Heavy metals pollution has become an environmental and public health concern all over the world, especially in China. Activated carbon, carbon nano-tubes and graphene are used to remove heavy metal ions from aqueous solutions due to their large surface area, high adsorption capacity and environmentally benign nature. Whereas, carbon-based materials assembled on functional groups possess excellent adsorption capacity for metal ions. In this study, the modification methods of activated carbon, carbon nano-tubes, graphene and biochar are reviewed, mainly including thiol-functionalization and amino-functionalization. The applications of functional carbon-based materials for heavy metal ions removal are also summarized. The removal efficiency and influential factors of heavy metal ions removal by different functionalized carbon-based materials are discussed in detail. In addition, the outlook and suggestion of heavy metal ions removal by functionalized carbon-based materials are presented.

Contents
1 Introduction
2 Preparation of functional carbon-based materials for removal of heavy metals from aqueous solution
2.1 Functional activated carbon
2.2 Functional graphene
2.3 Functional carbon nanotubes
2.4 Functional biochar
3 The influencing factors of heavy metal removal from water by functional carbon-based materials
3.1 The properties of composite materials
3.2 Environmental conditions
4 The application of functional carbon-based materials
5 Conclusion and outlook