Mercury ions, even an ultra-trace amount in water, present a serious environmental concern. Hence, searching for cost-effective and high-performance Hg 2+ adsorbents has acquired increasingly attention but still remained challenging. In this work, aminophosphonic acid was immobilized onto polyacrylonitrile fiber by chemical grafting approaches. The functionalized fiber (PAN AP F) possessed high adsorption selectivity and efficiency for Hg 2+ when compared with other coexisting ions viz. Pb 2+ , Cd 2+ , Ag + , Zn 2+ , Cu 2+ , Ni 2+ , Co 2+ , Ca 2+ and Mg 2+ . The adsorption results revealed that PAN AP F exhibited high removal capacities for Hg 2+ over a wide pH range from 3 to 11. The adsorption process was better described by the pseudo second-order kinetic model, indicating the chemical interaction between Hg 2+ and active groups on the PAN AP F. Moreover, the maximum adsorption capacity as calculated from the Langmuir adsorption model of 358mgg -1 was higher than that of many other adsorbents. The PAN AP F could be reused more than 10 times and it is able to decrease Hg 2+ below 50μgL -1 which is the maximum discharge standard for mercury containing wastewater in China. A continuous-flow process was also implemented to remove Hg 2+ . The results suggested the environmentally friendly PAN AP F could be a promising candidate for Hg 2+ removal in wastewater treatment., (Copyright © 2017 Elsevier B.V. All rights reserved.)