2.5. Separation experiments
The pure water permeance of the membranes was measured by filtering the
ultrapure water through the membranes and calculated by
\(J=V/(\text{Apt})\) (2)
where J is the permeance (L m-2h-1 bar-1), V is the volume
of the solution through the membranes (L), A is the effective
filtration area of the membranes (m2), p is the
pressure difference across the membranes (bar), and t is the
filtration time (h).
Six organic dye molecules were used as probes to evaluate nanofiltration
performances of the membranes, including TMPyP
(Mw 1363.60), direct yellow 50 (DY,Mw 956.82), EB (Mw897.88), congo red (CR, Mw 696.68), oil red (OR,Mw 408.50) and MB (Mw373.89). MgSO4 and NaCl were also used to evaluate
desalination performances. 50 mL of dye solution (10 μg
mL-1) or salt solution (1 mg mL-1)
was filtered under continuous stirring. When about one third of the
solution passed through the membranes, the concentration of dyes in the
feed, the retentate and the permeate was measured by the
ultraviolet-visible (UV-vis) absorption spectrometer (UV-1800, Shimadzu,
Japan) while the concentration of salts in the feed, the retentate and
the permeate was measured by the conductivity meter
(CON700,
Eutech, USA). The rejection was calculated by
\(R=(C_{f}-C_{p})/C_{f}\times 100\%\) (3)
where R is rejection (%), Cf andCp are the concentration of solutes in the feed
and the permeate (g L-1), respectively.