Synthesis of Zeolite a from Natural Ca-Bentonite Using a Direct Alkali Hydrothermal Approach

Ca-bentonite can be converted into zeolites A through hydrothermal alkaline treatment by varying the synthetic parameters. This study focuses on the effect of initial Si/Al molar ratio, NaOH concentration on the type of formed zeolite A. The Ca-bentonite (China, Fuxin)were mixed with an aqueous NaOH solution, Al(OH)3 powder and hydrothermally treated at about 90 ℃,12 h. Different types of zeolites (zeolite X, P, and A),sodalite were synthesized after the treatment. Zeolites were characterized and quantified by means of XRD and SEM analysis. Zeolite A predominantly formed with 0.5≤Si/Al≤2.0 was produced and zeolite X, P formed with Si/Al>2.0 under the 2.2mol/LNaOH concentration; Sodalite was also formed under high NaOH molarities. Shape of zeolite A is show the cube by the SEM micrograph.

Non-Isothermal Kinetic Analysis of Thermal Decomposition of the Ca-Bentonite from Santai, China

The thermal decompositions of Ca-bentonites (CaB) from Santai ,Shichuan Province, China over the temperature rage of 30-1100℃ were investigated by simultaneous thermal analyzer. Non-isothermal Kinetic analysis were employed to study the thermal decomposition mechanism by using Netzsch Thermokinetics software. The dependence of the activation energy on conversion degree were evaluated by isoconversional methods. The probably mechanism and the corresponding kinetic parameters were determined by multivariate non-linear regression program.

Soil-water characteristics of Gaomiaozi bentonite by vapour equilibrium technique

Soil-water characteristics of Gaomiaozi(GMZ)Ca-bentonite at high suctions(3–287MPa)are measured by vapour equilibrium technique.The soil-water retention curve(SWRC)of samples with the same initial compaction states is obtained in drying and wetting process.At high suctions,the hysteresis behaviour is not obvious in relationship between water content and suction,while the opposite holds between degree of saturation and suction.The suction variation can change its water retention behaviour and void ratio.Moreover,changes of void ratio can bring about changes in degree of saturation.Therefore,the total change in degree of saturation includes changes caused by suction and that by void ratio.In the space of degree of saturation and suction,the SWRC at constant void ratio shifts to the direction of higher suctions with decreasing void ratio.However,the relationship between water content and suction is less affected by changes of void ratio.The degree of saturation decreases approximately linearly with increasing void ratio at a constant suction.Moreover,the slope of the line decreases with increasing suction and they show an approximately linear relationship in semi-logarithmical scale.From this linear relationship,the variation of degree of saturation caused by the change in void ratio can be obtained.Correspondingly,SWRC at a constant void ratio can be determined from SWRC at different void ratios.