Ultra-fast green hydrogen production from municipal wastewater by an integrated forward osmosis-alkaline water electrolysis system.

Recent advancements in membrane-assisted seawater electrolysis powered by renewable energy offer a sustainable path to green hydrogen production. However, its large-scale implementation faces challenges due to slow power-to-hydrogen (P2H) conversion rates. Here we report a modular forward osmosis-water splitting (FOWS) system that integrates a thin-film composite FO membrane for water extraction with alkaline water electrolysis (AWE), denoted as FOWSAWE. This system generates high-purity hydrogen directly from wastewater at a rate of 448 Nm3 day-1 m-2 of membrane area, over 14 times faster than the state-of-the-art practice, with specific energy consumption as low as 3.96 kWh Nm-3. The rapid hydrogen production rate results from the utilisation of 1 M potassium hydroxide as a draw solution to extract water from wastewater, and as the electrolyte of AWE to split water and produce hydrogen. The current system enables this through the use of a potassium hydroxide-tolerant and hydrophilic FO membrane. The established water-hydrogen balance model can be applied to design modular FO and AWE units to meet demands at various scales, from households to cities, and from different water sources. The FOWSAWE system is a sustainable and an economical approach for producing hydrogen at a record-high rate directly from wastewater, marking a significant leap in P2H practice.

Sustainability in Membrane Technology: Membrane Recycling and Fabrication Using Recycled Waste.

Membrane technology has shown a promising role in combating water scarcity, a globally faced challenge. However, the disposal of end-of-life membrane modules is problematic as the current practices include incineration and landfills as their final fate. In addition, the increase in population and lifestyle advancement have significantly enhanced waste generation, thus overwhelming landfills and exacerbating environmental repercussions and resource scarcity. These practices are neither economically nor environmentally sustainable. Recycling membranes and utilizing recycled material for their manufacturing is seen as a potential approach to address the aforementioned challenges. Depending on physiochemical conditions, the end-of-life membrane could be reutilized for similar, upgraded, and downgraded operations, thus extending the membrane lifespan while mitigating the environmental impact that occurred due to their disposal and new membrane preparation for similar purposes. Likewise, using recycled waste such as polystyrene, polyethylene terephthalate, polyvinyl chloride, tire rubber, keratin, and cellulose and their derivates for fabricating the membranes can significantly enhance environmental sustainability. This study advocates for and supports the integration of sustainability concepts into membrane technology by presenting the research carried out in this area and rigorously assessing the achieved progress. The membranes' recycling and their fabrication utilizing recycled waste materials are of special interest in this work. Furthermore, this study offers guidance for future research endeavors aimed at promoting environmental sustainability.

Substrate-related factors and kinetic studies of Carbohydrate-Rich food wastes on enzymatic saccharification.

Food waste biorefinery is a sustainable approach to producing green chemicals, however the essential substrate-related factors hindering the efficacy of enzymatic hydrolysis have never been clarified. This study explored the key rate-limiting parameters and mechanisms of carbohydrate-rich food after different cooking and storing methods, i.e., impacts of compositions, structural diversities, and hornification. Shake-flask enzymatic kinetics determined the optimal dosages (0.5 wt% glucoamylase, 3 wt% cellulase) for food waste hydrolysis. First order kinetics and simulation results determined that reaction coefficient (K) of cooked starchy food was âˆ¼ 3.63 h-1 (92 % amylum digestibility) within 2 h, while those for cooked cellulosic vegetables were 0.25-0.5 h-1 after 12 h of hydrolysis. Drying and frying reduced âˆ¼ 71-89 % hydrolysis rates for rice, while hydrothermal pretreatment increased the hydrolysis rate by 82 % on vegetable wastes. This study provided insights into advanced control strategy and reduced the operational costs by optimized enzyme doses for food waste valorization.

Advancements in Nanoenabled Membrane Distillation for a Sustainable Water-Energy-Environment Nexus.

The emergence of nano innovations in membrane distillation (MD) has garnered increasing scientific interest. This enables the exploration of state-of-the-art nano-enabled MD membranes with desirable properties, which significantly improve the efficiency and reliability of the MD process and open up opportunities for achieving a sustainable water-energy-environment (WEE) nexus. This comprehensive review provides broad coverage and in-depth analysis of recent innovations in nano-enabled MD membranes, focusing on their role in achieving desirable properties, such as strong liquid-repellence, high resistance to scaling, fouling, and wetting, as well as efficient self-heating and self-cleaning functionalities. The recent developments in nano-enhanced photothermal-catalytic applications for water-energy co-generation within a single MD system are also discussed. Furthermore, the bottlenecks are identified that impede the scale-up of nanoenhanced MD membranes and a future roadmap is proposed for their sustainable commercialiation. This holistic overview is expected to inspire future research and development efforts to fully harness the potential of nano-enabled MD membranes to achieve sustainable integration of water, energy, and the environment.

Performance Evaluation of UF Membranes Derived from Recycled RO Membrane, a Step towards Circular Economy in Desalination.

Reverse osmosis (RO) spiral wound membrane generation reached 93.5% in 2020, resulting in 14,000 tons of used RO membranes being discarded annually into landfills, which is unprecedented. The current study aims to chemically convert the end-of-life RO membrane, followed by its performance evaluation and microbial removal efficiency on three different sources of water, i.e., tap water (TW), integrated constructed wetland permeate (ICW-P), and membrane bio-rector permeate (MBR-P), respectively. This was accomplished by selecting 6 years of spent Filmtech (LC-LE-4040) thin film composite type brackish water reverse osmosis (BWRO) membrane, followed by alkaline and acidic cleaning for 2 h. Finally, the conversion was carried out by 6% sodium hypochlorite (NaOCl) with 300,000 ppm/h exposure by active system (AS) using the clean in place CIP pump at 2 bars for 10 h duration. The membrane demonstrated 67% water recovery and 1% saltwater rejection, which means RO membrane now converted into recycled RO (R-RO) or (UF) by removal of the polyamide (PA) layer. Water recovery was 67% for TW, 68% for ICW-P, and 74% for MBR-P, respectively, with the consistent saltwater rejection rate of 1% being observed, while R-RO exhibited an effective COD removal of 65.79%, 62.96%, and 67.72% in TW, ICW-P, and MBR-P, respectively. The highest turbidity removal of 96% in the ICW-P was also recorded for R-RO. For morphological properties, SEM analysis of the R-RO membrane revealed a likewise appearance as a UF membrane, while pore size is also comparable with the UF membrane. The most probable number (MPN) also showed complete removal of total coliforms after passing through the R-RO membrane. These features made the R-RO membrane an excellent choice for drinking water treatment and wastewater treatment polishing steps. This solution can help developing nations to be efficient in resource recovery and contribute to the circular economy.

Reverse osmosis membrane functionalized with aminated graphene oxide and polydopamine nanospheres plugging for enhanced NDMA rejection and anti-fouling performance.

The use of reverse osmosis (RO) for water reclamation has become an essential part of the water supply owing to the ever-increasing water demand and the utmost performance of the RO membranes. Despite the global RO implementation, its inferior rejection against low molecular weight contaminants of emerging concerns (CECs) (i.e., N-nitrosodimethylamine (NDMA)) and propensity to fouling remain bottle-neck thus affecting process robustness for water reuse. This study aims to enhance both the rejection and antifouling properties of the RO membrane. Herein for the first time, we report RO membrane modification using polydopamine nanospheres (PDAns) followed by aminated-graphene oxide (AGO) deposition as an effective approach to overcome these challenges. The modification of the RO membrane using PDAns-AGO resulted in 89.3 ± 2.7% rejection compared to the pristine RO membrane which demonstrated 69.2 ± 2.1% NDMA rejection. This significant improvement can be ascribed to the plugging and shielding of defective areas (formed during interfacial polymerization) of the polyamide layer through active PDAns and AGO layers and to the added sieving mechanism that arose through narrow channels of the AGO owing to its reduction. Moreover, the in-situ and non-destructive fouling monitoring using optical coherence tomography (OCT) revealed that the PDAns-AGO coating enhanced both the anti-scaling and anti-biofouling characteristics. The improved hydrophilicity and bactericidal effect together with roughness and surface charge suppression synergistically enhanced anti-fouling properties. This study provides a new direction for safe and cost-effective water reuse practices. The membrane with high selectivity against CECs such as NDMA has the potential to eliminate permeate staging using second pass RO and other advanced oxidation processes which are utilized as a tertiary treatment to make reclaimed water suitable for potable/non-potable application.

In-situ 3D fouling visualization of membrane distillation treating industrial textile wastewater by optical coherence tomography imaging.

Membrane fouling, which is caused by the deposition of particles on the membrane surface or pores, reduces system performance in membrane distillation (MD) applications, resulting in increased operational costs, poor recovery, and system failure. Optical Coherence Tomography enables in-situ foulant monitoring in both 2D and 3D, however, the 2D images can only determine fouling layer thickness in severe fouling. Therefore, in this study, an advanced 3D imaging analysis technique using intensity range filters was proposed to quantify fouling layer formation during MD through the use of a single 3D image. This approach not only reduces computational power requirements, but also successfully separated the fouling layer from the membrane at the microscale. Thus, the thickness, fouling index, and fouling layer coverage can be evaluated in real time. To test this approach, Polyvinylidene fluoride (C-PVDF) and polytetrafluoroethylene (C-PTFE) membranes were used to treat a feed consisting of industrial textile wastewater. Thin and disperse foulants was observed on the C-PTFE, with a 22 µm thick fouling layer which could not be observed using 2D images after 24 h. Moreover, the C-PTFE demonstrated better antifouling ability than the C-PVDF as demonstrated by its lower fouling index, which was also supported by surface energy characterization. This work demonstrates the significant potential of 3D imagery in the long-term monitoring of membrane fouling process to improve membrane antifouling performance in MD applications, which can lead to lowered operational costs and improved system stability.

Macro-corrugated and nano-patterned hierarchically structured superomniphobic membrane for treatment of low surface tension oily wastewater by membrane distillation.

A hierarchically assembled superomniphobic membrane with three levels of reentrant structure was designed and fabricated to enable effective treatment of low surface tension, hypersaline oily wastewaters using direct contact membrane distillation (DCMD). The overall structure is a combination of macro corrugations obtained by surface imprinting, with the micro spherulites morphology achieved through the applied phase inversion method and nano patterns obtained by fluorinated Silica nanoparticles (SiNPs) coating. This resulted in a superomniphobic membrane surface with remarkable anti-wetting properties repelling both high surface tension water and low surface tension oils. Measurements of contact angle (CA) with DI water, an anionic surfactant, oil, and ethanol demonstrated a robust wetting resistance against low surface tension liquids showing both superhydrophobicity and superoleophobicity. CA values of 160.8 ± 2.3° and 154.3 ± 1.9° for water and oil were obtained, respectively. Calculations revealed a high liquid-vapor interface for the fabricated membrane with more than 89% of the water droplet contact area being with air pockets entrapped between adjacent SiNPs and only 11% come into contact with the solid membrane surface. Moreover, the high liquid-vapor interface imparts the membrane with high liquid repellency, self-cleaning and slippery effects, characterized by a minimum droplet-membrane interaction and complete water droplet bouncing on the surface within only 18 ms. When tested in DCMD with synthetic hypersaline oily wastewaters, the fabricated superomniphobic membrane demonstrated stable, non-wetting MD operation over 24 h, even at high concentrations of low surface tension 1.0 mM Sodium dodecyl sulfate and 400 ppm oil, potentially offering a sustainable option for treatment of low surface tension oily industrial wastewater.

Omniphobic re-entrant PVDF membrane with ZnO nanoparticles composite for desalination of low surface tension oily seawater.

In this study, an omniphobic membrane was fabricated by electrospraying fluorinated zinc oxide (ZnO) nanoparticles (NPs) mixed with polyvinylidene fluoride-co-hexafluoropropylene (PVDF-HFP) on the surface of an organosilane functionalized polyvinylidene difluoride (PVDF) membrane. Our results revealed that the functionalized ZnO NPs membrane exhibited a rough hierarchical re-entrant morphology with low surface energy which allowed it to achieve high omniphobic characteristics. It was observed that the addition of 30% ZnO (w/w of PVDF-HFP) was found to be optimal and imparted a high repulsive characteristic. The optimized PVDF/ZnO(30)/FAS/PVDF-HFP referred as cPFP-30Z membrane exhibited a high contact angle values of 159.0 ±â€¯3.1°, 129.6 ±â€¯2.2°, 130.4 ±â€¯4.1° and 126.1 ±â€¯1.2° for water, sodium dodecyl sulfate (SDS) saline solution (0.3 mM SDS in 3.5% NaCl), ethanol, and vegetable oil, respectively. The low surface energy and high surface roughness (Ra) of optimised membrane was assessed as 0.78 ±â€¯0.14 mN m-1 and 1.37 µm, respectively. Additionally, in contrast with the commercial PVDF membrane, the cPFP-30Z membrane exhibited superior anti-wetting/anti-fouling characteristics and high salt rejection performance (>99%) when operated with a saline oil solution (0.015 v/v) and SDS (0.4 mM) feed solutions.