Hydrothermal modification of natural zeolites to improve uptake of ammonium ions

Journal of Chemical Technology & Biotechnology (Impact Factor: 2.5). 03/2005; 80(4):376 - 380. DOI: 10.1002/jctb.1224

ABSTRACT The modification of natural zeolites was carried out under hydrothermal conditions to improve the effectiveness of the uptake of ammonium ions. Natural zeolites originating in Japan, such as mordenite and clinoptilolite with quartz, feldspar and a trace of layered silicate, were treated with 0.1, 0.3, 1.0 and 3.0 M NaOH solutions at temperatures from 25 to 150 °C under autogenous pressure for 7 days. After the hydrothermal treatment, the transformation of the zeolites to phillipsite, hydroxyl-sodalite and analcime was observed, depending on the temperature and NaOH concentration. The amounts of ammonium ions taken up into the hydrothermally-treated zeolites were compared with those of the starting materials. The treated products, containing mainly phillipsite, took up twice the amount of ammonium ions as the starting materials. The maximum uptake of ammonium ions was 1.92 mmol g−1. The number of ammonium ions taken up into phillipsite was equal to the number of Na+ ions released from phillipsite. These results indicate that the uptake of ammonium ions proceeds by an ion-exchange mechanism with Na+ ions. Copyright © 2005 Society of Chemical Industry

  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Natural zeolites are abundant and low cost resources, which are crystalline hydrated aluminosilicates with a framework structure containing pores occupied by water, alkali and alkaline earth cations. Due to their high cation-exchange ability as well as to the molecular sieve properties, natural zeolites have been widely used as adsorbents in separation and purification processes in the past decades. In this paper, we review the recent development of natural zeolites as adsorbents in water and wastewater treatment. The properties and modification of natural zeolite are discussed. Various natural zeolites around the world have shown varying ion-exchange capacity for cations such as ammonium and heavy metal ions. Some zeolites also show adsorption of anions and organics from aqueous solution. Modification of natural zeolites can be done in several methods such as acid treatment, ion exchange, and surfactant functionalisation, making the modified zeolites achieving higher adsorption capacity for organics and anions.
    Chemical Engineering Journal. 01/2010;
  • [Show abstract] [Hide abstract]
    ABSTRACT: The overlay of a wireless local loop system on the CDMA2000 cellular system is proposed. The CDMA2000 system uses 5, 10, 15 and 20 MHz of dispersion bandwidth and the WLL system uses 1.25 MHz of dispersion bandwidth. In this way, it is possible to have 3, 4, 8, 9, 12 and 16 frequency allocations for the WLL system depending on the different bandwidths of the CDMA2000 cellular system. As an overlay system the WLL can use only a fraction of the frequency allocations according to co-frequency allocation reuse distance, similar to FDMA and TDMA cellular systems. With this idea less interference is introduced in the WLL system (in the limit, the capacity will be similar to the isolated cell) keeping at the same value the interference introduced in the CDMA cellular system
    Vehicular Technology Conference, 2001. VTC 2001 Spring. IEEE VTS 53rd; 02/2001
  • Phosphorus Research Bulletin 01/2006; 20:89-100.

Full-text (2 Sources)

Available from
Jun 3, 2014