Using of g-C 3 N 4 nanosheets for the highly efficient scavenging of heavy metals at environmental relevant concentrations Qing Liao a , Wang Pan a , Dongsheng Zou a , Runpu Shen a, ⁎, Guodong Sheng a , Xue Li b, ⁎, Yuling Zhu a , Lijia Dong a , Abdullah M. Asiri c , Khalid A. Alamry c , Wensheng Linghu a, ⁎ a College of Chemistry and Chemical Engineering, Shaoxing University, Huancheng West Road 508, Shaoxing, Zhejiang 312000, PR China b College of Yuanpei, Shaoxing University, Shaoxing, Zhejiang 312000, PR China c Chemistry Department, Faculty of Science, King Abdulaziz University, Jeddah 21589, Saudi Arabia abstract article info Article history: Received 29 January 2018 Received in revised form 20 March 2018 Accepted 22 March 2018 Available online 03 April 2018 Graphitic-C 3 N 4 (g-C 3 N 4 ) nanosheets were prepared by a simple thermal and ultrasonic method. The crystal structure, surface functional groups and morphology of g-C 3 N 4 were characterized by XRD, FITR, SEM, TEM and XPS. The scavenging of heavy metals on g-C 3 N 4 was investigated at environmental relevant concentrations by using batch experiments. The results indicated that g-C 3 N 4 showed high adsorption capacities of 137.4 mg/g for Co(II), 136.9 mg/g for Ni(II), 134.1 mg/g for Cu(II), and 138.0 mg/g for Zn(II), respectively. The Temkin, Freundlich and Langmuir models were used to simulate the adsorption isotherms of heavy metals, dem- onstrating that the adsorption fitted well with Langmuir model. The ionic strength exhibited little effect on the adsorption of heavy metals on g-C 3 N 4 , indicating that the adsorption mechanism of Co(II), Ni(II), Cu(II), Zn(II) on g-C 3 N 4 was mainly dominated by inner-sphere complexation. The thermodynamic data calculated from ad- sorption isotherms suggested that the adsorption of heavy metals on g-C 3 N 4 was an endothermic and spontane- ous process. These results demonstrated that the g-C 3 N 4 was a potential material for the scavenging of heavy metals in water. © 2018 Elsevier B.V. All rights reserved. Keywords: Graphitic-C 3 N 4 nanosheets Adsorption Heavy metals Scavenging Environmental relevant concentrations 1. Introduction With the rapid development of industrialization, there is an ever- growing demand for metals in various products, such as steel industries, aeronautics, nuclear power plant, battery manufacturing and etc. [1–8]. Despite promoting the progress of society, it has a significant impact on environmental pollution and human health. Unlike organic pollutants, heavy metal ions, such as Co(II), Ni(II), Cu(II), Zn(II), Cr(VI), Pb(II), Hg (II), are difficult to biodegradation and can be accumulated easily, which cause adverse effects on living beings [9–18]. Therefore, in order to protect the ecosystem and public health, heavy metal ions should be removed to the permissible limit before being discharged into the natural environment. Currently, various treatment techniques and processes, such as precipitation [19,20], adsorption [21–29], ion-ex- change [30,31], reverse osmosis [32] and membrane separation [33–35] have been used to remove heavy metal ions from aqueous solutions. Of all the methods proposed, adsorption is one of the most commonly used methods due to its high-efficiency, convenience and simplicity. The ad- sorption of various heavy metals on a variety of adsorbents, such as car- bon-based materials [36–42] and iron-based granular materials [43– 50], has been extensively investigated in recent years. However, low ad- sorption capacity and the complicated procedures in the fabrication of materials limited their practical application in the removal of heavy metal ions from aqueous solutions. Therefore, it is a top priority to ex- plore novel adsorbents with high adsorption capacity and simple prep- aration method. In recent years, great attention has been paid to a polymeric semi- conductor, graphite-like carbon nitride (g-C 3 N 4 ), due to its unique structure and excellent properties. It has been widely applied in many fields, such as photocatalysis, fuel cells, hydrogen storage, oxygen re- duction and so on [51–54]. The g-C 3 N 4 is a 2D layered material, which is based on tri s triazine (C 6 N 7 ) units connected with planar amino groups as elementary building blocks. The tri s triazine units include several “nitrogen pots” in which six nitrogen lone-pair electrons have a negative charge function, and _N \\ / \\ NH \\ / \\ NH 2 groups on the surface of g-C 3 N 4 possess abundant active sites [55–57]. These func- tional groups of g-C 3 N 4 are quite applicable for interaction with the metal ions. Especially, it is discovered that g-C 3 N 4 nanosheets show more excellent electronic and physicochemical features compared with the bulk g-C 3 N 4 [58,59]. However, few works had been reported Journal of Molecular Liquids 261 (2018) 32–40 ⁎ Corresponding authors. E-mail addresses: srunpu@usx.edu.cn, (R. Shen), lixue@usx.edu.cn, (X. Li), wslinghu@usx.edu.cn. (W. Linghu). https://doi.org/10.1016/j.molliq.2018.03.093 0167-7322/© 2018 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Journal of Molecular Liquids journal homepage: www.elsevier.com/locate/molliq