PMS activation via alginate cross-linked TiO2 hybridized peanut shells biochar under visible light for boosted pharmaceutical pollutants oxidation

Water contamination by persistent pharmaceuticals, such as the antibiotic sulfamethoxazole (SMX), poses a significant threat to aquatic ecosystems and human health. Simultaneously, much agricultural waste remains underutilized as a potential sustainable resource. Peanut shells were converted into biochar (PSB) and subsequently hybridized with TiO 2 nanoparticles to catalyze peroxymonosulfate (PMS) under visible light for the oxidation of the SMX. PSB@TiO 2 was fabricated using a 3D sodium alginate (Alg) cross-linked matrix, which acts as a stabilizing scaffold and an active contributor to pollutant adsorption and charge transfer enhancement, obtaining Alg-PSB@TiO 2 . The Ti-O-C interfacial bridge formed between PSB and TiO 2 particles plays a crucial role in absorbing visible light and redox charge transfer. In the presence of PMS, 99.9% SMX degradation was achieved within 90 min by Alg-PSB@TiO 2 under simulated sunlight, with a photocatalytic performance of 6.13, 4.01, and 1.14 times higher than bare PSB, TiO 2 , and PSB@TiO 2 , respectively. Quenching tests demonstrate that h + , SO 4 •- , • OH, 1 O 2 , e - and • O 2 - were produced and contributed to SMX degradation, wherein h + , SO 4 •- , e - are the primary reactive species. Stability and recycling tests proved that Alg-PSB@TiO 2 photocatalyst sustained 90.6% efficiency after six cycles, exhibiting superior stability compared to most bead-based and powdered catalysts, with undetectable Ti leaching. In addition, LC–MS analysis and ECOSAR predictions indicate that the degradation pathways substantially reduce the toxicity of transformation products. Collectively, this work establishes the biochar–TiO 2 hybrid immobilized on Alg beads as a highly efficient, reusable, and environmentally safe photocatalyst for PMS activation. • Eco-friendly synthesis of alginate-crosslinked TiO 2 hybridized peanut shell biochar. • Alg-PSB@TiO 2 maintained high efficiency (up to 90%) even in real-world scenarios. • PSB mediates electrons, and alginate matrix stabilizes and enhances TiO 2 optics. • ROSs contributions to SMX degradation ranked as: h + > SO 4 •– > e - > 1 O 2 > • O 2 - > • OH. • Potential intermediates and plausible pathways of SMX degradation were outlined.