ORIGINAL PAPER Kinetic, equilibrium and thermodynamic studies of thiamethoxam adsorption by multi-walled carbon nanotubes S. Panic 1 • V. Guzsva ´ny 2 • Z. Ko ´nya 3,4 • A ´ . Kukovecz 3,5 • G. Boskovic 1 Received: 20 September 2016 / Revised: 27 October 2016 / Accepted: 26 December 2016 / Published online: 18 January 2017 Ó Islamic Azad University (IAU) 2017 Abstract Because of their high adsorption capacity, car- bon nanotubes have caught the attention of the scientific community and a number of experimental results con- firmed their ability to adsorb many toxins from water. The aim of this work was to study the kinetics, equilibrium and thermodynamics of thiamethoxam adsorption by multi- walled carbon nanotubes in aqueous solutions. To further elucidate the influence of nanotube structure on the adsorption mechanism, the experiments were performed on both fresh (pristine) and nitric acid-modified multi-walled carbon nanotubes. The results of the kinetic studies were analyzed using three kinetic models, while the adsorption equilibrium was tested against four different adsorption models. Based on the results, and the physico-chemical properties of the adsorbent and adsorbate, it is proposed that the dominant mechanism for thiamethoxam molecules attaching to multi-walled carbon nanotubes is caused by aromatic p–p interactions (electron donor–acceptor inter- actions). The results of thermodynamic calculations based on the adsorption data indicate the exothermic nature of the process, regardless of the carbon nanotube type used. The decrease in entropy and the consequent negative change in Gibbs free energy, as expected, confirm the spontaneity of thiamethoxam adsorption on both pristine and functional- ized multi-walled carbon nanotubes. Keywords Adsorption parameters Á Carbon nanoadsorbent Á Interaction mechanism Á Pesticide Á Physico-chemical properties Á Surface modification Introduction Widespread environmental pollution has recently initiated an extensive search for convenient adsorbents of various organic contaminants (Abdel-Ghani et al. 2015; Han et al. 2012; Zhou et al. 2006). Owing to their exceptional prop- erties, carbon nanotubes (CNTs) have found many appli- cations in various fields of science and engineering. In recent years, interest in these nanomaterials has focused on the elimination of different environmental contaminants, with the nanomaterials acting as a support for various catalysts (Serp and Castillejos 2010) and sorbents (Pyrzynska 2011). CNTs are a relatively new type of sor- bent, possessing several advantages over other types of carbon materials (Zhou et al. 2006; Lu et al. 2005). Their surface is chemically inert, which enables physical adsorption, and their structure at the atomic level is defined and uniform (in contrast to activated carbon, for example). Additional advantages are high porosity and specific sur- face area, low density and strong interaction with mole- cules of pollutants (Chen et al. 2009a). All this means that the use of CNTs for the removal of hazardous pollutants from gases and aqueous solutions has been intensively & G. Boskovic boskovic@uns.ac.rs 1 Faculty of Technology, University of Novi Sad, Bul. cara Lazara 1, 21000 Novi Sad, Serbia 2 Department of Chemistry Biochemistry and Environmental Protection, Faculty of Sciences, University of Novi Sad, Trg Dositeja Obradovica 3, 21000 Novi Sad, Serbia 3 Department of Applied and Environmental Chemistry, University of Szeged, Rerrich Belater 1., Szeged 6720, Hungary 4 MTA-SZTE Reaction Kinetics and Surface Chemistry Research Group, Rerrich Belater 1., Szeged, 6720, Hungary 5 MTA-SZTE ‘‘Lendu ¨let’’ Porous Nanocomposites Research Group, Rerrich Belater 1., Szeged 6720, Hungary 123 Int. J. Environ. Sci. Technol. (2017) 14:1297–1306 DOI 10.1007/s13762-016-1237-3