Preparation of consolidated zeolite body using mechanochemical phenomena and its application to removal of heavy metals

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Inorganic consolidated bodies were synthesized from water-glass (potassium or sodium silicate solution) and aluminum hydroxide. The possibility of transition of the consolidated body to bulky zeolite body was investigated. Mechanochemical effect of aluminum hydroxide on formation zeolite phase was also investigated. The removal capability of the synthesized bulky zeolite was estimated.For system of zeolite composed of potassium, zeolite F was synthesized when the precursor was heat-treated at a temperature higher than 140℃. The formation temperature was dependent on the amount of potassium. Addition of potassium remarkably decreased the formation temperature zeolite. For composition of K:Al:Si=1:1:1 in starting materials, for example, heat-treatment temperature higher than 140℃ was required to form zeolite phase. For composition of K:Al:Si=1.5:1:1 and K:Al:Si=2:1:1, on the contrary, the temperature decreased to 80℃ and 60℃, respectively. All of synthesized zeolites with different chemical composition were identified as type F. Excessive addition of potassium deteriorated the water resistance of the consolidated zeolite and the zeolite broke down in water.For system of zeolite composed of sodium, on the contrary, monolithic zeolite A (Na:Al:Si=1:1:1) could be synthesized as a consolidated body. Crystalline phase was greatly dependent on particle size of aluminum hydroxide as a starting material without mechanochemical treatment. For larger particle, faujasite type zeolite was synthesized and smaller particle promoted to form A type zeolite. In addition, mechanochemical treatment was very effective to synthesize monolithic zeolite A. The mechanochemical treatment had much effect on formation temperature of zeolite A. Aluminum hydroxide powder treated mechanically made the heat-treatment temperature of 60℃ enough to form bulky zeolite A.Both of zeolites, type F and type A, exhibited good characteristic of removal for heavy metals such as Pb and Cd.