comparison of two spiral-wound elements

permeate samples

Example 1: a manufacturer of dyes and specialty chemicals wants to desalinate a new product suspension. In some tests with the nanofiltration membrane used for liquid dye desalination and with ceramic microfiltration membranes he had no success: the permeate flux declined quickly to only a few l/m2h. PS Prozesstechnik was asked to find an alternative membrane in lab tests.

With first tests with ultrafiltration membranes (polysulfon, polyethersulfon) we had no success either (permeate flux declined quickly to 7 l/m2h).The inspection of the membrane showed strong product deposition on the membrane surface despite high cross-flow velocity. Next we tested a microfiltration membrane based on Teflon. We achieved a constant permeate flux of 60 l/m2h with total product rejection. Complete product desalination was possible.

Example 2: a manufacturer of plant extracts asked us to develop a process for mild concentration of the extract with molecular weight 450 in an aqueous solution with 10% isopropanol. The desired increase in concentration was by a factor of 100.

We have tested reverse osmosis and nanofiltration membranes of different suppliers. In a screening a first choice was made: the desired membrane should have a low retention for isopropanol in order to prevent an increase in concentration of isopropanol and osmotic pressure. On the other hand the membrane should have a low cut-off to minimize product losses.

With the remaining membranes tests with extraction solution were made. With sufficient operating pressure (in order to overcome the osmotic pressure of the slightly retained isopropanol) the desired concentration of product could be achieved.

We supported our customer in claiming a patent for this concentrating process for his product.

3 of our lab units for membrane process development

flat channel test cell

high pressure up to 100 bar

test elements

flatsheet