HF Membrane Research Articles

Hollow-Fiber Membrane Extraction of Copper from Aqueous Nitrate Media by LIX® Reagents: Comparison of Extraction Efficiency and Fractional Resistances

Extraction of copper from nitrate/nitric acid aqueous solutions was studied using a HF Membrane Module and four LIX reagents (LIX® 860N-I, LIX® 984N, LIX® 84-I, and LIX® 65N) containing different active compounds (ketoximes and/or salicylaldoximes). Kinetic experiments varying the flow rates of both phases, aqueous and organic, and the extractant concentration were carried out to compare the extraction rate and efficiency from nitrate-aqueous media. A mathematical model based on the “aqueous extraction mechanism” in which the chemical reaction takes place in an aqueous-reaction zone was applied to determine the individual resistances of the copper mass-transfer process. It was found that the fractional resistance due to chemical reaction in the aqueous reaction zone, which varied from 92.5% to 95.8% in the order LIX® 860N-I < LIX® 984N < LIX® 84-I < LIX® 65N, controlled the total rate of the hollow-fiber copper extraction from nitrate aqueous media.

Effect of sodium dodecyl sulfate on protein separation by hollow fiber flow field-flow fractionation

Effects of protein denaturation and formation of protein-sodium dodecyl sulfate (SDS) complexes on protein separation and identification were investigated using hollow fiber flow field-flow fractionation (HF5) and nanoflow liquid chromatography-electrospray ionization-tandem mass spectrometry (nLC-ESI-MS-MS). Denaturation and formation of protein-SDS complexes prior to HF5 separation resulted an increase in the retention of few protein standards due to unfolding of the protein structures and complexation, yielding ~30% increase in hydrodynamic diameter. In addition, low molecular weight proteins which could be lost from the HF membrane due to the pore size limitation showed an increase of peak recovery about 2-6 folds for cytochrome C and carbonic anhydrase. In the case of proteins composed of a number of subunits, denaturation resulted in a decrease in retention due to dissociation of protein subunits. A serum proteome sample, denatured with dithiothreitol and SDS, was fractionated by HF5, and the eluting protein fractions after tryptic digestion were analyzed for protein identification using nLC-ESI-MS-MS. The resulting pools of identified proteins were found to depend on whether the serum sample was treated with or without denaturation prior to the HF5 run due to differences in the aqueous solubility of the proteins. The enhancement of protein solubility by SDS also increased the number of identified membrane proteins (54 vs. 31).

Diffusive and convective transport in HF membrane reactors for biomedical applications

The efficient design of a membrane bioreactor for cells culture needs the complete characterization — both experimentally and theoretically — of the transport phenomena for metabolites, catabolites, cell regulatory and immune-related soluble factors. In this work, experiments and theoretical calculations have been carried out in order to discern the simultaneous influence of both diffusive and convective mechanisms to the transport of metabolites. In particular, the transmembrane mass flux of glucose, bovine serum albumin (BSA), apotransferrin and immunoglobulin G was experimentally measured, under pressure and concentration gradients, through high-flux microporous hydrophilic poly-ether-sulphone (PES-HFMs) and poly-sulphone hollow fiber membranes (PS-HFMs).

Matrix removal and analyte preconcentration before inductively coupled plasma spectrometric detection: use of a laboratory-made hollow fibre flow filtration unit

A hollow fibre flow filtration (HF-FF) was applied to perform matrix removal and analyte preconcentration before inductively coupled plasma optical emission spectrometric (ICP-OES) detection. Poly(ethylene imine), PEI, with a molecular weight of 750000 Da, was added to test solutions to form complexes with analyte elements (Ag, Cd, Co, Cu, Hg, Ni, Pb and Zn) but not the matrix elements (Ca, K, Mg and Na). Two flow streams were applied in opposing directions to introduce a large sample volume into the fibre membrane. With the use of a HF membrane made of poly(sulfone), having a pore size of 30000 Da, matrix elements were removed by filtering off through the membrane, whereas the PEI–analyte complexes remained in the channel and were subsequently eluted and detected. Various parameters were optimized to obtain a satisfactory matrix removal and preconcentration factor. These include PEI concentration, focusing time, and focusing point. With a PEI concentration of 200 mg l−1, focusing time of 15 min and the focusing point nearest to the detector, matrix removal efficiency was nearly 100%.

Basic options and two case studies for retrofitting hollow fiber elements by spiral-wound RO technology

Until the end of the 90's the RO desalination technology for medium and large capacities was based mainly upon two configurations of membrane modules: spiral-wound elements and hollow fiber bundles (HF). The retirement of Permasep® HF (DuPont) leaving HOLLOSEP® (Toyobo) as being the only alternative for the direct replacement of Permasep, brought a challenge to the makers of spiral elements in the sense of system retrofit to convert existing HF membrane plants into some of the most advanced spiral-wound membrane plants. The major criteria for success was to achieve substantial improvements in the economy and quality of the permeate produced at limited capital expenditure. Such improvements have become feasible with the considerable development of spiral-wound membranes in the recent years. In this paper the technical changes needed for the retrofitting have been systematically studied. After a short historical review, the paper discusses basic options for the retrofitting have been systematically studied. After a short historical review, the paper discusses basic options for two existing Permasep installations on the Canary Islands and in the Middle East, respectively. Specific characteristics, advantages and costs of various possible solutions are presented. Two case studies are discussed for the 3×4,700 m 3/d seawater RO plant in Agragua on the Canary Islands and for the 4×4,200 m 3/d seawater RO plant in Gela in Sicily. Plant performance data for 8 months and 19 months respectively is presented.

The thin-film composite low pressure reverse osmosis membranes

Reverse osmosis systems are generally designed and utilized on the basis of reference membrane water flux and desalting performance at 28 Kg/cm 2 (400 psi) net driving pressure (NDP). Low commercial stage are capable of equivalent performance at 14 Kg/cm 2 (200 psi) NDP. Further, possibly, super low pressure (SLP) membranes are capable of equivalent performanec at 7 Kg/cm 2 (100 psi) NDP. These LP and SLP membranes offer immediately obvious savings in energy cost for reverse osmosis desalting and water reclamation. In addition, they can make a most important contribution to reduced membrane replacement cost and improved permeate quality when operating on high salinity feeds at higher recevery levels. Two new series and four types of thin-film composite LP and/or SLP reverse osmosis membranes have been developed. These membranes, designated UTC series, give superior performance in such area as water flux, salt rejection, chemical stability and microbiological resistance. UTC-20 & 40 series membranes are designed for use at pressure of 5–15 kg/cm 2 (71–213 psi). UTC-20 series membranes are available in two grades. UTC-20 HR membrane has a high water flux over 2.4 m 3/m 2 day (60 gfd) and NaCl rejection above 70 % at 15 kg/cm 2. UTC-20 HF membrane has a very high water flux over 3.5 m 3/m 2 day (86 gfd) and NaCl rejection above 50 % at 15 kg/cm 2, while the magnesium sulfate rejections of UTC-20 HR & 20 HF membranes are above 99.0 %, respectively. UTC-40 series membranes are also available in two grades. UTC-40 HR membrane has high NaCl rejections above 98 % and 1.0 m 3/m 2 day (24.5 gfd) water flux at 15 kg/cm 2. UTC-40 HF membrane has very high water flux above 2.5 m 3/m 2 day (61.5 gfd) and over 90 % sodium chloride rejection at 15 kg/cm 2. UTC-20 & 40 series membrane are directed to use in the market for ultrapure water production and brackish water desalination at low or super low operating pressure. These new composite membranes have been successfully manufactured in continuous flat sheet form and wound into the spiral elements.