Natural zeolite clinoptilolite-phosphate composite Membranes for water desalination by pervaporation

Advanced Polymeric Nanocomposite Membranes for Water and Wastewater Treatment: A Comprehensive Review

Nanomaterials have been extensively used in polymer nanocomposite membranes due to the inclusion of unique features that enhance water and wastewater treatment performance. Compared to the pristine membranes, the incorporation of nanomodifiers not only improves membrane performance (water permeability, salt rejection, contaminant removal, selectivity), but also the intrinsic properties (hydrophilicity, porosity, antifouling properties, antimicrobial properties, mechanical, thermal, and chemical stability) of these membranes. This review focuses on applications of different types of nanomaterials: zero-dimensional (metal/metal oxide nanoparticles), one-dimensional (carbon nanotubes), two-dimensional (graphene and associated structures), and three-dimensional (zeolites and associated frameworks) nanomaterials combined with polymers towards novel polymeric nanocomposites for water and wastewater treatment applications. This review will show that combinations of nanomaterials and polymers impart enhanced features into the pristine membrane; however, the underlying issues associated with the modification processes and environmental impact of these membranes are less obvious. This review also highlights the utility of computational methods toward understanding the structural and functional properties of the membranes. Here, we highlight the fabrication methods, advantages, challenges, environmental impact, and future scope of these advanced polymeric nanocomposite membrane based systems for water and wastewater treatment applications.

Hydrochloric Acid Modification and Lead Removal Studies on Naturally Occurring Zeolites from Nevada, New Mexico, and Arizona

Four naturally occurring zeolites were examined to verify their assignments as chabazites AZLB-Ca and AZLB-Na (Bowie, Arizona) and clinoptilolites NM-Ca (Winston, New Mexico) and NV-Na (Ash Meadows, Nevada). Based on powder X-ray diffraction, NM-Ca was discovered to be mostly quartz with some clinoptilolite residues. Treatment with concentrated HCl (12.1 M) acid resulted in AZLB-Ca and AZLB-Na, the chabazite-like species, becoming amorphous, as confirmed by powder X-ray diffraction. In contrast, NM-Ca and NV-Na, which are clinoptilolite-like species, withstood boiling in concentrated HCl acid. This treatment removes calcium, magnesium, sodium, potassium, aluminum, and iron atoms or ions from the framework while leaving the silicon framework intact as confirmed via X-ray fluorescence and diffraction. SEM images on calcined and HCl treated NV-Na were obtained. BET surface area analysis confirmed an increase in surface area for the two zeolites after treatment, NM-Ca 20.0(1) to 111(4) m2/g and NV-Na 19.0(4) to 158(7) m2/g. 29Si and 27Al MAS NMR were performed on the natural and treated NV-Na zeolite, and the data for the natural NV-Na zeolite suggested a Si:Al ratio of 4.33 similar to that determined by X-ray fluorescence of 4.55. Removal of lead ions from solution decreased from the native NM-Ca, 0.27(14), NV-Na, 1.50(17) meq/g compared to the modified zeolites, 30 min HCl treated NM-Ca 0.06(9) and NV-Na, 0.41(23) meq/g, and also decreased upon K+ ion pretreatment in the HCl modified zeolites.

Worldwide Research Analysis on Natural Zeolites as Environmental Remediation Materials

Society faces a significant problem in regards to the spread of harmful products in the environment, primarily caused by accelerated growth and resource consumption. Consequently, there is a need for materials to be processed in less harmful ways and to remedy the contaminated sources they generate. Microporous materials have been studied for a long time and are used in waste treatment alternatives. Natural zeolites, on which this study is based, are attractive to the scientific and technological communities, due to their numerous applications as decontaminants and adsorption properties. This study analyzes the intellectual structures of publications related to natural zeolites in environmental remediation, using bibliometric methods to determine their volumes and trends. The methodology comprises of an analysis based on 1582 articles, using VOSviewer software, with data from 1974 to 2020, via the Scopus database. Results reflect a notable increase in publications from the end of the 1990s; the greatest contribution in the area comes from Eurasian countries. The study considers that development in this line of research will continue to increase and serve as a great contribution to preserve the environment in coming years, with themes that focus on water treatment (e.g., drinking water, wastewater, greywater), removal of heavy metals, ammonium, ammonia, and construction.

Produced Water Desalination via Pervaporative Distillation

Herein, we report on the performance of a hybrid organic-ceramic hydrophilic pervaporation membrane applied in a vacuum membrane distillation operating mode to desalinate laboratory prepared saline waters and a hypersaline water modeled after a real oil and gas produced water. The rational for performing “pervaporative distillation” is that highly contaminated waters like produced water, reverse osmosis concentrates and industrial have high potential to foul and scale membranes, and for traditional porous membrane distillation membranes they can suffer pore-wetting and complete salt passage. In most of these processes, the hard to treat feed water is commonly softened and filtered prior to a desalination process. This study evaluates pervaporative distillation performance treating: (1) NaCl solutions from 10 to 240 g/L at crossflow Reynolds numbers from 300 to 4800 and feed-temperatures from 60 to 85 °C and (2) a real produced water composition chemically softened to reduce its high-scale forming mineral content. The pervaporative distillation process proved highly-effective at desalting all feed streams, consistently delivering <10 mg/L of dissolved solids in product water under all operating condition tested with reasonably high permeate fluxes (up to 23 LMH) at optimized operating conditions.

Breakthroughs on tailoring pervaporation membranes for water desalination: A review

Due to the increase in worldwide population and urbanization, water scarcity is today one of the tough challenges of society. To date, several ongoing initiatives and strategies are aiming to find feasible alternatives to produce drinking water. Seawater desalination is addressed as a latent alternative to solve such an issue. When dealing with desalination, membrane-based technologies (such as reverse osmosis, membrane distillation, pervaporation, among others) have been successfully proposed. Pervaporation (PV) is likely the membrane operation with the less permeation rate but providing high rejection of salts. Thereby, "membranologists" are extensively working in developing new suitable membranes for pervaporation desalination. Therefore, the goal of this review paper is to elucidate and provide a comprehensive outlook of the most recent works (over the last 5-years) at developing new concepts of membranes (e.g. ultra-thin, mixed matrix/composite and inorganic) for desalination, as well as the relevant strategies in fabricating enhanced PV membranes. At this point, an important emphasis has been paid to the relevant insights in the field. This paper also addresses some principles of PV and the main drawbacks of the technique and its membranes. Through reviewing the literature, the future trends, needs, and recommendations for the new researchers are given.

Fabrication, Properties, Performances, and Separation Application of Polymeric Pervaporation Membranes: A Review

Membrane separation technologies have attracted great attentions in chemical engineering, food science, analytical science, and environmental science. Compared to traditional membrane separation techniques like reverse osmosis (RO), ultrafiltration (UF), electrodialysis (ED) and others, pervaporation (PV)-based membrane separation shows not only mutual advantages such as small floor area, simplicity, and flexibility, but also unique characteristics including low cost as well as high energy and separation efficiency. Recently, different polymer, ceramic and composite membranes have shown promising separation applications through the PV-based techniques. To show the importance of PV for membrane separation applications, we present recent advances in the fabrication, properties and performances of polymeric membranes for PV separation of various chemicals in petrochemical, desalination, medicine, food, environmental protection, and other industrial fields. To promote the easy understanding of readers, the preparation methods and the PV separation mechanisms of various polymer membranes are introduced and discussed in detail. This work will be helpful for developing novel functional polymer-based membranes and facile techniques to promote the applications of PV techniques in different fields.

Willow Catkins-Derived Porous Carbon Membrane with Hydrophilic Property for Efficient Solar Steam Generation

Biomass wastes are abundant and common in our daily life, and they are cost-effective, promising, and renewable. Herein, collected willow catkins were used to prepare a hydrophilic biochar composite membrane, which was placed in a tree-like evaporation configuration to simulate a natural transpiration process. The strong light absorption (∼96%) of the biochar layer could harvest light and convert it into thermal energy, which then is used to heat the surrounding water pumped by a porous water channel via capillary action. A hydrophilic light-absorber layer remarkably increased the attachment sites of water molecules, thereby maximizing the use of thermal energy. At the same time, hierarchically porous structure and large specific surface area (∼1380 m² g^-1) supplied more available channels for rapid water vapor diffusion. The as-prepared composite membrane with a low-cost advantage realized a high evaporation rate (1.65 kg m^-2 h^-1) only under 1 sun illumination (1 kW m^-2), which was improved by roughly 27% in comparison with the unmodified hydrophobic composite membrane. The tree-like evaporation configuration with excellent heat localization resulted in the evaporator achieving a high solar-to-vapor conversion efficiency of ∼90.5%. Besides, the composite membrane could remove 99.9% sodium ions from actual seawater and 99.5% heavy metal ions from simulated wastewater, and the long-term stable evaporation performance proved its potential in actual solar desalination. This work not only fabricated an efficient evaporator but also provided a strategy for reusing various natural wastes for water purification.

Waste Brick as Constructed Wetland Fillers to Treat the Tail Water of Sewage Treatment Plant

Adopting the concept of "using waste to treat waste", the waste bricks will be used for constructed wetland filling. Integrated vertical-flow constructed wetland (IVCW) studied on the purification effect in influent water under three hydraulic loads (0.15, 0.25, 0.35 m/day). The results show that the waste bricks can be used as the carrier for the growth of the system biofilm, and have positive effects on the removal of pollutants in the influent water. Under three different hydraulic load conditions, the vertical flow of CWs can significantly reduce the load of water intake. In the low hydraulic load condition of 0.15 m/day, the average removal rates of chemical oxygen demand (COD), ammonia nitrogen (NH₃-N), total nitrogen (TN), and total phosphorus (TP) can reach 66.52%, 72.10%, 56.53% and 91.55% in this system, respectively. The influent pool on removal efficiency of pollutants was obviously higher than that of the upper pool, especially in the inlet surface 0-30 cm ranges. This research has achieved the effect of using "waste" to treat wastewater, which has strong practical significance and popularization value.

Structures, Properties, and Performances-Relationships of Polymeric Membranes for Pervaporative Desalination

For the fulfilment of increasing global demand and associated challenges related to the supply of clean-and-safe water, PV has been considered as one of the most attractive and promising areas in desalinating salty-water of varied salinities. In pervaporative desalination, the sustainability, endurance, and structural features of membrane, along with operating parameters, play the dominant roles and impart paramount impact in governing the overall PV efficiency. Indeed, polymeric- and organic-membranes suffer from several drawbacks, including inferior structural stability and durability, whereas the fabrication of purely inorganic membranes is complicated and costly. Therefore, recent development on the high-performance and cost-friendly PV membrane is mostly concentrated on synthesizing composite- and NCP-membranes possessing the advantages of both organic- and inorganic-membranes. This review reflects the insights into the physicochemical properties and fabrication approaches of different classes of PV membranes, especially composite- and NCP-membranes. The mass transport mechanisms interrelated to the specialized structural features have been discussed. Additionally, the performance potential and application prospects of these membranes in a wide spectrum of desalination and wastewater treatment have been elaborated. Finally, the challenges and future perspectives have been identified in developing and scaling up different high-performance membranes suitable for broader commercial applications.

A zeolite-like aluminophosphate membrane with molecular-sieving property for water desalination

A fascinating membrane material composed of polycrystalline zeolite-like aluminophosphate with narrow pore and high water uptake is well developed, which exhibits superior desalination performance in terms of excellent ion rejection and record water flux.

Membrane desalination has been proposed as a promising strategy to address the worldwide challenge of water scarcity. The development of membrane desalination is impeded by the limited availability of membrane materials, thus, selective membranes with high water fluxes are in high demand. Therefore, the synthesis of a zeolite-like aluminophosphate membrane for water desalination is reported herein. An AlPO₄-18 membrane without visible cracks was prepared on stainless steel nets via a seeded approach. The specific adsorption and diffusion properties of the AlPO₄-18 membrane toward water were simultaneously investigated by vapor adsorption measurements and molecular simulation. A large adsorption capacity indicates the excellent water affinity of the AlPO₄-18 membrane, and water gathering around other water molecules suggests stronger water–water interactions than framework–water interactions. Meanwhile, water molecules transport rapidly through the pores, assisted by a built-in pathway and directed diffusion. The as-synthesized membranes are further evaluated for water desalination. The desalination tests of seawater containing both single and multi-component ions demonstrate that the AlPO₄-18 membrane is very selective for water transport, evidenced by very high rejection degrees for cations (>99%). Moreover, the AlPO₄-18 membrane exhibits unprecedented high water fluxes (2.14 kg m^–2 h^–1 in average). The superior performances of good selectivity, high water permeability and high stability ensure the potential application of supported aluminophosphate membranes in desalination.

Synthesis of graphene oxide/polyimide mixed matrix membranes for desalination

Graphene oxide (GO) was incorporated into polyimide (PI) to fabricate GO/PI mixed matrix membranes (MMMs), which show a high water flux (36.1 kg m⁻² h⁻¹) and a high salt rejection (99.9%) for desalination of 3.5 wt% seawater at 90 °C.