Evaluation of the Sorption Potential of Mineral Materials Using Tetracycline as a Model Pollutant

Jaime Cuevas,Carlos García Delgado,Raul Férnández,Felipe Yunta,Nisael Dirocie,Enrique Eymar,Daniel E González Santamaría,Ana Isabel Ruiz

doi:10.3390/min9070453

Abstract

Tetracycline (TC) is among the most used antibiotics in animal feedstock in the EU. Antibiotics’ persistence as emerging pollutants in the environment is evidenced by their long half-life in residual organic-mineral sediments and waters. The risk associated with this persistence favours antibiotic-resistant microbiota, affecting human health and ecosystems. The purpose of the present work is to assess the adsorption of TC into natural clay minerals, synthetic iron hydroxides and calcined sewage sludge. TC adsorption isotherms were performed in three replicated batch tests at three different pH values (4, 6, 8) and TC concentrations (33–1176 mg·L−1). X-Ray diffraction (XRD) mineralogy, cation exchange capacity (CEC), Brunauer, Emmett and Teller specific surface area (BET-SSA) and point of zero charge salt effect (PZSE) were determined for the characterization of materials. Sorption was analysed by means of fitting Langmuir and Freundlich adsorption models, which showed good fitting parameters for the studied materials. Low-charge montmorillonite (LC Mnt) is displays the best sorption capacity for TC at maximum TC concentration (350–300 mgTC·g−1) in the whole range of pH (4–8). Sepiolite and smectites adsorbed 200–250 mgTC·g−1, while illite, calcined sludge or iron hydroxides present the lowest adsorption capacity (<100 mgTC·g−1). Nevertheless, illite, sepiolite and ferrihydrite display high adsorption intensities at low to medium TC concentrations (<300 mg·L−1), even at pH 8, as is expected in wastewater environmental conditions.

Highlights

Tetracycline (TC) is the most used antibiotic in animal feedstock in the EU
They are used in medicine and agriculture [2]. The persistence of these emerging pollutants in the environment is due to their long half-life, on the order of magnitude of 0.5 years, so they become relatively immobilized in residual organic-mineral complexes incorporated into sediments and soils [3]
In the case of the calcined sewage sludge X-Ray diffraction (XRD) analysis showed that this is an amorphous glass with quartz and feldspar impurities (Figure 2)

Summary

Introduction

Tetracycline (TC) is the most used antibiotic in animal feedstock in the EU. In 2016, TCs, penicillin and sulphonamides were the most-sold antibiotics, accounting for 32%, 26% and 12%, respectively, of use in food-producing species for those 25 countries delivering data from 2011 to2016 [1]. Tetracycline (TC) is the most used antibiotic in animal feedstock in the EU. They are used in medicine and agriculture [2] The persistence of these emerging pollutants in the environment is due to their long half-life, on the order of magnitude of 0.5 years, so they become relatively immobilized in residual organic-mineral complexes incorporated into sediments and soils [3]. This behaviour favours their accumulation in sediments and eventual release due to seasonal flooding related to Mediterranean hydrological regimes [4]. The risk associated with this persistence is the development of antibiotic-resistant microbiota that can affect ecosystems and human health [6]

Objectives

Methods

Results

Conclusion