Ammonia removal from an aqueous solution by the use of a natural zeolite

A series of batch experiments were conducted to ascertain the ability of a natural zeolite (a crystalline aluminosilicate) to remove ammonia from synthetic wastewater samples composed of ammonium hydroxide (NH₄OH). The reaction with ammonia was observed to be very rapid, with half the amount of ammonium ions being sorbed in the first minute in some instances. Estimated ammonia uptake was favoured by low sorbate concentration, small particle size of sorbent, high temperature, and an alkaline medium. The sorption kinetics studies strongly indicated that the sorption process was largely governed by intraparticle pore diffusion. The effect of temperature on equilibrium at 14 °C and at room temperature (25 °C) showed the sorption process was endothermic, the rate and extent of sorption increasing appreciably with temperature. The equilibrium data fitted the Langmuir sorption model, a possible indication of a monolayer coverage of ammonium ions on the surface of the particle. The Langmuir correlation of the equilibrium data suggested that ion exchange might have been the dominant sorption mechanism. The zeolite seemed to have some fairly good potential for ammonia removal with the sorption capacity being about 4 mmol (NH₄⁺) per 100 g of sorbent. However, this needs to be investigated further through flow-through conditions and in the presence of other ions as in real wastewater. Key words: zeolite, aluminosilicate, sorbent, ammonia nitrogen, sorption, sorbate.