Hydroxy cancrinite

Figure 4. Infrared spectra of zeolites T and L, and hydroxy cancrinite (HC)...

Kim et al. [19] have synthesized Na-Pl zeolite from coal fly ash by using aqueous solution of 2-3 M NaOH at 100 to 150 °C. It has been reported that Faujasite and Hydroxy-sodaUte are formed when NaOH solution concentrations are maintained at 4 and 5 M, respectively. It has been observed that all MulUte, Quartz and Hematite disappeared after hydrothermal treatment at 160 °C. The final synthesis product containing zeolites, Analcime, with Na-Pl, and Cancrinite with Na-Pl, can be found corresponding to alkali concentration of 2 and 4 M, respectively. It has also been reported that Cancrinite increases if the NaOH concentration is 5 M or more. The authors have opined that Na-Pl zeolite having CEC value of 215 meq./lOO g would exhibit strong afftnity towards Pb and Sr. 

Park et al. [15, 16] have established the molten-salt method for the synthesis of zeolitic materials without any addition of water. The zeohtization of fly ash has been demonstrated by employing various mixtures of NaOH, KOH, or NH4F as mineralizers and NaNOs, KNO3, or NH4NO3 as solvent instead of demineralized water in hydrothermal method. It has been reported that zeolites like Hydroxy-sodalite and Cancrinite can get crystallized from mixture of NaOH and... 

Based on the X-ray diflEractograms of both these ashes (OLA and OHA) and their activated residues, as depicted in Fig. 5.21a, b, results obtained after peak matching with the help of JCPDS data files [35] have been listed in Table 5.38. It can be deciphered from these results that the ALA samples contain fewer crystals of zeolite Na-Pl (refer Fig. 5.6). Most specifically, the residue ALA6 exhibits the presence of the zeolite Na-Pl for M < and Hydroxy-sodalite for M > [23]. On the other hand. Fig. 5.4b exhibits the peaks corresponding to the zeolites Na-Pl and Hydroxy-sodalite in the residue, AHA2. However, as listed in Tables 5.4 and 5.5, the zeolites, Cancrinite and Analcime, were also found in the residue AHA6. This... 

F. 5.21 a XRD patterns of the OLA and the superior ALA samples, where Q, ML, P and S represent Quartz, Mullite, zeolite Na-Pl and Hydroxy-sodalite, respectively, and 0 is the angle of scattering of X-ray. b XRD patterns of the OHA and the superior AHA samples (where Q, ML, P, C, S and A represent Quartz, Mullite, zeolite Na-Pl, Cancrinite, Hydroxy-sodalite and Analcime, respectively)... 

On the other hand, from Fig. 6.9e it can be observed that the residues 3.0-R2-48 also contain the haU shaped crystals viz. Hydroxy-sodalite, larger in size ranging from 900 to 1000 nm. Apart from this, fewer ctystal shapes and sizes of Faujasite (prismatically shaped, 1 pm long) and zeohte Na-Pl (spherules of 100 nm size) are also found to he present in these residues. Accordingly, the higher CEC of the residues 1.5-R2-24, being die most superior residues, can be attributed to its polyciystalline zeoUtic phase (viz., Na-Pl, Cancrinite and Na-A) as compared to the residues 3.0-R2-48, which comprises of different types of zeolites (viz., Hydroxy-sodalite and Faujasite) and hence exhibits a lesser CEC. 

Fig. 6.10 Various sizes of surface pores in the residues a 1.5-R2-24 and b 3.0-R2-48, where A, C, F, S and P are designations for fly ash zeolites Na-A, Cancrinite, Faujasite, Hydroxy-sodalite and Na-Pl, respectively...

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