A novel phosphinic acid functionalized polyacrylonitrile fiber (PAN(Apc)F) was prepared and its adsorption properties were investigated. The PANApcF shows excellent selectivity and efficiency for Hg2+ in the presence of other common metal ions, viz. Pb2+, Cd2+, Ag+, Zn2+, Cu2+, Ni2+, Co2+, Ca2+, Mg2+. Adsorption kinetics studies show that PAN(Apc)F quickly captures Hg2+ and achieves equilibrium within 3 h. In addition, PAN(Apc)F is effective over a wide range of pH values (from 3 to 11). The maximum adsorption capacity for Hg2+ as calculated by a Langmuir isotherm model was 434 mg g(-1). PAN(Apc)F could also efficiently remove Hg2+ from practical wastewater and the concentration of Hg2+ could be decreased as low as 27 ppb, which is below the maximum contamination level of 50 ppb for mercury containing wastewater in China. Furthermore, the PANApcF can be used to remove Hg2+ from a flow process with a 99% removal efficiency even after ten cycles. Finally, XPS analysis proved that the P=O/P OH and -NH- functional groups play a major role in the adsorption mechanism. (C) 2017 Elsevier B.V. All rights reserved.