Showing papers on "Reverse osmosis published in 2021"

High performance polyester reverse osmosis desalination membrane with chlorine resistance

Abstract: Chlorination is a common practice to prevent biofouling in municipal water supplies, wastewater reuse and seawater desalination. However, polyamide thin-film composite reverse osmosis membranes—the premier technology for desalination and clean-water production—structurally deteriorate when continually exposed to chlorine species. Here, we use layer-by-layer interfacial polymerization of 3,5-dihydroxybenzoic acid with trimesoyl chloride to fabricate a polyester thin-film composite reverse osmosis membrane that is chlorine-resistant in neutral and acidic conditions. Strong steric hindrance and an electron-withdrawing group effectively prevent direct aromatic chlorination, and residual OH groups capped with isophthaloyl dichloride preclude reaction with active chlorine. The poly(isophthalester) membrane exhibits high salt rejection (99.1 ± 0.2%) and water permeability (2.97 ± 0.13 l m−2 h−1 bar−1), even after demonstrating biofouling prevention with chlorine (50 mg l−1 of NaOCl for 15 min). We anticipate that our chlorine-resistant membrane will greatly advance reverse osmosis desalination as a sustainable technology to meet the global challenge of water supply. Reverse osmosis membranes are the primary technology used for desalination and wastewater recycling, but they are prone to biofouling and subsequent performance deterioration due to poor tolerance to disinfecting agents such as chlorine. Here a chlorine-resistant polyester reverse osmosis membrane is developed to prevent biofouling and increase the sustainability of desalination and wastewater reuse.

Is direct seawater splitting economically meaningful

Abstract: Electrocatalytic water splitting is the key process for the formation of green fuels for energy transport and storage in a sustainable energy economy. Besides electricity, it requires water, an aspect that seldomly has been considered until recently. As freshwater is a limited resource (<1% of earth's water), lately, plentiful reports were published on direct seawater (around 96.5% of earth's water) splitting without or with additives (buffers or bases). Alternatively, the seawater can be split in two steps, where it is first purified by reverse osmosis and then split in a conventional water electrolyser. This quantitative analysis discusses the challenges of the direct usage of non-purified seawater. Further, herein, we compare the energy requirements and costs of seawater purification with those of conventional water splitting. We find that direct seawater splitting has substantial drawbacks compared to conventional water splitting and bears almost no advantage. In short, it is less promising than the two-step scenario, as the capital and operating costs of water purification are insignificant compared to those of electrolysis of pure water.

Optimisation of renewable energy powered reverse osmosis desalination systems: A state-of-the-art review

Abstract: Reverse osmosis (RO) desalination has become a prominent desalination method for fresh-water production from either saline seawater or brackish water to meet the ever-growing demand for water, especially in water-scarce regions. Its integration with renewable energy sources (RES) reduces the environmental impact of carbon emission by conventional fossil fuel energy sources. The optimisation of the RES-RO desalination system is intended mainly to minimise total system cost and energy requirements and to guarantee system reliability. In this study, an extensive review of the optimisation of the RES-RO desalination system is presented based on optimal system sizing, optimal system operation and optimal thermodynamic analysis. RES such as geothermal, ocean, wind and solar energy and their hybrids were considered alongside desalination methods. Important findings of the review were discussed, and recommendations made for future work. Key recommendations of this study include the suggestion that extensive optimisation and analysis of a RES-RO system should utilise optimisation approaches that combine the sizing, operation and thermodynamic effect of the system. Future work should furthermore incorporate both economic and reliability indices in the formation of objective functions. Finally, demand response programmes can be introduced to the RES-RO system for demand side management. This has the potential of minimising system cost while maximising fresh-water production.

Membrane distillation using low-grade energy for desalination: A review

Abstract: Water and energy are critical components for human, and govern the growth and progress of societies. Desalination is an important process to meet ever-increasing water demand, although it is an energy-intensive alternative compared to conventional water treatment techniques. Demand for desalination has been expanded rapidly as traditional water sources are getting overexploited. Membrane distillation (MD) is a promising water treatment process for highly saline water, including reject from the reverse osmosis plants. To compensate for high energy requirement for the MD process, low-grade heat sources (such as waste heat or renewable sources) can be used. Limitations of other desalination processes are discussed in this review to underline evolution and tweaking of alternatives for making them optimal. In this review, we examine the suitability of the MD process for harnessing energy from different types of low-grade heat sources to make it cost-effective. Financial aspects of the MD process for different heat sources are also highlighted. A summary of studies focusing on hybrid MD systems is also provided. Finally, challenges, opportunities and current implementation of the MD process by using low-grade heat-based MD systems are discussed.

Energy Consumption of Brackish Water Desalination: Identifying the Sweet Spots for Electrodialysis and Reverse Osmosis

Abstract: Though electrodialysis (ED) and reverse osmosis (RO) are both mature, proven technologies for brackish water desalination, RO is currently utilized to desalinate over an order of magnitude more bra...

Cost Comparison of Capacitive Deionization and Reverse Osmosis for Brackish Water Desalination

Abstract: Although the energy efficiency of brackish water capacitive deionization (CDI) and reverse osmosis (RO) have been extensively compared, their relative costs remain poorly defined. We develop a para...

Recent Desalination Technologies by Hybridization and Integration with Reverse Osmosis: A Review

Abstract: Reverse osmosis is the leading technology for desalination of brackish water and seawater, important for solving the growing problems of fresh water supply. Thermal technologies such as multi-effect distillation and multi-stage flash distillation still comprise an important portion of the world’s desalination capacity. They consume substantial amounts of energy, generally obtained from fossil fuels, due to their low efficiency. Hybridization is a strategy that seeks to reduce the weaknesses and enhance the advantages of each element that makes it up. This paper introduces a review of the most recent publications on hybridizations between reverse osmosis and thermal desalination technologies, as well as their integration with renewable energies as a requirement to decarbonize desalination processes. Different configurations provide improvements in key elements of the system to reduce energy consumption, brine production, and contamination, while improving product quality and production rate. A combination of renewable sources and use of energy and water storage systems allow for improving the reliability of hybrid systems.

Comparison analysis of different technologies for the removal of boron from seawater: A review

Abstract: Boron overabundance in drinking and irrigation water is a severe environment and health issues because it is toxic to various crops and induces many human and animals diseases with long-term exposition. Desalinated seawater from reverses osmosis (RO) plant, which is the most widely used technology in this field, often contains high boron concentration. Hence, a costly second pass RO process is required which makes most of the scientists into the obligation to find simple, sustainable and efficient alternatives in terms of quality and cost to comply with the WHO standards (2.4 mg L−1). In this trend, the present review aims to give an analysis of different existing processes for boron removal from seawater, including electrocoagulation, sorption processes encountered adsorption and ion exchange resins, and other membrane processes like electrodialysis, electro ionization, membrane distillation and adsorption membrane filtration. The performances of these processes are compared and their pros and cons are discussed. The fundamentals of each technique, the operating parameters effects and findings are also reported. Electrocoagulation as a pretreatment prior to reverse osmosis as a hybrid system seems to be more suitable and promising to mitigate boron from seawater due to its feasibility, sustainability and cheapness. Future perspectives for this hybrid system are discussed. This review also includes the economical assessment for each method. The focus of this paper is thus to provide updated information deboronation processes and exhibit the development of its guidance.

Reverse osmosis and nanofiltration membranes for highly efficient PFASs removal: overview, challenges and future perspectives.

Abstract: Today, it is extremely urgent to face the increasing shortage of clean and safe water resources, determined by the exponential growth of both world population and its consumerism, climate change and pollution. Water remediation from traditional chemicals and contaminants of emerging concerns (CECs) is supposed to be among the major methods to solve water scarcity issues. Reverse osmosis (RO) and nanofiltration (NF) membrane separation technologies have proven to be feasible, sustainable and highly effective methods for the removal of contaminants, comprising the extremely persistent and recalcitrant perfluoroalkyl substances (PFASs), which failed to be treated through the traditional water treatment approaches. So far, however, they have been unable to assure PFASs levels under the established guidance limits for drinking water and still suffer from fouling problems, which limit their large-scale application. Novel configurations, improvement in process design and the development of high-performant materials for membrane production are important steps to tackle these issues, especially in view of new more stringent regulations limiting PFASs content in drinking water. As a possible future strategy, nanocomposite mixed matrix membranes (MMMs) offer a platform of advanced materials which promise to revolutionize RO/NF technologies for water treatment. In particular, the introduction of MOFs as adsorbent fillers in the polymeric membrane matrix appears as a viable approach for the effective and selective capture and removal of PFASs from water. The objective of this review is to provide a dedicated outlook on the most recent advances in RO and NF membrane technologies for PFASs removal. The effects of membrane properties, the solution chemistry, and contaminant properties on the RO/NF performances will be discussed in detail. Future challenges are also discussed, offering new perspectives toward the development of new advanced membranes with improved performance for PFAS removal, which are likely to significantly progress RO and NF technology for water remediation.

Highly Water-Permeable Metal-Organic Framework MOF-303 Membranes for Desalination.

Abstract: New membrane materials with excellent water permeability and high ion rejection are needed. Metal-organic frameworks (MOFs) are promising candidates by virtue of their diversity in chemistry and topology. In this work, continuous aluminum MOF-303 membranes were prepared on α-Al2O3 substrates via an in situ hydrothermal synthesis method. The membranes exhibit satisfying rejection of divalent ions (e.g., 93.5% for MgCl2 and 96.0% for Na2SO4) on the basis of a size-sieving and electrostatic-repulsion mechanism and unprecedented permeability (3.0 L·m-2·h-1·bar-1·μm). The water permeability outperforms typical zirconium MOF, zeolite, and commercial polymeric reverse osmosis and nanofiltration membranes. Additionally, the membrane material exhibits good stability and low production costs. These merits recommend MOF-303 as a next-generation membrane material for water softening.

Nanocellulose-Based Materials for Water Treatment: Adsorption, Photocatalytic Degradation, Disinfection, Antifouling, and Nanofiltration.

Abstract: Nanocelluloses are promising bio-nano-materials for use as water treatment materials in environmental protection and remediation. Over the past decades, they have been integrated via novel nanoengineering approaches for water treatment processes. This review aims at giving an overview of nanocellulose requirements concerning emerging nanotechnologies of waster treatments and purification, i.e., adsorption, absorption, flocculation, photocatalytic degradation, disinfection, antifouling, ultrafiltration, nanofiltration, and reverse osmosis. Firstly, the nanocellulose synthesis methods (mechanical, physical, chemical, and biological), unique properties (sizes, geometries, and surface chemistry) were presented and their use for capturing and removal of wastewater pollutants was explained. Secondly, different chemical modification approaches surface functionalization (with functional groups, polymers, and nanoparticles) for enhancing the surface chemistry of the nanocellulose for enabling the effective removal of specific pollutants (suspended particles, microorganisms, hazardous metals ions, organic dyes, drugs, pesticides fertilizers, and oils) were highlighted. Thirdly, new fabrication approaches (solution casting, thermal treatment, electrospinning, 3D printing) that integrated nanocelluloses (spherical nanoparticles, nanowhiskers, nanofibers) to produce water treatment materials (individual composite nanoparticles, hydrogels, aerogels, sponges, membranes, and nanopapers) were covered. Finally, the major challenges and future perspectives concerning the applications of nanocellulose based materials in water treatment and purification were highlighted.