thermodynamic analysis of thermal desalination system with humidification–dehumidification cycle

Problems. Today desalination of seawaterprovides a worldwide fresh water productionof 24.5 million m 3 perday.One of the promising desalination methods is thermal humidification-dehumidification process. In spite of significant benefits this technology, it has a key drawback – high thermal energy consumption.The aim of the study. Determine the optimal thermodynamic parameters of working substances (air and water) in elements of desalination system with humidification–dehumidification cycleto obtain maximum performance with a minimum energy consumption.Methodology of implementation. Mathematical modeling of the humidification-dehumidification cycle at different input parameters.The thermodynamic model was createdusing equations of mass and energy balances of the desalination system.Research results. System Gain output ratio(GOR) increases with increasing salt watertemperature at the outlet of the dehumidifier.Maximum valuesof GORand recovery ratio (RR) are observed at the maximum temperature difference (maximum heating) of salt water in the dehumidifier. It is shown that values of GOR and RR increasewith increasing salt water temperature at the inlet to the humidifier. It is found that GOR value is independent of the temperature and humidity of the air at the inlet to the humidifier.Conclusions.The maximum valuesof GOR and RR for the humidification-dehumidification cycle with additional water heating are 3.75 and 6%, respectively. To obtain such results,the temperature of salt water at the inlet tothe system (dehumidifier) should be equal to 10 °C, and the temperature of salt water at the inlet to the humidifier – 70 °C. At the same time, temperature and humidity of the airсan have any values. The use of renewable energy for heating salt water in the heater will significantly increase system GOR

Performance evaluation of an HDH desalination system using direct contact packed towers: experimental and mathematical modeling study

Abstract Humidification–dehumidification desalination (HDH) is one of the suitable methods for desalination of saline and brackish water in a small scale. In this research, an HDH desalination method with a direct contact dehumidifier has been analyzed theoretically and experimentally. The setup consists of two similar packing towers for humidification and dehumidification, 10 inches in diameter, which are filled up to 1 m with Rushing packing. In this new HDH configuration, seawater and freshwater recirculation has been used in humidifier and dehumidifier sections, respectively. A steady-state mathematical model based on the mass and energy equations for each system component is presented. The effect of various input parameters on the freshwater production, gain output ratio (GOR) and specific energy consumption has been investigated. The results revealed that the inlet seawater and air temperature to the humidification tower had the highest and the lowest effect on the produced freshwater, respectively. Also, the maximum value of the GOR is 3.3, which is obtained in the equilibrium condition of the dehumidifier. The experiments show that the freshwater production of the proposed HDH device is 300 L/day, which can provide water for the domestic consumption of a small family.

Theoretical Study of the Influence of Seeding on the Dynamics of Propane Hydrate Nuclei Formation in Pure and Sea Water

The effect of the addition of a propane hydrate seed on the dynamics of nucleation in propane solutions based on pure or seawater is considered within the framework of the molecular dynamics method. The time dependencies of the number of long-lived hydrogen bonds and the number of 512 and 51264 cavities formed were calculated. It was shown that presence of the seed leads to the immediate increase in the number of “stable” hydrogen bonds and the growth of hydrate nuclei, which can significantly reduce the induction time of hydrate formation in industrial use and, consequently, enhance the efficiency of the hydrate method of seawater desalination.

Corrigendum to “A greener seawater desalination method by direct-contact spray evaporation and condensation (DCSEC): Experiments” [Appl. Therm. Eng. 179 (2020) 115629

Corrigendum to “A greener seawater desalination method by direct-contact spray evaporation and condensation (DCSEC): Experiments” [Appl. Therm. Eng. 179 (2020) 115629

Ti3C2Tx MXene Nanoflakes Embedded with Copper Indium Selenide Nanoparticles for Desalination and Water Purification through High-Efficiency Solar-Driven Membrane Evaporation.

Solar-driven interface evaporation recently emerges as one of the most promising methods for seawater desalination and wastewater purification, mainly due to its low energy consumption. However, there still exist special issues in the present material system based on conventional noble metals or two-dimensional (2D) nanomaterials etc., such as high costs, low light-to-heat conversion efficiencies, and unideal channels for water transport. Herein, a composite photothermal membrane based on Ti3C2Tx MXene nanoflakes/copper indium selenide (CIS) nanoparticles is reported for highly efficient solar-driven interface evaporation toward water treatment applications. Results indicate that the introduction of CIS improves the spatial accessibility of the membrane by increasing the interlayer spacings and wettability of MXene nanoflakes and enhances light absorption capability as well as reduces reflection for the photothermal membrane. Simultaneously, utilization of the MXene/CIS composite membrane improves the efficiency of light-to-heat conversion probably due to formation of a Schottky junction between MXene and CIS. The highest water evaporation rate of 1.434 kgm-2 h-1 and a maximum water evaporation efficiency of 90.04% as well as a considerable cost-effectiveness of 62.35 g h-1/$ are achieved by using the MXene/CIS composite membrane for solar interface evaporation, which also exhibits excellent durability and light intensity adaptability. In addition, the composite photothermal membrane shows excellent impurity removal ability, e.g., >98% for salt ions, >99.8% for heavy metal ions, and ∼100% for dyes molecules. This work paves a promising avenue for the practical application of MXene in the field of water treatment.

Sustainable Amelioration of Heavy Metals in Soil Ecosystem: Existing Developments to Emerging Trends

The consequences of heavy metal contamination are progressively degrading soil quality in this modern period of industry. Due to this reason, improvement of the soil quality is necessary. Remediation is a method of removing pollutants from the root zone of plants in order to minimize stress and increase yield of plants grown in it. The use of plants to remove toxins from the soil, such as heavy metals, trace elements, organic chemicals, and radioactive substances, is referred to as bioremediation. Biochar and fly ash techniques are also studied for effectiveness in improving the quality of contaminated soil. This review compiles amelioration technologies and how they are used in the field. It also explains how nanoparticles are becoming a popular method of desalination, as well as how they can be employed in heavy metal phytoremediation.

Photothermal Diatomite/Carbon Nanotube Combined Aerogel for High‐Efficiency Solar Steam Generation and Wastewater Purification

Solar‐driven interface evaporation is a sustainable and green method for seawater desalination and wastewater purification which has attracted great attention due to the expectation to solve the global fresh water crisis. Currently, its commercial application is still limited by high cost, a complicated preparation process, and unsatisfying photothermal conversion efficiency, which are difficult to be achieved simultaneously. Herein, a nontoxic, high efficient, low cost, and facile strategy to fabricate a solar steam generator is demonstraterd, in which biocompatible agar powder, carbon nanotubes, and diatomite are combined to achieve an aerogel. All materials involved are commercially available. The aerogel exhibits a water evaporation rate of 1.67 kg m−2 h−1 with 91% conversion efficiency under one sun illumination, and can produce drinkable water from sea water, lake water, and even strong acid/alkaline water with nearly 100% rejection of organic dyes. Most importantly, the cost to produce such an aerogel is only 6.67 $ m−2, and is expected to produce 5–8 kg m−2 of fresh water per day under natural sunlight, which is enough for a family of three to live normally for one day. Present high‐efficient and economic water purification system provides promise for commercial application in seawater desalination and wastewater purification.

Molecular dynamics modeling and simulation of water desalination through a double-walled carbon nanotube with Moiré pattern

Freshwater scarcity has emerged as a major challenge of our time. Under this context, the importance of an efficient and energy-saving water desalination method is highlighted. In recent years, carbon nanotube (CNT) membrane characterizing with high permeability has attracted much attention in research, and it is regarded as a promising alternative to the conventional reverse osmosis technology. This work aims at numerically investigating the water desalination ability of a novel type of CNT membrane structure, namely the double-walled carbon nanotube (DWCNT) with Moiré pattern. After establishing the physical CNT models and running the molecular dynamics (MD) simulation of the water desalination system, it is found that both the single-walled carbon nanotube (SWCNT) and DWCNT can desalinate the seawater successfully while the water permeability of DWCNT is at least 18.9% higher than that of SWCNT within the same time. As far as the Moiŕe pattern adopted in this study is concerned, the water permeability of DWCNT without Moiŕe pattern is 18.6% higher than that with Moiré pattern.

ОБЗОР МЕТОДОВ И ТЕХНОЛОГИЙ ОПРЕСНЕНИЯ ВОДЫ ДЛЯ ЦЕЛЕЙ ПИТЬЕВОГО ВОДОСНАБЖЕНИЯ

Purpose: review of existing technologies and methods of seawater desalination for drinking water supply. Discussion. Based on modern research methods using statistical data and a review of domestic and foreign literature, a review of methods and technologies for desalination and desaltation of highly mineralized natural waters was carried out. The use of sea water for domestic purposes is impossible due to the high content of minerals, however, after desalination, such water can be used for drinking. The choice of technologies and methods of desalination is primarily determined by the quality of source water, as well as the requirements for the quality of treated water, plant productivity and technical and economic calculations. For the drinking water supply purposes, the most efficient and cost-effective method is desalination using reverse osmosis technology, used for both sea and groundwater with high salinity. Reverse osmosis technology has significant advantages over thermal desalination, especially when applied to small-scale plants of small domestic water supply systems. The use of reverse osmosis plants will significantly increase productivity of drinking water output per watt of electricity consumed. Conclusions. The introduction of modern technologies and careful attention to water consumption play a significant role in maintaining water balance in different countries. The most cost-effective and efficient method is seawater desalination using reverse osmosis plants. Despite the fact that water desalination and desaltion plants are very expensive, the conservation of natural waters is a priority nowadays.