Nano-iron wrapped by graphitic carbon in the carbonaceous matrix for efficient removal of chlortetracycline

Abstract

A magnetic composite of nano-iron wrapped by graphitic carbon in the carbonaceous matrix with hierarchical pores is an efficient, regenerative, and versatile adsorbent to remove antibiotics from water. • The magnetic composite of nano-iron wrapped by graphitic carbon in the carbonaceous matrix with hierarchical pores (Fe in /C-700) was synthesized through one-step thermolysis of Fe in /Zn-MOF. • Excellent chlortetracycline adsorption performances maintained with respect to various coexisting ions and actual water. • Fe in /C-700 exhibited highly effective adsorption capacities for chlortetracycline, ciprofloxacin, and sulfamethoxazole in the mixed antibiotic system. • Fe in /C-700 showed perfect reusability via magnetic recovery. The stability, versatility, and reusability of an adsorbent are of great significance to its practicability to remove antibiotics from water due to their universal residual. Herein, a magnetic composite of nano-iron wrapped by graphitic carbon in the carbonaceous matrix with hierarchical pores (Fe in /C-700) was constructed by one-step pyrolysis using Fe in /Zn-MOF as a precursor. Fe in /C-700 exhibited a core–shell structure and superparamagnetism behavior, which showed excellent chlortetracycline (CTC) adsorption with the maximum adsorption capacity of 546.5 mg/g. The adsorption process matched well with the pseudo-second-order kinetics model and Langmuir model, indicating chemisorption was likely contributed to the CTC adsorption. Electrostatic interaction, surface complexation, hydrogen bond, and π-π EDA interaction were the dominant driving forces. Cl - and SO 4 2- significantly enhanced the CTC adsorption due to the electrostatic attraction or hydrogen bond formed among Fe in /C-700, anions, and CTC. Fe in /C-700 maintained high adsorption capacities in the mixed antibiotic system (255.1, 143.3, and 169.6 mg/g for CTC, ciprofloxacin, and sulfamethoxazole), in actual water (372.9, 383.3, 390.6, and 366.7 mg/g for CTC in Pearl River water, lake water, tap water, and ultrapure water), and regeneration (366.7, 354.2, 360.4, 314.6, and 301.0 mg/g for CTC in five runs), indicating a promising reusable adsorbent for the remediation of antibiotics in water. These findings provide a feasible and straightforward strategy to synthesize high stable magnetic nanoparticles derived from MOFs.