Hydrothermal modification of natural zeolites to improve uptake of ammonium ions

Journal of Chemical Technology & Biotechnology (Impact Factor: 2.35). 04/2005; 80(4):376 - 380. DOI: 10.1002/jctb.1224


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


Available from: Yujiro Watanabe
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    • "Zeolites can be readily synthesised in hydrothermal conditions and a lot of information is readily available concerning synthetic zeolites and chemical resolution for zeolite synthesis (Hawkins, 1981). The chemical preparation of synthetic zeolites from silica and alumina is expensive; zeolite researchers are thus seeking cheaper raw materials for zeolite synthesis to reduce costs, including clay minerals such as kaolinite (Breck, 1974; Barrer et al., 1974; Boukadir et al., 2002), halloysite (Klimkiewicz and Drąg, 2004), illite, smectite, interstratified illite-smectite (Baccouche et al., 1998), montmorillonite (Cañizares et al., 2000) and bentonite (Boukadir et al., 2002; Ruiz et al., 1997), natural zeolites (Kang and Kazuhiko, 1997; Watanabe et al., 2005; Covarrubias et al., 2006), volcanic glasses (Breck, 1974; Barrer, 1982; Vitarelli et al., 1983; Colella et al., 1985; Moirou et al., 2000), diatomite (Anderson et al., 2005; Holmes et al., 2001), high silica bauxite (Puerto and Benito, 1996), oil shale (Shawabkeh, 2004) and natural clinker (Ríos and Williams, 2008; Ríos et al., 2008; Sandoval et al., 2009). "
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    • "The ammonia removal appeared to proceed through rapid kinetics at neutral pH value, with removal capacities up to 0.68 meq NH 4 + /g. Watanabe et al. [61] carried out a modification of Japanese natural zeolites under hydrothermal conditions to improve the effectiveness of the uptake of ammonium ions. The samples 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. "
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