Recent Submissions

  • Counterintuitive Wetting Transitions in Doubly Reentrant Cavities as a Function of Surface Make‐Up, Hydrostatic Pressure, and Cavity Aspect Ratio

    Arunachalam, Sankara; Ahmad, Zain; Das, Ratul; Mishra, Himanshu (Advanced Materials Interfaces, Wiley, 2020-11-20) [Article]
    Surfaces that entrap air underwater serve numerous practical applications, such as mitigating cavitation erosion and reducing frictional drag. These surfaces typically rely on perfluorinated coatings. However, the non-biodegradability and fragility of the coatings limit practical applications. Thus, coating-free, sustainable, and robust approaches are desirable. Recently, a microtexture comprising doubly reentrant cavities (DRCs) has been demonstrated to entrap air on immersion in wetting liquids. While this is a promising approach, insights into the effects of surface chemistry, hydrostatic pressure, and cavity dimensions on wetting transitions in DRCs remain unavailable. In response, Cassie-to-Wenzel transitions into circular DRCs submerged in water are investigated and compared with those in cylindrical “simple” cavities (SCs). It is found that at low hydrostatic pressures (≈50 Pa), DRCs with hydrophilic (θo ≈ 40°) and hydrophobic (θo ≈ 112°) make-ups fill within 105 and 107 s, respectively, while SCs with hydrophilic make-up fill within <10−2 s. Under elevated hydrostatic pressure (P ≤ 90 kPa), counterintuitively, DRCs with hydrophobic make-up fill dramatically faster than the commensurate SCs. This comprehensive report should provide a rational framework for harnessing microtexturing and surface chemistry toward coating-free liquid repellency.
  • The use of UV/H2O2 to facilitate removal of emerging contaminants in anaerobic membrane bioreactor effluents

    Augsburger, Nicolas; Zaouri, Noor A.; Cheng, Hong; Hong, Pei-Ying (Environmental Research, Elsevier BV, 2020-11-16) [Article]
    Effluent from anaerobic membrane bioreactor (AnMBR) contains ammonia and would require post-polishing treatment before it can be disinfected by chlorine. However, additional post-treatment steps to remove nutrients offset the energetic benefits derived from anaerobic fermentation. The use of chlorine or ozone also promotes concerns associated with disinfection byproducts. This study evaluates UV/H2O2 as a potential strategy suited for the removal of pharmaceutical compounds as well as antibiotic resistant bacteria (ARB) and antibiotic resistance genes (ARGs) from AnMBR effluent. Our findings indicate that 10 mg/L H2O2 and 61.5 mJ/cm2 of UV fluence are able to achieve a 4-log removal of both Escherichia coli PI7 and Klebsiella pneumoniae L7. However, a higher fluence of 311 mJ/cm2 with the same amount of H2O2 would be required to achieve > 90% removal of atenolol, carbamazepine and estrone. The removal of the pharmaceutical compounds was driven by the hydroxyl radicals generated from H2O2, while UV exposure governed the inactivation of ARB and ARGs. UV/H2O2 increased overall mutagenicity of the treated wastewater matrix but did not result in any changes to the natural transformation rates. Instead, UV significantly reduced natural transformation rates by means of DNA damage. Overall, UV/H2O2 could be the ideal final disinfection strategy for AnMBR effluent without requiring additional post-treatment prior disinfection.
  • Effects of set cathode potentials on microbial electrosynthesis system performance and biocathode methanogen function at a metatranscriptional level.

    Ragab, Alaa I.; Shaw, Dario Rangel; Katuri, Krishna; Saikaly, Pascal (Scientific reports, Springer Science and Business Media LLC, 2020-11-13) [Article]
    Microbial electrosynthesis exploits the catalytic activity of microorganisms to utilize a cathode as an electron donor for reducing waste CO2 to valuable fuels and chemicals. Electromethanogenesis is the process of CO2 reduction to CH4 catalyzed by methanogens using the cathode directly as a source of electrons or indirectly via H2. Understanding the effects of different set cathode potentials on the functional dynamics of electromethanogenic communities is crucial for the rational design of cathode materials. Replicate enriched electromethanogenic communities were subjected to different potentials (- 1.0 V and - 0.7 V vs. Ag/AgCl) and the potential-induced changes were analyzed using a metagenomic and metatranscriptomic approach. The most abundant and transcriptionally active organism on the biocathodes was a novel species of Methanobacterium sp. strain 34x. The cathode potential-induced changes limited electron donor availability and negatively affected the overall performance of the reactors in terms of CH4 production. Although high expression of key genes within the methane and carbon metabolism pathways was evident, there was no significant difference in transcriptional response to the different set potentials. The acetyl-CoA decarbonylase/synthase (ACDS) complex were the most highly expressed genes, highlighting the significance of carbon assimilation under limited electron donor conditions and its link to the methanogenesis pathway.
  • Mapping groundwater abstractions from irrigated agriculture: big data, inverse modeling, and a satellite–model fusion approach

    Lopez Valencia, Oliver Miguel; Johansen, Kasper; Aragon Solorio, Bruno Jose Luis; Li, Ting; Houborg, Rasmus; Malbeteau, Yoann; Almashharawi, Samir; Altaf, Muhammad; Fallatah, Essam Mohammed; Dasari, Hari Prasad; Hoteit, Ibrahim; McCabe, Matthew (Hydrology and Earth System Sciences, Copernicus GmbH, 2020-11-12) [Article]
    Abstract. The agricultural sector in Saudi Arabia has witnessed rapid growth in both production and area under cultivation over the last few decades. This has prompted some concern over the state and future availability of fossil groundwater resources, which have been used to drive this expansion. Large-scale studies using satellite gravimetric data show a declining trend over this region. However, water management agencies require much more detailed information on both the spatial distribution of agricultural fields and their varying levels of water exploitation through time than coarse gravimetric data can provide. Relying on self-reporting from farm operators or sporadic data collection campaigns to obtain needed information are not feasible options, nor do they allow for retrospective assessments. In this work, a water accounting framework that combines satellite data, meteorological output from weather prediction models, and a modified land surface hydrology model was developed to provide information on both irrigated crop water use and groundwater abstraction rates. Results from the local scale, comprising several thousand individual center-pivot fields, were then used to quantify the regional-scale response. To do this, a semi-automated approach for the delineation of center-pivot fields using a multi-temporal statistical analysis of Landsat 8 data was developed. Next, actual crop evaporation rates were estimated using a two-source energy balance (TSEB) model driven by leaf area index, land surface temperature, and albedo, all of which were derived from Landsat 8. The Community Atmosphere Biosphere Land Exchange (CABLE) model was then adapted to use satellite-based vegetation and related surface variables and forced with a 3 km reanalysis dataset from the Weather Research and Forecasting (WRF) model. Groundwater abstraction rates were then inferred by estimating the irrigation supplied to each individual center pivot, which was determined via an optimization approach that considered CABLE-based estimates of evaporation and TSEB-based satellite estimates. The framework was applied over two study regions in Saudi Arabia: a small-scale experimental facility of around 40 center pivots in Al Kharj that was used for an initial evaluation and a much larger agricultural region in Al Jawf province comprising more than 5000 individual fields across an area exceeding 2500 km2. Total groundwater abstraction for the year 2015 in Al Jawf was estimated at approximately 5.5 billion cubic meters, far exceeding any recharge to the groundwater system and further highlighting the need for a comprehensive water management strategy. Overall, this novel data–model fusion approach facilitates the compilation of national-scale groundwater abstractions while also detailing field-scale information that allows both farmers and water management agencies to make informed water accounting decisions across multiple spatial and temporal scales.
  • Dead-end membrane distillation with localized interfacial heating for sustainable and energy-efficient desalination

    Mustakeem, Mustakeem; Qamar, Adnan; Alpatova, Alla; Ghaffour, NorEddine (Water Research, Elsevier BV, 2020-10-30) [Article]
    Membrane distillation (MD) has the high potential to circumvent conventional desalination limitations in treating highly saline brines. However, the performance of MD is limited by its low thermal efficiency and temperature polarization (TP) effect. Consequently, the driving force decreases when heat loss increases. In this study, we propose to minimize TP through localized heating where the thin feed channel was heated uniformly at the membrane-liquid interface without changing the properties of the membrane. This concept was further improved by implementing a new dead-end MD configuration. Investigated for the first time, this configuration eliminated circulation heat losses, which cannot be realized in conventional MD due to a rapid temperature stratification. In addition, the accumulation of foulants on the membrane surface was successfully controlled by intermittent flushing. 3-Dimensional conjugate heat transfer modeling revealed more uniform heat transfer and temperature gradient across the membrane due to the increased feed water temperature over a larger membrane area. The increase of water vapor flux (45%) and the reduction of heat loss observed in the new dead-end concept led to a decrease of the specific energy consumption by 57%, corresponding to a gain output ratio increase of about 132 %, compared to a conventional bulk heating, while preserving membrane integrity. A conjugate heat transfer model was deployed in ANSYS-Fluent framework to elucidate on the mechanism of flux enhancement associated with the proposed technique. This study provides a framework for future sustainable MD development by maintaining a stable vapor flux while minimizing energy consumption.
  • Sialic acids: An important family of carbohydrates overlooked in environmental biofilms

    Pinel, Ingrid S M; Kleikamp, Hugo B.C.; Pabst, Martin; Vrouwenvelder, Johannes S.; van Loosdrecht, Mark C.M.; Lin, Yuemei (Applied Sciences (Switzerland), MDPI AG, 2020-10-30) [Article]
    Sialic acids in the structural matrix of biofilms developing in engineered water systems constitute a potential target in the battle against biofouling. This report focuses specifically on the presence of sialic acids as part of the extracellular polymeric substances (EPS) of biofilms forming in cooling towers and the potential effect of nutrient starvation on sialic acid presence and abundance. Two cooling water compositions were compared in parallel pilot-scale cooling towers, one poor in nutrients and one enriched in nutrients. Fresh deposits from the two cooling towers were collected after a five-week operation period. EPS extractions and analyses by Fourier transform infrared spectroscopy (FTIR) and high-resolution mass spectrometry (MS), along with 16S rRNA gene amplicon sequencing were performed. The results of MS analyses showed the presence of pseudaminic/legionaminic acids (Pse/Leg) and 2-keto-3-deoxy-d-glycero-d-galacto-nononic acid (KDN) in both biofilm EPS samples. FTIR measurements showed the characteristic vibration of sialic acid-like compounds ν(C=O)OH in the nutrient poor sample exclusively. Our findings, combined with other recent studies, suggest that bacterial sialic acids are common compounds in environmental biofilms. Additionally, the conservation of sialic acid production pathways under nutrient starvation highlights their importance as constituents of the EPS. Further in-depth studies are necessary to understand the role of sialic acids in the structural cohesion and protection of environmental biofilm layer.
  • Fresh water production by membrane distillation (MD) using marine engine's waste heat

    Bahar, Rubina; Ng, Kim Choon (Sustainable Energy Technologies and Assessments, Elsevier BV, 2020-10-29) [Article]
    Ships cruising across the seas have to make sure of ample freshwater supply for the passengers. In this paper, a desalination technique using Multi-Stage Air Gap Membrane Distillation (AGMD) has been proposed to obtain freshwater with the waste heat recovery from a marine engine for on-board ships. The simulation was performed based on the experiments conducted on a lab-scale multi-stage AGMD unit. The seawater to cool marine engine is considered to be the feed solution while the sea surface water is selected as the coolant. The geographical distributions of sea surface salinity and temperature have been considered in the simulation. Effect of the process parameters including the temperature of engine cooling water and sea surface water, air gap thickness, and seawater salinity has been investigated. A transport model has been used to predict the distillate production rate and numbers of MD modules. It is found that this process combined with the ship's engine cooling water could provide a Specific Energy Consumption (SEC) range between 1.58 and 2.63 kWh/m3 for a freshwater demand between 1 to 15 m3/day, considering the pumping energy only. The optimum feed temperature range is found between 65°C and 70 °C for an exit temperature limit of 40 °C.
  • Addition of a carbon fiber brush improves anaerobic digestion compared to external voltage application

    Baek, Gahyun; Saikaly, Pascal; Logan, Bruce (Water Research, Elsevier BV, 2020-10-26) [Article]
    Two methods were examined to improve methane production efficiency in anaerobic digestion (AD) based on adding a large amount of surface area using a single electrically conductive carbon brush, or by adding electrodes as done in microbial electrolysis cells (MECs) to form a hybrid AD-MEC. To examine the impact of surface area relative to electrodes, AD reactors were fitted with a single large brush without electrodes (FB), half a large brush with two electrodes with an applied voltage (0.8 V) and operated in closed circuit (HB-CC) or open circuit (HB-OC) mode, or only two electrodes with a closed circuit and no large brush (NB-CC) (equivalent to an MEC). The three configurations with a half or full brush all had improved performance as shown by 57-82% higher methane generation rate parameters in the Gompertz model compared to NB-CC. The retained biomass was much higher in the reactors with large brush, which likely contributed to the rapid consumption of volatile fatty acids (VFAs) and therefore improved AD performance. A different microbial community structure was formed in the large-size brushes compared to the electrodes. Methanothrix was predominant in the biofilm of large-size carbon brush, while Geobacter (anode) and Methanobacterium (cathode) were highly abundant in the electrode biofilms. These results demonstrate that adding a high surface area carbon fiber brush will be a more effective method of improving AD performance than using MEC electrodes with an applied potential.
  • Future of Air Conditioning

    Kian Jon, Chua; Islam, Md Raisul; Ng, Kim Choon; Shahzad, Muhammad Wakil (Springer Singapore, 2020-10-22) [Book Chapter]
    Air conditioning is essential for maintaining thermal comfort in indoor environments, particularly for buildings located in the tropics where the weather is both hot and humid. Today, air conditioning, comprising cooling and dehumidification, has become a necessity in commercial and residential buildings and even in many industrial processes. In tropical climates, the energy consumed due to heating, ventilation and air-conditioning (HVAC) alone can exceed 50% of the total energy consumption of a building. This significant figure is primarily due to the heavy-duty placed on cooling systems to remove both sensible and latent heat loads. Therefore, there is tremendous potential to improve the overall efficiency of air-conditioning systems for building applications. One of the simplest and neatest ways to reduce energy consumption for air conditioning is to decouple the sensible and latent loads imposed on cooling systems. When a separate technology is solely able to dehumidify the supply air, the cooling load imposed on the cooling system can be markedly reduced. Accordingly, the energy efficiency for cooling is promoted. This review chapter provides a key update on recent developments in air-conditioning systems, particularly innovative technologies in cooling and dehumidification. Key technologies related to sustainable cooling include absorption/adsorption cooling and dew-point evaporative cooling. Technologies connected with dehumidification involve new generations of solid-based desiccant dehumidifiers, liquid-based desiccants and novel membranes that are able to sieve out water vapour when a transmembrane pressure is provided.
  • Liquid Desiccant Air-Conditioning Systems

    Kian Jon, Chua; Islam, Md Raisul; Ng, Kim Choon; Shahzad, Muhammad Wakil (Springer Singapore, 2020-10-22) [Book Chapter]
    The liquid desiccant air-conditioning system has been identified as a promising technology that has the potential of decoupling and preciously controlling the latent and sensible cooling loads of air-conditioning spaces. The issues of moulds and bacteria growth on the wet surface of chilled water coils of conventional air handling units can be resolved by employing liquid desiccant systems, where moisture is absorbed by antibacterial desiccant solutions instead of condensing at low temperature. Considerable progress has been made by researchers to enhance the dehumidification and cooling performances of liquid desiccant systems, which are coherently presented in this chapter. The thermophysical properties of several liquid desiccants have been evaluated and the opportunities for improving the desired properties by mixing different desiccant materials are explored. Techniques for improving the wettability and flow characteristics of the packing materials are also discussed. In addition, several theoretical models and solution techniques to study heat and mass transfer enhancement opportunities are systematically discussed and compared in this chapter. The potential of a hybrid liquid desiccant system incorporating either a conventional vapour compression system ora vapour absorption chiller is also documented. Finally, some challenges and future research directions are identified and discussed.
  • Present State of Cooling, Energy Consumption and Sustainability

    Kian Jon, Chua; Islam, Md Raisul; Ng, Kim Choon; Shahzad, Muhammad Wakil (Springer Singapore, 2020-10-22) [Book Chapter]
    The rise in temperature is an on-going issue due to global warming. The air-conditioning demand is expected to be triple by 2050 to provide comfortable environment at offices and residential buildings. In most of the deserted countries, the annual cooling degree days are over 4000 due to harsh weather conditions. Presently, over 6 billion air-conditioning units are installed globally including refrigeration systems and it is expected to increase exponentially in next decades. This inexorable growth in air-conditioners capacity not only increasing the energy demand due to low performance of conventional systems but also contributing a huge amount of CO2 and greenhouse gas emissions. The levelling-off the efficiency of conventional chillers at 0.85 ± 0.03 kW/Rton coupled with chemical-based refrigerants is the major limitation of conventional mechanical chillers covering 90% world air-conditioning market. To continue sustainable development, out-of-box solutions are required. The future air-conditioning systems must achieve the performance level of 0.60 ± 0.03 kW/Rton to fulfil the cooling demand in sustainable manner. Decoupling of dehumidification from cooling is one of the solutions to overcome the conventional system limitation to achieve satiable cooling goals.
  • Dissipative Losses in Cooling Cycles

    Kian Jon, Chua; Islam, Md Raisul; Ng, Kim Choon; Shahzad, Muhammad Wakil (Springer Singapore, 2020-10-22) [Book Chapter]
    To improve the energy efficiencies of cooling cycles, it is important to identify the key sources of internal dissipative losses, thus pinpointing the major inefficient components that require optimization. This chapter conducts a second-law analysis on different cooling systems, including a mechanical vapour compression chiller, an absorption chiller, an adsorption chiller, and an indirect evaporative cooler. Based on thermodynamic states of these systems, the entropy generation rates of each component are calculated which revealed that the compressor, the regenerative heat exchangers and the reactor beds account for the most dissipative losses in mechanical chillers, absorption and adsorption chillers. The exergy efficiency of mechanical chillers can be improved by promoting the heat transfer in the evaporators and the condensers. The system-level entropy generation rates are normalized with respect to the cooling capacities to allow a direct comparison of different systems. The indirect evaporative cooler is found to perform most efficiently among the compared cooling cycles, while the adsorption chiller incurs the most internal dissipations due to poor heat transfer in its porous adsorbents.
  • Adsorbent-Coated Heat and Mass Exchanger

    Kian Jon, Chua; Islam, Md Raisul; Ng, Kim Choon; Shahzad, Muhammad Wakil (Springer Singapore, 2020-10-22) [Book Chapter]
    This chapter specifically focuses on the development of the adsorbent coated heat and mass exchanger as a promising energy-efficient alternative for the dehumidification and cooling of air using the low-grade waste heat. A comprehensive and compact overview is conducted on the adsorption and desorption characteristics of different high-performance pure and composite adsorbents. The moisture adsorption performance of commonly used adsorbents, such as silica gel, activated carbon, Y-type zeolite, AQSOA-Z01, AQSOA-Z02, and AQSOA-Z03 are compared. Different techniques to facilitate durable and uniform coating of adsorbents on the heat exchanger surfaces are presented. The relative advantages and challenges of the adsorbent-coated heat and mass exchanger over the fixed-bed and the rotary wheel dehumidifiers are coherently analysed. Finally, the influences of key design and operating variables on the performance of dehumidification and cooling of air using standalone as well as various hybrid heat and mass exchanger systems are systematically documented and discussed.
  • Membrane Air Dehumidification

    Kian Jon, Chua; Islam, Md Raisul; Ng, Kim Choon; Shahzad, Muhammad Wakil (Springer Singapore, 2020-10-22) [Book Chapter]
    Membrane-based air dehumidification (MAD), a recently emerged air dehumidification technology, separates the moisture from the humid air by using a selective membrane. MAD is carried out by permitting only vapour molecules to transfer from one side of the membrane at a high concentration to the other side at a low concentration. The MAD process has superior performance translating to favourable energy and economic benefits than other traditional dehumidification technologies. This chapter comprehensively reviews the literature on MAD including membrane characteristics, membrane configuration, membrane-related mass transport mechanism, and system design and operation as well as the mass transfer modelling. State-of–the-art developments in MAD are presented and finally recommendations on future research directions are provided. This chapter provides a comprehensive discussion of the MAD technology including membrane materials, thermophysical characterization, membrane forms and modules, system configurations, and mass transport modelling.
  • Dew-Point Evaporative Cooling Systems

    Kian Jon, Chua; Islam, Md Raisul; Ng, Kim Choon; Shahzad, Muhammad Wakil (Springer Singapore, 2020-10-22) [Book Chapter]
    Maisotsenko cycle (M-cycle) is a promising air-cooling technique that can reduce the temperature of airflow to approaching dew-point condition, which was not possible either with direct contact techniques or indirect evaporative methods. M-cycle systems have been employed previously on gas turbines, air-conditioning systems, cooling towers, electronic cooling, etc. Due to the wide application of air conditioning systems, this chapter focuses on the application of M-cycle specifically for air conditioning purpose. Researchers have evaluated the M-cycle cooling characteristics via different methods including analytical solutions, numerical simulations, statistical design methods, and experimental techniques. The salient aspects of these methods are systematically discussed and compared in this chapter. In addition, the current status of the applying the dew-point evaporative cooling systems to meet industrial needs is summarized and some of the future research directions are also identified.
  • Efficacy Comparison for Cooling Cycles

    Kian Jon, Chua; Islam, Md Raisul; Ng, Kim Choon; Shahzad, Muhammad Wakil (Springer Singapore, 2020-10-22) [Book Chapter]
    Conventionally, mechanical vapour compression chillers are considered to be the most appropriate solutions for commercial and industrial air-conditioning applications. There are many categories of conventional chillers based on their cooling mechanism and operational arrangements. To evaluate their performance, numerous international and national test standards have been established. The most common efficiency parameter is coefficient of performance and it is accepted globally. On the other hand, the indirect evaporative cooler (IEC) has emerged to be an alternative air-conditioning solution but there is currently no international standard to evaluate its performance. A mathematical model is developed to evaluate the performance of both conventional chillers and indirect evaporative coolers. It showed that the indirect evaporative cooler performance is much higher (COP = 21.52 cooling only) when compared with the conventional chiller (COP = 3.26). In addition, the water consumption of the indirect evaporative cooler is also lower compared with conventional chillers. The indirect evaporative cooler can be one of the best solutions for future cooling needs. Presently, there are established performance measurement parameters for conventional chillers such as EER, SEER, COP and SCOP together with test standards for performance calculations. Unfortunately, there is no international standard available for IEC systems even though there are some regional standards employed to evaluate the performance of IEC systems. In this chapter, the details on available performance parameters are provided including all international standards. In addition, a sample calculation is provided to enable the performances of conventional chillers and IEC to be evaluated for commercial references.
  • Thermo-Economic Analysis for Cooling Cycles

    Kian Jon, Chua; Islam, Md Raisul; Ng, Kim Choon; Shahzad, Muhammad Wakil (Springer Singapore, 2020-10-22) [Book Chapter]
    The levelized cost of cooling accounts for the costs of cooling systems throughout their life cycle and is an effective measurement of the economic viability of cooling cycles. This chapter presents a life-cycle economic analysis of different cooling cycles. Economic and thermodynamic performance data are firstly collected from open literature. The cost of cooling over the plant lifetime is then calculated considering different energy sources. Results revealed that the mechanical chiller and the indirect evaporative cooler are the most cost-effective under the regular scenario, while heat-driven processes like absorption and adsorption cooling cycles are expensive due to high thermal energy costs. Costs of thermally driven cycles can be reduced if low-cost thermal energy sources are available, and under such situations, the absorption chiller can become a viable option. The cooling costs are also strongly impacted by interest rate, annual operation hour, and energy efficiency. Therefore, optimal design, selection, and energy efficiency are key to sustaining low capital and operating costs. The derived results offer a robust and convenient basis for selecting cooling systems in real applications.
  • Natural deep eutectic solvents in plants and plant cells: In vitro evidence for their possible functions

    Dai, Yuntao; Varypataki, Eleni Maria; Golovina, Elena A.; Jiskoot, Wim; Witkamp, Geert Jan; Choi, Young Hae; Verpoorte, Robert (Elsevier, 2020-10-21) [Book Chapter]
    The components of natural deep eutectic solvents (NADES) are abundant in plants. This led to our hypothesis that NADES may play an important role in solubilizing, storing, and transporting poorly water-soluble metabolites in living cells, adjusting the water content of plants, and protecting cells when in harsh conditions. In order to test these hypothetical roles, diverse plant materials were analyzed, including leaves, petals, plant secretions and seeds. Comparatively high amounts of ingredients of NADES are observed in those organs. In particular, resurrection plants in dry state contain a higher amount of NADES components than fresh ones, and the level of NADES components is specifically higher in the outside layer (aleurone and seed cover) of barley, than in the inside (endosperm and embryo) layer. A high accumulation of sugars, sugar alcohols, amines, amino acids, and organic acids dominate plant secretions such as sap and nectar, often in typical molar ratios of NADES. This strongly supports the hypothesis of the existence of NADES in plants. For the roles, experimentally, NADES and water were mixed resulting in liquids with different compositions and properties. In the case of plants, NADES and water co-exist in the cells and may form ideal solvents for metabolites of diverse polarities and macromolecules. Some NADES are hygroscopic, providing evidence for possible water level controlling effects of NADES in plants. Most importantly, NADES may accumulate around the lipid bilayers, form intermolecular bonds with the polar heads of lipids, and stabilize the membrane, as revealed in experiments with liposomes. This study gives in vitro evidence for the different roles NADES may play in living organisms, and opens perspectives for further exploring the existence and functions of NADES in plants cells. The omics allows now to identify all molecules in an organism or even in a cell. The challenge for future research will be to understand how there molecules interact in the dynamic cellular processes and their compartmentation on a nanoscale. In other words the challenge is to unravel the molecular interactions in the three dimensions of space and the one of time, which will require a true multidisciplinary collaboration.
  • Electrification at water–hydrophobe interfaces

    Nauruzbayeva, Jamilya; Sun, Zhonghao; Gallo Junior, Adair; Ibrahim, Mahmoud; Santamarina, Carlos; Mishra, Himanshu (Nature Communications, Springer Science and Business Media LLC, 2020-10-20) [Article]
    Abstract The mechanisms leading to the electrification of water when it comes in contact with hydrophobic surfaces remains a research frontier in chemical science. A clear understanding of these mechanisms could, for instance, aid the rational design of triboelectric generators and micro- and nano-fluidic devices. Here, we investigate the origins of the excess positive charges incurred on water droplets that are dispensed from capillaries made of polypropylene, perfluorodecyltrichlorosilane-coated glass, and polytetrafluoroethylene. Results demonstrate that the magnitude and sign of electrical charges vary depending on: the hydrophobicity/hydrophilicity of the capillary; the presence/absence of a water reservoir inside the capillary; the chemical and physical properties of aqueous solutions such as pH, ionic strength, dielectric constant and dissolved CO2 content; and environmental conditions such as relative humidity. Based on these results, we deduce that common hydrophobic materials possess surface-bound negative charge. Thus, when these surfaces are submerged in water, hydrated cations form an electrical double layer. Furthermore, we demonstrate that the primary role of hydrophobicity is to facilitate water-substrate separation without leaving a significant amount of liquid behind. These results advance the fundamental understanding of water-hydrophobe interfaces and should translate into superior materials and technologies for energy transduction, electrowetting, and separation processes, among others.
  • Impact of osmotic and thermal isolation barrier on concentration and temperature polarization and energy efficiency in a novel FO-MD integrated module

    Son, Hyuk Soo; Kim, Youngjin; Nawaz, Muhammad Saqib; Al-Hajji, Mohammed Ali; Abu-Ghdaib, Muhannad; Soukane, Sofiane; Ghaffour, NorEddine (Journal of Membrane Science, Elsevier BV, 2020-10-18) [Article]
    In this study, a novel integrated forward osmosis - membrane distillation (FO-MD) module equipped with an isolation barrier carefully placed between the FO and MD membranes is experimentally investigated, and its performance is compared with a conventional hybrid module. The function of the isolation barrier is to osmotically and thermally separate the FO draw solution (DS) and MD feed channels. A systematic approach is adopted to compare the flux through both modules under (i) different and similar hydrodynamic conditions, (ii) different DS concentrations and temperatures, and (iii) different feed solution concentrations. All experiments were performed for 9 h each in batch mode using a custom-made compact module. New FO and MD membrane sheets were mounted for each experiment to ensure similarity in operating conditions. The proposed module design increased the flux by 22.1% using the same module dimensions but different hydrodynamic conditions. The flux increased by 16.6% using the same hydrodynamic conditions but different module dimensions. The FO/MD energy ratio reduced from 0.89 to 0.64 for the novel module, indicating better utilization of energy (primarily from MD). The gain output ratio (GOR) increased on average by 15.8% for the novel module compared to the conventional module, with a maximum increment of 20.7%. The temperature and concentration polarization coefficients in the MD operations showed improvements of 17.4% and 2.6%, respectively. The presence of the isolation barrier inside the integrated module indicated promising improvements of the flux and internal heat recovery, and further significant enhancements are expected for larger scale modules. Additionally, the novel module design offers unprecedented process integration opportunities for FO-MD as well as other membrane hybrid systems.

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