Asymmetric Triacetate Membrane Research Articles

Efficacy of polymethylmethacrylate membrane hemodiafilter Filtryzer® PMF™-21A in improving pruritus in hemodialysis patients: a prospective interventional study

BackgroundHemodialysis-associated pruritus (HAP) occurs in 60–80% of hemodialysis patients. This significant complication not only decreases quality of life through sleep disturbance and depression, but also leads to poor survival outcomes. The polymethylmethacrylate (PMMA) membrane was the first synthetic polymer membrane for the hollow-fiber artificial kidney created in 1977. PMMA membrane dialyzers have been reported to be effective for improving various complaints, including pruritus, and nutritional status. In Japan, a PMMA membrane hemodiafilter Filtryzer® PMF™-A (PMF-A) was launched in November 2021 and subsequently became available for online hemodiafiltration (OHDF). This study aimed to determine whether PMF-A effectively improves pruritus in hemodialysis patients.MethodsParticipants were 20 patients (median age 74.5 years) on predilution OHDF (pre-OHDF) or postdilution OHDF (post-OHDF) using an Asymmetric Triacetate Membrane® hemodiafilter (FIX-210E eco or FIX-210S eco), who were experiencing pruritus of “very mild” or higher severity based on the Shiratori severity score either during the daytime or nighttime. After switching to post-OHDF with PMF-21A (substitution flow rate: 10 L/session), the substitution flow rate was gradually increased according to results of pruritus evaluation every 2 weeks over 3 months. The primary endpoint was the severity of pruritus evaluated using visual analogue scale (VAS) and the Shiratori severity score. Secondary endpoints included white blood cell count (WBC), hemoglobin level (Hb), platelet count (Plt), serum albumin level (Alb), high-sensitivity C-reactive protein (hsCRP), IL-6, dry weight (DW), and solute removal performance.ResultsThe median VAS score was significantly decreased 2 weeks after switching compared with baseline (44 mm) and remained significantly decreased at Week 12 (22 mm; p < 0.01). From baseline to Week 12, 16 patients (80%) showed improvement in VAS score. The percentage of patients with mild to moderate daytime pruritus according to the Shiratori severity score decreased significantly from 80.0% to 45.0% (p < 0.05), whereas no significant change was observed for nighttime pruritus (p = 0.267). Pre-dialysis serum β2-MG levels were significantly higher at Week 12 compared with baseline. No significant changes were observed in WBC, Hb, Plt, serum Alb, hsCRP, IL-6, or DW.ConclusionsOHDF with PMF-21A may be more effective in improving HAP.

Anti-Inflammatory Approach in Chronic Dialysis Patients with SARS-CoV-2: ATA or PMMA Dialyzers?

Introduction: High-flux hemodialysis membranes may modulate the cytokine storm of SARS-CoV-2, but their impact on chronic hemodialysis (CHD) patients is unknown. The aim of the study was the evaluation of asymmetric cellulose triacetate (ATA) and polymethylmethacrylate (PMMA) dialyzers on inflammatory markers and clinical outcomes in CHD patients with SARS-CoV-2. Methods: A prospective, observational study on CHD patients with SARS-CoV-2 was carried out. Patients were enrolled from March 2020 to May 2021. Pre- and postdialysis C-reactive protein (CRP), procalcitonin (PCT), and interleukin-6 (IL-6) were determined at each session. Patients who underwent on-line hemodiafiltration (OLHDF) with a PMMA dialyzer were compared with those treated with OLHDF with a ATA dialyzer. The primary endpoint was the differences in the reduction ratio per session (RR) of CRP, PCT, IL-6, and IL-6 RR >25%. Results: We consecutively enrolled 74 CHD patients with COVID-19, 48 were treated with ATA membrane, and 26 with PMMA. Median IL-6 RR was higher in the ATA group compared to PMMA (17.08%, IQR −9.0 to 40.0 vs. 2.95%, IQR −34.63 to 27.32). Median CRP RR was 7.77% (IQR 2.47–13.77) in the ATA group versus 4.8% (IQR −2.65 to 11.38) in the PMMA group (p = 0.0017). Median PCT-RR% was 77.38% (IQR 70.92–82.97) in ATA group versus 54.59% (IQR 42.62–63.16) in the PMMA group (p < 0.0001). A multiple logistic regression analysis with IL-6 RR >25% as the outcome including the membrane employed, pre-dialysis IL-6, CRP, PCT, and ferritin showed that ATA led to a higher probability to reach the outcome (OR 1.891, 95% CI 1.273–2.840, p = 0.0018) while higher CRP favors the risk of lower IL-6 RR values (OR 0.910, 95% CI 0.868–0.949, p ≤ 0.0001). Conclusions: In SARS-CoV-2 CHD patients treated with OLHDF, ATA showed a better anti-inflammatory profile, regarding IL-6 RR, compared to PMMA.

Halving Sodium Heparin While Maintaining Dialytic Clearances During Hemodiafiltration With an Asymmetric Cellulose Triacetate Membrane

Halving Sodium Heparin While Maintaining Dialytic Clearances During Hemodiafiltration With an Asymmetric Cellulose Triacetate Membrane

Antibiotics Removal by Continuous Venovenous Hemofiltration with a Novel Asymmetric Triacetate Membrane Hemofilter: An in vitro Study

Introduction: Continuous renal replacement therapies (CRRTs) are essential in the treatment of critically ill patients with acute kidney injury and are also discussed as a supporting sepsis therapy. CRRT can affect antibiotics plasma concentrations. Objective: The effect of continuous venovenous hemofiltration (CVVH) with an asymmetric triacetate (ATA) membrane hemofilter on concentrations of antibiotics with low (meropenem), medium (vancomycin), and high (daptomycin) protein binding (PB) was investigated. Methods: 1 L human whole blood supplemented with antibiotics was recirculated and filtrated for 6 h in vitro. Clearances and sieving coefficients (SC) were determined from antibiotics concentrations measured at filter inlet, outlet, and filtrate side. Reservoir concentration data were fitted using a first-order kinetic model. Results: Meropenem and vancomycin concentrations decreased to 5–10% of the initial plasma level, while only 50% of daptomycin were removed. Clearances and SCs were (10.8 [10.8–17.4] mL/min, SC = 0.72 [0.72–1.16]) for meropenem, (13.4 [12.3–13.7] mL/min, 0.89 [0.82–0.92]) for vancomycin, and (2.1 [1.8–2.1] mL/min, 0.14 [0.12–0.14]) for daptomycin. Removal by adsorption was negligible. Conclusions: The clearances and SCs presented are comparable with findings of other authors. Meropenem and vancomycin, which exhibit low and medium PB, respectively, were strongly removed, while considerably less daptomycin was removed because of its high PB. Our results suggest that in clinical use of the tested antibiotics during CRRT with the ATA hemofilter, the same factors have to be considered for determining the dosing strategy as with filters with other commonly applied membrane materials.

Insights into the Influence of Membrane Permeability and Structure on Osmotically-Driven Membrane Processes.

The success of osmotically-driven membrane (OM) technology relies critically on high-performance membranes. Yet trade-off of membrane properties, often further complicated by the strongly non-linear dependence of OM performance on them, imposes important constraint on membrane performance. This work systematically characterized four typical commercial osmotic membranes in terms of intrinsic separation parameters, structure and surface properties. The osmotic separation performance and membrane scaling behavior of these membranes were evaluated to elucidate the interrelationship of these properties. Experimental results revealed that membranes with smaller structural parameter (S) and higher water/solute selectivity underwent lower internal concentration polarization (ICP) and exhibited higher forward osmosis (FO) efficiency (i.e., higher ratio of experimental water flux over theoretical water flux). Under the condition with low ICP, membrane water permeability (A) had dominant effect on water flux. In this case, the investigated thin film composite membrane (TFC, A = 2.56 L/(m2 h bar), S = 1.14 mm) achieved a water flux up to 82% higher than that of the asymmetric cellulose triacetate membrane (CTA-W(P), A = 1.06 L/(m2 h bar), S = 0.73 mm). In contrast, water flux became less dependent on the A value but was affected more by membrane structure under the condition with severe ICP, and the membrane exhibited lower FO efficiency. The ratio of water flux (Jv TFC/Jv CTA-W(P)) decreased to 0.55 when 0.5 M NaCl feed solution and 2 M NaCl draw solution were used. A framework was proposed to evaluate the governing factors under different conditions and to provide insights into the membrane optimization for targeted OM applications.

Evaluation of the pressure variation and lifetime of a newly developed asymmetric triacetate membrane hemofilter

Evaluation of the pressure variation and lifetime of a newly developed asymmetric triacetate membrane hemofilter

How biocompatible haemodialysers can conquer the need for systemic anticoagulation even in post-dilution haemodiafiltration: a cross-over study.

BackgroundWhile systemic anticoagulation is most widely used in haemodialysis (HD), contraindications to its use might occur in particular settings. The Solacea™ haemodialyser with an asymmetric triacetate membrane claims improved biocompatibility and has already shown promising results when used in combination with only half dose of anticoagulation. To quantify the performance of the Solacea™ when further decreasing anticoagulation to zero, fibre blocking was assessed by micro-computed tomography (micro-CT).MethodsTen maintenance HD patients underwent six dialysis sessions at midweek using a Solacea™ 19H dialyser, consecutively in pre-dilution haemodiafiltration (pre-HDF), HD and post-dilution HDF (post-HDF). After the first three sessions with only a quarter of their regular anticoagulation dose (one-quarter), the last three sessions were performed without anticoagulation (zero). Dialyser fibre blocking was quantified in the dialyser outlet potting using a 3D micro-CT scanning technique post-dialysis.ResultsEven in case of reduced (one-quarter) anticoagulation, the relative number of open fibres post-dialysis was almost optimal, i.e. 0.96 (0.87–0.99) with pre-HDF, 0.99 (0.97–0.99) with HD and 0.97 (0.92–0.99) with post-HDF. Fibre patency was mildly decreased for pre-HDF and HD when anticoagulation was decreased from one-quarter to zero, i.e. to 0.76 (0.61–0.85) with pre-HDF (P = 0.004) and to 0.80 (0.77–0.89) with HD (P = 0.013). Comparing the results for zero anticoagulation, post-HDF [i.e. 0.94 (0.82–0.97)] performed as well as HD and pre-HDF.ConclusionsThe Solacea™ dialyser provides promising results for use in conditions where systemic anticoagulation is contraindicated. Post-HDF, although inducing haemoconcentration in the dialyser, is equally effective for fibre patency in case of zero anticoagulation as pre-HDF and HD when using Solacea™.

Strategies for asymmetrical triacetate dialyser heparin-free effective haemodialysis: the SAFE study.

BackgroundIn haemodialysis, maintaining patency of the extracorporeal circuit requires the use of anticoagulants. Although (low molecular weight) heparins are the mainstay, these are not well tolerated in all patients. Alternative approaches include saline infusion, citrate-containing dialysate, regional citrate anticoagulation or the use of heparin-coated membranes. Asymmetric cellulose triacetate (ATA) dialysers have a low degree of platelet contact activation and might be an alternative to heparin-coated dialysers. The aim of this study was to test the clotting propensity of ATA when used without systemic anticoagulation.MethodsWe performed a Phase II pilot study in maintenance dialysis patients. The ‘Strategies for Asymmetrical Triacetate dialyzer heparin-Free Effective hemodialysis’ (SAFE) study was a two-arm open-label crossover study. In Arm A, patients were dialysed using 1.9 m2 ATA membranes in combination with a citrate-containing dialysate (1 mM). In Arm B, the ATA membrane was combined with high-volume predilution haemodiafiltration (HDF) without any other anticoagulation. The primary endpoint was the success rate to complete 4 h of haemodialysis without preterm clotting. Secondary endpoints included time to clotting and measures of dialysis adequacy.ResultsWe scheduled 240 dialysis sessions (120/arm) in 20 patients. Patients were randomized 1:1 to start with Arm A or B. All patients crossed to the other arm halfway through the study. A total of 232 (96.7%) study treatments were delivered. Overall, 23 clotting events occurred, 7 in Arm A and 16 in Arm B. The success rate in Arm A (ATA + citrate-containing dialysate) was 90.8/94.0% [intention to treat (ITT)/as treated]. The success rate in Arm B (ATA + predilution HDF) was 83.3/86.2% (ITT/as treated). Time to clotting was borderline significantly better in Arm A (Mantel-Cox log rank P = 0.05).ConclusionATA dialysers have a low clotting propensity and both predilution HDF and a citrate-containing dialysate resulted in high rates of completed dialysis sessions.

P1064HEPARIN-FREE DIALYSIS: A PHASE II PILOT STUDY USING ASYMMETRIC TRIACETATE (ATA) CELLULOSE DIALYZERS

Abstract Background and Aims Not all dialysis patients tolerate heparin anticoagulation. Heparin should be avoided in patients at high risk of bleeding. Strategies include saline infusion, citrate-containing dialysate, regional citrate anticoagulation and heparin-coated membranes. We recently studied the combination of a heparin-coated membrane and citrate-containing dialysate, with a success rate of 94% . Although this combination resulted in low rates of clotting, heparin-coated membranes are not ubiquitously available. The quest for easy to perform, safe and affordable heparin-free dialysis is on. Asymmetric cellulose triacetate (ATA) dialyzers have a low degree of platelet contact activation and might be an alternative to heparin-coated dialyzers. Method We performed a phase II pilot study in maintenance dialysis patients. The ‘Strategies for Asymmetrical Triacetate dialyzer heparin-Free Effective hemodialysis (SAFE study)’ was a two-arm open-label cross-over study. In Arm 1, patients were dialyzed using a 1.9 m2 ATA membrane (Solacea™-19H, Nipro Corp., Japan) in combination with citrate (1 mM) containing dialysate. In Arm 2, patients were dialyzed with the same 1.9 m2 ATA membrane, in combination with high volume predilution hemodiafiltration. The primary endpoint was the success rate to complete 4 hours of hemodialysis without preterm clotting. Results We scheduled 240 dialysis sessions (120 per arm) in twenty patients. Ten patients were randomized to start in Arm 1, the others to Arm 2. All patients crossed to the other arm halfway the study. 232 (96.7%) study treatments were delivered. Overall, 23 clotting events occurred, 7 in Arm 1 and 16 in Arm 2. Success rate in Arm 1 (ATA + citrate containing dialysate) was 90.8 / 94.0 % (intention to treat/ as treated). Success rate in Arm 2 (ATA + predilution HDF) was 83.3 / 86.2 % (intention to treat/ as treated). Therapy survival was borderline significantly better in Arm 1(Mantel-Cox log rank P = 0.05). Conclusion Asymmetric cellulose triacetate (ATA) dialyzers have a low clotting propensity. In combination with citrate-containing dialysate, asymmetric cellulose triacetate (ATA) may be a suitable alternative to heparin-coated membranes for systemic heparin-free hemodialysis.

P1058COMPARISON OF THE REMOVAL EFFICIENCY AND THE BIOCOPATIBILITY BETWEEN PRE- AND POST-DILUTION ON-LINE HEMODIAFILTRATION

Abstract Background and Aims On-line HDF (OL-HDF) performed in Japan is characterized by the fact that pre-dilution OL-HDF (pre-HDF) accounts for 95% of the cases. In Europe, post-dilution OL-HDF (post-HDF) is the mainstream mode, and particularly high-volume post-HDF is reportedly associated with a favorable prognosis in patients. Last year, we reported favorable biocompatibility and removal efficiency of low-volume post-HDF using high-performance hemodiafilters. Here, we performed pre-HDF and post-HDF for 4 weeks each under the same conditions in the previous study and compared the removal efficiency and the biocompatibility. Method Nine stable dialysis patients who had received pre-HDF for at least 6 months (age, 60.8±15.4 years; dry weight, 54.5±9.5 kg) were included in this study. Fineflux-210 Seco (asymmetric triacetate membrane, NIPRO) was used as a hemodiafilter. Post-HDF (replacement fluid rate, 12 L/session) was performed in the first session and pre-HDF (replacement fluid rate, 60 L/session) in the second, each lasting 4 weeks. Each study parameter was evaluated on the last day of each session. In either session, HDF was performed at a blood flow rate of 250 mL/min and a total dialysate flow rate of 500 mL/min. Each HDF cycle lasted 4 h. The removal efficiency was evaluated in terms of Kt/V, as well as the removal rates and removal volumes of urea, creatinine, β2-microglobulin (MG), and α1-MG. Biocompatibility was evaluated in terms of the rates of changes in the levels of CRP, interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), pentraxin-3 (PTX3), and intercellular adhesion molecule-1 (ICAM-1) before and after dialysis. Changes in the levels of CD62P during dialysis were also examined. Paired t-test was used for statistical analysis. Results Removal efficiency results: The removal efficiency for small molecular weight solutes was significantly higher in post-HDF. The removal rate (%) and removal volume (g/session) of β2-MG were 81.4±3.6 and 0.224±0.051 in post-HDF and 80.7±3.3 and 0.218±0.029 in pre-HDF, respectively. The removal rate (%) and removal volume (g/session) of α1-MG were 37.0±4.0 and 0.151±0.024 in post-HDF and 33.3±4.1 and 0.133±0.026 in pre-HDF, respectively. The amount of albumin leakage (g/session) was 3.7±0.6 in post-HDF and 3.1±0.7 in pre-HDF, indicating a significant difference. Biocompatibility results: There were no significant differences between the two modes in the rates of changes in the levels of CRP, PTX3, IL-6, TNF-α, or ICAM-1 before and after treatment. The rate of expression of CD62P was also not significantly different. Conclusion Under the present conditions using high-performance filters, post-HDF and pre-HDF demonstrated favorable removal efficiency for both small and large molecular weight solutes, and the biocompatibility was also favorable, indicating no significant differences between the two modes.

A randomized cross-over study with objective quantification of the performance of an asymmetric triacetate and a polysulfone dialysis membrane using different anticoagulation strategies.

BackgroundDifferent strategies can be used to counteract coagulation of extracorporeal systems. Systemic anticoagulation is most widely used in routine clinical practice, but can be contraindicated in specific settings. The Solacea™ dialyser, containing the asymmetric triacetate membrane, claims improved biocompatibility, which should result in decreased tendency for coagulation. We quantified the performance of the Solacea™ versus the FX800CORDIAX dialyser regarding resistance to fibre blocking as assessed by micro-computed tomography (CT).MethodsThis cross-over study with four arms randomized consecutively 10 maintenance haemodialysis patients to a 4-h post-dilution haemodiafiltration session at midweek, using either Solacea™ 19 H or FX800CORDIAX, with either regular or half dose of anticoagulation (EC2017/1459-NCT03820401). Dialyser fibre blocking was visualized in the dialyser outlet potting using a 3D CT scanning technique on micrometre resolution. Extraction ratios of middle molecules [myoglobin, lambda and kappa free light chains (FLCs)] were determined.ResultsThe relative number of open fibres post-dialysis was lower in FX800CORDIAX versus Solacea™ dialyser, and this was irrespective of the anticoagulation dose used or the threshold for counting open fibres. Extraction ratios of FLCs were not different at regular anticoagulation between Solacea™ and FX800CORDIAX (21% ± 4% for kappa and 32% ± 8% for lambda with Solacea™ versus 23% ± 7% and 38% ± 6% for FX800CORDIAX), but were superior with the Solacea™ (34% ± 12% versus 22% ± 8% with FX800CORDIAX; P = 0.02) for myoglobin in case of halving anticoagulation dose. No clinically relevant albumin loss was detected.ConclusionsThe Solacea™ dialyser seems to be promising for use in conditions where systemic anticoagulation is contraindicated, as even under conditions of low systemic anticoagulation, virtually no signs of fibre blocking could be observed using the sensitive micro-CT scanning technique. This finding is in line with its presumed good performance in terms of biocompatibility.

Multipotentials of new asymmetric cellulose triacetate membrane for on-line hemodiafiltration both in postdilution and predilution

BackgroundOn-line hemodiafiltration (OL-HDF) has been generally provided mainly by the postdilution method in Europe and the rest of the world; however, in Japan, it has been provided mostly by the predilution method in order to ameliorate dialysis-related symptoms of dialysis patients by removing larger low molecular weight proteins. This study aimed to elucidate the removal properties of a newly launched asymmetric triacetate (ATA) membrane in OL-HDF both in the postdilution and predilution comparison with other synthetic polymer membranes.MethodsSix patients treated by OL-HDF at the Kawashima Hospital Group were randomly chosen for each membrane study. The removal properties of low molecular weight proteins were evaluated by β2-microglobulin (β2-MG), α1-microglobulin (α1-MG), albumin leakage, selective removal index of α1-MG for albumin, and transmembrane pressure for each treatment group. Two types of ATA membrane were evaluated in the study: FIX-S with mild protein permeability and FIX-U with higher protein permeability in the comparisons with other three types of synthetic polymer membranes.ResultsThe removal rate of β2-MG showed almost no significant differences between the postdilution and predilution methods in most membrane groups at around 75–80% without relations to the membrane material and the substitution volume.The removal rates of α1-MG were markedly different depending on the dilution method of HDF, the membranes, and the substitution volume. Generally, the removal rates of α1-MG were better in the postdilution than the predilution but the selective removals of α1-MG were better in the predilution. The high volume OL-HDF had the risk of excessive albumin leakage in a certain membrane choice.In the FIX series, the removal rates of α1-MG were sufficient both in the postdilution and predilution with the increase of the substitution volume with suppressing the albumin leakage during the dialysis session. Especially, FIX-U showed higher removal of α1-MG with suppressing the albumin leakage.ConclusionsThe newly launched ATA membrane could remove α1-MG, selectively suppressing the excessive albumin leakage and increasing the substitution volume safely even in high-volume postdilution.Trial registrationTrial registration: University hospital Medical Information Network (UMIN), UMIN 000035705. Registered 28 January 2019 - Retrospectively registered, https://www.umin.ac.jp/ctr/index-j.htm.

Thrombogenicity and long-term cytokine removal capability of a novel asymmetric triacetate membrane hemofilter

Hemofilters applied in continuous renal replacement therapies (CRRTs) for the treatment of acute kidney injury must meet high standards in biocompatibility and permeability for middle and large molecules over extended treatment times. In general, cellulose-based membranes exhibit good biocompatibility and low fouling, and thus appear to be beneficial for CRRT. In this in vitro study, we compared a novel asymmetric cellulose triacetate (ATA) membrane with three synthetic membranes [polysulfone (PS), polyethersulfone (PES), and polyethylenimine-treated acrylonitrile/sodium methallyl sulfonate copolymer (AN69 ST)] regarding thrombogenicity and cytokine removal. For thrombogenicity assessment, we analyzed the thrombin-antithrombin complex (TAT) generation in human whole blood during 5h recirculation and filtration. Sieving coefficients of interleukin-6 (IL-6), IL-8, IL-10, and tumor necrosis factor-alpha (TNF-α) were determined using human plasma as test fluid. ATA and AN69 ST membrane permeability were determined also during long-term experiments (48.5h). ATA exhibited the lowest TAT generation (6.3µg/L at 5h), while AN69 ST induced a pronounced concentration increase (152.1µg/L) and filter clogging during 4 out of 5 experiments. ATA (IL-8: 1.053; IL-6: 1.079; IL-10: 0.898; TNF-α: 0.493) and PES (0.973; 0.846; 0.468; 0.303) had the highest sieving coefficients, while PS (0.697; 0.100; 0.014; 0.012) and AN69 ST (N/A; 0.717; 0; 0.063) exhibited lower permeability. Long-term experiments revealed stronger fouling of the AN69 ST compared to the ATA membrane. We observed the highest permeability for the tested cytokines, the lowest thrombogenicity, and the lowest fouling with the ATA membrane. In CRRT, these factors may lead to increased therapy efficacy and lower incidence of coagulation-associated events.

Proteomic Characterization of a New asymmetric Cellulose Triacetate Membrane for Hemodialysis.

The artificial membrane inside the haemodialyzer is the main determinant of the quality and success of haemodialysis therapy. The performances of haemodialysis membranes are highly influenced by the interactions with plasma proteins, which in turn are related to the physical and chemical characteristics of the membrane material. The present cross-over study is aimed to analyse the haemodialysis performance of a newly developed asymmetric cellulose triacetate membrane (ATA) in comparison to the conventional parent symmetric polymer (CTA). In four chronic non diabetic haemodialysis patients, the protein constituents of the adsorbed material from the filters after the haemodialysis session, and the proteins recovered in the ultrafiltrate during the session, are identified using a bottom-up shotgun proteomics approach. The ATA membrane shows a lower protein adsorption rate and a lower mass distribution pattern of the proteinaceous material. By highlighting the differences between the two haemodialysis filters in terms of adsorbed proteins and flow through, it is demonstrated the higher biocompatibility of the novel ATA membrane, that fulfils the indications for the development of more performant membranes and may represent a step forward for the treatment of patients on chronic haemodialysis.

Evaluation of blood adsorption onto dialysis membranes by time-of-flight secondary ion mass spectrometry and near-field infrared microscopy.

Blood adsorption onto the inside surface of hollow fiber dialysis membranes was investigated by means of time-of-flight secondary ion mass spectrometry (TOF-SIMS) and near-field infrared microscopy (NFIR) in order to evaluate the biocompatibility and permeability of dialysis membranes. TOF-SIMS is useful for the imaging of particular molecules with a high spatial resolution of approximately 100nm. In contrast, infrared spectra provide quantitative information and NFIR enables analysis with a high spatial resolution of less than 1μm, which is close to the resolution of TOF-SIMS. A comparison was made of one of the most widely used dialysis membranes made of polysulfone (PSf), that has an asymmetric and inhomogeneous pore structure, and a newly developed asymmetric cellulose triacetate (ATA) membrane that also has an asymmetric pore structure, even though the conventional cellulose triacetate membrane has a symmetric and homogeneous pore structure. As a result, it was demonstrated that blood adsorption on the inside surface of the ATA membrane is more reduced than that on the PSf membrane. Graphical abstract Analysis of blood adsorption on inside surface of hollow fiber membrane.

Fundamental Characteristics of the Newly Developed ATA™ Membrane Dialyzer.

Dialysis membranes are often made from synthetic polymers, such as polysulfone. However, membranes made from cellulose triacetate have superior biocompatibility and have been used since the 1980s. On-line hemodiafiltration treatment accompanied by massive fluid replacement is increasingly being used in Europe and Japan, but cellulose triacetate is not suitable for this treatment. Our newly developed asymmetric triacetate membrane, the ATA™ membrane, substantially improved the filtration properties and blood compatibility because of the asymmetric structure and smooth surface of this cellulose acetate membrane. Key Message: The ATA membrane maintains its high permeability even after massive filtration and shows less temporal variation in its permeation performance, lower protein adsorption, and superior biocompatibility compared with conventional membranes.

Power generation with pressure retarded osmosis: An experimental and theoretical investigation

Pressure retarded osmosis (PRO) was investigated as a viable source of renewable energy. In PRO, water from a low salinity feed solution permeates through a membrane into a pressurized, high salinity draw solution; power is obtained by depressurizing the permeate through a hydroturbine. A PRO model was developed to predict water flux and power density under specific experimental conditions. The model relies on experimental determination of the membrane water permeability coefficient ( A), the membrane salt permeability coefficient ( B), and the solute resistivity ( K). A and B were determined under reverse osmosis conditions, while K was determined under forward osmosis (FO) conditions. The model was tested using experimental results from a bench-scale PRO system. Previous investigations of PRO were unable to verify model predictions due to the lack of suitable membranes and membrane modules. In this investigation, the use of a custom-made laboratory-scale membrane module enabled the collection of experimental PRO data. Results obtained with a flat-sheet cellulose triacetate (CTA) FO membrane and NaCl feed and draw solutions closely matched model predictions. Maximum power densities of 2.7 and 5.1 W/m 2 were observed for 35 and 60 g/L NaCl draw solutions, respectively, at 970 kPa of hydraulic pressure. Power density was substantially reduced due to internal concentration polarization in the asymmetric CTA membranes and, to a lesser degree, to salt passage. External concentration polarization was found to exhibit a relatively small effect on reducing the osmotic pressure driving force. Using the predictive PRO model, optimal membrane characteristics and module configuration can be determined in order to design a system specifically tailored for PRO processes.

Ultrafiltration of black liquor using rotating disk membrane module

One of the major reasons of reluctance by industries to implement ultrafiltration (UF) of black liquor (BL) is flux decline and associated fouling. Several attempts have been made in the past to study and to analyze the performance of ultrafiltration of BL using various module combinations under different conditions. BL, spent liquor from alkaline sulfite pulping industries, is known to contain organics (mainly lignosulphonates of wide range of molecular weights) as well as inorganics; thus posing design restrictions for its treatment. The present work employs a laboratory fabricated stirred and rotating disk batch UF cell in an attempt to minimize flux decline and thereby obtain enhanced flux for the treatment of BL obtained from sulfite pulping industries. Asymmetric cellulose triacetate membrane of 5000-molecular weight cut-off was used for experimentations. Reduction of concentration polarization was observed with membrane rotation in this shear induced dynamic filtration unit and correlations have been obtained with different operating variables, like transmembrane pressure (TMP), stirrer speed and membrane rotation speed. The rejection of solutes, measured in terms of total solids (mostly containing lignosulphonates) was also correlated with different operating parameters. Pretreatment methods like, centrifugation, followed by microfiltration were utilized to remove any traces of suspended solids; thus minimizing the occurrences of membrane fouling. Pretreatment steps proved to be highly efficient in restoring the permeability of the membrane during experimentations. Finally, a new model was developed based on pore-plugging theory in order to assess the performance of UF, which clearly showed the reduction in pore-plugging phenomenon as a result of membrane rotation. Further, membrane rotating was proved to be more efficient in reducing concentration polarization compared to stirring action.

Performance study during ultrafiltration of Kraft black liquor using rotating disk membrane module

Kraft processes require a large volume of water and accordingly a substantial amount of spent liquor; known as black liquor (BL) is produced. Attempts have been made in this study to analyze the performance of BL ultrafiltration using batch stirred rotating disk module. The flux enhancement and the reduction of concentration polarization phenomena have been observed with membrane rotation in this shear enhanced dynamic filtration and correlations have been drawn with different operating variables like transmembrane pressure (TMP), stirrer speed and membrane rotation speed. The rejection of solutes, mostly lignin and lignosulfonates has also been correlated with different operating parameters. Pretreatment centrifugation, followed by microfiltration has been used to remove traces of suspended solids to minimize the chances of membrane fouling. These pretreatment steps proved to be highly efficient in restoring the water flux completely in all the cases of experimentation. The work in this paper was done with specific emphasis on the environmental aspects; accordingly the effect of ultrafiltration on different variables like BOD, COD, oil and grease, total solids, turbidity, etc has been monitored in detail and the reduction in each of these parameters was correlated with different operating variables. Asymmetric cellulose triacetate membrane of 5000-molecular weight cut-off was used for the purpose of experimentation. A very good reduction in each of the aforementioned water quality parameters was observed. The research documented that ultrafiltration of BL with necessary pretreatment can produce good, disposable quality, water and on the other hand it can also provide a sound method for recovery of lignin.

Separation of carbon dioxide by asymmetric hollow fiber membrane of cellulose triacetate

AbstractPermeation behavior of pure CO2, O2, and N2 and separation characteristics of CO2–air mixtures were examined using hollow fiber modules of asymmetric cellulose triacetate membrane at 30°C. The ideal separation factor for CO2 relative to N2 ranged from 21 to 24. Permeation behavior for pure CO2 was interpreted in terms of the total immobilization model, i.e., a limiting case of the dual‐mode mobility model for glassy polymer, where the diffusion coefficient for Henry's law mode is not assumed to be constant and depends on gas pressure via a modified free‐volume model. Based on pure gas permeabilities to CO2, O2, and N2, simulation for the separation of CO2–air mixtures was made using a counter‐current plug flow model, and the result fitted the corresponding experimental data fairly well. Membrane plasticization induced by CO2 had negligible effect on permeation to mixture of CO2 and air in the range of CO2 composition up to 50% and upstream total pressure up to 1.5 MPa.