Effects of green synthesis, magnetization, and regeneration on ciprofloxacin removal by bimetallic nZVI/Cu composites and insights of degradation mechanism.

In this study, nanoscale zerovalent iron (nZVI) with copper (Cu) bimetallic particles, whichare applied for degradation of Ciprofloxacin (CIP) under weak magnetic field (WMF), were synthesized using green tea extracts (GT-nZVI/Cu). The surface morphology and physicochemical properties of the novel catalytic materials were characterized. It was found that GT-nZVI was more stable and performed better in oxidation resistance than the nZVI synthesized by traditional chemical methods. Besides, the catalytic reactivity of GT-nZVI/Cu was measured with and without WMF, it is obvious from the experimental results the performance of GT-nZVI/Cu system was enhanced significantly with WMF. Moreover, WMF still had a certain effect even after being removed, which is called remanence effect. The mass spectrometry (MS) was utilized to analyze the degradation products of CIP, and the contribution of adsorption and Fenton/Fenton-like oxidation of GT-nZVI/Cu during CIP removal process was further evaluated. It was found that as the removal process progressed, the contribution ratio of Fenton/Fenton-like oxidation rose rapidly and exceeded adsorption after 20 min. Eventually, attempts have been made to regenerate GT-nZVI/Cu, in which physical recovery (ultrasonic) was the main route, and the CIP removal rate decreased as the regeneration times increased. This research provides new insights into the green synthesis and regeneration of nZVI and is expected to realize the practical application of nZVI.

Removal of tridecane dicarboxylic acid in water by nanoscale Fe0/Cu0 bimetallic composites.

In this study, nanoscale zerovalent Fe0/Cu0 bimetallic composites were synthesized by liquid-phase reduction of Fe(II)/Cu(II) and applied for decomposition of tridecane dicarboxylic acid (DC13). The removal performance of Fe0/Cu0 bimetallic composites for DC13 in terms of Fe/Cu ratios, addition amount, reaction time and initial pH were studied. The as-prepared nanoscale composites were characterized by a transmission electron micrographs (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), BET surface area, fourier transform infrared spectroscopy (FT-IR) and inductively coupled plasma-atomic emission spectrometry (ICP). Finally, the degradation mechanisms of DC13 utilizing the Fe0/Cu0 nanocomposites were investigated by using mass spectrumetry (MS). The results indicated that the Fe0/Cu0 bimetallic composites exerted a remarkable removal capacity for DC13 through the multiple reactions, e.g., coagulation, adsorption and •OH reduction in the Fe0/Cu0 system. XPS indicated that the Fe0/Cu0 reduction reaction of hydroxyl radicals (•OH) system played a significant role in degradation of DC13 and the LC-MS result suggested that DC13 was degraded into inorganic small molecules by •OH radicals generated from the corrosion of Fe0. The experimental results indicated that the nanoscale Fe0/Cu0 could be used as a potential material to remove DC13 because of its remarkable degradability.

Memory effect and redistribution of cavitation nuclei in a thin liquid layer.

Temporal evolution and spatial distribution of acoustic cavitation structures in a thin liquid layer were investigated experimentally with high-speed photography. The inception and disappearance processes of cavitation bubble cloud revealed that the metastable cavitaton structures formed in the thin liquid layer caused a long-term "memory effect". A factor which weakens the memory effect was identified. The distribution of cavitation nuclei was investigated by changing the temporal decay of the memory effect.