|nZVI TESTER: the measurement of nZVI content in a slurry|
nZVI TESTER is destined for the measurement of zero-valent iron nanoparticles content in a slurry. The method is based on the measurement of hydrogen volume, which is evolving during chemical reaction of zero-valent iron and an acid. This test is very simple and particularly fair minded: the volume of hydrogen is directly proportional to the amount of zero-valent iron, the amount of iron-oxides does not influence the volume of generated hydrogen, it only slows down the reaction speed.
The "Hydrogen method" was compared to Mössbauer spectroscopy and X-ray powder diffraction - please see the following chart [thanks to Prof. Radek Zbořil, Ph.D.; Regional Centre of Advanced Technologies and Materials (RCPTM)].
Reaction of nZVI and the acid (KHSO4) proceeds according to the following formula:
2KHSO4 + Fe -> FeSO4 + K2SO4 + H2
55,85 g Fe -> 22,41 dm3 H2
From previous formula it comes through, that 22,41 dm3 of hydrogen is generated by reaction of 55,85 g of iron and sufficient amount of acid (2KHSO4). The weight and the concentration of nZVI in slurry is consequently calculated from the volume of evolved hydrogen.
Measurement process brief description:
1. Set-up nZVI TESTER.
2. Take a sample of slurry by syringe and apply it to the reaction bottle containing acid.
3. The weight of applied sample mslurry = weight of syringe containing sample - weight of empty syringe (after sample application).
4. Read the volume of evolved hydrogen (VH2 [ml])
5. Calculate nZVI weight: mnZVI = (55,85 • 101,325 • VH2) / [8314,3 • (273,15 + t)]
6. Calculate nZVI slurry content: cnZVI = (mnZVI ÷ mslurry) • 100
slurry application to the reaction bottle (2)
read the volume of evolved hydrogen (4)
EXAMPLE OF MEASUREMENT
Sample: Nanofer 25S (20% of iron nanoparticles; 80% of water+stabilizer), age: 3days
Manufacturing date: 4.5.2010 ; Measurement date: 7.5.2010
Sample weight: mslurry = 4,95g
Volume of evolved hydrogen: VH2 = 350ml
Teperature = 20°C
nZVI weight: mnZVI = (55,85 • 101,325 • 350) / [8314,3 . (273,15 + 20]= 0,81304g
nZVI in slurry content: cnZVI = (0,81304 ÷ 4,95) • 100 = 16,43%
Iron-oxides content: cFe(oxides) = 20 - 16,43 = 3,57%
Ratio cnZVI to cFe(oxides) : 82% nZVI; 18% Fe(oxides)