A natural zeolite tuff was obtained from Zeolite Australia Ltd. The main phase is clinoptilolite, together with minor amounts of mordenite, quartz, smectite and mica. The chemical compositions are SiO2 (68.3%), Al2O3 (13.0%), CaO (2.1%), K2O (4.1%) and Fe2O3 (1.4%). The cation exchange capacity of the natural zeolite is >120 mequiv./100 g. The sample is stable down to pH 2. Nitrogen adsorption shows that it has a mesoporous structure with pore size centred at 40 Å and that the BET surface area of the zeolite is 16 m2/g [13]. The particle size of natural zeolite is in the range of 10–75 μm. Humic acid was obtained from Aldrich. Lead nitrate and copper nitrate were obtained from AJAX.