Abstract
The occurrence, persistence, and accumulation of antibiotics and non-steroidal anti-inflammatory drugs (NSAIDs) represent a new environmental problem due to their harmful effects on human and aquatic life. A suitable absorbent for a particular type of pollutant does not necessarily absorb other types of compounds, so knowing the compatibility between a particular pollutant and a potential absorbent before experimentation seems to be fundamental. In this work, the molecular interactions between some pharmaceuticals (amoxicillin, ibuprofen, and tetracycline derivatives) with two potential absorbers, chitosan and graphene oxide models (pyrene, GO-1, and coronene, GO-2), were studied using the ωB97X-D/6-311G(2d,p) level of theory. The energetic interaction order found was amoxicillin/chitosan > amoxicillin/GO-1 > amoxicillin/GO-2 > ibuprofen/chitosan > ibuprofen/GO-2 > ibuprofen/GO-1, the negative sign for the interaction energy in all complex formations confirms good compatibility, while the size of Eint between 24–34 kcal/mol indicates physisorption processes. Moreover, the free energies of complex formation were negative, confirming the spontaneity of the processes. The larger interaction of amoxicillin Gos, compared to ibuprofen Gos, is consistent with previously reported experimental results, demonstrating the exceptional predictability of these methods. The second-order perturbation theory analysis shows that the amoxicillin complexes are mainly driven by hydrogen bonds, while van der Waals interactions with chitosan and hydrophobic interactions with graphene oxides are modelled for the ibuprofen complexes. Energy decomposition analysis (EDA) shows that electrostatic energy is a major contributor to the stabilization energy in all cases. The results obtained in this work promote the use of graphene oxides and chitosan as potential adsorbents for the removal of these emerging pollutants from water.
Highlights
The greatest challenge facing humanity today is the preservation of the Earth as a habitat [1,2,3]
The global minimum structures for pharmaceuticals along with GO-1, GO-2, and CS are shown in Figure 1 along with their electrostatic potential (ESP) surface
According to results in this study, electrostatic potential surfaces and frontier molecular orbitals analysis can be used to infer if the absorbent and an adsorbate can drive to molecular recognition
Summary
The greatest challenge facing humanity today is the preservation of the Earth as a habitat [1,2,3]. The challenge becomes even more dramatic when one considers the exponential growth of the world’s population, which demands more clean water sources and modern water treatment methods [4]. Freshwater supplies are threatened by the increase in pharmaceutical pollutants, with around 70% coming from domestic water and 30% from industrial residues, which are discharged directly into rivers without prior treatment [5,6]. Pharmaceuticals are strictly regulated for patient safety, the side effect on the environment is not yet regulated. The side effect of any type of drug (antibiotics, analgesics, antipyretics, etc.) on the environment is not well known. Most pharmaceutical pollutants have a considerable prevalence in low concentrations; the risk of this accumulation in critical concentrations affecting life, especially in the aquatic environment, seems probable [7,8,9]
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