Mechanistic Interpretation of Ionic Azo Dye Flux Decline through Compacted Na-montmorillonite Membrane
The decrease in filtrate flux of ionic azo dyes through compacted Na-montmorillonite membrane can be adequately described by (i) analytical and empirically derived transport equations, (ii) solute rejection and intrinsic retention equations and (iii) X-ray diffraction. Experiments were performed using two ionic azo dyes, Orange G (7-hydroxy-8-phenlyazo-1,3-naphthalenedisulfonic acid disodium salt), a molecular biology reagent and brilliant yellow (C.I. 24890 direct yellow 4). Filtrate samples were collected using a static head setup consisting of a longitudinal flow acrylic cylinder cell through compacted Na-montmorillonite membrane. The results indicated that there was initial rapid flux reduction for the first 3 days due to surficial fouling owing to affinity of hydrophilic organic compounds rapidly getting attached to exchange sites at the dye-membrane interface before slowing down to a quasi-steady-state (5-7 days) and gradual gelation period (8-16 days) during steady-state. The ratio of flux reduction was approximately 3:5 for brilliant yellow to Orange G. The flux values were higher than mass transfer coefficients. Flux decline for the dyes followed an exponential decay described by J ∝ 1/tn, with n = 0.9556 for yellow dye and n = 0.8923 for Orange G. X-ray diffraction indicated that both the lower molecular weight Orange G (452.4 g mol−1) and higher molecular weight brilliant yellow (624.6 g mol−1) dyes are less preferentially retained within the basal spacing of Na-montmorillonite due to only a slight shift in the range 5.8-6° 2θ region. The results offer a preliminary study in the fate, transport and recyclability of these ionic azo dyes through smectitic membranes.
P. G. Oduor and T. M. Whitworth, "Mechanistic Interpretation of Ionic Azo Dye Flux Decline through Compacted Na-montmorillonite Membrane," Journal of Membrane Science, Elsevier, Jan 2005.
The definitive version is available at http://dx.doi.org/10.1016/j.memsci.2005.04.038
Geosciences and Geological and Petroleum Engineering
Keywords and Phrases
Basal Spacing; Concentration Polarization; Diffusion Coefficient; Ion Exchange; Mass Transfer
Article - Journal
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