Catalytic Wet Air Oxidation (CWAO) is an efficient and promising oxidative pollution removal process for the treatment of effluents which are too diluted to be incinerated and too concentrated to consider any biological treatment [1]. CWAO is known as a green process whose powerfulness is based on the combination of high temperature (130–300°C) and oxygen or air pressure (5–60 bar) together with a high active catalyst. The key factor for this process to achieve wider industrial applications is the catalyst. Indeed, for a perennial process, this latter must be ecologically and economically acceptable, that is a catalyst without the presence of noble metals, stable in the CWAO operating conditions, inexpensive and abundant in nature. This is a very challenging task. Clays could be the right solution.<br/>In this work, a Tunisian clay has been successfully pillared with Al and Al-Fe, which means the intercalation of large polyoxocations, which generate stable oxide pillars by calcination. The resulting interlamellar galleries are accessible to molecules. The pillaring process was performed using a conventional method and a microwave assisted method.<br/>The resulting materials were tested as heterogeneous catalysts for the CWAO of phenol. The modification of the clay induces an increase of the catalytic properties. The presence of iron induces an increase of the mineralization. Moreover, despite the severe conditions of reaction, which are acidic medium, high pressure and temperature, pillared clays appear to be quite stable since the Fe leaching is almost negligible (ICP on the CWAO remaining solutions). Moreover, the contribution of the homogeneous phase reaction has been evaluated. The oxidation takes place essentially on the catalyst surface through a heterogeneous mechanism. Al-Fe pillared clays seem promising as catalysts for CWAO phenolic industrial water treatment.<br/>Furthermore, the microwave irradiation method, by comparison to the conventional one, presents the advantage of reducing considerably the time of synthesis and the consumption of water. Hence, the resulting materials are ecologically and economically viable. These materials could be then produced at large scale, increasing so the added value of clay that is an abundant natural resource. Therefore, CWAO, which is a green process to degrade organics into carbon dioxide, could achieve wider industrial applications.

Wastewater treatment by catalytic wet air oxidation process over a Tunisian clay pillared with Al-Fe

255th National Meeting (2018)

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