Hypothesis: The purpose of the present work is the development of a kinetic model for the adsorption of As(III) and As(V) onto tetravalent manganese feroxyhyte (delta-Fe0.75Mn0.25OOH), which have been recently proved to be very efficient adsorbent for the particular species. Experiments: In this respect equilibrium and adsorption kinetic experiments onto this type of adsorbent for As(III) and As(V) were performed. Two sizes of adsorbate particles are tested in order to acquire better insight to the adsorption process. Results: The adsorption kinetic curves cannot be described by the well-known adsorption kinetic models so a detailed model that takes into account the structure of the adsorbent particle is developed. The model parameters were extracted by the requirement of agreement between model and experimental results. The batch model developed here is necessary for the development of models for fixed bed adsorption devices in order to exploit the commercial prospects of the particular adsorbent. This work constitutes the first attempt of kinetic study and adsorption model development for the specific very promising adsorbent. (C) 2015 Elsevier Inc. All rights reserved.