Vol.:(0123456789) 1 3 Journal of the Iranian Chemical Society https://doi.org/10.1007/s13738-018-1318-y ORIGINAL PAPER C‑dots/Fe 3 O 4 magnetic nanocomposite as nanoadsorbent for removal of heavy metal cations Azam Masoudi 1  · Fatemeh Honarasa 1 Received: 16 May 2017 / Accepted: 3 February 2018 © Iranian Chemical Society 2018 Abstract In this work, C-dots/Fe 3 O 4 magnetic nanocomposite as nanoadsorbent was implemented for adsorption of Cu(II), Cr(III) and Pb(II) cations from aqueous solutions. The efect of various parameters on adsorption process of all three mentioned cations such as nanoadsorbent dosage, initial cation concentration, contact time and pH were explored to fnd the mecha- nism of adsorption. Diferent kinetic models including pseudo-frst-order, pseudo-second-order, Elovich and intra-particle difusion kinetic models were used to ft experimental data. In this way, pseudo-second-order model described the kinetic data of all three cations well. Also, equilibrium isotherm studies were examined by application of diferent conventional isotherms such as Langmuir, Freundlich, Tempkin and Dubinin–Radushkevich models to explain the experimental data. The Freundlich isotherm ftted equilibrium data of all three cations, whereas other models were not ftted well. Results indicate that the adsorption of all three cations is followed by chemisorption mechanism via electrostatic attraction at heterogeneous surface of nanoadsorbent. Keywords C-dots/Fe 3 O 4 nanocomposite · Carbon quantum dots · Magnetic nanostructure · Heavy metals · Nanoadsorbent Introduction One of the major water pollutants is heavy metals because this kind of materials is not biodegradable and accumulates in living organisms. So, due to their toxicity and carcino- genic efects, heavy metals removal is a challenging task [1, 2]. Copper, lead and chromium ions in industrial wastewa- ters are toxic heavy metals of particular concern [2]. Nowa- days, various approaches were proposed for heavy metals removal in industrial wastewaters [1]. But between them, adsorption is preferred because of their advantages includ- ing efectiveness, convenient operation, wide adaptability, high efciency and low cost [3–5]. So, various kinds of sorbents have been proposed such as activated carbon [6], clays [7], zeolites [8], biomass [9] and nanomaterials [1, 4]. Among the available adsorbents, nanosized materials are the promising ones and were used extensively for environmental treatment and remediation [10], because nanomaterials show high chemical activities and adsorption capacities [3, 4]. In this way, magnetic nanoparticles due to the ease of separa- tion were widely implemented in water treatment [1, 11–16]. Another kind of nanoadsorbents is carbon nanostructures including carbon nanotubes [17–19], graphene oxide [20, 21], nanocarbons [22] and carbon nanocomposites [23–25]. On the other hand, nanocomposites represent improved or unusual features which lead to the development of innova- tive applications [26]. One of the important kinds of nano- composites is magnetic carbon nanocomposites. Magnetic carbon nanocomposites show great application potential in diferent felds [27]. In this way, magnetic graphene nano- composites were used for removal of heavy metal ions [5]. Recently, C-dots/Fe 3 O 4 magnetic nanocomposite was intro- duced as a new synergic nanozyme [28]. In the present work, applicability of C-dots/Fe 3 O 4 magnetic nanocomposite as nanoadsorbent for removal of heavy metal cations, i.e., Cu(II), Pb(II) and Cr(III) ions, was explored. In this way, mechanism of adsorption process for all three cations was obtained by calculation of kinetic parameters and interopera- tion of isotherm models. Electronic supplementary material The online version of this article (https://doi.org/10.1007/s13738-018-1318-y) contains supplementary material, which is available to authorized users. * Fatemeh Honarasa fhonarasa@gmail.com; honarasa@iaushiraz.ac.ir 1 Department of Chemistry, Shiraz Branch, Islamic Azad University, Shiraz, Iran