Optimizing filters of activated carbons obtained from biomass residues for ethylene removal in agro-food industry devices

Abstract

A series of adsorbents (activated carbons, ACs) were synthesized by physical and chemical activation of olive stones (OS) and their textural and chemical characteristics determined by complementary techniques such as N2 and CO2 physisorption, pH of the point zero of charge (pHPZC), HRSEM or XPS. Samples with a wide range of physicochemical properties were obtained by fitting the activation procedure. The performance of these adsorbents in filters working under dynamic conditions was studied by determining the corresponding breakthrough curves for the ethylene removal. The physicochemical transformations of OS during activation were related with the adsorptive performance of derivative ACs. Results were compared to those obtained using commercial carbons, in particular ACs, carbon black or carbon fibers, in order to identify the properties of these materials on influencing the adsorptive performance. In general, ACs from OS perform better than the commercial samples, being also easily regenerated and properly used during consecutive adsorption cycles. CO2-activation showed to be the best synthesis option, leading to granular ACs with a suitable microporosity and surface chemistry. These results could favour the integration of this type of inexpensive materials on devices for the preservation of climacteric fruits, in a clear example of circular economy by reusing the agricultural residues.