Rapid sonocatalytic degradation of phenol by TiO2@CeO2 core-shell structure prepared via metal alkoxide coating: Influential parameters and machine learning modelling

Abstract

This work focuses on the rapid heterogeneous sonocatalytic (HSC) degradation of high-concentration phenol effluent (100–500 mg/L) using TiO₂@CeO₂ core-shell structure. In this regard, the TiO₂ shell was synthesized using the metal alkoxide hydrothermal coating method around different amounts of ceria (CeO₂) nanocubes (TC(x), x = 0.025, 0.050, 0.075, and 0.100 g). The structural, textural, morphological and optical characteristics of the prepared sonocatalysts were identified using different analyses (PXRD, Raman, PL, DRS, AFM, FESEM/EDS, TEM, N₂ physisorption, and Mott-Schottky). At optimum conditions (0.3 g/L catalyst dosage, pH of 5, initial concentration of 400 mg/L, and duration of 30 min), the HSC removal of phenol reached 100 % using TC(0.05). The acute toxicity, developmental toxicity and mutagenicity assessment of phenol and its degradation products was performed using the Toxicity Estimation Software Tool (T.E.S.T). TC(0.05) (catalyst dosage of 0.3 g/L and US irradiation of 60 min) reduced more than 90 % COD of Merox wastewater (provided from the demercaptation unit) from 20466 mg/L to 1990 mg/L. Two predictive models, including KNN and RF, were developed to estimate the HSC degradation of phenol, and their performance was evaluated using statistical metrics. A higher coefficient of determination (R²_train= 0.98 and R²_test = 093) indicates that the RF model has a stronger correlation between predicted and actual values, as further supported by the low error function ( MAE and RMSE) values. The present contribution can be considered the first study to achieve rapid sonocatalytic degradation of high concentrations of phenol (100–500 mg/L) using core-shell structures consisting of CeO₂ nanocubes and TiO₂ nanoparticles within 30 min of irradiation. These results of HSC degradation and their environmental toxicity evaluation disclosed that the designed TC(x) core-shell structures could open new avenues for green environmental researchers.