the percentage adsorption of As(III) on coconut fiber increases rapidly upto 10 g/L and becomes almost constant thereafter. This may be because of the increase in surface area with increase in adsorbent dose for arsenic to be adsorbent. Further increment of adsorbent does not affect much due to limited availability of adsorbate around the adsorbent. 91.37% As (III) removal was obtained at 10 g/L adsorbent dose.