Removal of norfloxacin using coupled synthesized nanoscale zero-valent iron (nZVI) with H2O2 system: Optimization of operating conditions and degradation pathway

Abstract

a b s t r a c tIn this study, nanoscale zero-valent iron (nZVI) was synthesized in the laboratory by the borohydride reduction method. nZVI was characterized by transmission electron microscopy (TEM), scan electronic microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). In addition, the degradation performance of norfloxacin (NOR) in nZVI/H 2 O 2 Fenton-like system was investigated in detail under various experimental conditions. It was found that the removal of NOR depended on its initial concentration, initial pH, temperature, H 2 O 2 concentration and nZVI dose. At the ambient temperature, the degradation rate of NOR by nZVI/H 2 O 2 Fenton-like reaction under the acidic medium (pH = 3-4) was more than 95% within 40 min of the reaction time, and the mineralization degree was around 50% in terms of total organic carbon (TOC) measurement. Optimal temperature for NOR removal was 308 K, and higher temperature would cause useless decomposition of H 2 O 2 and consequently reduction of NOR degradation. The degradation rate and total removal efficiency of NOR were favored by increasing the nZVI and H 2 O 2 dosages. The optimal conditions for NOR degradation were: initial pH = 4.0, H 2 O 2 concentration = 20 mmol/L, nZVI dose = 100 mg/L, temperature = 308 K. The rate constants (K obs ) of NOR degradation could be fitted well with a pseudo-second-order kinetic equation. Several degradation intermediates of NOR were detected and confirmed, including C 15 H 20 FN 3 O (m/z 278), C 9 H 11 FN 2 (m/z 167), C 7 H 7 FN 2 (m/z 139), and C 7 H 8 FN (m/z 126), respectively. Based on the identified intermediates and the Gaussian quantum statistics molecular bonding energy calculation, the possible pathway for NOR degradation under nZVI/H 2 O 2 Fenton-like reaction was discussed.

Fenton-Like Oxidation of Antibiotic Ornidazole Using Biochar-Supported Nanoscale Zero-Valent Iron as Heterogeneous Hydrogen Peroxide Activator

“…After each cycle, the nZVI-BC was collected via vacuum filtration and washed several times for further use. As shown in Figure 7, the removal efficiency decreased from 80.1% to 63.2% after three recycling runs, owing to the release and consumption of Fe 0 from nZVI-BC [23,24]. However, this was still a good value considering that a high concentration of the ONZ solution was treated in the experiments.…”

“…nZVI was prepared via the same method without the addition of BC. The process can be described by the following reaction [13,24]:…”

Effect of pH on Zero Valent Iron Performance in Heterogeneous Fenton and Fenton-Like Processes: A Review

“…Zhang et al have studied the ZVI-Fenton removal of norfloxacin [77], which is strongly pH-dependent. The best degradation efficiency was observed at pH 3–4, where almost 90% of norfloxacin was removed within 10 min.…”

Synergistic adsorption-photocatalytic degradation effect and norfloxacin mechanism of ZnO/ZnS@BC under UV-light irradiation

“…Traditional methods such as adsorption 5 , 6 , oxidation 7 , 8 , and photocatalysis 9 , 10 have been used to remove NOF from water and produce certain effects. The light-sensitive character of NOF makes photocatalytic degradation a common method.…”