The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Long D. Nghiem - One of the best experts on this subject based on the ideXlab platform.
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liquid desiccant lithium chloride regeneration by membrane distillation for air conditioning
Separation and Purification Technology, 2017Co-Authors: Hung C Duong, Ali Hussein Aljubainawi, Tao He, Long D. NghiemAbstract:Abstract Liquid desiccant air conditioning (LDAC) has emerged as an attractive technology for improving indoor air quality and thermal comfort. Regeneration of liquid desiccants is critical to sustain the process efficiency of LDAC. This study explores membrane distillation (MD) for regeneration of lithium chloride (LiCl) desiccant solution commonly used in LDAC. The results demonstrate the viability of MD for LiCl regeneration. The MD process at the Feed Temperature of 65 °C could increase the LiCl concentration up to 29 wt.% without any observable LiCl loss. Given the high concentration of the LiCl solution Feed, unlike traditional desalination applications, the impact of concentration polarisation on the process water flux was significant. Indeed, the calculated water flux obtained by excluding the concentration polarisation effect was more than twice the experimentally measured water flux from a concentrated LiCl solution (>20 wt.%). The regeneration process can be optimised in terms of regeneration capacity (Δ C ) and specific thermal energy consumption ( α ) by regulating several operating conditions, including LiCl concentration, Feed Temperature, and circulation cross flow velocity. Increasing Feed Temperature and circulation cross flow velocity was beneficial to the process efficiency, enhancing water flux and Δ C while reducing α . On the other hand, increasing LiCl concentration resulted in a linear decrease in both water flux and Δ C , but an increase in α following a hyperbolic function.
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scaling control during membrane distillation of coal seam gas reverse osmosis brine
Journal of Membrane Science, 2015Co-Authors: Hung Cong Duong, Tzahi Y Cath, Stephen K Gray, Mikel Duke, Long D. NghiemAbstract:Abstract We systematically assess the efficiency of chemical cleaning and report a simple but elegant approach to control scaling during membrane distillation (MD) of brine from reverse osmosis (RO) treatment of coal seam gas (CSG) produced water. Results reported here show that increased Feed water salinity and the permeation of CO2 from the Feed solution resulted in only a small and gradual decrease in water flux. On the other hand, the precipitation of sparingly soluble salts on the membrane at high water recovery (>70%) led to a significant flux decline. Among the three chemical cleaning agents investigated, a reverse osmosis scale cleaning agent (denoted as MC3) was the most effective at restoring the water flux; however, MC3 cleaning was not able to completely remove scale deposits from the membrane and restore its surface hydrophobicity to the original value because of the complexation of scalants with CSG RO brine. The remaining scalants (i.e., silicates) reduced the membrane surface hydrophobicity and could possibly enhance concentration polarisation and act as seeding for further scale formation. Thus, a gradual decrease in MD performance with respect to both water flux and salt leakage was observed after each MC3 cleaning cycle. It was noted that the chemical cleaning agents themselves did not alter the hydrophobicity of the membrane; thus, the gradual decline in MD performance was attributed to the remaining scale deposits on the membrane after each cleaning cycle. Results reported here highlight the need to prevent membrane scaling and only use chemical cleaning as the last resort during MD treatment of CSG RO brine. Moreover, membrane scaling could be prevented by reducing concentration polarisation via limiting Feed Temperature and thus water flux. MD treatment of CSG RO brine with up to 80% water recovery without any observable membrane scaling was achieved at the Feed Temperature and the water flux of 35 °C and 10 L/m2 h, respectively.
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optimising thermal efficiency of direct contact membrane distillation by brine recycling for small scale seawater desalination
Desalination, 2015Co-Authors: Hung Cong Duong, Paul Cooper, Bart Nelemans, Tzahi Y Cath, Long D. NghiemAbstract:Abstract A technique to optimise thermal efficiency using brine recycling during direct contact membrane distillation (DCMD) of seawater was investigated. By returning the hot brine to the Feed tank, the system water recovery could be increased and the sensible heat of the hot brine was recovered to improve thermal efficiency. The results show that in the optimal water recovery range of 20 to 60% facilitated by brine recycling, the specific thermal energy consumption of the process could be reduced by more than half. It is also noteworthy that within this optimal water recovery range, the risk of membrane scaling is negligible — DCMD of seawater at a constant water recovery of 70% was achieved for over 24 h without any scale formation on the membrane surface. In contrast, severe membrane scaling was observed when water recovery reached 80%. In addition to water recovery, other operating conditions such as Feed Temperature and water circulation rates could influence the process thermal efficiency. Increasing the Feed Temperature and reducing the circulation flow rates increased thermal efficiency. Increasing the Feed Temperature could also mitigate the negative effect of elevated Feed concentration on the distillate flux, particularly at a high water recovery.
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the effects of Feed solution Temperature on pore size and trace organic contaminant rejection by the nanofiltration membrane nf270
Separation and Purification Technology, 2014Co-Authors: Hai Quang Dang, William E Price, Long D. NghiemAbstract:Abstract This study investigated the effect of Feed Temperature on membrane pore size and the rejection of trace organic contaminants (TrOCs) by the nanofiltration (NF) membrane NF270. Filtration experiments were conducted using a cross flow membrane system at 20, 30 and 40 °C. The membrane pore radius was estimated using the pore hindrance transport model at each Temperature and the rejection data of three reference organic solutes (i.e. erythritol, xylose and glucose) experimentally obtained in this study. The results suggest that the pore size of an NF membrane is dependent on the Feed solution Temperature. An increase in the Feed Temperature from 20 to 40 °C led to an increase in the effective pore radius from 0.39 to 0.44 nm. Consequently, the increase in the Feed Temperature also caused a considerable drop in the rejection of all TrOCs investigated in this study. The decrease in rejection observed here could be attributed to not only the increase in the solute diffusivity but also the enlargement of the membrane pore size. As the Feed Temperature increased, the decrease in rejection of neutral TrOCs was more severe than that of negatively charged compounds. This is because in addition to size exclusion (or steric hindrance) the rejection of negatively charged TrOCs is also governed by electrostatic interaction given that the membrane surface is also negatively charged.
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n nitrosamine removal by reverse osmosis for indirect potable water reuse a critical review based on observations from laboratory pilot and full scale studies
Separation and Purification Technology, 2012Co-Authors: Takahiro Fujioka, Yvan Poussade, Jorg E Drewes, Stuart J. Khan, Long D. NghiemAbstract:Abstract N-nitrosodimethylamine (NDMA) and several other N-nitrosamines have been identified as probable human carcinogens. Here, we review key aspects related to the occurrence and removal of N-nitrosamines by reverse osmosis (RO) membranes in the context of indirect potable water reuse. A comprehensive analysis of the existing data reveals significant variations in the rejection of NDMA by RO membranes reported in the literature, ranging from negligible up to 86%. This review article provides some insight into the reasons for such variations by examining the available data on the effects of operating conditions on NDMA rejection. Amongst several operating parameters investigated so far in the literature, Feed Temperature, membrane permeate flux, Feed solution pH and ionic strength were found to have considerable impact on NDMA rejection by RO membranes. In particular, it has been recently shown that seasonal changes in Feed Temperature (e.g. from 20 to 30 °C) can result in a significant decrease in NDMA rejection (from 49% to 25%). However, the combined effects of all operating parameters identified in the literature to date can only account for some of the variations in NDMA rejection that have been observed in full-scale RO plants. The impacts of membrane fouling and particularly chemical cleaning on the rejection of N-nitrosamines have not been fully investigated. Finally, this review article presents a roadmap for further research required to optimise the rejection of NDMA and other N-nitrosamines by RO membranes.
Noreddine Ghaffour - One of the best experts on this subject based on the ideXlab platform.
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multi effect distillation brine treatment by membrane distillation effect of antiscalant and antifoaming agents on membrane performance and scaling control
Desalination, 2020Co-Authors: Harun Elcik, Luca Fortunato, Alla Alpatova, Sofiane Soukane, Jamel Orfi, Emad Ali, Hany Alansary, Torove Leiknes, Noreddine GhaffourAbstract:Abstract One of the main advantages of the membrane distillation (MD) process is its ability to treat highly saline Feed waters such as thermal desalination brines at moderate Temperatures. However, scaling remains one of the major obstacles, causing a significant flux decline and membrane pore wetting. Furthermore, antiscalant and antifoaming agents are commonly utilized in conventional thermal desalination to prevent scale formation, and their effects on MD operation are not yet well understood. This study explores a multi-effect distillation (MED) brine as a potential Feed source for MD system with respect to process performance and membrane scaling. The influence of chemicals present in MED brine as well as Feed Temperature on the scaling process is addressed in terms of vapor flux and salt crystals formation. The scale formation was monitored with the non-invasive optical coherence tomography (OCT) imaging, and results were validated by scanning electron microscopy (SEM). Additionally, the elemental composition of the scale was determined and its effect on membrane contact angle was evaluated. We found that depending on its concentration, the antiscalant prolonged the induction time of salt crystallization whereas antifoaming showed the opposite effect. Scaling mostly occurred due to calcium sulfate crystals formation with the large size needle-shaped crystals favored at higher Feed Temperature. However, no pore wetting was observed including locations where crystal deposition occurred. Results show that thermal desalination brine, which is already preheated and chemically pretreated, could be an appropriate Feed source for MD to further increase the overall water recovery and reduce the marine environmental impact by reducing the brine discharge volume and its Temperature.
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transport phenomena and fouling in vacuum enhanced direct contact membrane distillation experimental and modelling
Separation and Purification Technology, 2017Co-Authors: Gayathri Naidu, Sanghyun Jeong, Noreddine Ghaffour, Wanggeun Shim, Youngkwon Choi, S VigneswaranAbstract:Abstract The application of vacuum to direct contact membrane distillation (vacuum enhanced direct contact membrane distillation, V-DCMD) removed condensable gasses and reduced partial pressure in the membrane pores, achieving 37.6% higher flux than DCMD at the same Feed Temperature. Transfer mechanism and Temperature distribution profile in V-DCMD were studied. The empirical flux decline (EFD) model represented fouling profiles of V-DCMD. In a continuous V-DCMD operation with moderate Temperature (55 °C) and permeate pressure (300 mbar) for treating wastewater ROC, a flux of 16.0 ± 0.3 L/m 2 h and high quality distillate were achieved with water flushing, showing the suitability of V-DCMD for ROC treatment.
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evaluation of air gap membrane distillation process running under sub atmospheric conditions experimental and simulation studies
Journal of Membrane Science, 2015Co-Authors: Ahmad S Alsaadi, Lijo Francis, Husnul Maab, Gary L Amy, Noreddine GhaffourAbstract:Abstract The importance of removing non-condensable gases from air gap membrane distillation (AGMD) modules in improving the water vapor flux is presented in this paper. Additionally, a previously developed AGMD mathematical model is used to predict to the degree of flux enhancement under sub-atmospheric pressure conditions. Since the mathematical model prediction is expected to be very sensitive to membrane distillation (MD) membrane resistance when the mass diffusion resistance is eliminated, the permeability of the membrane was carefully measured with two different methods (gas permeance test and vacuum MD permeability test). The mathematical model prediction was found to highly agree with the experimental data, which showed that the removal of non-condensable gases increased the flux by more than three-fold when the gap pressure was maintained at the saturation pressure of the Feed Temperature. The importance of staging the sub-atmospheric AGMD process and how this could give better control over the gap pressure as the Feed Temperature decreases are also highlighted in this paper. The effect of staging on the sub-atmospheric AGMD flux and its relation to membrane capital cost are briefly discussed.
Azam Marjani - One of the best experts on this subject based on the ideXlab platform.
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Simulation of Membrane Distillation for Purifying Water Containing 1,1,1‐Trichloroethane
Chemical Engineering & Technology, 2014Co-Authors: Mehdi Ghadiri, Vahid Abkhiz, Mehdi Parvini, Azam MarjaniAbstract:Vacuum membrane distillation is modeled for the purification of water containing organic matter. The separation medium is a hollow-fiber membrane contactor that is simplified to a two-dimensional structure with a single porous membrane wall. The model considers the transport phenomena of a vacuum membrane distillation system in porous media, in which the aqueous volatile organic solution was considered as an incompressible and steady fluid. The numerical simulation of the two-dimensional model of vacuum membrane distillation for an aqueous solution of 1,1,1-trichloroethane was established under steady state. The effects of the bulk Feed Temperature and the Feed flow rate on the percentage of 1,1,1-trichloroethane removal from an aqueous solution are discussed.
Nidal Hilal - One of the best experts on this subject based on the ideXlab platform.
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produced water treatment application of air gap membrane distillation
Desalination, 2013Co-Authors: Abdullah Alkhudhiri, Naif A Darwish, Nidal HilalAbstract:Abstract Air Gap Membrane Distillation (AGMD) has been implemented to treat produced water. The permeate fluxes, rejection factor and energy consumption for three different membranes, TF200, TF450 and TF1000, with pore sizes of 0.2, 0.45 and 1 μm, respectively, are measured at different operating parameters. The influence of membrane pore size is investigated for the produced water. Also, the effect of Feed flow rate, coolant Temperature and Feed Temperature on permeate flux is studied. The flux increases as the Feed Temperature and flow rate increase, and declines as the coolant Temperatures increase. Moreover, the energy consumption was measured at different pore size and was found to be independent of membrane pore size.
Jorg E Drewes - One of the best experts on this subject based on the ideXlab platform.
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n nitrosamine removal by reverse osmosis for indirect potable water reuse a critical review based on observations from laboratory pilot and full scale studies
Separation and Purification Technology, 2012Co-Authors: Takahiro Fujioka, Yvan Poussade, Jorg E Drewes, Stuart J. Khan, Long D. NghiemAbstract:Abstract N-nitrosodimethylamine (NDMA) and several other N-nitrosamines have been identified as probable human carcinogens. Here, we review key aspects related to the occurrence and removal of N-nitrosamines by reverse osmosis (RO) membranes in the context of indirect potable water reuse. A comprehensive analysis of the existing data reveals significant variations in the rejection of NDMA by RO membranes reported in the literature, ranging from negligible up to 86%. This review article provides some insight into the reasons for such variations by examining the available data on the effects of operating conditions on NDMA rejection. Amongst several operating parameters investigated so far in the literature, Feed Temperature, membrane permeate flux, Feed solution pH and ionic strength were found to have considerable impact on NDMA rejection by RO membranes. In particular, it has been recently shown that seasonal changes in Feed Temperature (e.g. from 20 to 30 °C) can result in a significant decrease in NDMA rejection (from 49% to 25%). However, the combined effects of all operating parameters identified in the literature to date can only account for some of the variations in NDMA rejection that have been observed in full-scale RO plants. The impacts of membrane fouling and particularly chemical cleaning on the rejection of N-nitrosamines have not been fully investigated. Finally, this review article presents a roadmap for further research required to optimise the rejection of NDMA and other N-nitrosamines by RO membranes.
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effects of Feed solution characteristics on the rejection of n nitrosamines by reverse osmosis membranes
Journal of Membrane Science, 2012Co-Authors: Takahiro Fujioka, Long Duc Nghiem, Yvan Poussade, James A Mcdonald, Jorg E Drewes, Stuart J. KhanAbstract:Abstract The rejection of eight N-nitrosamines was investigated in this laboratory-scale study, focusing on the influence of Feed solution characteristics on their separation by low pressure reverse osmosis membranes. The rejection mechanisms of N-nitrosamines were first examined using one nanofiltration (NF90) and two reverse osmosis (TFC-HR and SWC5) membranes. The TFC-HR membrane was used to investigate the effects of Feed solution characteristics. The rejection of a particular N-nitrosamine was generally membrane dependent and increased in the order of NF (NF90), low pressure RO (TFC-HR) and seawater RO (SWC5) membranes. In general, the rejection of N-nitrosamines by a given membrane also increased in the order of increasing molecular weight. These results suggested that steric hindrance was a dominating rejection mechanism of N-nitrosamines. Nevertheless, it was also observed from the result of N-nitrosomorpholine (NMOR) that the rejection of N-nitrosamines may also depend on other physicochemical properties such as hydrophobicity. A decrease in the Feed solution pH (from 9 to 3) resulted in a decrease in the rejection of the two smallest molecular weight N-nitrosamines, namely N-nitrosodimethylamine (NDMA) and N-nitrosomethylethylamine (NMEA). Changes in the Feed solution ionic strength (from 26 to 260 mM) caused a discernible decrease only in NDMA rejection, while no apparent impact on rejection was observed for an increase in the Feed concentration. On the other hand, it is striking that an increase in the Feed Temperature led to a significant decrease in the rejection of all N-nitrosamines and the impact was more pronounced for the small molecular weight N-nitrosamines. For example, a significant drop in NDMA rejection (from 49 to 25%) was observed as the Feed Temperature increased from 20 to 30 °C. The results also indicate that pH, ionic strength, and Temperature of the Feed solution can exert some influence on the rejection of NDMA and in some cases other N-nitrosamines. The combined effects of these Feed solution characteristics, particularly Feed Temperature, may account for some of the variation of NDMA rejection by RO membranes previously reported in the literature.