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 m_slurry = weight of syringe containing sample - weight of empty syringe (after sample application).

4. Read the volume of evolved hydrogen (V_H2 [ml])

5. Calculate nZVI weight: m_nZVI = (55,85 • 101,325 • V_H2) / [8314,3 • (273,15 + t)]

6. Calculate nZVI slurry content: c_nZVI = (m_nZVI ÷ m_slurry) • 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: m_slurry = 4,95g

Volume of evolved hydrogen: V_H2 = 350ml

Teperature = 20°C

nZVI weight: m_nZVI = (55,85 • 101,325 • 350) / [8314,3 . (273,15 + 20]= 0,81304g

nZVI in slurry content: c_nZVI = (0,81304 ÷ 4,95) • 100 = 16,43%

Iron-oxides content: c_Fe(oxides) = 20 - 16,43 = 3,57%

Ratio c_nZVI to c_{Fe(oxides) : 82% nZVI; 18% Fe(oxides)}