Fig. 1. Preparation steps of ceria via redox method.
2.3. Clinoptilolite treatment
The Clinoptilolite treatment procedure using NH4NO3 solution is shown in Fig. 2. During this process, the structural properties of clinoptilolite were changed. Firstly, 1 M NH4NO3 solution was prepared. Then clinoptilolite and NH4NO3 solution mixed at a ratio of 10 [ml NH4NO3 solution]/[g zeolite]. The resulted mixture was heated and stirred for 8 h at 80 °C. Then, the mixture was filtered and in the next step the mixture was washed by deionized water until its pH reached 7. The mixture was dried under air flow at 110 °C for 24 h. Sample was calcined at 500 °C for 3 h Fig. 3 illustrates the X-ray diffraction patterns of non-treated clinoptilolite. As seen, clinoptilolite has a good accordance with the reference pattern (JCPDS no 00-025-1349). Also, the chemical analysis of non-treated and treated clinoptilolite is shown inFig. 4. The treatment process changes the percent of Si and Al and decrease the Si/Al ratio. As mentioned previously, the Si/Al ratio for clinoptilolite is greater than or equal to 4. This value for non-treated and treated clinoptilolite is 4.85 and 4.24, respectively. The EDX analysis shows well distribution and dispersion of Si and Al elements. This result has a positive effect on catalyst performance.