Surfactant modified coir pith, an agricultural solid waste as adsorbent for phosphate removal and fertilizer carrier to control phosphate release.

The surface of coir pith, an agricultural solid waste was modified using a cationic surfactant, hexadecyltrimethylammonium bromide (HDTMA) and the modified coir pith was investigated to assess the capacity for the removal of phosphate from aqueous solution. Optimum pH for maximum phosphate adsorption was found to be 4.0. Langmuir and Freundlich isotherms were used to model the adsorption equilibrium data. Kinetic studies showed that the adsorption obeyed second order kinetics. Thermodynamic parameters were evaluated and the overall adsorption process was spontaneous and endothermic. Effect of coexisting anions has also been studied. The feasibility of using spent adsorbent as fertilizer carrier to control phosphate release was also investigated.