Improved membranes for the extraction of heavy metals

This work presents a series of experimental tests on new practical approaches in membrane design to improve extraction capacity and rate. We chose an extraction system involving Aliquat 336 as the extractant and Cd(II) as the metal ion to be extracted to demonstrate these new approaches. The core element in the new membrane assembly was the extractant loaded sintered glass filter. This membrane assembly provided a large interface area between the extractant and the aqueous solution containing metal ions. By recycling the aqueous solution through the membrane assembly, the extraction rate was significantly improved. The membrane assembly also offered good extraction capacity.

Polypyrrole-coated electrospun nanofibre membranes for recovery of Au(III) from aqueous solution

In this paper, for the first time, polypyrrole-coated electrospun nanofibre mats have been used as separation membranes to electrolessly recover Au from aqueous [Au(III)Cl₄]− solutions, based on a continuous-flow membrane separation process. With a [Au(III)Cl₄]− solution passing through the nanofibre membrane, the Au(III) ions were converted into elemental Au. The gold recovered was deposited on the nanofibre membranes in the form of Au particles, as confirmed by EDX and XPS measurements. It has been found that the polypyrrole-coated electrospun nanofibres are good candidate membrane material for the recovery of Au, and the recovery efficiency is affected by the membrane thickness, the permeate flux rate and the initial [Au(III)Cl₄]− concentration.

Electrospun nanofibre membranes as wound dressing materials

An effective wound dressing is not only able to protect the wound area from its surroundings to avoid infection and dehydration, but also to speed up the healing process by providing an optimum microenvironment for healing, removing any excess wound exudates, and allowing continuous tissue reconstruction. In this study, two biodegradable polymers, polycaprolactone (PCL) and polyvinyl alcohol (PVA), were used to electrospin nanofibre membranes. The wound dressing performances of these two membranes were compared with the wound dressing performances of protein coated membranes and conventional non-woven cotton wound dressings. In addition, fibre morphology, porous structural property, mechanical properties of the nanofibre membranes, and their drainage capacity and wound skin histology were examined.

Use of a decision aid for prenatal testing of fetal abnormalities to improve women's informed decision making: a cluster randomised controlled trial [ISRCTN22532458]

Objective To evaluate the effectiveness of a decision aid for prenatal testing of fetal abnormalities compared with a pamphlet in supporting women's decision making.
Design A cluster randomised controlled trial.
Setting Primary health care.
Population Women in early pregnancy consulting a GP.
Methods GPs were randomised to provide women with either a decision aid or a pamphlet. The decision aid was a 24-page booklet designed using the Ottowa Decision Framework. The pamphlet was an existing resource available in the trial setting.
Main outcome measures Validated scales were used to measure the primary outcomes, informed choice and decisional conflict, and the secondary outcomes, anxiety, depression, attitudes to the pregnancy/fetus and acceptability of the resource. Outcomes were measured at 14 weeks of gestation from questionnaires that women completed and returned by post.
Findings Women in the intervention group were more likely to make an informed decision 76% (126/165) than those in the control group 65% (107/165) (adjusted OR 2.08; 95% CI 1.14–3.81). A greater proportion of women in the intervention group 88% (147/167) had a 'good' level of knowledge than those in the control group 72% (123/171) (adjusted OR 3.43; 95% CI 1.79–6.58). Mean (SD) decisional conflict scores were low in both groups, decision aid 1.71 (0.49), pamphlet 1.65 (0.55) (adjusted mean difference 0.10; 95% CI −0.02 to 0.22). There was no strong evidence of differences between the trial arms in the measures of psychological or acceptability outcomes.
Conclusion A tailored prenatal testing decision aid plays an important role in improving women's knowledge of first and second trimester screening tests and assisting them to make decisions about screening and diagnostic tests that are consistent with their values.

Thermodynamics of lipophilic drug binding to intestinal fatty acid binding protein and permeation across membranes

Intestinal fatty acid binding protein (I-FABP) is present at high levels in the absorptive cells of the intestine (enterocytes), where it plays a role in the intracellular solubilization of fatty acids (FA). However, I-FABP has also been shown to bind to a range of non-FA ligands, including some lipophilic drug molecules. Thus, in addition to its central role in FA trafficking, I-FABP potentially serves as an important intracellular carrier of lipophilic drugs. In this study we provide a detailed thermodynamic analysis of the binding and stability properties of I-FABP in complex with a series of fibrate and fenamate drugs to provide an insight into the forces driving drug binding to I-FABP. Drug binding and selectivity for I-FABP are driven by the interplay of protein−ligand interactions and solvent processes. The Gibbs free energies (ΔG°) determined from dissociation constants at 25 °C ranged from −6.2 to −10 kcal/mol. The reaction energetics indicate that drug binding to I-FABP is an enthalpy−entropy driven process. The relationship between I-FABP stability and drug binding affinity was examined by pulse proteolysis. There is a strong coupling between drug binding and I-FABP stability. The effect of an I-FABP protein sink on the kinetics and thermodynamics of tolfenamic acid permeation across an artificial phospholipid membrane were investigated. I-FABP significantly decreased the energy barrier for desorption of tolfenamic acid from the membrane into the acceptor compartment. Taken together, these data suggest that the formation of stable drug−I-FABP complexes is thermodynamically viable under conditions simulating the reactant concentrations likely observed in vivo and maybe a significant biochemical process that serves as a driving force for passive intestinal absorption of lipophilic drugs.

The influence of geometry and wall character of pores on the permeation of ions and water through desalination membranes

The transport of water and ions across mimicked nanotube membranes with pseudo atoms is studied using molecular dynamics simulations under equilibrium conditions and hydrostatic pressure. Different pore surface properties are constructed by assigning partial charges on the sites of specified atoms to explore the influence of charges and polarity. The energetics of water and ion transports through the nanopores was calculated to evaluate their filterability to water. The simulation results show that the free energy barriers to water and ion conductions much depend on the charges at the pore entrance and the dipole within the pore. The membranes with hydrophobic pores and negatively charged entrances would be very efficient in the water transport and ion rejection. The charges and dipoles of the pore wall and the aligned dipoles of water molecules in the pore can create a significant force on ions.

Characterization of membranes with X-ray ultramicroscopy

Non-invasive characterization and observation of synthetic membranes is an important practice to monitor the performance of membrane process. Primarily there are two techniques—optical and non-optical for this purpose. Among them, X-ray computed tomography, as a non-optical technique, has been extensively used for the measurement of fibre distribution and air pockets trapped in the modules. However, the micro resolution of most commercial systems has limited its application which can hardly be used for the sub-micro characterization of membrane processes. A novel micro and nano characterization method is introduced in the current work by exploring an innovative development of the X-ray ultramicroscope (XuM) and micro-tomographic techniques. The XuM, based on using a scanning electron microscope as host, provides a new approach to X-ray projection microscopy. It has demonstrated the ability to characterize very small features in objects, down to of order 100 nm, including the use for dry, wet and even liquid samples. It can also distinguish objects with very subtle difference in density.

Evaluation of a decision aid for prenatal testing of fetal abnormalities : a cluster randomised trial [ISRCTN22532458]

Background: By providing information on the relative merits and potential harms of the options available and a framework to clarify preferences, decision aids can improve knowledge and realistic expectations and decrease decisional conflict in individuals facing decisions between alternative forms of action. Decision-making about prenatal testing for fetal abnormalities is often confusing and difficult for women and the effectiveness of decision aids in this field has not been established. This study aims to test whether a decision aid for prenatal testing of fetal abnormalities, when compared to a pamphlet, improves women's informed decision-making and decreases decisional conflict.

Methods/design: A cluster designed randomised controlled trial is being conducted in Victoria, Australia. Fifty General Practitioners (GPs) have been randomised to one of two arms: providing women with either a decision aid or a pamphlet. The two primary outcomes will be measured by comparing the difference in percentages of women identified as making an informed choice and the difference in mean decisional conflict scores between the two groups. Data will be collected from women using questionnaires at 14 weeks and 24 weeks gestation.

The sample size of 159 women in both arms of the trial has been calculated to detect a difference of 18% (50 to 68%) in informed choice between the two groups. The required numbers have been adjusted to accommodate the cluster design, miscarriage and participant lost – to – follow up.

Baseline characteristics of women will be summarised for both arms of the trial. Similarly, characteristics of GPs will be compared between arms.

Differences in the primary outcomes will be analysed using 'intention-to-treat' principles. Appropriate regression techniques will adjust for the effects of clustering and include covariates to adjust for the stratifying variable and major potential confounding factors.

Discussion: The findings from this trial will make a significant contribution to improving women's experience of prenatal testing and will have application to a variety of maternity care settings. The evaluation of a tailored decision aid will also have implications for pregnancy care providers by identifying whether or not such a resource will support their role in providing prenatal testing information.

The optimisation of ultrasonic cleaning procedures for dairy fouled ultrafiltration membranes

Ultrafiltration (UF) of whey is a major membrane based process in the dairy industry. However, commercialization of this application has been limited by membrane fouling, which has a detrimental influence on the permeation rate. There are a number of different chemical and physical cleaning methods currently used for cleaning a fouled membrane. It has been suggested that the cleaning frequency and the severity of such cleaning procedures control the membrane lifetime. The development of an optimal cleaning strategy should therefore have a direct implication on the process economics. Recently, the use of ultrasound has attracted considerable interest as an alternative approach to the conventional methods. In the present study, we have studied the ultrasonic cleaning of polysulfone ultrafiltration membranes fouled with dairy whey solutions. The effects of a number of cleaning process parameters have been examined in the presence of ultrasound and results compared with the conventional operation. Experiments were conducted using a small single sheet membrane unit that was immersed totally within an ultrasonic bath. Results show that ultrasonic cleaning improves the cleaning efficiency under all experimental conditions. The ultrasonic effect is more significant in the absence of surfactant, but is less influenced by temperature and transmembrane pressure. Our results suggest that the ultrasonic energy acts primarily by increasing the turbulence within the cleaning solution.

The use of ultrasonic cleaning for ultrafiltration membranes in the dairy industry

The ultrafiltration of whey solutions is a common feature of dairy processes. However, the frequent fouling of ultrafiltration membranes and the subsequent cleaning cycle significantly affect the economics of such a process. In this work, we investigated the effect of ultrasonics on the cleaning of whey-fouled membranes and examined the variables that influence this effect. Experiments were conducted using a small single sheet membrane unit that was immersed totally within an ultrasonic bath.

Results show that the use of ultrasonics enhances the flux recovery following fouling. The extent of flux recovery is independent of the length of sonication time and increases with ultrasonic power. The use of surfactants in combination with ultrasonic irradiation shows a synergistic effect, providing a better efficiency than either cleaning process alone. Repetitive use of ultrasonic cleaning over a 1 month period does not result in any significant change in the permeate flux of a cleaned membrane, indicating that the ultrasonic treatment does not appear to damage the membrane structure itself.

Power ultrasound offers an environmentally friendly approach to cleaning dairy UF membranes

Flat sheet polymeric UF membranes of 30000 MWCO were obtained from Millipore Inc. Polypropylene spacers of a 50 mil (1.3 mm) thickness were obtained from KOCH membrane systems. A single 30 cm^sup 2^ membrane sheet was sandwiched with a spacer on the feed side of a cross flow Minitan S unit (Millipore Inc). The unit was immersed in a 50 kHz ultrasonic bath that was switched on as required. All experiments used re-constituted spray-dried whey powder to foul the membrane.

Cholesterol is necessary both for the toxic effect of Abeta peptides on vascular smooth muscle cells and for Abeta binding to vascular smooth muscle cell membranes

Accumulation of beta amyloid (Aβ) in the brain is central to the pathogenesis of Alzheimer's disease. Aβ can bind to membrane lipids and this binding may have detrimental effects on cell function. In this study, surface plasmon resonance technology was used to study Aβ binding to membranes. Aβ peptides bound to synthetic lipid mixtures and to an intact plasma membrane preparation isolated from vascular smooth muscle cells. Aβ peptides were also toxic to vascular smooth muscle cells. There was a good correlation between the toxic effect of Aβ peptides and their membrane binding. 'Ageing' the Aβ peptides by incubation for 5 days increased the proportion of oligomeric species, and also increased toxicity and the amount of binding to lipids. The toxicities of various Aβ analogs correlated with their lipid binding. Significantly, binding was influenced by the concentration of cholesterol in the lipid mixture. Reduction of cholesterol in vascular smooth muscle cells not only reduced the binding of Aβ to purified plasma membrane preparations but also reduced Aβ toxicity. The results support the view that Aβ toxicity is a direct consequence of binding to lipids in the membrane. Reduction of membrane cholesterol using cholesterol-lowering drugs may be of therapeutic benefit because it reduces Aβ-membrane binding.

Recent developments in carbon nanotube membranes for water purification and gas separation

Carbon nanotubes (CNTs) are nanoscale cylinders of graphene with exceptional properties such as high mechanical strength, high aspect ratio and large specific surface area. To exploit these properties for membranes, macroscopic structures need to be designed with controlled porosity and pore size. This manuscript reviews recent progress on two such structures: (i) CNT Bucky-papers, a non-woven, paper like structure of randomly entangled CNTs, and (ii) isoporous CNT membranes, where the hollow CNT interior acts as a membrane pore. The construction of these two types of membranes will be discussed, characterization and permeance results compared, and some promising applications presented.