BACKGROUND: A new adsorbent, Zr-doped akaganeite, having a tunnel structure and efficient arsenic adsorption capacity, was prepared by homogeneous co-precipitation with urea. Formation of the synthesized adsorbent was studied in detail. RESULTS: The adsorbent was characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), and the determination of Cl leakage showed that an appropriate amount of Zr4+ was doped into akaganeite (-FeOOH) by substitution of Fe3+ and possessed a similar tunnel structure to Fe3+. The morphology, surface area and tunnel structure changed greatly compared with -FeOOH with more OH groups and Cl introduced into the tunnel structure after doping with Zr4+. The Zr-doped -FeOOH exhibited highly effective adsorption of arsenic with a capacity for As(III) and As(V) of 120 and 60 mg g1 at neutral pH. On the basis of Cl release during adsorption and analyses of zeta potential along with XPS and FTIR spectra, the adsorption of arsenic on Zr-doped -FeOOH was verified as inner-sphere adsorption with the OH groups in the tunnel structure of the adsorbent the main adsorption sites at arsenic high concentrations. CONCLUSION: The Zr4+ was doped into -FeOOH by substitution of Fe3+. The OH groups in the tunnel structure of the adsorbent were the main adsorption sites at high arsenic concentrations, and the adsorption occurred by an inner-sphere adsorption process. (c) 2012 Society of Chemical Industry