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Abstract

This research aimed to synthesize zeolites from perlite obtained from Lopburi Province, Thailand, and from rice husk ash, under hydrothermal condition. The experiments were carried out in an autoclave with SiO 2 /Al 2 O 3 molar ratios of 1 to 40, NaOH concentrations of 1 to 4 N, and starting pressure of 1 atm. The rice husk ash and AlCl 3 •6H 2 O were used to adjust the SiO 2 /Al 2 O 3 molar ratio. The autoclave was heated with the rate of 1.5 °C/min to the set points of 140 and 170 °C at which it was kept isothermally for 2 h. The results showed that the products detected were analcime, Na-P1, and sodalite octahydrate. However, at very low SiO 2 /Al 2 O 3 ratio and NaOH concentration, no zeolite could be formed at 140 °C. The analcime could be formed at almost all conditions, except at low concentration of NaOH and the SiO 2 /Al 2 O 3 ratio below 25. Furthermore, the Na-P1 could be detected in every area except at high concentration of NaOH and high SiO 2 /Al 2 O 3 ratio at which only analcime and sodalite octahydrate were found. The sodalite octahydrate was formed preferably at high concentration of NaOH and high ratio of SiO 2 /Al 2 O 3. At temperature of 170 °C, the formation of analcime was enhanced, while the others seemed to be unaffected. Finally, phase diagrams of detected zeolites were constructed.

Polydopamine‐coated silk yarn for improving the light fastness of natural dyes

“…This is consistent with the known light fastness properties of anthraquinone-based dyes [10]. The colour fastness to washing and light in this work compared with results reported by others [32][33][34][35][36][37] are shown in Table 4. The wash and light fastness properties for silk/PDA (0.10 mg ml À1 DA solution) and silk/PDA (2.00 mg ml À1 DA solution) were found to be good, at the rating levels of 3-4 and 4, respectively.…”

Low-temperature synthesis of zeolite from perlite waste — Part I: review of methods and phase compositions of resulting products

“…Using perlite as the starting material for the synthesis of zeolites on laboratory scale has been the subject of numerous papers. Zeolites possible to obtain are as follows: hydroxysodalite, analcime, zeolite A, zeolite X and zeolite Na-P 1 as well as phillipsite, merlinoite, chabazite, edingtonite and also epistilbite or heulandite [11,[13][14][15][16][17].…”

“…Zeolite Na-P 1 (gismondite type structure) is the most stable product of the synthesis carried out at 100°C for 1 to 4 days [11,15]. At higher temperatures zeolite Na-P 1 tends to transform into analcime [15,17], however, its quantity and degree of crystallinity depends on the time of synthesis.…”

“…At higher temperatures zeolite Na-P 1 tends to transform into analcime [15,17], however, its quantity and degree of crystallinity depends on the time of synthesis. Phase diagrams of zeolite synthesized at 140 and 170°C from perlite depending on the NaOH concentration and the SiO 2 /Al 2 O 3 ratio were developed [15]. To adjust the SiO 2 /Al 2 O 3 ratio, rice husk ash (a source of amorphous silica) and AlCl 3 ·6H 2 O were used.…”

“…The latter presumably tends to be formed at high concentrations of NaOH [18]. A higher temperature, in turn, promotes the formation of analcime [4,15,19].…”