Near-infrared turbidity of {beta}-FeOOH particle suspensions

Journal Article · Tue Feb 01 04:00:00 EST 2000 · Applied Spectroscopy

DOI:https://doi.org/10.1366/0003702001949195· OSTI ID:20217319

Berdahl, P ^[1]; Espinoza, L H ^[1]; Littlejohn, D ^[1]; Lucas, D ^[1]; Perry, D L ^[1]

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1. Environmental Energy Technologies Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)

Near-infrared transmission spectroscopy can be complicated by the light scattering from heterogeneous materials. For the examination of an evolving system exhibiting such light scattering, transmission spectra near wavenumber {nu}=10{sup 4} cm{sup -1} were obtained during the hydrolysis of FeCl{sub 3} solutions. At first, the resulting turbid suspension of cigar-shaped {beta}-FeOOH particles exhibits single-particle scattering, including a Rayleigh regime (attenuation{proportional_to}{nu}{sup 4}). At later times, the scattering increases strongly as the particles aggregate, and becomes proportional to {nu}{sup {alpha}}, with {alpha}{approx_equal}2, consistent with scattering models that interpret the structure of aggregates in terms of a fractal dimension d{sub f} roughly equal to 2. In all cases investigated, the attenuation due to scattering is spectrally smooth and increases monotonically with wavenumber. It can be written in the simple form {nu}{sup {alpha}} with 1{<=}{alpha}{<=}4. While over limited spectral ranges {alpha} may be taken independent of {nu}, over wide ranges it decreases with increasing {nu}. This behavior is consistent with the theoretical limits of {alpha}=4 at {nu}=0, and {alpha}=0 at {nu}={infinity}. Overall, the results suggest that a useful form for simulating scattering backgrounds in near-infrared spectroscopy is A{nu}{sup {alpha}}, with A and {alpha} fitted constants. (c) 2000 Society for Applied Spectroscopy.

• OSTI ID: 20217319
• Journal Information: Applied Spectroscopy, Journal Name: Applied Spectroscopy Journal Issue: 2 Vol. 54; ISSN 0003-7028; ISSN APSPA4
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
ABSORPTIVITY
EXPERIMENTAL DATA
IRON HYDROXIDES
LIGHT SCATTERING
REFLECTION
SPECTROSCOPY
TURBIDITY