Nanofiltration performance of lead solutions: effects of solution pH and ionic strength

2010 ◽  
Vol 10 (2) ◽  
pp. 193-200 ◽  
Author(s):  
Wuthikorn Saikaew ◽  
Supatpong Mattaraj ◽  
Ratana Jiraratananon
Keyword(s):  
Ionic Strength ◽  
Membrane Surface ◽  
Aromatic Polyamide ◽  
Solution Chemistry ◽  
Lead Ion ◽  
Solution Ph ◽  
Dead End ◽  
Flux Decline ◽  
Charged Membrane ◽  
Double Layer Thickness

Nanofiltration performance (i.e. rejection and flux decline) of lead solutions was investigated using a dead-end test cell at room temperature. An aromatic polyamide NF-90 membrane was chosen to determine the impacts of solution chemistry. The experimental results revealed that solution flux decline was dependent on solution pH, ionic strength, and type of lead solutions. Solution flux conducted with different types of lead solutions (i.e. PbCl2 and Pb(NO3)2) decreased with increased solution pH. Solutions having high pH exhibited greater flux decline than those having low solution pH, while lead ion rejections were relatively high. Increased ionic strengths resulted in a greater flux decline, while lead ion rejections decreased with decreasing solution pH and increasing ionic strengths. Such results were related to low solution pH, suggesting an increase in fixed charge of proton (H+), decreasing electrical double layer thickness within membrane, thus allowing increased lead concentration passing through the membrane surface. Solution flux and rejection decreased further at higher ionic strengths, which caused a reduced negatively charged membrane, and thus decreased rejections. It was also found that lead ion for PbCl2 solution exhibited higher rejections than that of Pb(NO3)2 solution.

Prevention of Membrane Fouling Using Electric Pulse in Dead End Microfiltration of Titanium Suspensions

2012 ◽  
Author(s):  
Abdul Latif Ahmad ◽  
Suzylawati Ismail
Keyword(s):  
Ionic Strength ◽  
Pulse Duration ◽  
Applied Voltage ◽  
Membrane Fouling ◽  
Electric Pulse ◽  
Membrane Surface ◽  
Pulse Interval ◽  
Electric Pulses ◽  
Average Percentage ◽  
Dead End

Denyutan elektrik merupakan salah satu kaedah yang berkesan untuk menyingkirkan bahan–bahan endapan pada permukaan membran polimerik dan mampu mencegah permukaan daripada tersumbat. Hasil–hasil dapatan uji kaji pencegahan permukaan membran dari tersumbat menggunakan denyutan elektrik bagi proses penurasan mikroampaian titanium dibentangkan. Kesan beberapa pembolehubah proses seperti selang masa antara denyutan elektrik, jangkamasa sesuatu denyutan elektrik, pH larutan, kekuatan ionik bagi elektrolit dan kekuatan voltan sesuatu denyutan elektrik telah dikaji dari segi prestasi dan keberkesanannya dalam mencegah membran dari tersumbat. Didapati bahawa fluks meningkat secara ketara dengan adanya pergerakan elekroforetik butiran bahan endapan menjauhi permukaan membran dan berlakunya proses elektroosmosis di dalam bahan endapan itu sendiri. Keputusan–keputusan telah dianalisis dari segi purata fluks, purata kepekatan bahan endapan, peratus purata perolehan semula bahan endapan dan peratus perolehan semula air. Didapati bahawa sifat fizikal dan kimia larutan (pH dan kekuatan ionik elektrolit) memberi kesan yang besar ke atas kaedah pencegahan permukaan membran dari tersumbat. Ampaian titanium pada pH 8 dan dengan kekuatan ionik elektrolit 0.01M memberi prestasi terbaik dalam pembersihan permukaan membran. Selang masa antara dua denyutan yang singkat dan jangkamasa 10 saat sesuatu denyutan dengan kekutan voltan 100V merupakan keadaan optimum bagi denyutan elektrik untuk menyingkirkan bahan–bahan endapan dari permukaan membran menggunakan denyutan elektrik. Kata kunci: pemisahan membran; penurasan mikro; membran tersumbat; denyutan elektrik;titanium dioksida. Electric pulse in an effective means of removing particulate materials from polymeric membrane and preventing the membrane fouling. The experimental results for dead end microfiltration of titanium suspension to prevent membrane fouling using electric pulses are presented. The effect of processing variables such as the pulse interval, pulse duration, pH of the solution, ionic strength of the electrolyte and the strength of the applied voltage for dead end microfiltration of titanium suspensions were studied on the performance and effectiveness of this prevention of membrane fouling. The flux was significantly increased by both electrophoretic motion of particles away from the membrane surface and electroosmosis occurring in the filtercake. The results were analyzed for its average flux, average cake concentration, average percentage recovery of cake and average percentage recovery of water. It is found that the physical and chemical properties of the solution (pH and ionic strength of the electrolyte) have a great effect on this membrane fouling prevention method. Titanium suspension at pH 8 and ionic strength of 0.01M electrolyte strength gave the best membrane cleaning performance. Shorter pulse interval with 10 seconds pulse duration with 100V applied voltage were the optimum conditions to remove the filtercake from the membrane surface. Key words: membrane separation; microfiltration; membrane fouling; electric pulses; titanium dioxide

Bisphenol a Removal by Nanofiltration Process

2010 ◽  
Vol 113-116 ◽  
pp. 1648-1652
Author(s):  
Cong Li ◽  
Nai Yuan Gao
Keyword(s):  
Liquid Chromatography ◽  
Ionic Strength ◽  
Bisphenol A ◽  
Yeast Cell ◽  
Membrane Surface ◽  
Solution Chemistry ◽  
Environment Problem ◽  
Inorganic Matter ◽  
Abnormal Increase ◽  
Negative Effect

It is well known that bisphenol A(BPA), as one EDC, has an oestrogenic effect, causing an abnormal increase in the growth of yeast cell in polycarbonate flasks. Moreover, BPA significantly contributes to the environment problem, as evidenced by a number of recent studies[1](Inoue et al., 2003). This study examined the ability of nanofiltration (NF) membranes to retain bisphenol A(BPA). In the study, BPA retention was quantified by liquid chromatography. The effect of solution chemistry, inorganic matter and pH were investigated on the rejection of BPA and its adsorption on membranes. The results indicate that BPA has a high adsorptive affinity for the membrane and more than 80% of BPA was absorbed on the membrane surface. In addition, the increase of initial BPA concentration has negative effect on BPA rejection. It also indicates that the removal of BPA is higher with lower BPA concentrations. In addition, the rejection of BPA decreases with the increase of pH when pH < 7 and increases with the increase of pH when pH ≥ 7. The experimental results of ionic strength indicate there is a slight decrease in the rejection of BPA when the ionic strength increases.

scholarly journals Interdependence of Contributing Factors Governing Dead-End Fouling of Nanofiltration Membranes

Membranes ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 47
Author(s):  
Oranso Themba Mahlangu ◽  
Bhekie Brilliance Mamba
Keyword(s):  
Membrane Surface ◽  
Contact Angles ◽  
Permeate Flux ◽  
Contributing Factors ◽  
Pore Blocking ◽  
Dead End ◽  
Flux Decline ◽  
Cake Formation ◽  
Affinity Interaction

Cake-enhanced concentration polarization (CECP) has been ascribed as the main cause of flux decline in dead-end filtration. An unfamiliar approach was used to investigate the role of CECP effects in the fouling of a nanofiltration membrane (NF-270) that poorly reject salts. Membrane–foulant affinity interaction energies were calculated from measured contact angles of foulants and membrane coupons based on the van der Waals/acid–base approach, and linked to resistance due to adsorption (Ra). In addition, other fouling mechanisms and resistance parameters were investigated using model organic and colloidal foulants. After selection, the foulants and membranes were characterized for various properties, and fouling experiments were conducted under controlled conditions. The fouled membranes were further characterized to gain more understanding of the fouling layer properties and flux decline mechanisms. Sodium alginate and latex greatly reduced membrane permeate flux as the flux declined by 86% and 59%, respectively, while there was minor flux decline when aluminum oxide was used as model foulant (<15% flux decline). More flux decline was noted when fouling was conducted with a combination of organic and colloidal foulants. Contrary to other studies, the addition of calcium did not seem to influence individual and combined fouling trends. Foulants adsorbed more on the membrane surface as the membrane–foulant affinity interactions became more attractive and pore blocking by the foulants was not important for these experiments. Hydraulic resistance due to cake formation (Rc) had a higher contributing effect on flux decline, while CECP effects were not substantial.

Titration of sulphates and lead using lead ion selective electrode

1981 ◽  
Vol 46 (2) ◽  
pp. 368-376 ◽  
Author(s):  
Josef Veselý
Keyword(s):  
Ionic Strength ◽  
Electrode Surface ◽  
Salt Content ◽  
Ion Selective Electrode ◽  
Lead Ion ◽  
Selective Electrode ◽  
Limit Of Determination ◽  
Total Salt Content ◽  
Automatic Titration

Titration of sulphates with lead perchlorate employing lead ion selective electrode indication was studied using additions of various organic solvents at different pH' and ionic strength values. As the optimum emerged systems with 60-70% 1,4-dioxane, pH' 5.3-5.6. After dehydration with sodium hydroxide, dioxane must be freed from the electrode surface-oxidizing impurities by their reduction with sodium metal and subsequent distillation. The method was applied to determination of sulphates in mountain spring waters. Units of ppm can be determined; the limit of determination, however, depends considerably on the content of dioxane, total salt content in the sample, and speed of the semi-automatic titration. Lead can be determined with EDTA in concentrations down to c(Pb2+) = 5 . 10-6 mol l-1.

scholarly journals Potential Pitfalls in Membrane Fouling Evaluation: Merits of Data Representation as Resistance Instead of Flux Decline in Membrane Filtration

Membranes ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 460
Author(s):  
Bastiaan Blankert ◽  
Bart Van der Bruggen ◽  
Amy E. Childress ◽  
Noreddine Ghaffour ◽  
Johannes S. Vrouwenvelder
Keyword(s):  
Membrane Fouling ◽  
Membrane Filtration ◽  
Data Representation ◽  
Strong Impact ◽  
Experimental Conditions ◽  
Permeable Membrane ◽  
Dead End ◽  
Flux Decline ◽  
The Difference ◽  
Filtration Flux

The manner in which membrane-fouling experiments are conducted and how fouling performance data are represented have a strong impact on both how the data are interpreted and on the conclusions that may be drawn. We provide a couple of examples to prove that it is possible to obtain misleading conclusions from commonly used representations of fouling data. Although the illustrative example revolves around dead-end ultrafiltration, the underlying principles are applicable to a wider range of membrane processes. When choosing the experimental conditions and how to represent fouling data, there are three main factors that should be considered: (I) the foulant mass is principally related to the filtered volume; (II) the filtration flux can exacerbate fouling effects (e.g., concentration polarization and cake compression); and (III) the practice of normalization, as in dividing by an initial value, disregards the difference in driving force and divides the fouling effect by different numbers. Thus, a bias may occur that favors the experimental condition with the lower filtration flux and the less-permeable membrane. It is recommended to: (I) avoid relative fouling performance indicators, such as relative flux decline (J/J0); (II) use resistance vs. specific volume; and (III) use flux-controlled experiments for fouling performance evaluation.

scholarly journals Influence of bulk concentration on the organisation of molecules at a membrane surface and flux decline during reverse osmosis of an anionic surfactant

2016 ◽  
Vol 499 ◽  
pp. 257-268 ◽  
Author(s):  
Zhaohuan Mai ◽  
Vincent Butin ◽  
Mohammed Rakib ◽  
Haochen Zhu ◽  
Murielle Rabiller-Baudry ◽  
...  
Keyword(s):  
Reverse Osmosis ◽  
Anionic Surfactant ◽  
Membrane Surface ◽  
Bulk Concentration ◽  
Flux Decline

Membrane filtration of wastewater effluents for reuse: effluent organic matter rejection and fouling

2001 ◽  
Vol 43 (10) ◽  
pp. 225-232 ◽  
Author(s):  
C. Jarusutthirak ◽  
G. Amy
Keyword(s):  
Organic Matter ◽  
Membrane Filtration ◽  
Treated Wastewater ◽  
High Concentration ◽  
Effluent Organic Matter ◽  
Dead End ◽  
Flux Decline ◽  
Uf Membranes ◽  
Stirred Cell ◽  
Filtration Unit

The reuse of treated wastewater to augment natural drinking water supplies is receiving serious consideration. Treatment of secondary and tertiary effluent by membrane filtration was investigated by assessing nanofiltration (NF) membrane and ultrafiltration (UF) membranes in bench-scale experiments. It was found that secondary and tertiary effluent contained high concentration of effluent organic matter (EfOM), contributing EfOM-related fouling. Flux decline and EfOM rejection tests were evaluated, using a dead-end stirred cell filtration unit. Surface charge and molecular weight cut-off (MWCO) of membranes were significant factors in membrane performance including permeability and EfOM-rejection.

Electroflocculation as potential pretreatment in colloid ultrafiltration

2006 ◽  
Vol 6 (1) ◽  
pp. 69-78 ◽  
Author(s):  
T. Harif ◽  
M. Hai ◽  
A. Adin
Keyword(s):  
Membrane Fouling ◽  
Colloidal Suspension ◽  
Membrane Surface ◽  
Constant Current ◽  
Permeate Flux ◽  
Batch Mode ◽  
Membrane Behavior ◽  
Flux Decline ◽  
Stainless Steel Cathode ◽  
Marginal Improvement

Electroflocculation (EF) is a coagulation/flocculation process in which active coagulant species are generated in situ by electrolytic oxidation of an appropriate anode material. The effect of colloidal suspension pretreatment by EF on membrane fouling was measured by flux decline at constant pressure. An EF cell was operated in batch mode and comprised two flat sheet electrodes, an aluminium anode and stainless steel cathode, which were immersed in the treated suspension, and connected to an external DC power supply. The cell was run at constant current between 0.06–0.2A. The results show that pre-EF enhances the permeate flux at pH 5 and 6.5, but only marginal improvement is observed at pH 8. At all pH values cake formation on the membrane surface was observed. The differences in membrane behavior can be explained by conventional coagulation theory and transitions between aluminium mononuclear species which affect particle characteristics and consequently cake properties. At pH 6.5, where sweep floc mechanism dominates due to increased precipitation of aluminium hydroxide, increased flux rates were observed. It is evident that EF can serve as an efficient pretreatment to ultrafiltration of colloid particles.

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