New TiO₂-Ag/BEA composites with dual Ag-functionalization for specific adsorption and catalytic sites. Synergism between phases in the ethylene removal for climateric fruit conservation

A new series of TiO 2 -Ag/BEA composites was specifically designed for use in filter/photo-reactors intercalated in air recirculation circuits in storage facilities for climacteric fruits. The sol-gel procedure for TiO 2 deposition was combined with ionic exchange (IE) or incipient wet impregnation (IWI) techniques for Ag doping, with the proportions of both fractions also varying. The prepared materials were thoroughly characterized in terms of their porous texture, chemical composition, crystalline structure, and Ag dispersion, among other properties. Dynamic ethylene adsorption was recorded in the dark. After saturation, ethylene photooxidation was analyzed under UV or UVA-visible light, with varying contact times, flow rates, and concentrations, and with or without humidity present. The maximum ethylene adsorption capacity (361 μmol g −1 ) corresponds to the sample with the highest Ag content (5 wt%), added by IE, while the best photocatalytic performance is obtained for samples doped by IWI. The performance of the samples was found to be correlated with their physicochemical properties and was specifically determined by the nature and dispersion of the silver species in the composites. Total ethylene photooxidation is achieved even under UV–Vis radiation; the reaction develops selectively to CO 2 in all cases, despite the strong negative effect of humidity on the formation of more active HO• radicals. The high adsorption capacity and effective photooxidation of ethylene enable control of this maturation hormone below the established limits. • The synergetic effects of each phase in Ag-TiO 2 - BEA composites is analyzed. • Doping with Ag-species is determinant on the adsorption/photocatalytic performance. • Ionic exchange stabilized Ag + which strongly enhances ethylene adsorption. • Impregnation (IWI) stabilized Ag 0 which enhances ethylene photo-oxidation. • Promising Ag-TiO 2 - BEA composites for ethylene removal and fruit preservation.