(562az) Modeling and Kinetics Study of Methyl Orange Degradation over a Cu/?-Al2O3 Fenton-like Catalyst in Continuous Fixed Bed Reactor | AIChE

(562az) Modeling and Kinetics Study of Methyl Orange Degradation over a Cu/?-Al2O3 Fenton-like Catalyst in Continuous Fixed Bed Reactor


Ding, D. - Presenter, State Key Laboratory of Chemical Engineering, East China University of Science and Technology
Tian, P., East China University of Science and Technology
Sun, Y., East China University of Science and Technology
Xu, J., East China University of Science and Technology
Han, Y. F., East China University of Science and Technology

wet peroxide oxidation (CWPO) is recognized as one of the most promising and
environmental-friendly techniques for reclamation of wastewater containing
toxic and bio-refractory compound. It takes advantage of the great oxidative
capacity of the hydroxyl radical (HO∙) driving from hydrogen peroxide (H2O2)
at moderate conditions (< 373 K, 0.1 − 0.5 MPa). Compared with the batch
reactor, continuous fixed bed reactor (FBR) was a superior configuration for industrial
application of CWPO process [1, 2]. However, a lack of study on the
diffusion and kinetics for this liquid-solid system in the continuous FBR results
in poor understanding of this process, which further hinders its scale-up and
commercial use.

this work, copper supported on alumina pellets (Cu/¦Ã-Al2O3)
were synthesized by impregnation method, and the average diameter of pellets
size was 2.3 mm. The as-prepared catalyst was denoted as 2.3Cu/¦Ã-Al2O3.
The morphology of pellets exhibits good sphericity with a rough surface (Fig.
1(a)), however, the hardening phenomenon was more serious for the surface
comparing with the inside of the pellet (Fig. 1(b − d)). In addition, Al, O and
Cu elements are well-dispersed for the whole pellet (Fig. 1(e)).

series of performance tests were conducted in an up-flow FBR for methyl orange
(MO) degradation. The 2.3Cu/¦Ã-Al2O3 exhibited high
activity and excellent leaching resistance during 200 h testing (leaching
amount of Cu < 0.6 mg/L). The
conversion of MO and COD equal to 97% and 92% was achieved over 2.3Cu/¦Ã-Al2O3
catalyst (reaction conditions: pH0 = 8.2, flow rate = 2 mL/min, [catalyst]
= 9.9 g, [MO]0 = 30 ¦ÌM, [H2O2]0 =
29 mM, and 50¡æ). The apparent reaction kinetics was investigated on the basis
of the pseudo-first order simplification for the MO degradation and H2O2
decomposition, and the apparent Ea were calculated to be 21.0 and
13.8 kJ/mol, respectively. Compared with the intrinsic Ea studied for MO
degradation (57.8 kJ/mol) and H2O2 decomposition (47.7
kJ/mol) in batch reactor, the mass transfer was significant for MO/H2O2/2.3Cu/¦Ã-Al2O3
system in the FBR.

Fig.1 SEM and EDX
images of 2.3Cu/¦Ã-Al2O3 catalysts: (a − b) SEM images of 2.3
Cu/¦Ã-Al2O3 pellet and corresponding enlarged image, (c − b)
SEM images of cross-section for 2.3Cu/¦Ã-Al2O3 pellet and corresponding
enlarged image, (e) EDX mappings of Al, Cu and O elements for cross-section of 2.3Cu/¦Ã-Al2O3

addition, the apparent kinetic study for MO oxidation and H2O2
decomposition were modeled with account for the external and internal diffusion
limitation, which were quantified by measuring the apparent kinetic rate
constant by changing the pellets sizes (mean dp = 2.3, 3.5, 4.2 mm) and
flow rate (1 − 20 mL/min). As shown in Fig. 2, modified experimental
correlation (Sh = 1.5Re1.10Sc0.42) was proposed for the
calculation of external mass transfer coefficient. Additionally, intrinsic
kinetics was studied in the batch reactor to determine the effectiveness factor
(¦Ç) in FBR to provide accuracy description of the experimental data.

Fig. 2 (a)
Values of kc for MO oxidation, ([H2O2]0
= 29 mM, [MO]0= 30 ¦Ìm, flow rate = 2 − 20
mL/min, mean dp = 2.3 mm, and [Catalyst] = 9.9 g). (b) Fitting
results of the relationship between Sh, Re and Sc. (c) Calculated ¦Ç and ¦µ for
H2O2 decomposition and MO oxidation (blue square: H2O2,
red triangle: MO)

summary, Cu/¦Ã-Al2O3 pellet catalysts
prepared by impregnation method showed outstanding activity and stability
against leaching for H2O2 decomposition and MO degradation
in the FBR. Quantified analysis showed that H2O2
decomposition and MO degradation in the FBR was both controlled by the external
and internal mass transfer resistance, especially the latter. The geometric
size of the pellet catalysts exert a pronounced effect on the apparent kinetic
of the process.

the predication of apparent kinetic rate in the FBR, a combined diffusion-kinetic
model was proposed. A modified empirical correlation for the external mass
transfer at low Re was determined by fitting the experimental data in FBR and the
effective factor (¦Ç) for internal mass transfer resistance was calculated according
to the intrinsic kinetics measured in the batch reactor. This diffusion-kinetic
model provided a reasonable description of the experimental data and can be
expanded to other pollutants degradation, which provided a good solution for
the CWPO process analysis and reactor design.


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[2] Esteves BM, Rodrigues CSD.Madeira LM, in
Applications of Advanced Oxidation Processes (AOPs) in Drinking Water
Treatment, eds. Gil, Galeano,Vicente, Springer International Publishing, Cham,