Adsorption in a Fixed-Bed Column and Stability of the Antibiotic Oxytetracycline Supported on Zn(II)-[2-Methylimidazolate] Frameworks in Aqueous Media.

Daniel López Malo,Marcos Nogueira Eberlin,Janine dos Santos Ferreira da Silva,Gilberto Fernandes de Sá,Giovana Anceski Bataglion,Célia Machado Ronconi,Andrew C Singer,Severino Alves Júnior

doi:10.1371/journal.pone.0128436

Abstract

A metal-organic framework, Zn-[2-methylimidazolate] frameworks (ZIF-8), was used as adsorbent material to remove different concentrations of oxytetracycline (OTC) antibiotic in a fixed-bed column. The OTC was studied at concentrations of 10, 25 and 40 mg L-1. At 40 mg L-1, the breakthrough point was reached after approximately 10 minutes, while at 10 and 25 mg L-1 this point was reached in about 30 minutes. The highest removal rate of 60% for the 10 mg L-1 concentration was reached after 200 minutes. The highest adsorption capacity (28.3 mg g-1) was attained for 25 mg L-1 of OTC. After the adsorption process, a band shift was observed in the UV-Vis spectrum of the eluate. Additional studies were carried out to determine the cause of this band shift, involving a mass spectrometry (MS) analysis of the supernatant liquid during the process. This investigation revealed that the main route of adsorption consisted of the coordination of OTC with the metallic zinc centers of ZIF-8. The materials were characterized by thermal analysis (TA), scanning electron microscopy (SEM), powder X-ray diffraction (XRD), and infrared spectroscopy (IR) before and after adsorption, confirming the presence of OTC in the ZIF-8 and the latter’s structural stability after the adsorption process.

Highlights

Studies of environmental impacts caused by chemical pollution usually focus on conventional pollutants such as dyes, heavy metals and carcinogenic substances [1,2,3,4]
It was found that more than 5% of the initial concentration of oxytetracycline was adsorbed at the beginning of the adsorption process of the 40 mg L-1 concentration, indicating that the breaking point was reached very quickly
A methodology was developed to minimize the amount of oxytetracycline in aquatic media using Zeolitic Imidazolate Frameworks (ZIF)-8 as adsorbent material, and its performance was considered satisfactory

Summary

Introduction

Studies of environmental impacts caused by chemical pollution usually focus on conventional pollutants such as dyes, heavy metals and carcinogenic substances [1,2,3,4]. Several tons of pharmaceutical drugs are synthesized every year for human and veterinary use, and are considered contaminants of emerging concern [5,6,7]. The toxic effects of drugs have not PLOS ONE | DOI:10.1371/journal.pone.0128436. Adsorption of the Antibiotic on Zn-[2-Methylimidazolate] Frameworks. Education) for a fellowship granted to D.L.M. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript

Methods

Results

Conclusion