Mercury ions, even an ultra-trace amount in water, present a serious environmental concern. Hence, searching for cost-effective and high-performance Hg2+ 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 Hg2+ when compared with other coexisting ions viz. Pb2+, Cd2+,Ag-*, Zn2+, Cu2+, Ni2+, Co2+, Ca2+ and Mg2+. The adsorption results revealed that PAN(AP)F exhibited high removal capacities for Hg2+ 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 Hg2+ and active groups on the PAN(AP)F. Moreover, the maximum adsorption capacity as calculated from the Langmuir adsorption model of 358 mg g(-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 Hg2+ below 50 mu g L-1 which is the maximum discharge standard for mercury containing wastewater in China. A continuous-flow process was also implemented to remove Hg2+. The results suggested the environmentally friendly PAN(AP)F could be a promising candidate for Hg2+ removal in wastewater treatment. (C) 2017 Elsevier B.V. All rights reserved.