The role of membrane ξ-potential in solute rejection by low-pressure reverse osmosis membrane

2002 ◽  
Vol 2 (5-6) ◽  
pp. 321-328
Author(s):  
H. Ozaki ◽  
N. Ikejima ◽  
S. Matsui ◽  
Y. Terashima ◽  
S. Takeda ◽  
...  
Keyword(s):  
Reverse Osmosis ◽  
Organic Compounds ◽  
Water Flux ◽  
Streaming Potential ◽  
High Water ◽  
Low Pressure ◽  
Bulk Solution ◽  
Inorganic Salts ◽  
Operating Pressure ◽  
Water And Wastewater Treatment

A new generation of reverse osmosis membranes, low-pressure reverse osmosis (LPRO) membranes, have been developed for operation under very low pressure (below 0.5 MPa). LPRO membranes have received attention especially for their application in the field of water and wastewater treatment, to provide a high water flux at low operating pressure while maintaining very good rejection levels of salts and organics. Our previous work on LPRO has shown that the rejection of some inorganic salts and organic compounds depends appreciably on the pH of the bulk solution, probably because LPRO membranes can have an electric charge. In this study we investigated experimentally the effectiveness of different LPRO membranes in separating inorganic salts and organic compounds from a bulk solution with different pH conditions. We also tried to measure membrane ξ-potential by using a streaming potential method. The results indicated that the membrane ξ-potential as well as the ion size or molecular weight of organics can be considered key factors in the rejection of ionic salts and dissociated organic compounds including pesticides and endocrine disruptors.

Analysis and calculation of the process of low-pressure reverse osmosis during recycling of hygienic water

2019 ◽  
pp. 28-36
Author(s):  
Leonid S. Bobe ◽  
Nikolay A. Salnikov
Keyword(s):  
Mass Transfer ◽  
Reverse Osmosis ◽  
Life Support ◽  
Space Station ◽  
Low Pressure ◽  
Operating Pressure ◽  
Life Support System ◽  
Cleaning Agent ◽  
The Difference ◽  
Pressure Channel

Analysis and calculation have been conducted of the process of low-pressure reverse osmosis in the membrane apparatus of the system for recycling hygiene water for the space station. The paper describes the physics of the reverse osmosis treatment and determines the motive force of the process, which is the difference of effective pressures (operating pressure minus osmotic pressure) in the solution near the surface of the membrane and in the purified water. It is demonstrated that the membrane scrubbing action is accompanied by diffusion outflow of the cleaning agent components away from the membrane. The mass transfer coefficient and the difference of concentrations (and, accordingly, the difference of osmotic pressures) in the boundary layer of the pressure channel can be determined using an extended analogy between mass transfer and heat transfer. A procedure has been proposed and proven in an experiment for calculating the throughput of a reverse osmosis apparatus purifying the hygiene water obtained through the use of a cleaning agent used in sanitation and housekeeping procedures on Earth. Key words: life support system, hygiene water, water processing, low-pressure reverse osmosis, space station.

Removal of endocrine disrupting chemicals (EDCs) using low pressure reverse osmosis membrane (LPROM)

2007 ◽  
Vol 56 (8) ◽  
pp. 161-168 ◽  
Author(s):  
A.R.A. Razak ◽  
Z. Ujang ◽  
H. Ozaki
Keyword(s):  
Reverse Osmosis ◽  
Endocrine Disrupting Chemicals ◽  
Cross Flow ◽  
Low Pressure ◽  
Endocrine Function ◽  
Operating Parameters ◽  
Operating Pressure ◽  
Reverse Osmosis Membrane ◽  
Adverse Health Effects ◽  
Endocrine Disrupting

Endocrine disrupting chemicals (EDCs) are the focus of current environmental issues, as they can cause adverse health effects to animals and human, subsequent to endocrine function. The objective of this study was to remove a specific compound of EDCs (i.e. pentachlorophenol, C6OCL5Na, molecular weight of 288 g/mol) using low pressure reverse osmosis membrane (LPROM). A cross flow module of LPROM was used to observe the effects of operating parameters, i.e. pH, operating pressure and temperature. The design of the experiment was based on MINITABTM software, and the analysis of results was conducted by factorial analysis. It was found that the rejection of pentachlorophenol was higher than 80% at a recovery rate of 60 to 70%. The rejection was subjected to increase with the increase of pH. The flux was observed to be increased with the increase of operating pressure and temperature. This study also investigated the interaction effects between operating parameters involved.

scholarly journals Improving performance of low pressure reverse osmosis systems by intermittent autoflushing

2018 ◽  
Vol 9 (1) ◽  
pp. 1
Author(s):  
I N Widiasa ◽  
N Sinaga ◽  
D Ariyanti
Keyword(s):  
Reverse Osmosis ◽  
Membrane Surface ◽  
Magnesium Silicate ◽  
Operating Mode ◽  
Low Pressure ◽  
Calcium Sulphate ◽  
Feed Water ◽  
Low Grade ◽  
Operating Pressure ◽  
Permeate Flux

Improving performance of low pressure reverse osmosis systems by intermittent autoflushing Scaling formation on the membrane surface in the form of calcium carbonate, calcium sulphate, silica, and/or magnesium silicate is a main problem of the reverse osmosis (RO) application for upgrading low grade water. Scaling in RO system is generally controlled by softening the feed water, limiting the recovery and/or the addition of antiscalants which is impractical for household RO system. In this work, the feasibility of intermittent autoflushing to prevent scale formation in household RO systems was investigated. All experiments were carried out using commercially available RO membrane (CSM RE-1812LP) which operated for 6 hours under operating pressure 5 kg/cm2 and total recycle operating mode. Model solution of feed water contain CaCl2 and NaHCO3 were prepared to meet various LSI values in the range of 0 to 1.5. Duration and interval time of autoflush were in the range of 60 to 15 s and 5 to 60 min respectively. The results shown that the permeate flux of the system which operated using intermittent autoflushing relatively stable. It is emphasized that intermittent autoflushing may improve the performance of household reverse osmosis systems.Keywords: Autoflushing, scaling, physical cleaning, reverse osmosis  Abstrak Pembentukan kerak (scaling) pada permukaan membran berupa kerak kalsium karbonat, kalsium sulfat, silika dan atau magnesium silikat merupakan permasalahan utama pada aplikasi sistem membran reverse osmosis (RO) pada proses pemurnian air. Scaling pada sistem RO umumnya dikontrol dengan melakukan pretreatment terhadap air umpan seperti softening, menambahkan zat antiscalant pada saat proses pemisahan serta membatasi tingkat recovery, dimana proses-proses tersebut tidak praktis apabila diaplikasikan pada sistem RO skala rumah tangga. Penelitian ini bertujuan untuk melihat kemungkinan metode intermittent autoflush dapat diaplikasikan untuk menghambat terjadinya scaling pada sistem RO skala rumah tangga. Penelitian ini dilakukan dengan menggunakan satu unit membran spiral wound jenis CSM RE-1812LP yang dioperasikan dengan tekanan operasi 5 kg/cm2 dan waktu operasi ± 6 jam. Larutan umpan sintesis dibuat dengan melarutkan CaCl2 dan NaHCO3 hingga nilai LSI mencapai kisaran 0-1,5. Durasi dan interval dari metode intermittent autoflush divariasikan pada kisaran 60-15 detik dan 5-60 menit. Hasil penelitian menunjukkan bahwa fluks permeat relatif stabil pada sistem RO yang menggunakan metode intermittent autoflush. Hal ini menandakan bahwa metode intermittent autoflush ini dimungkinkan untuk meningkatkan kinerja dari sistem RO skala rumah tangga.Kata Kunci: Autoflushing, scaling, physical cleaning, reverse osmosis

Performance of low pressure reverse osmosis membrane (LPROM) for separating mono- and divalent ions

1998 ◽  
Vol 38 (4-5) ◽  
pp. 521-528 ◽  
Author(s):  
Zaini Ujang ◽  
G. K. Anderson
Keyword(s):  
Heavy Metals ◽  
Reverse Osmosis ◽  
Metal Removal ◽  
Feed Solution ◽  
Low Pressure ◽  
Operating Conditions ◽  
Operating Pressure ◽  
Reverse Osmosis Membrane ◽  
Permeate Flux ◽  
Feed Concentration

This paper describes an investigation on the rejection of the divalent anions from ZnSO4 using LPROMs, and to establish the effect of operating pressure, feed concentration and temperature on metal removal, then to compare with the monovalent anions, ZnCl2. A bench-scale spiral wound configuration of sulphonated polysulphone low pressure reverse osmosis membrane (LPROM) was used to remove heavy metals at various operating conditions, i.e. operating conditions, solute concentrations and temperature. The results show that the higher the operating pressure the greater will be the permeate flux for heavy metals from both mono- and divalent anions. At low operating pressure however, metals from the divalent anions give a higher permeate flux than did the monovalent anions. Permeate flux in both mono- and divalent anions is shown to be subsequently increased by a decrease of the concentration of feed solution. Regarding metal removal, metals from divalent anions were rejected more effectively than monovalent anions at all levels of feed concentration.

scholarly journals Transport Models of Ammonium Nitrogen in Wastewater from Rare Earth Smelteries by Reverse Osmosis Membranes

2020 ◽  
Vol 12 (15) ◽  
pp. 6230
Author(s):  
Shuanglin Gui ◽  
Zhaohuan Mai ◽  
Jiaqi Fu ◽  
Yuansong Wei ◽  
Jinbao Wan
Keyword(s):  
Rare Earth ◽  
Reverse Osmosis ◽  
Membrane Fouling ◽  
Driving Force ◽  
Water Flux ◽  
Ammonium Nitrogen ◽  
Salt Transport ◽  
Salt Flux ◽  
Operating Pressure ◽  
Concentration Difference

Wastewater from rare earth smelteries contains large amounts of ammonium nitrogen (NH4+-N), which causes severe environmental problems. In this contribution, the desalination efficiency of reverse osmosis (RO) was investigated in the treatment of NH4Cl or NaCl solutions from 0.1 to 40 g/L under different operating pressures with a commercial RO membrane. Experimental results showed that when an operating pressure above 30 bar is applied to the 5 g/L NH4Cl solution, the permeate was found to meet the discharge standards of NH4+-N. Compared to NH4Cl, the permeate fluxes of NaCl solutions were higher due to the higher net driving force and lower propensity to membrane fouling. Theoretical models indicate a linear relationship between water flux and the net driving force for both NH4Cl and NaCl solutions. On the contrary, a power function between the salt flux and concentration difference correlated well with the experimental data for salt transport. The equations for water and salt transport obtained by this work would provide a facile and practical means for predicting the membrane performance in design and optimization of RO processes for the treatment of wastewater from the rare earth industry.

Membrane filtration for tertiary treatment of biologically treated effluents from the pulp and paper industry

2007 ◽  
Vol 55 (6) ◽  
pp. 99-107 ◽  
Author(s):  
M. Mänttäri ◽  
M. Nyström
Keyword(s):  
Reverse Osmosis ◽  
Organic Compounds ◽  
Membrane Filtration ◽  
Paper Industry ◽  
Pulp And Paper Industry ◽  
Low Pressure ◽  
Chloride Ions ◽  
Pulp And Paper ◽  
Monovalent Ions ◽  
Activated Sludge Processes

Discharge waters from activated sludge processes in the pulp and paper industry and from a municipal wastewater treatment plant were filtered with various nanofiltration (NF) and low pressure reverse osmosis (RO) membranes. The purpose was to study flux, retention, and permeate quality after membrane filtration by using a high shear (CR-250/2) filter. The suitability of the achieved permeates for reuse at the industrial site is also discussed. The NF permeate was practically free from colour and organic compounds but contained significant amount of inorganic compounds e.g. chloride ions, especially when a high amount of sulphate containing discharge waters were filtered, in which case a low pressure RO membrane was needed to successfully remove monovalent anions. Organic compounds were almost completely retained by NF and RO membranes and organic carbon in the permeate was less than 10 mg/dm3 on average. The achieved permeate can easily be reused in paper production. Nanofiltration has a significantly higher flux and also a lower fouling tendency than reverse osmosis but it passes through monovalent ions when there is a high sulphate concentration in the water. Therefore, RO might be needed in such cases to produce excellent process water.

scholarly journals A New Method for a Polyethersulfone-Based Dopamine-Graphene (xGnP-DA/PES) Nanocomposite Membrane in Low/Ultra-Low Pressure Reverse Osmosis (L/ULPRO) Desalination

Membranes ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 439
Author(s):  
Lwazi Ndlwana ◽  
Mxolisi M. Motsa ◽  
Bhekie B. Mamba
Keyword(s):  
Reverse Osmosis ◽  
Photoelectron Spectroscopy ◽  
Phase Inversion ◽  
Low Pressure ◽  
Inversion Method ◽  
Synthetic Approach ◽  
Operating Pressure ◽  
Cross Sectional ◽  
Drying Time ◽  
Salt Rejection

Herein we present a two-stage phase inversion method for the preparation of nanocomposite membranes for application in ultra-low-pressure reverse osmosis (ULPRO). The membranes containing DA-stabilized xGnP (xGnP-DA-) were then prepared via dry phase inversion at room temperature, varying the drying time, followed by quenching in water. The membranes were characterized for chemical changes utilizing attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS). The results indicated the presence of new chemical species and thus, the inclusion of xGnP-DA in the polyethersulfone (PES) membrane matrix. Atomic force microscopy (AFM) showed increasing surface roughness (Ra) with increased drying time. Scanning electron microscopy (SEM) revealed the cross-sectional morphology of the membranes. Water uptake, porosity and pore size were observed to decrease due to this new synthetic approach. Salt rejection using simulated seawater (containing Na, K, Ca, and Mg salts) was found to be up to stable at <99.99% between 1–8 bars operating pressure. After ten fouling and cleaning cycles, flux recoveries of <99.5% were recorded, while the salt rejection was <99.95%. As such, ULPRO membranes can be successfully prepared through altered phase inversion and used for successful desalination of seawater.

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