Supporting online material for
Rapid and Large-Scale Separation of Magnetic Nanoparticles by Low-Field
Permanent Magnet with Gas Assistance
Wensong Li, Liangrong Yang*, Xiaopei Li, Zhini Liu, Fuchun Wang, Na Sui,
Chuanxu Xiao, Huizhou Liu *
Experimental Section
The preparation of BSA-loaded CMNs feed solution: A known amount of CMNs
was mixed with 0.02 M acetate buffer of pH 4.8 with certain concentration of BSA,
and the adsorption was carried out at room temperature for 4 h. BSA-loaded CMNs
were separated from remaining BSA solution by magnetic decantation and diluted to
0.5 mg ml-1 concentration by buffer at pH 4.8.
Small batch gas-assisted magnetic separation experiments were carried out in a
glass flotation column with the inner diameter of 43 mm and length of 500mm, in
which a hanging quadrate magnet with side lengths of 25 mm was equipped, shown in
Figure 1b. After the gas of N2 was got through, the hanging magnet was rapidly
touched with the surface of feed solution and simultaneously, a stopwatch didn’t begin
timing until the solution became clear. The separation rate was calculated as the ratio
of solution volume separated and time. The standard deviation of repeated
experiments at identical conditions is in the range of 3–12%.
Continuous gas-assisted magnetic separation experiments were done in a
gas-assisted magnetic separator (shown in Figure 3a) including a flotation column
1
with the inner diameter of 64 mm and the length of 650 mm and a sintered glass
sparger (pore size: 3-4 μm) as the distributor, and magnetic roller with the inner
diameter of 64 mm and the length of 70 mm (shown in Figure 3b). The flotation
column was filled with 0.02 M acetate buffer (pH 4.8) without particles, and then the
magnetic roller started to run at a given speed after aeration began. The above feed
solution, stirring continuously in the mixing tank, was transported into the flotation
column at the position of 60 mm from the magnetic roller, via peristaltic pump.
Simultaneously, the liquid level was adjusted by the overflow pipe to keep a proper
touch with the magnetic roller. After this continuous process was in a steady flow, the
particles concentration in the effluent was determined. The standard deviation of
recovery of repeated experiments at identical conditions is in the range of 2–16%.
All particles concentration was determined by a spectrophotometer at 650 nm. The
recovery was calculated as the percentage of the differences of concentration between
feed solution and effluent and feed concentration.
Figure S1. A free body diagram of forces acting on magnetic particles in
gas-assisted magnetic separation. Fb-p is force of bubbles on particles, Fd , Fv , Fg
2
denote diffusion force of particles, fluid drag force, and gravity force, respectively.
Figure S2. Flotation performance of the CMNs with different amount of BSA
adsorption. 50 mg of CMNs was permitted to adsorb above different amount of BSA
at room temperature for 4 h by mixing with the solution at pH 4.8 with different
concentration of BSA, and the BSA-loaded CMNs were isolated from BSA solution
by magnetic decantation, were then diluted to 100 ml with the water solution at pH
4.8. Flotation experiments were carried out at 20 ml/min of gas flow rate in a glass
flotation column in our previous work,1 with the addition of 50 mg BSA as foaming
agent. Recovery is defined as the percentage of mass of magnetic nanoparticles in the
foam phase and those in the initial feed solution.
3
Figure S3. Effect of amount of loaded BSA on contact angle of CMNs. pH: 4.8.
The measurement of advancing contact angle of particles was directly carried out on a
flat film of the powder by an optical contact angle measuring device of KRUSS
DSA100.
4
Figure S4. TEM micrograph of Fe3O4 nanoparticles. The material was synthesized
by a conventional co-precipitation method, briefly, 11.8 g FeCl3.6H2O and 4.30 g
FeCl2.4H2O were dissolved in 200 ml deionized water under nitrogen gas with
vigorous stirring at 80℃. 25 ml 25% NH3.H2O was then added quickly into the
solution. The reaction was allowed to proceed for 2 h under continuous stirring. The
resultant product was repeatedly washed with deionized water by magnetic
decantation. The mean size of particles is found to be about 10 nm from the image.
References
(1) Li, W.; Yang, L.; Wang, F.; Zhou, H.; Xing, H.; Li, X.; Liu, H. Gas-Assisted Superparamagnetic
Extraction for Potential Large-Scale Separation of Proteins. Industrial & Engineering Chemistry
Research 2013, 52, 4290.
5