In this work, a novel composite adsorbent with three-dimensional cross-linked polymeric networks based on chitosan (CTS) and attapulgite (APT) was prepared via in situ copolymerization in aqueous solution, and its efficacy for removing ammonium nitrogen (NH4(+)-N) from synthetic wastewater was investigated using batch adsorption experiments. In the adsorption test, the pH effect, adsorption kinetics, isotherms, and desorbability were examined. A comparison between as-prepared adsorbent and clay, powdered activated carbon (PAC), and other reported adsorbents was also carried out. The results indicate that as-prepared composite adsorbent is pH-dependent and has faster adsorption kinetics and higher adsorption capacity. At natural pH, the composite adsorbent with 20 wt.% APT can adsorb 21.0mg NH4(+)-N per gram, far higher than the other adsorbents involved. The adsorbed NH4(+)-N can be completely desorbed by 0.1 mol/L NaOH within 10 min. All information obtained give an indication that the composite can be used as a novel type, fast-responsive and high-capacity sorbent material for NH4(+)-N removal. (C) 2009 Elsevier B.V. All rights reserved.