Recently, the discharge of ammonia nitrogen from wastewater treatment plants into freshwater bodies has led to serious problems of eutrophication. Many new tertiary treatment systems have been developed to address this problem. This study introduces a novel ammonium-selective adsorbent (Cu-HCIX), a polymer-supported sorbent loaded with CuO microparticles within cation exchanger. Batch static adsorption tests were conducted to evaluate sorption capability. The static adsorption data agreed well with pseudo-second-order model and Langmuir model. Removal of low-concentration ammonium (1.0-10 mg N L-1) was also investigated in fixed-bed column runs. The results indicate that both the adsorption capacity and selectivity of the Cu-HCIX were enhanced after dispersing CuO microparticles within the cation exchanger. Dynamic breakthrough data were observed to follow the Thomas model. The separation factors of Cu-HCIX, representation selectivity, for ammonium over other competitive cations, were approximately five times greater than the original exchanger. The high selectivity of Cu-HCIX for ammonium results from the introduction of dispersed Cub microparticles. The exhausted Cu-HCIX can be repeatedly utilized after regeneration by NaOH solution. Cu-HCIX shows considerable potential for removal of ammonium from surface freshwaters and secondary wastewater. (C) 2015 Elsevier B.V. All rights reserved.