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Catalytic wet air oxidation of caffeine by using a Pt based-catalyst supported on a lignocellulosic activated carbon
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1  Chemical Engineering Department, Faculty of Chemistry, Complutense University, Madrid, Spain



Wastewater usually contains a great variety of hazardous organic compounds, being of special concern the so-called emerging compounds. Among these substances, the priority compounds are considered as especially toxic, showing most of them endocrine disruption effects.

The objective of this work was to evaluate the removal of caffeine from water by catalytic wet air oxidation (CWAO), using a Pt based-catalyst supported on a lignocellulosic activated carbon. The effect of the operation conditions, e.g., pressure, temperature and weight of catalyst on the removal of the contaminant and Total Organic Carbon was studied.


The tested catalytic support was based on a mesoporous activated carbon synthesized from peach stones by chemical activation using H3PO4 solution. The active phase of the catalyst was platinum with a metallic content of 3%, using H2PtCl6x6H2O as precursor. The metal was incorporated to the support by incipient wetness impregnation. The textural and morphological properties of the catalyst were explored. The tested operation conditions were the total pressure (20-40 bar), temperature (130-170 ºC) and the weight of catalyst (0.1-0.3 g). The sample analysis were carried out by using HPLC technique.


N2 adsorption-desorption isotherm of the catalyst can be classified as IV-type, characteristic of mesoporous solids. The specific surface area of the catalyst was of 1100 m2.g-1. BET area decreased after the CWAO process until 900 m2.g-1, probably due to the formation of a carbon deposit on the catalyst surface. Referring to the CWAO process, caffeine and TOC concentration gradually decreased along the reaction time, reaching to a final conversion, after 180 min, of 78-94% and 14-72%, respectively and depending on the reaction temperature.


The results of the study showed that CWAO of caffeine and TOC in water was successfully carried out using Pt(3%)/activated carbon as catalyst at the tested conditions. This material provides an efficient removal of caffeine, a trace compound of the domestic wastewater pollution.


The authors gratefully acknowledge the financial support from Ministerio de Economía y Competitividad Contact CTM2014-53485-REDC TRAGUANET, CTQ2014-59011-R REMEWATER and by Comunidad de Madrid through REMTAVARES Network S2013/MAE-2716.

Keywords: Carbon materials; Catalytic wet air oxidation; Emerging contaminants; Wastewater