4-chlorophenol kinetic parameters

Table 8.5. Examples of kinetic parameters for chlorophenol degradation modeled by Monod or Haldane (Kl involved) equations... 

Removal rates greater than 90% were observed for all of the phenols studied. The decay kinetics for phenol p-methoxyphenol p-cresol p-fluo-rophenol p-chlorophenol p-bromophenol 4-hydroxyacetophenone a,a,a-trifluoro-p-cresol p-cyanophenol and p-iodophenol were found to be consistent with the Langmuir-Hinshelwood kinetic model. After employing all the substituents, little variation on the Langmuir-Hinshelwood kinetic parameters was observed. 

The reaction progress is monitored ofF-Une by HPLC. Flow rates, residence times and initial concentrations of 4-chlorophenol are varied and kinetic parameters are calculated from the data obtained. It can be shown that the photocatalytic reaction is governed by Langmuir-Hinshelwood kinetics. The calculation of Damkohler numbers shows that no mass transfer limitation exists in the microreactor, hence the calculated kinetic data really represent the intrinsic kinetics of the reaction. Photonic efficiencies in the microreactor are still somewhat lower than in batch-type slurry reactors. This finding is indicative of the need to improve the catalytic activity of the deposited photocatalyst in comparison with commercially available catalysts such as Degussa P25 and Sachtleben Hombikat UV 100. The illuminated specific surface area in the microchannel reactor surpasses that of conventional photocatalytic reactors by a factor of 4-400 depending on the particular conventional reactor type. 

The kinetic parameters measured by batch-experiments [2] for the sorption of 3-chlorophenol on Na bentonite at 25 °C (viz. the subsequent list of data and Fig. 2) are transformed to the transport in a model soil column. The model soil column is assumed to consist of Na bentonite particles, to have the porosity of natural soil, and to be saturated with water. There is a 1-day injection of aqueous 3-chlorophenol into the column. Model calculations are made for a non-precharged column and a column precharged by irreversibly adsorbed 3-chlorophenol. Observation time is 1.5 days. The experimental conditions for the calculations have model character with respect to the transfer of data and do not consider possible experimental difficulties in the soil column, e.g., by swelling of Na bentonite. 

Theurich et al. [59] in a study of the degradation of 4-chlorophenol also found the kinetics of the photocatalytic destruction process could also be described by the L-H model. Although the rate of 4-CP was uninfluenced by pH it was found the level of mineralisation was particularly sensitive to changes in this parameter. The mechanism of destruction also appeared to be affected by the nature of titania used. With Degussa P25 seven intermediates were detected while with Hombicat UV100 only three by-products were generated (Scheme 1). 

Two researches studied the adsorptive properties of montmorillonite clay modified by tetra-butyl ammonium (Akgay, 2004, 2005). The adsorption of p-chlorophenol in this clay was done in batch with 20 mL of pollutant solution to 0.1 g of clay, at 25°C for 16 h. The adsorption isotherms were adjusted according to the models of Freundlich and Dubinin-Radushkevich. The kinetic and thermodynamic parameters pointed to the application of organoclay as adsorbent effective of phenolic compounds in contaminated effluents. 

---