Thermodynamic study of triclosan adsorption from aqueous solutions on activated carbon Modelling of experimental adsorption isotherm and calorimetry data Valentina Bernal 1 • Liliana Giraldo 1 • Juan Carlos Moreno-Piraja ´n 2 Received: 22 October 2018 / Accepted: 10 June 2019 Ó Akade ´miai Kiado ´, Budapest, Hungary 2019 Abstract The change in the thermodynamic properties of triclosan adsorption on three activated carbons with the different surface chemistry was studied through immersion calorimetry and equilibrium data; the amount adsorbed of triclosan (Q) during calorimetry was determined and correlated with the energy associated with adsorbate–adsorbent interactions in the adsorption process. It was noted that triclosan adsorption capacity decreases with an increase in oxygenated surface groups. For an activated carbon oxidized with HNO 3 (OxAC), the amount adsorbed was 8.50 9 10 -3 mmol g -1 , for a activated carbon without modification (GAC) Q = 10.3 9 10 -3 mmol g -1 and for a activated carbon heated at 1073 K (RAC1073) Q = 11.4 9 10 -3 mmol g -1 . The adsorbed amounts were determined by adjusting the isotherms to the Sips model. For the activated carbon RAC1073, the immersion enthalpy (DH imm ) was greater than those of the other two activated carbons due to the formation of interactions with the solvent (DH imm OxAC = - 27.3 J g -1 \ DH imm GAC = - 40.0 J g -1 \ DH imm RAC1073 = - 60.7 J g -1 ). The changes in the interaction enthalpy and Gibbs energy are associated with adsorbate– adsorbent interactions and side interactions such as the adsorbate–adsorbate and adsorbate–solvent interactions. Keywords Activated carbon  Adsorption  Entropy change  Gibbs energy change  Immersion enthalpy  Interaction enthalpy  Triclosan Introduction Triclosan is a chemical compound used in more than 2000 personal care products and cosmetics due to its antimi- crobial properties; however, the FDA (Food and Drug Administration) prohibited its use in over-the-counter products in 2016 due to the little evidence that exists about its effectiveness in preventing the propagation of diseases and infections, as well as its long-term safety [1–3]. One of the problems associated with the massive use of products containing triclosan is its presence in wastewater, soil, vegetables, milk, urine and adipose tissue; the pres- ence of this compound in different matrixes has generated alarm in the European Union (EU) and different govern- mental agencies such as the FDA because this compound is associated with breast cancer, lower gestation time in humans, greater susceptibility to allergens, hormone dis- ruption, oxidative stress, infertility in rats and neurotoxicity in fish, among other effects [4–7]. According to the FDA report, existing regulation is insufficient to protect the population and the ecosystem from the damage generated by molecules of this type present in water and soil; therefore, it is required that effluent treatments are effective in removing this contam- inant with the aim of mitigating its toxic effects [8, 9]. One of the main problems with the presence of triclosan in water resources is its persistence in the environment and & Juan Carlos Moreno-Piraja ´n jumoreno@uniandes.edu.co 1 Departamento de Quı ´mica, Facultad de Ciencias, Universidad Nacional de Colombia, Cra 30 No. 45–03, Bogota ´, DC, Colombia 2 Departamento de Quı ´mica, Facultad de Ciencias, Universidad de los Andes, Cra. 1a No. 18A-10, Bogota ´, DC, Colombia 123 Journal of Thermal Analysis and Calorimetry https://doi.org/10.1007/s10973-019-08474-4