Efficient Water Purification via Dual Pb(II) Capture and Tetracycline Elimination Using Rod-Shaped Co@nZVI Nanohybrids: Mechanism and Performance

The escalating ecological threats posed by co-existing heavy metals and antibiotics necessitate innovative remediation strategies. Herein, a magnetic rod-like nano-cobalt/zero-valent iron composite (Co@nZVI) was synthesized via a dual-phase approach integrating the rheological phase reaction and liquid-phase reduction, demonstrating exceptional dual functionality for simultaneous Pb²⁺ immobilization and tetracycline (TC) degradation. Comprehensive characterization of the materials confirmed the successful synthesis and structural properties of the materials. Batch experiments evaluated removal efficiency of TC and Pb²⁺ under varying pH, temperature, and initial concentration conditions. Optimal removal (TC, 87.6%; Pb²⁺, 97.7%) was achieved at pH 7, 20 °C, and 1 g L^-1 dosage, reducing 20 mg L^-1 contaminants to trace levels within 120 min. Langmuir-type monolayer chemisorption and pseudo-second-order adsorption behavior were demonstrated by kinetic and isotherm studies, with maximal capacities of 22.43 mg g^-1 (TC) and 23.07 mg g^-1 (Pb²⁺). Thermodynamic analysis confirmed the spontaneity of the adsorption process. Mechanistically, the removal of Pb²⁺ is governed by surface complexation, cation exchange, and electrostatic interactions, whereas the degradation of TC relies on the interaction with adsorbents via ion exchange and the presence of Co@nZVI nanomaterials activating H₂O₂ to trigger a Fenton-like reaction, with ^•OH acting as the main reactive oxygen species (ROS) for TC to be degraded. The material is not only environmentally friendly, cheap, and efficient but also shows great potential in the remediation of composite-contaminated sites.