1 research outputs found
Improving Membrane Filtration for Copper Speciation: Optimal Salt Pretreatments of Polyethersulfone Membranes to Prevent Analyte Retention
Membrane filtration has been increasingly used to separate
dissolved
metal ions from dispersed particles, commonly using ultrafiltration
membranes, for example, polyethersulfone (PES) membranes with a molecular
weight cut-off of 3 kDa. The disadvantage of this technique is an
undesired retention of ions, resulting from Coulomb interactions with
sulfonic acid groups of the membrane. Therefore, such a membrane acts
similar to a cation exchanger column. We solved this drawback by a
pretreatment of the PES membrane by other cations. Using CuSO4 as a model compound, we compared the effectiveness of five
cations using their salt solutions (Ca2+, Mg2+, Fe2+, Ag+, Ba2+) as pretreatment
agents and identified the most effective pretreatment component for
a high recovery of copper ions. After membrane filtration without
pretreatment, only 52 ± 10%, 64 ± 5%, 75 ± 8%, and
89 ± 7% of nominal Cu concentrations were obtained using initial
concentrations of 0.2, 0.5, 1.0, and 4.0 mg L–1,
respectively. The efficiency of the investigated cations increased
in the order Fe < Ag < Mg < Ca < Ba. Furthermore, we analyzed
the most efficient concentration of the pretreatment agent. The best
performance was achieved using 0.1 mol L–1 CaCl2 which increased copper recovery to slightly below 100%, even
at the lowest tested Cu concentration (recovery 93 ± 10% at 0.2
mg L–1). In the environmentally relevant Cu concentration
range of 0.2 mg L-1, 0.1 mol L–1 BaCl2 was identified as the most efficient pretreatment (103 ±
11%)