Flux-stabilized cellulose acetate membranes and their applications to reverse osmosis for water desalination and purification

Developing antibacterial and biodegradable cellulose acetate (CA) membrane materials is one of the main challenges in multiple application fields. CA membrane materials are widely used in gas purification, water purification, and biomedical fields due to their environmental friendliness, high chemical and mechanical stability, excellent processability, and low cost. However, antibacterial modification of CA membrane materials to enhance their utilization value in the application process has always been the direction of researchers' efforts. This review focuses on the preparation and application of antibacterial CA and its derivatives membranes, especially the types and introduction methods of antibacterial agents. First, a brief introduction of CA-based polymer membranes is presented, followed by an overview of the antibacterial agent types and their introduction methods, and antibacterial mechanisms. After that, various membranes prepared using CA-based polymers as the main matrix or as additives are discussed. Then, specific applications of antibacterial CA-based membrane materials in water purification, gas purification, biomedical, food packaging, and other fields are outlined.

To reduce the concentration of heavy metal ions in drinking, natural and wastewater to the established standards, a dynamic membrane with a surface layer of cellulose acetate particles on a nylon substrate was obtained. A dynamic membrane layer was formed from cellulose acetate particles with sizes from 42 to 130 nm. The cellulose acetate content was 14 % by weight, upon receipt from a 10 % solution of cellulose acetate in acetone. After applying a layer of cellulose acetate to the surface of a nylon substrate, a decrease in the specific productivity of the membranes is observed more than 10 times due to the formation of a dynamic layer on the surface and in the pores of the substrate. During the operation of the membrane for 1 hour, there is a decrease in the specific productivity of the membrane by 1.5 times and an increase in the working pressure from 0.35 to 0.41 MPa by 1.2 times. A high selectivity of the dynamic nylon-ACd membrane with respect to iron ions 96%, copper 93% and chromium 93% was established with a specific productivity of 300 dm3/m2·h and a pressure of 0.4 MPa. After purification of tap water with a dynamic membrane, the concentration of heavy metal ions does not exceed the MPC for water bodies for drinking water.

Novel highly stable Guanazole-incorporated ultrathin loose nanofiltration membrane with superior permeability for water desalination and purification

The world's population is growing, leading to an increasing demand for freshwater resources for drinking, sanitation, agriculture, and industry. Interfacial solar steam generation (ISSG) can solve many problems, such as mitigating the power crisis, minimizing water pollution, and improving the purification and desalination of seawater, rivers/lakes, and wastewater. Cellulosic materials are a viable and ecologically sound technique for capturing solar energy that is adaptable to a range of applications. This review paper aims to provide an overview of current advancements in the field of cellulose‐based materials ISSG devices, specifically focusing on their applications in water purification and desalination. This paper examines the cellulose‐based materials ISSG system and evaluates the effectiveness of various cellulosic materials, such as cellulose nanofibers derived from different sources, carbonized wood materials, and two‐dimensional (2D) and 3D cellulosic‐based materials from various sources, as well as advanced cellulosic materials, including bacterial cellulose and cellulose membranes obtained from agricultural and industrial cellulose wastes. The focus is on exploring the potential applications of these materials in ISSG devices for water desalination, purification, and treatment. The function, advantages, and disadvantages of cellulosic materials in the performance of ISSG devices were also deliberated throughout our discussion. In addition, the potential and suggested methods for enhancing the utilization of cellulose‐based materials in the field of ISSG systems for water desalination, purification, and treatment were also emphasized.

Graphene oxide–silver nanoparticle membrane for biofouling control and water purification

This presentation will discuss the development of a portable water purification and desalting system to address water insecurity in regions with limited basic water infrastructure, water contamination, or frequent interruptions caused by climate change or natural disasters. Current membrane desalination technologies, such as reverse osmosis (RO) and electrodialysis (ED), are more suitable for urban areas than for resource-limited environments or places sensitive to natural disasters, e.g., flood or drought [2]. Most of the few commercially available portable RO systems require high-pressure pumping and water preconditioning before purification. RO systems are also prone to membrane fouling and require continuous maintenance, which limits deployment flexibility and adds to the total system cost. ED systems have higher energy loss than RO systems, especially for high salinity water purification [2-4]. Even with advancements in low-resistance membranes to improve power efficiency, ED systems still struggle to avoid ion diffusion from the concentrated brine and to remove microparticles (e.g., microplastics) [3]. Thus, alternative point-of-use water purification systems are urgently needed.We have developed a water desalting and purification method that employs a nonlinear electrokinetic phenomenon to divert charged species (salts, molecular ions, bacteria, microplastics) from flowing feedwater into a physically separated waste stream. This electrokinetic phenomenon, ion concentration polarization (ICP), occurs when a voltage bias is applied across ion-selective features such as electrodes or highly charged membranes. This process selectively transports ions, subsequently creating ion depletion and enrichment zones (IEZ & IDZ) at the opposing ends of the ion-selective feature. For water desalination, ICP captures or redirects charged particles at the boundary between the background electrolyte and the IDZ, effectively removing not only salts but also bacteria and oil-in-water emulsions with negative zeta potential. While planar membrane-based desalination using ICP has been demonstrated, its throughput is insufficient for practical use due to the instability of the electric field and electroconvective vortices generated. Figure 1

Efforts have been rendered by researchers to address water purification and desalination challenges through membrane separation processes. However, the trade-off phenomenon in permeability and selectivity constrained the membranes’ usage. Recent advances made in fabricating membranes, especially thin film nanocomposite (TFN) membranes using functionalized nanofillers, have high performance in water purification and desalination. In this review, state-of-the-art thin film composite (TFC) membranes in water purification and desalination along with their drawbacks are discussed. The urgent demands as an alternative of TFC membranes are highlighted for high-performance membranes. Then, the fabrication and development of high permeability and selectivity of TFN membranes are discussed. Thin film nanocomposite membranes manufactured using rational nanofillers are systematically summarized. Finally, the applications of TFN membranes in water purification and desalination are reported.

Development of technologies for water desalination and purification is critical to meet the global challenges of insufficient water supply and inadequate sanitation, especially for point-of-use applications. Conventional desalination methods are energy and operationally intensive, whereas adsorption-based techniques are simple and easy to use for point-of-use water purification, yet their capacity to remove salts is limited. Here we report that plasma-modified ultralong carbon nanotubes exhibit ultrahigh specific adsorption capacity for salt (exceeding 400% by weight) that is two orders of magnitude higher than that found in the current state-of-the-art activated carbon-based water treatment systems. We exploit this adsorption capacity in ultralong carbon nanotube-based membranes that can remove salt, as well as organic and metal contaminants. These ultralong carbon nanotube-based membranes may lead to next-generation rechargeable, point-of-use potable water purification appliances with superior desalination, disinfection and filtration properties.

Can graphene-based composites and membranes solve current water purification challenges - a comprehensive review

Utilization of plasma in water desalination and purification

Exergy costs analysis of water desalination and purification techniques by transfer functions

An efficient approach in water desalination using high flux induced magnetic-field hydroxyl-functionalized MgFe2O4 /CA RO membranes with organic/inorganic fouling control capability

Synergistic Tandem Solar Electricity-Water Generators

The growing scarcity of fresh water is a major political and economic challenge in the 21st century. Compared to thermal-based distillation technique of water production, pressure driven membrane-based water purification process, such as ultrafiltration (UF), nanofiltration (NF) and reverse osmosis (RO), can offer more energy-efficient and environmentally friendly solution to clean water production. Potential applications also include removal of hazardous chemicals (i.e., arsenic, pesticides, organics) from water. Although those membrane-separation technologies have been used to produce drinking water from seawater (desalination) and non-traditional water (i.e., municipal wastewater and brackish groundwater) over the last decades, they still have problems in order to be applied in large-scale operations. Currently, a major huddle of membrane-based water purification technology for large-scale commercialization is membrane fouling and its resulting increases in pressure and energy cost of filtration process. Membrane cleaning methods, which can restore the membrane properties to some degree, usually cause irreversible damage to the membranes. Considering that electricity for creating of pressure constitutes a majority of cost (~50%) in membrane-based water purification process, the development of new nano-porous membranes that are more resistant to degradation and less subject to fouling is highly desired. Styrene-ethylene/butylene-styrene (SEBS) block copolymer is one of the best knownmore » block copolymers that induces well defined morphologies. Due to the polarity difference of aromatic styrene unit and saturated ethylene/butylene unit, these two polymer chains self-assemble each other and form different phase-separated morphologies depending on the ratios of two polymer chain lengths. Because the surface of SEBS is hydrophobic which easily causes fouling of membrane, incorporation of ionic group (e,g, sulfonate) to the polymer is necessary to reduces fouling. Recently, sulfonated SEBS became commercially available and has been extensively explored for membrane-mediated water purification technology. The sulfonated block copolymer creates a well developed nano-sale phase-separated morphologies composed of hydrophilic domains (sulfonated polystyrene) and hydrophobic domains (polyethylene/polybutylene). The hydrophilic domains determines transport properties (water transport, salt and/or ion rejection, etc) and the hydrophobic domains provides mechanical stability of the membrane. Unfortunately, a high degree of sulfonation of SEBS induces excessive swelling and deterioration of mechanical stability of the membrane. In an effort to develop robust polymeric membrane materials for water purification technology, phosphonic acid-functionalized SEBS membranes are investigated during this report period. In compare to sulfonated polymers, the corresponding phosphonated polymers are known to swell less because of the formation of extensive hydrogen bonding networks between phosphonates. In addition to the expected better mechanical stability, phosphonated polymers has another advantage over sulfonated polymers for the use water purification membrane; each phosphonate can accommodate two ions while each sulfonate accommodates only one ion. Membrane properties (ion type, ionic density, etc) of new membranes will be studied and their separation performance will be evaluated in water purification and desalination process. Through systematic study of the relationship of chemical structure–surface property–membrane performance, we aim to better understand the nature of membrane fouling and develop more fouling-resistant water purification membranes. The basic understanding of this relationship will lead to the development of advanced membrane materials which can offer a solution to environmentally sustainable production of fresh water.« less

Water scarcity is one of the significant issues many countries face due to the increased demand for freshwater and exhaustion of water resources. Therefore, developing efficient technologies for water purification is anticipated. Nowadays, nanofiltration (NF) separation processes are gaining importance in water purification and pre-treatment for desalination due to their capability in eliminating hardness, salts, and multivalent ions. In addition, NF can be operated under relatively lower pressure than reverse osmosis (RO), where its membrane pore size lies between ultrafiltration (UF) and RO membrane. Polymeric membranes such as polyamide, cellulose acetate, and polyethersulfone are generally used in NF. Many polymeric membranes offer flexibility in the fabrication process and are relatively inexpensive. However, the application of ceramic membranes in water purification has increased hastily due to their beneficial characteristics such as longer life span, fouling resistance, high stability towards corrosive media, and greater mechanical strength. Hence, this chapter discusses the recent signs of progress in ceramic NF membranes for water purification. Various kinds of composite ceramic NF membranes were elaborated in detail, including ceramic-ceramic, ceramic membranes incorporated with nanoparticles and metal–organic frameworks, and ceramic-polymeric membranes. In addition, the implementation of ceramic NF membranes for various water purification methods such as desalination, heavy metal ion removal, removal of dyes, etc., were discussed.