Experimental study of the effects of hypochlorite on polysulfone membrane properties

Although chemical solutions are widely employed to clean membranes, they can also be responsible for changes in membrane properties. The two major drawbacks are then either the functional properties of the membrane gradually change, so the production can no longer meet requirements in terms of volume or quality, or the membrane simply breaks up (hollow fibers), and the system has to be shut down during maintenance. The aim of this experimental study was to gain a better understanding of the effect of hypochlorite cleaning solutions in different conditions (various pHs and temperatures) on the changes observed on an ultrafiltration hollow fiber membrane made from polysulfone (PSf) and polyvinylpyrrolidone (PVP). A wide range of methods characterizing the material have been used, from the atomic scale (ESCA) up to the module scale by force measurements on fibers. Exposure to sodium hypochlorite at rather high concentration seems to lead to chain breaking in the PSf molecules (gel permeation chromatography results). The consequences are changes in the membrane texture (scanning electron microscopy images), which are closely related to changes in the mechanical properties of the membrane. Membrane permeability appears to be poorly sensitive to such changes, which can be related to the fact that the permeability relies on the skin properties mainly

Improvement of a method for the characterization of ultrafiltration membranes by measurements of tracers retention

The aim of this study is to improve protocols for assessing accurate characteristic retention curve and cut-off of membranes, thus enabling the manufacture and performance of the membrane to be monitored. Different data treatments are considered in order to determine membrane retention for fractions of tracer filtered (PEGs in the molar mass range of 1–100 kg mol−1). In the most advanced method of treatment, the observed retention is expressed as a combination of solute transfer coefficients in the boundary layer (kBL) and porous structure (kpore), and the asymptotic retention (Rinf ), which is an intrinsic characteristic of the membrane to solute as it is independent of operating conditions. The developed method has proved to be accurate and reproducible in two cases: (i) monitoring of UF membrane integrity during accelerated aging; (ii) for quantification of cut-off change due to UF membrane modification by UV grafting. We propose a simplified procedure that allows a reduction in experimental workload, without loss of sensitivity, for the most advanced method

Ageing of polysulfone membranes in contact with bleach solution: Role of radical oxidation and of some dissolved metal ions

In water production plants using membrane processes, contact with chemicals such as chlorine plays an important role in membrane ageing. This experimental study was aimed at gaining a better understanding of the effect of hypochlorite cleaning solutions on the properties of a polysulfone ultrafiltration membrane. Accelerated ageing of the membrane was simulated by soaking it in chlorine solutions and the mechanical properties of the membrane were monitored versus soaking time. An oxidation mechanism is validated which involves the catalytic effect of dissolved metal ions and the inhibitor effect of an antioxidant when these are present in soaking solutions

Income Redistribution and Public Good Provision: an Experiment

We provide a new experimental investigation of the neutrality theorem of Warr (1983), who states ”when a single public good is provided at positive levels by private individuals, its provision is unaffected by a redistribution of income”. Instead of comparing different income distributions across groups as Chan et al. (1996), in our experiment the total group endowment is redistributed after a 10 rounds sequence. We compare an unequalizing redistribution (EI) and an equalizing redistribution (IE), to two benchmark treatments for which the 10 rounds sequence is repeated, either with an equal distribution (EE) or an unequal distribution (II). The constituent game has a unique interior dominant strategy equilibrium. Our data support the neutrality theorem (after controlling for the restart effect): redistribution has no effect on the total amount of public good in none of the tested treatments. However, the analysis of individual behavior shows that ”poor” subjects over-contribute with respect to their Nash-contribution, while ”rich” subjects tend to play their Nash-contribution or under-contribute slightly. Furthermore, after a redistribution, subjects react asymetrically: subjects who get poorer reduce their contribution of a larger amount than the amount of contribution added by subjects who become richer. And it is shown that the latter do not react enough to the redistribution.

Evaluating capacity auction design for electricity : An experimental analysis

Acknowledgement: Research funds for this work were provided by a PhD scholarship co-funded by the Energy Technology Partnership (ETP), the Scottish Government and the University of Aberdeen. We would like also to thank the late Professor Joseph (Joe) E. Swierzbinski who was an inspiration for this work. He is sorely missed. We would also like to thank the referees for their helpful comments. All usual caveats apply.Peer reviewedPostprin

In flight performance and first results of FREGATE

The gamma-ray detector of HETE-2, called FREGATE, has been designed to detect gamma-ray bursts in the energy range [6-400] keV. Its main task is to alert the other instruments of the occurrence of a gamma-ray burst (GRB) and to provide the spectral coverage of the GRB prompt emission in hard X-rays and soft gamma-rays. FREGATE was switched on on October 16, 2000, one week after the successful launch of HETE-2, and has been continuously working since then. We describe here the main characteristics of the instrument, its in-flight performance and we briefly discuss the first GRB observations.Comment: Invited lecture at the Woods Hole 2001 GRB Conference, 8 pages, 15 figure

Development of a modular CdTe detector plane for gamma-ray burst detection below 100 keV

We report on the development of an innovative CdTe detector plane (DPIX) optimized for the detection and localization of gamma-ray bursts in the X-ray band (below 100 keV). DPIX is part of an R&D program funded by the French Space Agency (CNES). DPIX builds upon the heritage of the ISGRI instrument, currently operating with great success on the ESA INTEGRAL mission. DPIX is an assembly of 200 elementary modules (XRDPIX) equipped with 32 CdTe Schottky detectors (4x4 mm2, 1 mm thickness) produced by ACRORAD Co. LTD. in Japan. These detectors offer good energy response up to 100 keV. Each XRDPIX is readout by the very low noise front-end electronics chip IDeF-X, currently under development at CEA/DSM/DAPNIA. In this paper, we describe the design of XRDPIX, the main features of the IDeF-X chip, and will present preliminary results of the reading out of one CdTe Schottky detector by the IDeF-X V1.0 chip. A low-energy threshold around 2.7 keV has been measured. This is to be compared with the 12-15 keV threshold of the ISGRI-INTEGRAL and BAT-SWIFT instruments, which both use similar detector material.Comment: 5 pages, 4 figures in color, Advances in Space Research, COSPAR meeting, Beijing (2006

Fibers and sol-gel matrix based thermal barrier coating systems for outstanding durability

Thermal barrier coatings (TBC) are critical elements of the turbomachines. On turbine blades for aircraft engines, their preparation is based on EB-PVD industrial process. Such TBCs on first generation AM1 superalloy with a beta-NiPtAl bond coating exhibit 20% of surface spallation after about 600 1h oxidation cycles at 1100°C. In this work, a new method of TBC preparation was proposed and high durability of such structures was obtained with more than 1000 1h cycles at 1100°C before 20% of spallation. More than 1400 1h cycles was even obtained with the most performing formulations. A key point was that the surface spallation was lower than 10 % after 1000 cycles for TBCs made with the 70% and 80% fiber mix (Figure 1a). In the same conditions, EB-PVD TBCs exhibit 50-80% of spallation. The preparation process relied on the addition of a high temperature binder, namely a zirconia sol, to a mix of zirconia powder and fibers. TBCs with equiaxed porosity were obtained (Figure 1b). After thermal treatments, ceramic sintering bridges between the powder, the fibers and the ceramic derived from the sol transformation formed (Figure 1c). Another benefit was obtained from the anchoring of the fibers in the thermally grown oxide (TGO), inducing a tougher TGO layer. The outstanding durability of these fibers and sol-gel matrix based thermal barrier coatings is believed to be the consequence of higher toughness of both the TBC coating and modified TGO. Indeed, crack deviations were observed in these two elements. Moreover, contrary to EB-PVD TBCs, the porosity is isotropically distributed, limiting heat diffusion towards the superalloys. Please click Additional Files below to see the full abstract