Mechanistic study of tetracycline removal and degradation in water using nCo@nZVI composite materials within a Fenton system

Abstract

In response to the escalating issue of antibiotic pollution in water bodies, with tetracycline (TC) serving as a representative example, this study introduced a novel magnetic nano cobalt @ nano zero valent iron (nCo@nZVI) composite material. To synthesize this material, the rheological phase reaction method was employed to produce sheet-like nZVI, followed by the liquid-phase reduction method to formulate the nCo@nZVI compound. Various advanced characterization techniques, including FESEM, HRTEM, EDS, XPS, XRD, BET, and FTIR, were utilized to systematically evaluate the physical, chemical properties, and structure of the material.Moreover, the study experimentally assessed the TC removal efficiency of nCo@nZVI, exploring the impacts of pH, temperature, and initial heavy metal ion concentration on this efficiency. It is worth noting that, under conditions of a neutral pH of 7, a temperature of 20 °C, and a material dosage of 1 g/L, the initial TC concentration of 20 mg/L in the wastewater was reduced to nearly zero (or completely removed) within 120 min. The adsorption kinetics and isotherm analysis revealed that the TC adsorption process by nCo@nZVI conforms to the pseudo-second-order kinetic model and Langmuir isotherm model, suggesting a predominantly chemical adsorption mechanism. The adsorption capacity derived from the Langmuir model was 25.33 mg/g.Further thermodynamic investigations demonstrated that the TC adsorption by nCo@nZVI is a spontaneous process. Additionally, the material primarily removes TC through an adsorption-degradation mechanism within the Fenton system. This eco-friendly and cost-effective material retains a removal rate of 65.87% after five cycles of regeneration treatment and can be recycled and reused under the influence of an external magnetic field, showcasing significant potential for the remediation of antibiotic-contaminated sites.

Graphical abstract