Defect free hollow fiber reverse osmosis membranes by combining layer-by-layer and interfacial polymerization

Hollow fibre RO membranes would be desired for many applications, but are notoriously difficult to fabricate. Here we demonstrate that combining layer-by-layer and interfacial polymerization (IP) allows straightforeward production of defect-free hollow fiber RO membranes. A polyelectrolyte multilayer (PEM) is used to fill the pores of a support membrane, to provide a controlled and smooth surface that can nevertheless act as an IP monomer reservoir. This approach is first demonstrated on a model surface, with IP layers being successfully applied on both poly(diallyldimethylammonium chloride) (PDADMAC)/poly(4-styrene sulfonate) (PSS) and poly(ethyl-eneimine) (PEI)/PSS PEMs. On plain hollow fiber support membranes, IP coating was found to have a success rate as low as 40%. However, by application of a PEM interlayer the success rate increases to 72% for PDAD-MAC/PSS and 90% for PEI/PSS. Also the separation performance of the successfully prepared IP membranes was significantly better when a PEM interlayer was applied, with higher NaCl retentions (from 94% to 97%), and better removal of organic micro-pollutants (from 96% to 98%), with just a small decrease in permeability (from 0.9 L/m(2)hbar to 0.7 L/m(2)hbar). Combining layer-by-layer and IP approaches can thus lead to the fabrication of defect free RO membranes with improved separation performance

Antimicrobial effects in food and prevention of contamination in food industry

Microbial Contaminants and Contamination Routes in Food Industry - 1st Open Seminar arranged by SAFOODNET; Espoo; Finland; 22 January 2007 through 23 January 2007The most commonly recognized food-borne infections are caused by Campylobacter jejuni and Salmonella spp. In the past 25 years, Listeria monocytogenes has become increasingly important as a food-associated pathogen. Though, an annual incidence of human listeriosis is between two and ten reported cases per million in EU countries. Because of its high case fatality rate, listeriosis ranks among the most frequent causes of death due to food-borne illness. L. monocytogenes and C. jejuni has been shown to adapt to different environmental stress factors, including disinfectants. Salmonella enteritidis, C. jejuni and L. monocytogenes may also form a biolfim which helps to survive in the environment. For that reason, the food industrial hygiene has become important to avoid contamination of raw food and food products with these pathogens