Engineered 3D copper ferrite/kaolinite/polypyrrole carbon black hydrogels for efficient persulfate activation in tetracycline degradation: kinetics, mechanistic insights, toxicity, and green metrics

Abstract

This research focuses on the development of a novel, reusable copper ferrite/kaolinite/polypyrrole carbon black (PCB) impregnated carboxymethyl cellulose (CKP) hydrogel. It explores the degradation of tetracycline under LED light using persulfate activation. The CKP hydrogels, prepared via blend crosslinking methods, achieved 98% tetracycline degradation in 15 minutes under LED light irradiation via persulfate activation. The CKP hydrogels remained highly reusable for up to 20 consecutive cycles. The degradation kinetics were successfully modeled using a machine learning algorithm, and pseudo-first-order kinetics is proposed. The enhanced catalytic performance is attributed to the synergistic interaction between copper ferrite, kaolinite, and PCB within the carboxymethyl cellulose framework, which facilitates the effective separation of reactive oxygen species (ROS), such as sulfate (˙SO₄⁻) and hydroxyl (˙OH) radicals. The presence of polypyrrole carbon black (PCB) leads to higher electrical conductivity in CKP hydrogels. It acts as an efficient electron reservoir, facilitating the rapid transfer of electrons to the CKP hydrogels and helping to suppress charge recombination. The presence of kaolinite enhances the performance of CKP hydrogels by contributing to their high adsorption capacity. The 3D porous network of CKP hydrogels provides abundant reactive sites, further supporting rapid mass transfer and sustained efficiency. The key degradation intermediates were identified via high-resolution mass spectrophotometry (HRMS), their toxicity was assessed using ecological structure–activity relationships (ECOSAR), and the overall greenness of the CKP hydrogel system was validated through sustainability metrics analysis.