Separation of potassium clavulanate and potassium chloride by nanofiltration: Transport and evaluation of membranes

In this work, four commercial nanoporous membranes (NF and NF90 from FilmtecTM, and NP010 and NP030 from Microdyn Nadir) have been characterized and evaluated in order to use them to separate potassium clavulanate and potassium chloride.Their charge density has been investigated by Tangential Streaming Potential measurements for several concentrations of KCl and pH. The isoelectric point of the membranes has been found to be between pH 5.0 and 6.0.Their rejection for KCl has also been measured and the corresponding concentration polarization effect has been taken into account. Nanofiltration modeling, that considers the steric, electric and dielectric exclusion and the charge variation along the pores (SEDE-VCh model), satisfactorily describes the retention of KCl by using the dielectric constant inside the pores, εp, as the only fitting parameter.Although all the studied membranes are highly retentive for the potassium clavulanate, KCA, the most suitable membranes for KCA purification, attending to the KCl/KCA selectivity are NF or NF90 membranes at all pH. Lower pH values give higher selectivity for all the membranes.

► The charge of several NF membranes has been evaluated versus concentration and pH.
► NF is modeled, the fitted εp increases with pore radius and decreases with c.
► Low pH, high pressures and narrow pores give higher KCl/KCA selectivities.