Comparison of synthesis methodologies to prepare more sustainable and stable catalysts for their application in agrochemical degradation processes. A Metal speciation study

VASCHETTO, ELIANA G.; OCHOA RODRÍGUEZ, PABLO A.; CARRARO, PAOLA M.; PÉREZ-PARIENTE, JOAQUÍN; EIMER, GRISELDA A.

Congreso; WCCE 11 - 11th World Congress of Chemical Engineering; 2023

Since the creation of the mesoporous catalysts, there has been intense research activity on their synthesis. Various molding agents have been evaluated however, these are expensive and non-biodegradability. This leads to industrialscale applications of mesoporous silica being disadvantageous. Therefore, the development of more ecological and economical routes remains as a challenge. In this work, Fe modified mesoporous materials were successfully synthesized from renewable molding agents (glyceryl monostearate and glycerol) by wet impregnation and direct incorporation methods. Both biomass-derived porogens allow a mesoporous structure to be achieved which was corroborated by XRD and physisorption of N2. Thus, these solids are presented as potential substitutes for conventional mesoporous catalysts synthesized from precursors derived from petrochemical industry. The materials were catalytically evaluated in the glyphosate degradation through wet oxidation reaction with air under extremely mild reaction conditions. While catalysts synthesized by Fe impregnation lead to high levels of degradation but decaying over reaction time, those synthesized by Fe direct incorporation (Si/Fe=20) present higher levels ofdegradation which are maintained through reaction time. It was confirmed by diffuse reflectance UV-vis spectroscopy, that the direct incorporation synthesis methodology manages to incorporate a higher content of Fe species (as isolated cations or very small nanoclusters) more strongly anchored into the structure. These, in addition to providing greater stability by reducing the Fe leaching from solids, are the main sites responsible for the formation of glyphosate-Fe complex [2]. The best result (around 70% of glyphosate degradation after 15 min of reaction) was obtained by using a solid prepared by direct incorporation with molar ratio Si/Fe = 20, glyceryl monostearate as porogen, 3h of initial gel agitation and 3 days of hydrothermal treatment at 85°C. Finally, in order to promote the use of biomass as potential raw material for the catalyst synthesis, a novel route isproposed to obtain Fe-modified mesoporous silica based in the use of glyceryl monostearate and glycerol as porogens. By this way it may be possible envisage the large-scale development of mesoporous materials with a reasonable cost and relatively less impact on the environment. In addition, the material engineering applied to the development of advanced remediation technologies allowed the degradation of a pollutant of great global concern as glyphosate towardsless toxic and more biodegradable ions (mainly short-chain ions) at 1 atm and room temperature.