Resin Adsorption of Phenolic Compounds from Olive Leaf and Coffee Residue Extracts: Batch and Packed Column Adsorption Experimental Investigation and Mathematical Modeling

Abstract

Phenolic compounds are important secondary metabolites often found in nature, and most prominently in plants. Plant biomass residues can be a sustainable source of this high-added-value group of compounds that can be used in the food and cosmetics industries due to their antioxidant properties. Olea europaea is a widely studied source of phenolic compounds, with olive leaves being an untapped solid residue with high phenolic content. Coffee residues after coffee extraction is another biomass residue stream rich in phenols. In this work, phenolic extracts of these two substrates, alongside different fractions produced through ultrafiltration and nanofiltration, were examined in resin adsorption experiments. Amberlite XAD16N was used as adsorbent in both batch and packed column experiments, with the experimental results being fitted with mathematical models for batch kinetics, adsorption isotherms, and column adsorption. The tested adsorbent proved capable of separating the target compounds, exhibiting a capacity of 72 mg of olive leaf phenols from nanofiltration retentate per g of resin in batch adsorption experiments, second order kinetics better described the batch adsorption process, while the use of the Thomas model sufficiently described the continuous adsorption process in packed columns (R2 > 0.9).