Adsorption of direct dye on cross-linked chitosan fiber: breakthrough curve

Abstract

The recovery of direct dye by adsorption on cross-linked fiber (ChF-B), which we have developed, appeared technically feasible. The concentration of amino group fixed in the adsorbent phase was 3.30 mol/kg dry fiber. A typical direct dye, Brilliant Yellow (M.W.=625, divalent anion) was used in this experimental study. The breakthrough curves for adsorption of the dye were measured for different flow rates, bed heights, influent concentrations of the dye, and temperatures. The experimental breakthrough curves showed that ChF-B recovered the dye efficiently even from the hot dye solution. Axial dispersion coefficient Ez (m2/s) in fibrous bed was measured and the following correlation for the dispersion coefficient was obtained: Ez = 5.4 × 10−6Re′1.1 (ɛ = 0.698) Ez = 4.7 × 10−6Re′1.2 (ɛ = 0.813) where ɛ denotes void fraction of the bed. The theoretical breakthrough curve obtained by considering the effect of axial dispersion was close to that obtained from the analytical solution for rectangular isotherm system without considering the axial dispersion in Re′ > 0.46. The experimental breakthrough curves in pH ≤ 4 agreed well with the analytical solution. The intrafiber effective phase diffusivity of the dye at 323 K was about two times larger than that at 298 K and the bed capacity at 323 K was almost the same as that at 298 K.