Contamination of natural water with heavy metals is a significant global issue. Heavy metals removal from aqueous solution by functional magnetic Fe₃O₄ nanoparticles, characterized in low cost, high efficiency, easiness of separation and regeneration, has received increasing attention in recent years. In this work, the advances on heavy metals removal by functional magnetic Fe₃O₄ nanoparticles are reviewed. The surface modification materials, synthesis methods, including amino-functionalization, thiol-functionalization, carboxy-functionalization and other functionalizations, and application of functional magnetic Fe₃O₄ nanoparticles applied for heavy metals removal are elaborated. The advantages and disadvantages of synthesis of functional magnetic Fe₃O₄ nanoparticles are further compared, and the influencing factors and mechanisms of heavy metals removal by functional magnetic Fe₃O₄ nanoparticles are briefly discussed. Finally, the suggestions on further study of heavy metals removal by functional magnetic Fe₃O₄ nanoparticles are presented.

Contents
1 Introduction
2 Synthesis and application of functional magnetic Fe3O4 nanoparticles for heavy metals removal from wastewater
2.1 Amino-functionalization
2.2 Thiol-functionalization
2.3 Carboxy-functionalization
2.4 Other functionalizations
3 Influencing factors of heavy metals removal by functional magnetic Fe₃O₄ nanoparticles
3.1 pH
3.2 Natural organic matter
3.3 Ionic strength
3.4 Competitive ions
3.5 Particle size
4 Mechanisms of heavy metals removal by functional magnetic Fe₃O₄ nanoparticles
5 Outlook