The present study showed that the new adsorbent developed using coconut fiber adsorbent has a potential to remove As(III) ion from water. The adsorption of As(III) on coconut fiber adsorbent was influenced by adsorbent dose, initial adsorbate concentration, contact time and temperature. Optimum adsorbent dose was found to be 10 g/L. Adsorption capacity increased with increase of the initial As(III) concentration. 96.20% As(III) removal was obtained at an adsorbent dose of 10 g/L, contact time of 8 h and mixing speed of 80 rpm and 50 C, when initial adsorbate concentration was 0.5 mg/L. The As(III) adsorption on coconut fiber adsorbent can be best described by the Freundlich isotherm. The kinetic data correlated well with the pseudo first-order kinetic model. The estimated thermodynamic parameters established the
suitability of As(III) adsorption process. The negative DG values confirm the feasibility of the adsorption process and the
spontaneous nature of As(III) adsorption onto the adsorbent. The more negative values of DG with the rise in temperature imply a greater driving force to the adsorption process and show an increase in feasibility of adsorption at higher temperatures. The positive value of enthalpy change (DH) confirms the endothermic nature of As(III) adsorption on coconut fiber adsorbent.