Yc. Huang et al., CROSS-FLOW SURFACTANT-BASED ULTRAFILTRATION OF HEAVY-METALS FROM WASTE STREAMS, Separation science and technology, 29(15), 1994, pp. 1979-1998
Five heavy metals (cadmium, lead, copper, nickel, and zinc) in a simul
ated wastewater, alone and together, were substantially removed by sur
factant-based ultrafiltration using natural surfactants such as a deri
vative of cholesterol (deoxycholic acid) and lecithins. Selective and
total removal of metal ions has been achieved by applying an appropria
te level of surfactant-to-metal ratio (S/M). The underlying principle
is to increase the size of the target metal ions by fixing them to lar
ger surfactant macromolecules so they can be retained by a compatible
membrane. Deoxycholic acid exhibited more efficiency in metal removal
than did lecithin and sodium dodecyl sulfate. This research showed tha
t transmembrane pressure had a minimal effect on metal removal whereas
S/M had a substantial influence. The optimal SIM for considerable met
al removal (99.9 + rejection ratio) is around 2.5 and 5 for deoxycholi
c acid and sodium dodecyl sulfate, respectively. The binding of metals
to surfactant in the absence of membrane interferences was also deter
mined by a centrifuge method.