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Zeolite L is a crystalline aluminosilicate compound and a typical chemical composition of K9Al9Si27O72•nH2O (n = 0-36). The structure and chemical properties, as well as their sizes and morphologies of zeolite L has led to various applications in different fields. The aim of this study is to investigate the effects of chemical compositions of the starting gel on the synthesis, size and morphology of zeolite L crystals. Zeolite L had been synthesized hydrothermally at 180 ˚C for 2 days, from gels with the molar compositions of 2.62-3.78 K2O: 0.8-1.4 Al2O3: 8-12 SiO2: 80-200 H2O. The variation of chemical compositions led to the differences in morphologies and crystal sizes. Their morphologies varied from ice hockey to cylindrical shapes and their crystal sizes varying from 1.50-7.53 µm. With an increase in H2O and SiO2, the crystal size was also increased but decreased with an increase in K2O. In varying Al2O3, there was no effect on their shapes which were still cylindrical but with different crystal sizes. Moreover, the adsorption of ethylene on zeolite L samples depended significantly on crystal shapes and sizes.

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Zeolite LTL (K_LTL and H_LTL) was used as adsorbent for the adsorption of herbicide paraquat from an aqueous solution. The characterization of zeolite LTL has been carried out through various techniques: X-ray diffraction, X-ray fluorescence spectroscopy, Fourier transform infrared spectroscopy and surface analysis. The adsorption occurred through cation exchange and the results showed that the adsorption capacity of paraquat onto K_LTL (161.71 mg/g) is higher than H_LTL (25.67 mg/g). These results can be explained by the amount of Al in the structure of zeolite and affinities of negative sites in zeolite and extra-framework cations (K + and H + ). The equilibrium data was best adjusted using the Langmuir model which has high correlation coefficient values (0.99).

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