Evaluation of two cross-flow ultrafiltration membranes for isolating marine organic colloids

. .Laboratory and field studies were performed to evaluate two 1 kilo-Dalton kD cross-flow ultrafiltration CFF membranes a Millipore Prep-scale CFF membrane constructed primarily from regenerated cellulose and an Amicon CFF. polysulfone membrane to isolate colloids operationally defined as particles or macromolecules between 1 kD and 0.2–1.mm from sea water. We focused on three crucial aspects when applying the CFF technique: retention characteristics, sorptive potential and ultrafilter breakthrough. Lab results showed that both CFF systems retained G91 % of a 3000 nominal .molecular weight NMW dextran standard, consistent with the manufacturer’s rated cutoff. The Millipore membrane showed essentially no loss of a dextran standard, while 33 % was lost for the same molecule onto the Amicon CFF .membrane. Both membranes showed higher losses of a protein standard Lactalbumin added to sea water. For bulk organic . .carbon OC, both membranes usually had reasonable recovery 100"10 % as long as the membranes were preconditioned. This was true for both lab experiments and field investigations in open ocean water off Bermuda. However, data from 234Th and 230Th analysis of samples from a station off Bermuda showed very large losses and hence low recovery from CFF. Results of these fractionated OC and 234Th distributions are also discussed in the context of prior studies. Ultrafilter . .breakthrough of both high molecular weight HMW and low molecular weight LMW compounds may occur throughout the CFF process, especially when processing coastal sea water where COC is relatively enriched. A permeation coefficient model provides an overall reasonable fit to the data characterizing the permeation behaviour of CFF; the retentate predictio