scholarly journals Flux Enhancement in Membrane Distillation Using Nanofiber Membranes

2016 ◽  
Vol 2016 ◽  
pp. 1-7 ◽  
Author(s):  
T. Jiříček ◽  
M. Komárek ◽  
J. Chaloupek ◽  
T. Lederer
Keyword(s):  
Reverse Osmosis ◽  
Membrane Distillation ◽  
Optimum Conditions ◽  
Operational Conditions ◽  
Application Potential ◽  
Mass And Heat Transfer ◽  
Nanofiber Membranes ◽  
Specific Membrane ◽  
Vapour Pressure Difference ◽  
The Ideal

Membrane distillation (MD) is an emerging separation technology, whose largest application potential lies in the desalination of highly concentrated solutions, which are out of the scope of reverse osmosis. Despite many attractive features, this technology is still awaiting large industrial application. The main reason is the lack of commercially available membranes with fluxes comparable to reverse osmosis. MD is a thermal separation process driven by a partial vapour pressure difference. Flux, distillate purity, and thermal efficiency are always in conflict, all three being strictly connected with pore size, membrane hydrophobicity, and thickness. The world has not seen the ideal membrane yet, but nanofibers may offer a solution to these contradictory requirements. Membranes of electrospun PVDF were tested under various conditions on a direct contact (DCMD) unit, in order to determine the optimum conditions for maximum flux. In addition, their performance was compared to commonly available PTFE, PE, and PES membranes. It was confirmed that thinner membranes have higher fluxes and a lower distillate purity and also higher energy losses via conduction across the membrane. As both mass and heat transfer are connected, it is best to develop new membranes with a target application in mind, for the specific membrane module and operational conditions.

scholarly journals Employing full factorial design and response surface methodology for optimizing direct contact membrane distillation operational conditions in desalinating the rejected stream of a reverse osmosis unit at Esfahan refinery–Iran

2018 ◽  
Vol 19 (2) ◽  
pp. 492-501 ◽  
Author(s):  
M. Ebadi ◽  
M. R. Mozdianfard ◽  
M. Aliabadi
Keyword(s):  
Response Surface Methodology ◽  
Reverse Osmosis ◽  
Flow Rate ◽  
Direct Contact ◽  
Membrane Distillation ◽  
Permeate Flux ◽  
Operational Conditions ◽  
Direct Contact Membrane Distillation ◽  
Full Factorial ◽  
Feed Temperature

Abstract Optimized condition for desalination of the reverse osmosis (RO) rejected stream from Esfahan Oil Refining Company (EORC) using direct contact membrane distillation (DCMD) with polytetrafluoroethylene (PTFE) membrane was investigated here, having designed a set of 34 experiments using response surface methodology (RSM) and full factorial design (FFD) modelling, carried out in a laboratory scale set-up built for this purpose. Statistical criteria for validation, significance, accuracy and adequacy confirmed the suitability of the quadratic polynomial model employed. Response plots and regression equations suggested that the permeate flux response improved with increased feed temperature, reduced permeate temperature and enhanced feed flow rate. Optimizing DCMD process showed that maximum permeate flux of 60.76 L/m2·h could be achieved at the following optimum operational conditions: feed temperature and flow rate of 70 °C and 2 L/min, respectively, as well as the permeate temperature of 15 °C. At this point, the mean annual energy required for 90% water recovery (36 m3/h off the RO brackish rejected stream) at EORC refinery was found to be 96 GJ, which could be supplied using solar or conventional energy systems at Isfahan, facing a very critical water shortage at present.

scholarly journals Electrospun Nanostructured Membrane Engineering Using Reverse Osmosis Recycled Modules: Membrane Distillation Application

Nanomaterials ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 1601
Author(s):  
Jorge Contreras-Martínez ◽  
Carmen García-Payo ◽  
Mohamed Khayet
Keyword(s):  
Reverse Osmosis ◽  
Polyvinylidene Fluoride ◽  
Membrane Distillation ◽  
Permeate Flux ◽  
Electrospinning Technique ◽  
Salt Rejection ◽  
Rejection Factor ◽  
Nanofibrous Membranes ◽  
Membrane Engineering ◽  
Desalination Plants

As a consequence of the increase in reverse osmosis (RO) desalination plants, the number of discarded RO modules for 2020 was estimated to be 14.8 million annually. Currently, these discarded modules are disposed of in nearby landfills generating high volumes of waste. In order to extend their useful life, in this research study, we propose recycling and reusing the internal components of the discarded RO modules, membranes and spacers, in membrane engineering for membrane distillation (MD) technology. After passive cleaning with a sodium hypochlorite aqueous solution, these recycled components were reused as support for polyvinylidene fluoride nanofibrous membranes prepared by electrospinning technique. The prepared membranes were characterized by different techniques and, finally, tested in desalination of high saline solutions (brines) by direct contact membrane distillation (DCMD). The effect of the electrospinning time, which is the same as the thickness of the nanofibrous layer, was studied in order to optimize the permeate flux together with the salt rejection factor and to obtain robust membranes with stable DCMD desalination performance. When the recycled RO membrane or the permeate spacer were used as supports with 60 min electrospinning time, good permeate fluxes were achieved, 43.2 and 18.1 kg m−2 h−1, respectively; with very high salt rejection factors, greater than 99.99%. These results are reasonably competitive compared to other supported and unsupported MD nanofibrous membranes. In contrast, when using the feed spacer as support, inhomogeneous structures were observed on the electrospun nanofibrous layer due to the special characteristics of this spacer resulting in low salt rejection factors and mechanical properties of the electrospun nanofibrous membrane.

scholarly journals Metagenomics, gene discovery and the ideal biocatalyst

2004 ◽  
Vol 32 (2) ◽  
pp. 298-302 ◽  
Author(s):  
D.A. Cowan ◽  
A. Arslanoglu ◽  
S.G. Burton ◽  
G.C. Baker ◽  
R.A. Cameron ◽  
...  
Keyword(s):  
New Technologies ◽  
Rapid Development ◽  
Gene Discovery ◽  
Metagenomic Library ◽  
Metagenomic Sequencing ◽  
Optimum Conditions ◽  
Enzyme Screening ◽  
Specific Amplification ◽  
The Ideal

With the rapid development of powerful protein evolution and enzyme-screening technologies, there is a growing belief that optimum conditions for biotransformation processes can be established without the constraints of the properties of the biocatalyst. These technologies can then be applied to find the ‘ideal biocatalyst’ for the process. In identifying the ideal biocatalyst, the processes of gene discovery and enzyme evolution play major roles. However, in order to expand the pool genes for in vitro evolution, new technologies, which circumvent the limitations of microbial culturability, must be applied. These technologies, which currently include metagenomic library screening, gene-specific amplification methods and even full metagenomic sequencing, provide access to a volume of ‘sequence space’ that is not addressed by traditional screening.

Electrospun Nanofiber Membranes for Membrane Distillation

2019 ◽  
pp. 107-140
Author(s):  
Jiaxin Guo ◽  
Bhaskar Jyoti Deka ◽  
Alicia Kyoungjin An
Keyword(s):  
Membrane Distillation ◽  
Electrospun Nanofiber ◽  
Nanofiber Membranes

scholarly journals OPTIMIZATION OF THE USE OF FLY ASH AS AN ADDITIVE PORTLAND COMPOSITE CEMENT (PCC)

2019 ◽  
Vol 4 (2) ◽  
pp. 61-72 ◽  
Author(s):  
Leni Rumiyanti ◽  
Listiani Listiani ◽  
Tika Damayanti
Keyword(s):  
Fly Ash ◽  
Setting Time ◽  
Quality Analysis ◽  
Insoluble Residue ◽  
Optimum Conditions ◽  
Free Lime ◽  
Composite Cement ◽  
Ideal Composition ◽  
Physical And Chemical ◽  
The Ideal

Research has been carried out on the optimization of the use of Lahat Fly Ash as an Additive Portland Composite Cement (PCC) which aims to determine the optimum conditions for adding Lahat fly ash to produce cement with physical and chemical requirements in accordance with SNI 7064:2014 and discover the ideal composition of cement with fly additions Lahat ash from various cement compositions. The quality analysis in making PCC cement is chemically in the form of Insoluble Residue (IR), Loss of Ignition (LOI), and free lime (FCaO) as well as the quality of physics in the form of Blaine, setting time, and cement mortar compressive strength. The results obtained after the process of making PCC cement with the addition of 14% Lahat fly ash, namely PCC cement in optimum conditions with physical and chemical requirements in accordance with SNI 7064: 2014 where the ideal composition of PCC cement manufacture is 14% Lahat fly ash, clinker 62%, 3% gypsum, 18% limestone, and 3% pozzolans in making PCC cement. Therefore, Lahat fly ash can be used as an alternative mixture in making PCC cement.

scholarly journals Ozonation Pretreatment for Reduction of Landfill Leachate Fouling on Membranes: A Response Surface Methodology Analysis

Processes ◽  
2020 ◽  
Vol 8 (5) ◽  
pp. 506
Author(s):  
Everton Gripa ◽  
Alyne M. Costa ◽  
Juacyara C. Campos ◽  
Fabiana V. da Fonseca
Keyword(s):  
Response Surface Methodology ◽  
Experimental Design ◽  
Response Surface ◽  
Reverse Osmosis ◽  
Organic Compounds ◽  
Landfill Leachate ◽  
Operational Conditions ◽  
Toxicity Factor ◽  
High Concentrations ◽  
Modified Fouling Index

Batch ozonation was performed to assess its efficacy as a pretreatment for reverse osmosis (RO) membranes for treating leachate with high concentrations of recalcitrant organic compounds. Leachate samples from two different landfills were collected and characterized. The modified fouling index (MFI) was used to estimate the fouling potential of raw and ozonized leachates. A response surface experimental design was applied to optimize operational pH and ozone dose. The results demonstrate that the best operational conditions are 1.5 g/L of O3 at pH 12.0 and 1.5 g/L of O3 at pH 9.0 for Landfills 1 and 2, which reduce MFI by 96.22% and 94.08%, respectively. Additionally, they show toxicity factor decays of 98.44% for Landfill 1 and 93.75% for Landfill 2. These results, along with the similar behavior shown by leachate samples from distinct landfills, suggest that ozonation is a promising technology to fit this kind of wastewater into the requirements of RO membranes, enabling their use in such treatment.

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