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Na–montmorillonite (Na–Mt) and kaolinite as low-cost adsorbent were performed to remove thallium(I) from aqueous solutions, and their adsorption behavior toward Tl(I) was evaluated. The adsorption of Tl(I) was strongly ionic strength and pH-dependent. Pseudo-first-order and pseudo-second-order models fitted well with the adsorption kinetic studies for all materials with an equilibrium time of 5 min. Furthermore, the adsorption isotherm were analyzed and fitted best by the Langmuir model. The adsorption capacity of Na–Mt was, 29.3 mg/g, much higher than that of kaolinite under the chosen conditions. The adsorption of Tl(I) on Na–Mt was an endothermic process, but on kaolinite, it was exothermic process. The desorption and regeneration studies demonstrated that Na–Mt and kaolinite, which underwent five consecutive adsorption–desorption processes, still retained high Tl(I) removal efficiency. The possible adsorption mechanisms in view of cation exchange and surface complexation predominated that the Tl(I) adsorption processes were interpreted, and the X-ray diffraction and desorption results also verified the possible mechanisms. This work suggested that Na–Mt and kaolinite may be promising candidates for the removal of Tl(I) ions from aqueous solutions.

In this study, the effect of suppression on phosphate liberation from eutrophic lake sediment by using fly ash and ordinary Portland cement (OPC) was investigated by small scale experiment. A system including sediment, lake water, and several kinds of capping materials was designed to clarify the suppression of phosphate liberation from sediment under the anaerobic condition. The suppression efficiencies of fly ash, OPC and glass bead used as control material were also determined, and these effects were discussed. The suppression efficiency of glass bead was 44.4%, and those of fly ash and OPC were 84.4%, 94.9%, respectively. The suppression by fly ash and OPC was mainly carried out by the adsorption effect, in addition to the covering effect. The suppression efficiency depended on the amounts of the material used, and about 90% of liberated phosphate was suppressed by fly ash of 10.0 Kg m(-2), and OPC of 6.0 Kg m(-2). The concentrations of heavy metals, such as mercury, cadmium, lead, copper, zinc, chromium, silver, arsenic and nickel, in fly ash and OPC were lower than those in the environmental materials. And it was considered that the concentrations of heavy metals in fly ash and OPC were too low to influence the ecosystem in natural water region.