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PubMed1999

Ultrafiltration of Micellar Solutions Containing Phenols.

Micellar-enhanced ultrafiltration represents a potentially attractive tool for the removal of different contaminants from wastewaters. The ultrafiltration of micellar solutions containing phenol or 4-nitrophenol was studied. Sodium dodecyl sulfate (SDS), hexadecyltrimethyl ammonium sulfate, alkyl polyglucoside Glucopon 215 SC UP, and oxyethylated methyl dodecanoates with the average degree of oxyethylation equal to 5 and 9 were used as surfactants and NaHCO(3) as an electrolyte and alkalizing agent. Filtration and phenol rejection depends on the presence of NaHCO(3) and the type of surfactant. NaHCO(3) depresses to the filtration rate, especially in the case of SDS and hydrophobic oxyethylated methyl dodecanoate. The highest filtration rates are obtained for hexadecyltrimethyl ammonium bromide (CTAB) and alkyl polyglucoside micellar solutions. The best separations, both of phenol and 4-nitrophenol (almost 100% rejection), are obtained for CTAB micellar solutions at the pH range from 3 to 11. Nonionic surfactants are not effective enough for the separation of phenol and 4-nitrophenol. SDS solutions permit only the separation of phenol. Copyright 1999 Academic Press.

Journal Article↗
PubMed2002

Comparison of polysulfone and ceramic membranes for the separation of phenol in micellar-enhanced ultrafiltration.

Micellar-enhanced ultrafiltration (MEUF) of phenol and a cationic surfactant, cetylpyridinium chloride (CPC), is studied using two polysulfone membranes of 5- and 50-kDa molecular weight cutoff (MWCO) and two ceramic membranes of 15- and 50-kDa MWCO. Filtrations are run under laminar cross-flow and steady-state conditions. The effect of operation variables (pressure and retentate flux) and membrane properties (nature and MWCO) on permeate flux, surfactant, and phenol rejections is analyzed. The permeate flux depends, among other variables, on the fouling favored by membrane-micelle interactions, which are strongest in the 50-kDa MWCO ceramic membrane. On the other hand, surfactant rejection is mainly determined by the pore size and influenced by the pressure for both 50-kDa MWCO membranes. An equilibrium distribution constant, K(s), of phenol between surfactant micelles and water is calculated. Its value is not significantly affected by operation conditions and membrane type. K(s) is also approximately 20% lower than the value determined in a previous work with batch dead-end ultrafiltration.

Journal Article↗
PubMed2002

Effects of modified ultrafiltration on coagulation factors in pediatric cardiac surgery.

PURPOSE: Modified ultrafiltration (MUF) after cardiopulmonary bypass (CPB) in children has been reported to reduce the need for postoperative blood transfusion and minimize postoperative blood loss. This study was undertaken to quantify the effects of MUF on coagulation factors in pediatric patients. METHODS: Seven children scheduled to undergo open-heart surgery for congenital heart defects were studied. CPB circuits were primed with crystalloid solutions and no blood transfusions were performed. Hematocrit, platelet count, total plasma proteins, albumin, fibrinogen, prothrombin, factor VII, factor IX, and factor X were measured preoperatively, at the termination of cardiopulmonary bypass, and at the end of modified ultrafiltration. RESULTS: MUF was associated with significant (P < 0.05) increases in hematocrit (17.6% +/- 1.6% to 21.6% +/- 2.4%), platelet count 11.1 +/- 2.5 to 12.8 +/- 2.4 x 10(4)/mm3), total plasma proteins (2.7 +/- 0.3 to 3.4 +/- 0.4 g/dl), and albumin (1.6 +/- 0.2 to 2.1 +/- 0.2 g/dl). Fibrinogen, prothrombin, and factor VII also increased significantly (P < 0.05) during MUF, but factor IX and factor X did not change. CONCLUSION: We conclude that MUF attenuates the dilutional coagulopathy that occurs during CPB in children. There were slight improvements in the coagulation factors when MUF was employed.

Blood Coagulation Factors↗
PubMed1994

Alternative method of ultrafiltration after cardiopulmonary bypass.

A revised circuit design for modified ultrafiltration is presented rendering the technique more convenient for use after cardiopulmonary bypass when blood cardioplegia is used. The procedure employs a hollow-fiber ultrafiltration device attached to the cardioplegia circuit. A bubble trap, heat exchanger, and a pressure monitor are incorporated as safety features. The technique has been used in 80 patients (30 pediatric and 50 adult) and has been associated with relevant increases in colloid osmotic pressure and hematocrit.

Adult↗
PubMed1993

Effects of growth hormone and IGF-I on glomerular ultrafiltration in growth hormone-deficient rats.

In growth hormone deficient states glomerular filtration rate (GFR) and renal plasma flow rate (RPF) are both reduced. Studies were performed in growth hormone deficient rats to delineate the physiologic mechanisms by which growth hormone and IGF-I contribute to the regulation of glomerular function. Growth hormone deficient dw/dw rats received, for one week, subcutaneous infusions of vehicle, des(1-3)IGF-I or were injected i.m. with recombinant human growth hormone. Subsequent renal micropuncture and clearance studies revealed a low GFR and single nephron GFR (SNGFR) in vehicle treated growth hormone deficient animals. Glomerular function became normal with growth hormone or IGF-I treatment, respectively. Both treatments raised SNGFR by reducing arteriolar resistance and increasing the glomerular ultrafiltration coefficient. Furthermore, the two treatments also increased the glomerular tuft volume and the kidney weight which may contribute to the rise in SNGFR and GFR. It is concluded that, (1) in growth hormone deficiency glomerular function is reduced secondary to a high renal arteriolar resistance and a low ultrafiltration coefficient. Both result from a lack in IGF-I rather than the growth hormone deficiency state per se. (2) The growth hormone-IGF-I axis may contribute to the maintenance and physiologic regulation of GFR.

Animals↗
PubMed1983

Plasma protein binding of sulphadiazine, sulphamethoxazole and trimethoprim determined by ultrafiltration.

The plasma protein binding of trimethoprim, sulphadiazine and sulphamethoxazole was studied at 37 degrees C by ultrafiltration. Plasma samples contained steady state levels of the drugs from ten volunteers from a cross-over comparative pharmacokinetic study on co-trimazine and co-trimoxazole. The three compounds were determined in plasma and ultrafiltrate by HPLC, the recoveries being close to 100% in each case. Freezing of spiked samples had no influence on the binding. Trimethoprim was 48.5-52.2% bound (mean 50.0%); sulphadiazine was 50.9-60.6% bound (mean 56.2%); and sulphamethoxazole was 74.3-80.8% bound (mean 76.9%). The significantly lower protein binding of sulphadiazine compared to sulphamethoxazole means that equivalent non-protein bound plasma levels of the two sulphonamides are achieved from smaller doses of co-trimazine than co-trimoxazole. Use of co-trimazine may thus minimize the risk of adverse reactions.

Journal Article↗
PubMed2006

Specific determination of intact cisplatin and monohydrated cisplatin in human plasma and culture medium ultrafiltrates using HPLC on-line with inductively coupled plasma mass spectrometry.

We have developed a specific assay for cisplatin in human plasma ultrafiltrate (PUF) and cell culture medium ultrafiltrate (MUF) using HPLC on-line with inductively coupled plasma mass spectrometry (ICP-MS). Separation of cisplatin (6 min) and monohydrated cisplatin (12 min) was achieved using a muBondapak C(18) column (Waters) and a mobile phase (0.075 mM sodium dodecyl sulfate and 3% methanol, adjusted to pH 2.5 with triflic acid) pumped at a flow rate of 0.5 mL/min. The analytes were detected with little background interference by ICP-MS monitoring of platinum masses (m/z 194/195). Calibration curves were linear over three orders of magnitude (0.05-8 microM) and the limit of quantitation was 0.1 microM. Intra- and inter-assay accuracy (range 91.6-113%) and precision (range 1.00-12.3%) were acceptable for PUF and MUF. The method was applied to determining cisplatin during ex vivo incubation of the drug in whole human blood at 37 degrees C. In conclusion, a specific, sensitive and reliable HPLC-ICP-MS assay has been established for determining intact cisplatin in PUF and MUF.

Calibration↗
PubMed2004

Resistance in series model for micellar enhanced ultrafiltration of eosin dye.

A study has been performed to quantify the extent of flux decline during micellar enhanced ultrafiltration (MEUF) of an acid dye (eosin red) using hexadecyl (cetyl) pyridinium chloride as the cationic surfactant. Effects of the operating conditions, e.g., transmembrane pressure drop and feed-surfactant-to-dye ratio, on the permeate flux profile and observed retention have been investigated in an unstirred batch ultrafiltration (UF) cell. A simple resistance-in-series model has been used to quantify the flux decline. From the flux decline history, it has been found that the membrane permeability decreases rapidly due to reversible pore blocking and further flux decline is caused by the growth of a gel-type layer over the membrane surface. The different resistances and growth kinetics of the gel layer have been investigated as functions of the operating conditions.

Journal Article↗
PubMed2004

Validation of cross-flow ultrafiltration for sampling of colloidal particles from aquatic systems.

The use of cross-flow ultrafiltration (CFF) for the isolation of colloids from the bulk aquatic matrices has been increasing over the last decade; however, a thorough validation of each CFF system is needed before its application to natural samples. Laboratory experiments have been conducted to validate a 1-kDa Millipore Pellicon 2 cartridge type CFF system, using a range of molecular probes spiked in natural waters. Using the separation data of these probes, key validation parameters have been calculated, including retention coefficient (RC), concentration factor (cf), colloid concentration, recovery, and mass balance. The permeation behaviour of these molecules has also been studied using a simple permeation model. Results show that good retention (>80%) of high molecular weight (HMW, >1 kDa) molecules and low retention (<20%) of low molecular weight (LMW, <1 kDa) molecules can be achieved at high cf values or over long timescales. In addition, permeation modelling and the calculation of colloid concentration demonstrate the same findings, again recommending high cf values or long timescales for ultrafiltration to minimise the retention of LMW molecules. The retention characteristics of 3-kDa dextran change slightly with salinity. Mass balance calculations show good recoveries for all of the molecules tested. The apparent membrane molecular cut-off of the CFF system has been estimated to be between 2.1 and 2.5 kDa, which is slightly greater than the manufacturer's nominal MW cut-off of 1 kDa.

Journal Article↗
PubMed2006

Interaction behavior in ultrafiltration of nonionic surfactant micelles by adsorption.

Adsorption of nonionic surfactant micelles onto ultrafiltration (UF), membranes was studied. Two homologous series of nonionic surfactants, namely, Tritons (alkylphenol ethoxylates) and Neodols (alcohol ethoxylates), were used to characterize surface properties of two polymeric ultrafiltration membranes with 20,000 nominal cutoff. Particularly, a cellulose acetate and a polysulfone membrane were investigated. Static adsorption experiments were carried out using surfactant solutions at concentrations above their critical micelle concentration. The characterization of surface properties of UF membranes was based on the adsorption behavior of surfactant species. The adsorption extent on UF membranes was affected by the hydrophobicity-to-hydrophilicity ratio mainly determining the interactions developed at the membrane-surfactant species interface. Adsorption experimental data seem generally to fit the Langmuir isotherm model. Atomic force microscopy was used to examine the alteration of the top membrane surface morphology.

Journal Article↗
PubMed2006

A concentration polarization model for the ultrafiltration of nonionic surfactants.

A theoretical model has been developed that describes ultrafiltration of nonionic surfactants. The model takes into account the fact that surfactants start to aggregate and form micelles at the critical micelle concentration. The model can be used to predict the performance of the membrane if the transport properties inside and at the membrane surface as well as the surfactant association behavior, are known. Three hydrophilic ultrafiltration membranes, made of regenerated cellulose, were used in the investigation. The cut-offs of the membranes were 10,000, 20,000, and 30,000 Da. The surfactant used in the investigation was the nonionic surfactant Triton X-100. The influence of the concentration of surfactant, transmembrane pressure and pure water flux were studied theoretically and experimentally. From the results presented in this work it can be concluded that the calculated values are in good agreement with experimental data.

Journal Article↗
PubMed2006

Self-generation of concentration gradients of divalent cations in commercial bentonite membrane during ultrafiltration.

Research workers, working with commercial bentonite-based membranes, reported different diffusivity for co- and counterions through those membranes. Many of these researchers called this difference in diffusivity ultrafiltration. Some of these workers also noted that commercial bentonite membranes often contain divalent metal carbonates as impurities. Recently it has been suggested that the ultrafiltration is associated with the co-diffusion of divalent metal ions. Previous workers did not recognize this co-diffusion, probably due to an absence of imposed concentration gradient for the divalent metal ions. The present investigation suggests that the required concentration gradient is self-generated by increased solubility of the divalent metal carbonates with increasing concentration of alkali halide in solution. The presence of dissolved divalent metal ions alters the interfacial potentials at the outside solution and bentonite membrane junctions and reduces the electrostatic potential gradient across the membrane. A reduction in the electrostatic potential gradient across the membrane reduces the coupling between the diffusing co- and counterions and alters their diffusivity.

Letter↗
PubMed2004

Treatment of silica effluents: ultrafiltration or coagulation-decantation.

In the electronics industry, the preparation of silicon plates generates effluents that contain a great amount of colloidal silica. Two processes--decantation and ultrafiltration--are studied with in view the treatment of the effluents released by the firm Rockwood Electronic Materials. The feasibility of each of the two processes is studied separately and their operating parameters optimized. Both processes allow the recovery of a great proportion of the initial effluent (over 89%) as transparent and colorless water that can be reused at the start of a line. In view of the results and of the compared advantages and disadvantages of the two processes, ultrafiltration will be selected for the industrial unit.

Colloids↗
PubMed2004

The effect of pretreatment to ultrafiltration of biologically treated sewage effluent: a detailed effluent organic matter (EfOM) characterization.

Ultrafiltration alone can remove only a portion of the effluent organic matter (EfOM) from biologically treated sewage effluent (BTSE). Use of pretreatment not only improves the EfOM removal but also reduces the membrane fouling. In this research, NTR 7410 ultrafiltration membrane was employed to remove EfOM from BTSE. Different pretreatments namely FeCl(3) flocculation and powder activated carbon adsorption were evaluated. The highest removal of organic matter was observed when flocculation followed by adsorption was used as pretreatment. The flocculation and adsorption removed 68.5% and 71.4% of hydrophobic organics, respectively. The molecular weight (MW) of the EfOM in BTSE ranged from 300 to about 400000 Da. After the flocculation pretreatment, the majority of large MW organic matter was removed. The pretreatment of the flocculation followed by adsorption led to very high removal of both small and large organic matter. Further, this pretreatment led to practically no filtration flux decline.

Filtration↗
PubMed1999

Effect of modified ultrafiltration on plasma thromboxane B2, leukotriene B4, and endothelin-1 in infants undergoing cardiopulmonary bypass.

BACKGROUND: Plasma thromboxane B2 (TXB2), leukotriene B4 (LTB4), and endothelin-1 (ET-1) levels increase on cardiopulmonary bypass (CPB). Elevated levels of TXB2 and ET-1 have been correlated with postoperative pulmonary hypertension in infants undergoing repair of congenital heart defects. LTB4 is a potent chemotactic cytokine whose levels correlate with leukocyte-mediated injury. Modified ultrafiltration (MUF) has been associated with improved hemodynamics and pulmonary function, in addition to its beneficial effects on fluid balance and blood conservation. Recent investigations have suggested that removal of cytokines may be the cause of the improved cardiopulmonary function seen with MUF. METHODS: Plasma TXB2, ET-1, and LTB4 levels were measured in 34 infants undergoing CPB: 22 underwent MUF (group 1), and 12 did not (group 2). Samples were obtained at various time points. All patients underwent conventional ultrafiltration during the rewarming phase of cardiopulmonary bypass. RESULTS: In group 1, mean end-CPB TXB2 level was 101.2 pg/mL versus 46.9 pg/mL post-MUF (p < 0.05). The mean TXB2 level 1 hour post-CPB (54.1 pg/mL) was not significantly different from the post-MUF level. In group 2, the mean end-CPB TXB2 level was 123.6 pg/mL versus 53.2 pg/mL 1 hour post-CPB. Hence, TXB2 levels decreased by similar amounts and to similar levels by 1 hour post-CPB in both groups. ET-1 levels increased after CPB and were unaffected by MUF: 1.45, 1.80, 2.55 pg/mL at end-CPB, post-MUF, and 1 hour post-CPB, respectively, in group 1; and 1.51, and 2.73 pg/mL at end-CPB and 1 hour post-CPB in group 2. LTB4 levels post-MUF were 119% of pre-MUF values, and were similar at 1 hour post-CPB in both groups. CONCLUSIONS: Despite reduction in TXB2 by MUF, values were similar and approached baseline 1 hour post-CPB in both groups. LTB4 levels increased slightly with MUF. ET-1 levels increased during and post-CPB and were unaffected by MUF. MUF does not appear to have a significant effect on post-CPB levels of TXB2, ET-1, and LTB4. Therefore, the improved hemodynamics observed with MUF do not appear to be related to removal of these cytokines.

Cardiopulmonary Bypass↗
PubMed2003

Use of surfactant modified ultrafiltration for perchlorate (Cl(O)(4-)) removal.

Determinations of perchlorate anion (ClO(4)(-)) transport and rejection were performed using a surfactant modified ultrafiltration (UF) membrane. Perchlorate anion (at a concentration of 100 microg/L of ClO(4)(-), spiked with KClO(4)) was introduced to the membrane as a pure component, in binary mixtures with other salts, cationic and anionic surfactants, and at various ionic strength conditions (conductivity). Also, a natural source water was spiked with perchlorate in the presence of cationic and anionic surfactants and used to determine the effects of a complex mixture (including natural organic matter (NOM)) on the observed rejection. All filtration measurements were performed at approximately the same permeate flow rate in order to minimize artifacts from mass transfer at the membrane interface. The objective of this study was to modify a negatively charged UF membrane in terms of the fundamental mechanisms, steric/size exclusion and electrostatic exclusion and to enhance perchlorate rejection, with synthetic water and a blend of Colorado River water and State Project water (CRW/SPW). Previous work suggested that perchlorate was dominantly rejected by electrostatic exclusion for charged nanofiltration (NF) and UF membranes (Rejection of perchlorate by reverse osmosis, nanofiltration and ultrafiltration (UF) membranes: mechanism and modeling. Ph.D. dissertation, University of Colorado, Boulder, USA, 2001). In that research, perchlorate rejection capability was quickly lost in the presence of a sufficient amount of other ions. However, this study showed that ClO(4)(-) was excluded from a (negatively) charged UF membrane with pores large with respect to the size of the ion. Although perchlorate rejection capability due to apparent electrostatic force was reduced in the presence of a cationic surfactant, a desired amount of the ClO(4)(-) was excluded by steric exclusion. The steric exclusion was due to decreasing membrane pore size caused by the adsorption of the cationic surfactant.

Filtration↗
PubMed2000

Hydrolysis and large scale ultrafiltration study of alfalfa protein concentrate enzymatic hydrolysate.

Batch enzymatic hydrolysis of insoluble Alfalfa Protein Concentrate by Delvolase was carried out at laboratory and at pilot-plant scale coupled to an ultrafiltration reactor with a mineral tubular membrane. Parametric studies were carried out on the batch system to determine the biochemical and hydrodynamical optimum conditions. The hydrolysis conditions selected were 40 degrees C, pH 9.5, initial substrate level 3 g protein/100 g and the enzyme substrate ratio 152 U/g protein. After 5 h of hydrolysis, 96% of the total amount of initial nitrogen was solubilized. The ultrafiltration conditions selected were a 10 000 Nominal Molecular Weight Cut-Off, a transmembrane pressure of 1.5 bar, a flux velocity of 0.8 m/s. Fifty percent of the initial nitrogen appeared in the permeate.

Journal Article↗
PubMed1997

Comparison of the effects of red cell separation and ultrafiltration on heparin concentration during pediatric cardiac surgery.

OBJECTIVE: To determine the effects of red cell separation and ultrafiltration on heparin concentration. DESIGN: Prospective study. SETTING: University-affiliated, pediatric medical center. PARTICIPANTS: Thirty-one children undergoing cardiac surgery. INTERVENTIONS: Blood sampled for heparin concentration and coagulation tests. MEASUREMENTS AND MAIN RESULTS: Thirteen infants under-went modified veno-venous ultrafiltration (UF) after cardiopulmonary bypass (CPB). In addition, residual blood in the CPB circuit was hemoconcentrated by UF and reinfused (UF group). Heparin concentration increased from 2.0 +/- 0.6 to 2.5 +/- 0.8 U/mL, following modified UF; while activated coagulation time (ACT) decreased from 701 +/- 177 to 627 +/- 107 seconds. Heparin concentration of CPB circuit residual increased from 1.9 +/- 0.7 to 3.1 +/- 1.0 U/mL. In 18 children (older than 1 year old), the residual blood in the CPB circuit was hemoconcentrated by cell separation (CS) and reinfused (CS group). Heparin concentration of CPB circuit residual decreased from 2.6 +/- 0.6 to 0.3 +/- 0.2 U/mL. After reinfusion, patient heparin concentration remained unchanged at < 0.05 U/mL. Thrombin time increased from 28 +/- 6 to 48 +/- 29 seconds and did not correlate with H. CONCLUSIONS: The plasma concentration of heparin increased after veno-venous modified UF of the patient. Heparin concentration also increased after UF of residual CPB circuit blood. In contrast, circuit blood hemoconcentrated by CS contained minimal heparin, and, when infused, did not increase patient's heparin concentration. ACT and thrombin time did not correlate with heparin concentration.

Blood Transfusion↗