Search Results (56)

Hybrid gas separation technologies combining different physicochemical mechanisms represent a promising approach for the efficient treatment of complex natural gas mixtures. In this work, a hybrid process integrating gas hydrate crystallization and membrane gas separation was investigated for the upgrading of multicomponent natural gas-containing hydrocarbons (C₁–C₄), acid gases (CO₂ and H₂S), and inert components. Polysulfone hollow-fiber membranes were fabricated, and their gas transport properties were experimentally determined using an eight-component quasi-real natural gas mixture under elevated pressure conditions. The obtained mixed-gas permeance values were used as input parameters for the development of a detailed mathematical model of a hollow-fiber membrane module implemented in the Aspen Custom Modeler. The model was applied to simulate membrane separation of both gas- and hydrate-derived streams produced by the gas hydrate crystallizer. Simulation results were analyzed in terms of hydrocarbon composition, acid gas removal efficiency, and hydrocarbon recovery as a function of the stage-cut. The modeling predictions were validated experimentally using a laboratory membrane module integrated with the gas hydrate crystallization unit. Good agreement between the experimental data and simulation results was observed for all major components. The deviation between modeled and experimental concentrations remained small, while the discrepancy in hydrocarbon recovery was higher and reached approximately 10–20%, which is attributed to the cumulative uncertainty of flow rate and composition measurements. These results confirm the adequacy of the developed model. The hybrid process demonstrates strong complementarity between the thermodynamic selectivity of hydrate formation and the transport selectivity of membrane separation, enabling efficient removal of acid gases while maintaining acceptable hydrocarbon recovery. The results indicate that the proposed gas hydrate–membrane hybrid process is a promising strategy for advanced natural gas purification and upgrading. Full article

The global energy transition and the implementation of carbon capture, utilization, and storage (CCUS) strategies require energy-efficient and scalable CO₂ separation technologies. Mixed-matrix membranes (MMMs), combining polymer matrices with functional inorganic or hybrid nanofillers, have emerged as advanced separation platforms capable of surpassing the conventional permeability–selectivity trade-off observed in neat polymer membranes. This review critically evaluates recent developments in modern hybrid membranes for CO₂ separation from synthetic and industrial gas mixtures, including CO₂/N₂ (flue gas), CO₂/CH₄ (natural gas and biogas upgrading), and syngas systems. Particular emphasis is placed on MMMs incorporating covalent organic frameworks (COFs), metal–organic frameworks (MOFs), graphene oxide (GO), MXenes, transition metal dichalcogenides (TMDs), carbon nanotubes (CNTs), g-C₃N₄, layered double hydroxides (LDH), zeolites, metal oxides, and magnetic nanoparticles. Reported performance ranges include CO₂ permeability (P_CO2) typically between 100 and 800 Barrer, CO₂/N₂ selectivity up to 319, and CO₂/CH₄ selectivity up to 249, depending on filler chemistry, loading, and interfacial compatibility. The mechanisms governing gas transport—molecular sieving, selective adsorption, facilitated transport, and diffusion-pathway engineering—are systematically discussed. Key challenges addressed include filler dispersion, polymer–filler interfacial defects, physical aging, moisture sensitivity, oxidation (particularly in MXenes), and scalability toward industrial membrane modules. Future perspectives focus on sub-nanometer pore engineering, surface functionalization to enhance CO₂ affinity, controlled alignment of 2D nanosheets to promote directional transport, multifunctional core–shell and hollow structures, and the integration of computational modeling and machine learning for accelerated material design. Modern hybrid MMMs are identified as strategically important materials enabling high-efficiency CO₂ separation processes aligned with decarbonization and energy transition objectives. Full article

Membrane technology demonstrates broad prospects in the field of methane capture and purification due to its high efficiency and low energy consumption characteristics. This paper systematically reviews the research progress in membrane technology for methane separation in recent years, focusing on the design and optimization of membrane material systems, in-depth analysis of mass transfer mechanisms, and practical applications in areas such as biogas upgrading and natural gas decarbonization. Researchers have significantly enhanced membrane separation performance for CO₂/CH₄, CH₄/N₂, and other systems by developing novel material systems such as polymer membranes, inorganic membranes, and mixed matrix membranes (MMMs), combined with strategies like pore structure regulation, interface optimization, and functionalization. Although membrane technology has shown good economic feasibility and application potential in some scenarios, challenges such as long-term material stability, anti-plasticization capability, and large-scale manufacturing remain the main current obstacles. Future research should further focus on the development of novel membrane materials, process integration optimization, and intelligent process control to promote a greater role for membrane technology in the efficient utilization of methane resources and energy structure transformation. Full article

Landfill leachate is considered one of the most recalcitrant wastewaters due to its high organic strength, elevated ammonia concentrations, and complex chemical composition. This study evaluates integrated technologies for treating highly loaded landfill leachate from the Wadi Al-Asla landfill, Jeddah Saudi Arabia, using GPS-X^TM modeling combined with regulatory compliance and techno-economic assessment (TEA). The characterized mature leachate exhibited extremely high average concentrations of COD (17,050 mg L⁻¹), BOD₅ (10,058 mg L⁻¹), ammonia-N (989 mg L⁻¹), and total nitrogen (1223 mg L⁻¹), indicating severe pollution levels requiring integrated treatment technologies. Five (5) different scenarios involving integrated biological, physicochemical, and membrane-based processes were modelled, simulated and evaluated against local discharge standards complaince. Conventional and municipality-proposed upgrade configurations achieved ~80–83% COD removal, producing effluent COD > 2900 mg L⁻¹ and 1790–1801 mg L⁻¹ BOD₅, indicating persistent non-compliance for organic pollutants. Nitrogen removal improved substantially (93.7–95.7% ammonia-N and 91–93% total nitrogen removal), yet residual ammonia-N (44–63 mg L⁻¹) and total nitrogen (92–108 mg L⁻¹) remained above regulatory limits. Advanced hybrid systems achieved complete TSS removal and strong phosphorus control (TP ≤ 0.42 mg L⁻¹), while three(3) compartmental aerobic–anoxic membrane bioreactor coupled with reverse osmosis (MBR + RO) achieved near-complete nitrogen removal and reduced 90% COD removal. The lifecyle economic assessment indicated OPEX ranging from USD 1.1 to 5.6 m⁻³ of treated leachate with the aerobic–anoxic MBR + RO configuration yieding footprint advantage, lower CAPEX and moderate OPEX By combining process modeling, regulatory compliance evaluation, and economic assessment, this study provides a practical screening framework for selecting sustainable treatment strategies for high-strength landfill leachate and wastewater matices. Full article

As an emerging wastewater treatment technology, the membrane-aerated biofilm reactor (MABR) process is increasingly being coupled with anaerobic anoxic aerobic (AAO) process. However, there is currently a lack of systematic research and clear consensus on which of these two arrangements is more significant in improving overall process efficiency in practical applications. This study established GPS-X models of the conventional AAO process and two AAO-MABRs (anoxic or aerobic) under different concentrations of influent and effluent water quality conditions, and systematically compared their effluent quality, operation cost and greenhouse gas emissions. The results indicate that, compared with the conventional AAO process, the AAO-MABR coupled process improved the denitrification rate by 37.46%~47.71% (Anoxic), reduced energy consumption by an average of 0.11 kWh/m³, and lowered the operating cost by 0.036 USD/m³. In terms of carbon emission intensity, the AAO-MABR process achieved an average reduction of 0.67 kgCO₂eq/m³. Notably, the AAO-MABR (Anoxic) configuration exhibited superior robustness under varying influent and effluent conditions, yielding the lowest average operational cost (0.047 USD/m³) and carbon intensity (0.61 kgCO₂eq/m³). This study provides a reference for the practical application of MABR process, especially for the upgrading of traditional AAO processes. Full article

Biogas upgrading and bottling represent essential processes in transforming raw biogas produced via the anaerobic digestion of organic waste into high-purity biomethane (≥95% CH₄), a renewable energy source suitable for applications in cooking, transportation, and electricity generation. Upgrading technologies, such as membrane separation, pressure swing adsorption (PSA), water and chemical scrubbing, and emerging methods, like cryogenic distillation and supersonic separation, play a pivotal role in removing impurities like CO₂, H₂S, and moisture. Membrane and hybrid systems demonstrate high methane recovery (>99.5%) with low energy consumption, whereas chemical scrubbing offers superior gas purity but is limited by high operational complexity and cost. Challenges persist around material selection, safety standards, infrastructure limitations, and environmental impacts, particularly in rural and off-grid contexts. Bottled biogas, also known as bio-compressed natural gas (CNG), presents a clean, portable alternative to fossil fuels, contributing to energy equity, greenhouse gases (GHG) reduction, and rural development. The primary aim of this research is to critically analyze and review the current state of biogas upgrading and bottling systems, assess their technological maturity, identify performance optimization challenges, and evaluate their economic and environmental viability. The research gap identified in this study demonstrates that there is no comprehensive comparison of biogas upgrading technologies in terms of energy efficiency, price, scalability, and environmental impact. Few studies directly compare these technologies across various operational contexts (e.g., rural vs. urban, small vs. large scale). Additionally, the review outlines insights into how biogas can replace fossil fuels in transport, cooking, and electricity generation, contributing to decarbonization goals. Solutions should be promoted that reduce methane emissions, lower operational costs, and optimize resource use, aligning with climate targets. This synthesis highlights the technological diversity, critical barriers to scalability, and the need for robust policy mechanisms to accelerate the deployment of biogas upgrading solutions as a central component of a low-carbon, decentralized energy future. Full article

The demand for heavy-duty 5% (HD5) propane is expected to increase in the future due to the use of the gas as a fuel for engines. A refinery produces HD10 propane, and it is looking to upgrade to HD5 propane using either the conventional process (distillation) or an energy-saving unit (membrane). This study compared the two technologies in terms of product quality and quantity using process simulation in UniSIM^®. The software also provided the design parameters and power consumption for the two processes. The results show that the membrane was competitive with distillation and was capable of producing 96 mol% propane with a recovery of 99.3%. On the other hand, distillation achieved a maximum propane quality of 95 mol% with a recovery of 99.9%. Surprisingly, the energy consumption in the membrane was 669 kWh, which was higher than that of distillation (540 kWh) due to the requirement for a pre-heating step. Therefore, the technology should be selected based on either the quality or quantity of propane. Full article

Energy security is a growing societal and industrial concern that leads research and development toward more sustainable options. Biogas, a bio-alternative to conventional fuels, is a product generated from the anaerobic digestion of organic matter. This source of fuel production is more environmentally friendly compared to traditional fossil fuels, leading to a lower carbon footprint, higher air quality, and the promotion of a circular economy. Impurities of raw biogas, such as carbon dioxide, hydrogen sulfide, and other trace contaminants, make biogas conditioning necessary for most applications. In addition, biogas upgrading, technologies furthering biogas purity, is an important factor in the production of biomethane, a sustainable biofuel known more commonly as renewable natural gas (RNG). Diversifying fuel sources and providing energy sustainability while mitigating negative environmental effects makes RNG an attractive alternative to conventional natural gas. This document, Part I, provides an overview of current technologies related to biogas conditioning, such as sorption, oxidation, and biological treatments aimed at the removal of a wide variety of contaminants. Processes developed for biogas upgrading are also discussed, including physical/chemical absorption, pressure swing adsorption, and membrane separation. The focus of upgrading applies approaches in meeting a higher quality biofuel by further carbon dioxide exclusion to ease pipeline transport and increase combustion efficiency. These technologies present the core foundation of processes in the production of RNG; however, all face inherent challenges that deem further research and development a requirement for global adoption. The biggest challenges are either in the cost of reaching higher purities or the inability to do so without other operations. Thus, in conjunction with this document, emerging and developing technologies are provided in a separate analysis deemed Part II. Together, these documents offer a comprehensive understanding of current practices and growing technological developments. Full article

Membrane innovations have become a key solution for overcoming the bottlenecks in efficiency upgrade in many green energy fields. Membrane performance depends on two key parameters permeability and selectivity, which typically follow a trade-off relationship: improving one often diminishes the other. Two-dimensional (2D) materials, which have atomic-level thickness, tunable pore sizes, and reasonable functionalization, offer great promises to break through the trade-off effect and redesign high-efficiency mass transfer pathways. This review systematically presents recent efforts in both preparation and potential applications of 2D materials for overcoming the permeability–selectivity trade-off. It highlights four prevailing fabrication strategies: chemical vapor deposition, interfacial synthesis, solution-phase synthesis, and exfoliation, and shows some major optimization techniques for various 2D materials. Additionally, this review discusses emerging applications of 2D materials across critical fields from water treatment (seawater desalination, metal ion extraction) to energy technologies (osmotic power generation, direct methanol fuel cells, and vanadium redox flow batteries). Finally, the challenges and future prospects of 2D materials in ion separation and energy conversion are discussed. Full article

Membrane separation technology can be operated in moderate conditions with low energy consumption and has been widely explored and increasingly applied in the water treatment, food, chemical, and pharmaceutical industries. As an upgraded counterpart, stimulus-responsive membranes can respond to external stimuli (such as light, temperature, pH, electric field, magnetic field, etc.) and actively modulate their own physical and chemical properties, thus showing self-adaptive ability and improved performance. This review provides a comprehensive overview of the recent advancements in the design principles, fabrication methods, and applications of these stimulus-responsive membranes. The challenges and future directions in this field are also prospectively discussed, highlighting the potential for further innovation and industrial applications of stimulus-responsive membranes. Full article

Cryogenic upgrading represents a promising route for the production of high-purity biomethane, aligning with current decarbonization goals and the increasing demand for renewable gases. This review provides a critical assessment of cryogenic technologies applied to biogas purification, focusing on process fundamentals, technological configurations, energy and separation performance, and their industrial integration potential. The analysis covers standalone cryogenic systems as well as hybrid configurations combining cryogenic separation with membrane or chemical pretreatment to enhance efficiency and reduce operating costs. A comparative evaluation of key performance indicators—including methane recovery, specific energy demand, product purity, and technology readiness level—is presented, along with a discussion of representative industrial applications. In addition, recent techno-economic studies are examined to contextualize cryogenic upgrading within the broader landscape of CO₂ separation technologies. Environmental trade-offs, investment thresholds, and sensitivity to gas prices and CO₂ taxation are also discussed. The review identifies existing technical and economic barriers, outlines research and innovation priorities, and highlights the relevance of process integration with natural gas networks. Overall, cryogenic upgrading is confirmed as a technically viable and environmentally competitive solution for biomethane production, particularly in contexts requiring liquefied biomethane or CO₂ recovery. Strategic deployment and regulatory support will be key to accelerating its industrial adoption. The objectives of this review have been met by consolidating the current state of knowledge and identifying specific gaps that warrant further investigation. Future work is expected to address these gaps through targeted experimental studies and technology demonstrations. Full article

Membrane-based CO₂ capture has emerged as a promising technology for industrial decarbonization, offering advantages in energy efficiency, modularity, and environmental performance. This review presents a comprehensive assessment of membrane processes applied across major emission-intensive sectors, including power generation, cement, steelmaking, and biogas upgrading. Drawing from pilot-scale demonstrations and simulation-based studies, we evaluate how flue gas characteristics, such as CO₂ concentration, pressure, temperature, and impurity composition, govern membrane selection, process design, and operational feasibility. Case studies highlight the technical viability of membrane systems under a wide range of industrial conditions, from low-CO₂ NGCC flue gas to high-pressure syngas and CO₂-rich cement emissions. Despite these advances, this review discusses the key remaining challenges for the commercialization of membrane-based CO₂ capture and includes perspectives on process design and techno-economic evaluation. The insights compiled in this review are intended to support the design of application-specific membrane systems and guide future efforts toward scalable and economically viable CO₂ capture across industrial sectors. Full article

The electrocatalytic hydrogenation (ECH) of biomass-derived phenolic compounds is a promising approach to the production of value-added chemicals and biofuels in a sustainable way under moderate reaction conditions. This study provides a comprehensive comparison of electrochemical and thermochemical hydrogenation processes, highlighting their relative advantages in terms of energy efficiency, product selectivity, and environmental impact. Several electrocatalysts (Pt, Pd, Rh, Ru), membranes (Nafion, Fumasep, GO-based PEMs), and reactor configurations are tested for the selective conversion of model compounds such as phenol, guaiacol, furfural, and levulinic acid. The contributions made by the electrode material, electrolyte composition, membrane nature, and reaction conditions are critically evaluated in relation to Faradaic efficiency, conversion rates, and product selectivity. The enhancement in the performance achieved by a new catalyst architecture is emphasized, such as MOF-based systems and bimetallic/trimetallic catalysts. In addition, a demonstration of graphite-based membranes and membrane-separated slurry reactors (SSERs) is provided, for enhanced ion transport and reaction control. The results illustrate the potential of using ECH as a low-carbon, scalable, and tunable method for the upgrading of biomass. This study offers valuable insights and guidelines for the rational design of next-generation electrocatalytic systems toward green chemical synthesis and emphasizes promising perspectives for the strategic development of electrochemical technologies in the pathway of a sustainable energy economy. Full article

Palm oil mill effluent (POME), a byproduct of palm oil processing, has substantial resource recovery potential. Its rich biodegradable content supports methane (CH₄) production via anaerobic digestion, enabling renewable energy generation. Additionally, the significant water content of POME can be reclaimed for use in boiler feed, irrigation, and drinking water. However, selecting appropriate technologies to recover valuable resources from POME is challenging, particularly for the purification and upgrading of biogas. Membrane technologies offer an effective approach for transforming POME treatment from an energy-intensive process into a resource recovery system, supporting the decarbonization of palm oil production and advancing global sustainability objectives. This technique is cost-effective and ecofriendly for biogas purification and water reclamation. For biogas purification and upgrading, membrane systems offer the lowest capital and operational costs at 5.654 USD/m³, compared to other technologies, such as 6.249 USD/m³ for water scrubbers and 6.999 USD/m³ for chemical absorbers. This review primarily explores the potential of membranes for gas purification from POME and examines their integration with other processes to develop advanced systems, such as ultrasonicated membrane anaerobic systems and membrane anaerobic systems, to enhance biogas production. In addition, water reclamation from POME is discussed, with ultrafiltration membranes emerging as the most promising candidates. Proton exchange membranes, such as Nafion, are used extensively in microbial fuel cells to improve electricity generation, and this is also summarized. Finally, challenges and future perspectives are highlighted, emphasizing the broader potential of membrane technology in POME wastewater resource recovery. Full article