The SEM image of coconut fiber adsorbent before adsorption of As(III) ions is shown in Fig. 1a. It reveals that the adsorbent had porous structure. BET surface area of the adsorbent was 226.83 m2/g. It exists in clustered, aggregated shapes and their actual size could not be determined. Fig. 1b shows SEM image of the adsorbent after adsorption of As(III). It is observed that a coating of adsorbed layer of arsenite is formed over the coconut fiber particles after adsorption.