Lj. Graham et G. Jovanovic, Dechlorination of p-chlorophenol on a Pd Fe catalyst in a magnetically stabilized fluidized bed; Implications for sludge and liquid remediation, CHEM ENG SC, 54(15-16), 1999, pp. 3085-3093
p-Chlorophenol is dechlorinated using a Pd/Fe bimetallic micro-size catalys
t in a magnetically stabilized fluidized bed (MSFB) reactor. The catalyst i
s used in both powder form (d(c) = 7 mu m) and entrapped in alginate beads
(d(b) = 2.0 mm). The dechlorination reaction is performed in aqueous soluti
on containing p-chlorophenol with and without the presence of soil particle
s (20% w/w). Several important operating parameters involved in this comple
x chemical process are studied: Pd/Fe weight ratio, the extent of palladiza
tion or the ratio of Pd (Fe) interface area to the amount of chlorine to be
removed, system pH, and dissolved O-2. Important process resistances inclu
ding formation of Fe(OH)(2), Fe(OH)(3), and hydrogen gas bubbles, which are
dependent on the mentioned operating parameters, are identified for accura
te representation of the overall reaction kinetics. Pseudo first-order kine
tics (k = 3.81 +/- 0.08 m(3)/kg min) with first order deactivation of catal
yst (k(d) = 0.12 1/min) are found to excellently represent dechlorination c
hemical reaction. Once the chemical kinetics were defined, the active Pd/Fe
catalyst was entrapped in alginate beads for use in a magnetically stabili
zed fluidized bed. Diffusion constraints (D-e = 8.0 x 10(-10) m(2)/s) throu
gh the bead material (1.5% alginate + 98.5% H2O) are not severe and are rep
orted as being approximately 85-90% of the diffusivity measured in water (S
hishido et al., Chem. Engng. Res. Design: Trans. Inst. Chem. Eng. 73(6), 71
9-725, 1995; Oyaas et al., 1995a Biotechnol. Bioengng 47, 492-500). It can
be further moderated by decreasing the size of the beads and by using a nan
o size Pd/Fe catalyst particles (Wang and Zhang, 1997). Overall, the Pd/Fe
bimetallic catalyst has been shown to effectively dechlorinate p-chlorophen
ol both as a powder and entrapped in 2 mm alginate beads. Integration of th
e catalyst entrapped in the beads with the MSFB introduces a novel method f
or the treatment of difficult to handle materials, and toxic compounds. The
MSFB and alginate beads are shown to be an excellent engineering platform
which can be implemented in a variety of catalytic and non-catalytic liquid
-solid reaction processes. (C) 1999 Elsevier Science Ltd. All rights reserv
ed.