Olive Pomace-Based Nanobiochar as an Adsorbent Biomass for the Removal of Simple Phenols from Oil Mill Effluents: Experimental Modeling and Computational Approaches

Abstract

This study evaluated the sustainability of removing phenolic compounds from olive mill effluents using a nanobiochar synthesized from olive pomace. Catechol, tyrosol, hydroxytyrosol, and homovanillic alcohol were chosen as model pollutants due to their presence in agro-industrial wastewater. The surface morphology, elemental composition, crystallographic structure, functional groups, porosity, and thermal stability of the nanobiochar were investigated by SEM, EDX, XRD, FTIR, BET analysis, and TGA/DTA. The developed nanobiochar exhibited a predominantly amorphous carbon structure, enriched in carbon (85.6%), with localized graphitic domains. Its mesoporous architecture (SBET = 15.478 m2 g−1; Dp = 2.14 nm) promotes accessibility to active sites, while its thermal stability confirmed its suitability for adsorption applications. In this batch adsorption study, the technological aspect considered is the influence of operating parameters on adsorption efficiency, using kinetic and equilibrium models. Pseudo-first-order and pseudo-second-order kinetic models, as well as Freundlich and Langmuir isotherms, were used to analyze the experimental data. The pseudo-second-order model proved to be the most suitable for describing adsorption, suggesting that the process is primarily dominated by chemisorption. Similarly, the Langmuir model gave the least satisfactory results regarding equilibrium data, indicating monolayer adsorption on homogeneous active sites. The adsorption capacity of phenolic compounds was variable. The highest adsorption capacities were observed for catechol (250 mg g−1), tyrosol (19.23 mg g−1), homovanillic alcohol (15.38 mg g−1), and hydroxytyrosol (13.16 mg g−1). The results of this research indicate that adsorption affinity depends on molecular structure and electronic properties. Furthermore, computer modeling based on molecular simulations and electronic descriptors was performed to explain the adsorption mechanism. Linear regression, principal component analysis, and elastic regression revealed strong correlations between adsorption parameters and molecular descriptors. These results demonstrate that olive pomace-based nanobiochar is an environmentally friendly adsorbent for the treatment of phenolic effluents, with adsorption primarily controlled by surface interactions.