engleski

Process intensification in phenolic wastewater treatment

Water pollution is characterized mainly by the volume of waste to be treated and by the nature, concentration and toxicity of pollutants that form it. These parameters are all factors that have to be taken into account when choosing the treatment method to use. Due to its presence in various processes in pharmaceutical, chemical and petrochemical industry, where it is used either as reagent, intermediate substance or solvent, phenol and its derivatives are known as one of the most common organic water pollutants. The effective removal of such pollutants, for safe discharge, is a challenging task as environmental laws and regulations are becoming more and more stringent. Catalytic Wet Air Oxidation (CWAO) is presented as an effective technology to treat aqueous hazardous wastes, especially when these are too diluted to incinerate or too concentrated for a biological treatment. CWAO process uses molecular oxygen as oxidant operates at T ~ 353-475 K and p ~ 10-100 bars. The addition of hydrogen peroxide as a source of free radicals makes the process more attractive by achieving high conversion at considerably lower temperature. In this regard the use of catalytic wet peroxide oxidation (CWPO) which utilize free radicals as the oxidizing species, thus providing lower reaction conditions (T ≤ 373 K, atmospheric pressure) is one the most simple and effective techniques for partial oxidation of persistent organic pollutants into biologically amenable intermediates. The main objective of this work is to integrate the benefits CWAO and CWPO in an intensified technique, to obtain high conversion of pollutant in wastewater and to give end effluent that could be more easily biologically treated. In that purpose, activity and stability of copper based zeolite catalysts were tested in batch reactor by performing different phenol oxidation processes. The experimental profiles for phenol and TOC conversions using hydrogen peroxide as promoter in CWAO have been compared to those obtained in the CWAO and CWPO process. Acquired experimental data was tested to a proposed kinetic model for phenol oxidation and hydrogen peroxide decomposition.

heterogeneous catalysis; zeolite; process intensification; phenol oxidation

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