Contents lists available at ScienceDirect Colloids and Surfaces A journal homepage: www.elsevier.com/locate/colsurfa Study of the interactions of the hazardous amoxicillin antibiotic inside the MCM-41/CTA hydrophobic cavities Tatiana A. Ribeiro-Santos, Luisa E. Milagre, Mateus C.M. de Castro, Fernando F. Henriques, Welington F. Magalhães, Dario Windmöller, Rochel M. Lago, Ana P.C. Teixeira, Maria H. Araujo ⁎ Departamento de Química, Instituto de Ciências Exatas, Universidade Federal de Minas Gerais, Belo Horizonte, MG, 31270-901, Brazil GRAPHICAL ABSTRACT ARTICLE INFO Keywords: Antibiotic Sorption Composite MCM-41 Positron annihilation Isosteric heat ABSTRACT In this work, it was studied the interaction of the hazardous antibiotic amoxicillin (AMX) molecules inside the mesocavities of a composite MCM-41/cetyltrimethylammonium (MCTA). MCTA with low surface area (5 m 2 g −1 ) showed high sorption efciency of AMX (55 mg AMX g −1 ) comparable with high surface area activated carbon (980 m 2 g −1 ). Positron annihilation spectroscopy and isosteric heats suggested that the AMX molecules are not adsorbed by a classical surface process but are attracted and trapped by the CTA C 18 hydrophobic chains inside the MCM-41 mesocavities. Preliminary kinetic data suggests that the AMX sorption process takes place in three stages, the external adsorption, interaction with the CTA molecules and difusion inside the mesocavities. 1. Introduction Recently, the presence of antibiotics in the environment has re- ceived special attention due to their limited biodegradation, accumu- lation and harmful efects on bacterial resistance. In special, β-lactam antibiotics such as penicillins and amoxicillin (AMX), which are the most used antibiotics worldwide [1–3]. To mitigate this problem dif- ferent approaches have been investigated such as biological process, fltration, coagulation, focculation and sedimentation, advanced oxidation processes and adsorption [4–9]. A electrochemical degrada- tion have also been investigated using a 1.0% Cu-PbO 2 electrode, 0.1 mol L −1 of the electrolyte concentration, initial AMX concentration of 100 mg L −1 , current density of 30 mA cm −2 and initial pH 3.5. The antibiotic removal and the chemical treatment rate obtained in this process was 99.4% and 46.3%, respectively, after 150 min [10]. An- other study used three advanced oxidative process methods: ultra- sound, ozonation and ozone coupled ultrasound. When only ultrasound was applied the degradation rate was slow and the mineralization was https://doi.org/10.1016/j.colsurfa.2019.123873 Received 26 June 2019; Received in revised form 26 August 2019; Accepted 27 August 2019 ⁎ Corresponding author. E-mail address: mharaujo@ufmg.br (M.H. Araujo). Colloids and Surfaces A 582 (2019) 123873 Available online 28 August 2019 0927-7757/ © 2019 Published by Elsevier B.V. T