Photocatalytic oxidation of phenols on modified palygorskite or chars from the pyrolysis of aveloz ( Euphorbia Tirucalli Linn) and sewage sludge using a slurry reactor

The scope of this work was to evaluate the photocatalytic performance of pyrolysis chars derived from sewage sludge and aveloz, as well as modified palygorskite, for phenol degradation in dilute aqueous solution under UV irradiation. The effects of pH (3.0, 5.5, 6.9, and 10.7) and initial phenol concentration (0.25 and 0.50 g L −1 ) were investigated in a continuously oxygen‐fed photoreactor operated at 50°C. Phenol and intermediate products were quantified by high‐performance liquid chromatography, and a lumped kinetic model based on apparent homogeneous and heterogeneous reaction steps coupled with Langmuir–Hinshelwood competitive adsorption was developed to describe the experimental concentration profiles. Model parameters were estimated using particle swarm optimization coupled with the DASSL differential equation solver. Photocatalytic tests resulted in phenol conversion ranging from 42.34% to 64.65%, with the highest conversion achieved using aveloz char at pH 3.0, while the sewage sludge char exhibited the highest mineralization potential, with a rate constant of 1.2759 L mol −1 min −1 . The proposed model accurately described the experimental data, yielding a pseudo‐first‐order dependence with respect to phenol (, ). The main scientific contribution of this work is the development and experimental validation of a unified phenomenological kinetic framework that incorporates adsorption effects and enables the quantitative comparison of different waste‐derived photocatalysts using a consistent set of kinetic parameters.