SIMULTANEOUS REMOVAL OF NH4+ AND PO43- FROM SIMULATED RECLAIMED WATERS BY MODIFIED NATURAL ZEOLITE. PREPARATION, CHARACTERIZATION AND THERMODYNAMICS

摘要

Natural zeolite was modified by NaCl, AlCl3 and thermal treatment for the removal of NH4+ and PO43- ions. The characteristics of the modified zeolite (AlZ) and its mechanism for the NH4+ and PO43- removal were studied and compared. The results showed that the surface area and the Na+ and Al3+ content increased whereas the content of Ca2+, K+ and Mg2+ decreased after zeolite modification. On natural zeolite when activated with the 1 M NaCl and 10 cm(3)/g of pillaring dosage, high adsorption efficiencies for the NH4+ (97.80%) and PO43- (98.60%) were obtained. The results of various analyses indicated that the Na+ exchange is the main mechanism for NH4+ removal whereas the adsorption mechanism for PO43- followed the complexation with Al-OH groups present in the AlZ. In addition, the kinetics study showed that the adsorption of NH4+ and PO43- followed pseudo-second order model while the adsorption isotherm of NH4+ and PO43- is consistent with the Langmuir isotherm model. Moreover, the Gibbs free energy change for the simultaneous removal of the ions indicates that NH4+ is adsorbed faster compared to PO43-. The simultaneous removal of NH4+ and PO43- by AlZ adsorbent is cost effective in water treatment at low ion concentrations.