توصيفگر ها :
زئوليت A , ذوب قليايي , سنگ بازالت , گرانيت سفيد , گرانيت سياه , مشخصهيابي
چكيده انگليسي :
Nowadays, the increasing development of stone-cutting factories and mines on the one hand and the widespread use of building stones in construction in the country, on the other hand, has increased their wastes, which requires proper environmental management. Optimal usage of wastes leads to environmental pollution reduction and preservation of non-renewable natural resources. Granite and basalt stones contain significant amounts of silisium and aluminium oxides, which are suitable raw material for zeolite synthesis. Zeolites are aluminosilicate crystals containing a set of quadrilaterals SiO4 and AlO4 that share oxygen atoms. Zeolite A is one of the synthetic zeolites that has different applications in the chemical industry due to its catalytic properties, ion exchange, and molecular sieving. In the recent years, the zeolite synthesis with smaller crystal size has become important for improvement of the mentioned properties. Using cheap and available raw materials to produce zeolites has always been taken attention. In this study, the rock waste samples (basalt, black granite, and white granite) and sodium aluminate as a source of aluminium were used to synthesize the zeolite A. Characterization of rock samples was performed by XRD and XRF analysis. The results of XRF analysis showed that silica (47.37-62.18%) and aluminium (13.2-15%) are the most constituent elements of the rocks. The alkaline melting method during the hydrothermal process was used to synthesize zeolite with various parameters, including the ratio of sodium hydroxide to the rock sample (1:1.2), temperature and residence time in the furnace (400, 500, 600, and 700 °C; 2 h), the ratio of sodium aluminate to molten sample (1:0.25, 1:0.5 and 1:0.75), aging time (24 h), and temperature and crystallization time in the hydrothermal process (90 °C, 2, 4 and 6 h). The XRD, XRF, CEC, SEM, EDX, BET, BJH, and FT-IR were used to study the characteristics of the synthesized zeolites. Type X and A were with high purity according to qualitative and quantitative analysis of the synthesized zeolites. Therefore, based on the results of the zeolite A synthesis, the optimum temperature of 500 °C, the ratio of sodium aluminate to molten sample (1:0.5), and crystallization time of 6 hours were considered. The specific surface area for the synthesized zeolites of basalt, black granite, and white granite stones was 36.8, 25.8, and 16.8 m2/g. The cation exchange capacity of basalt, black granite, and white granite was 3.2, 4.7, and 5.7 meq/kg, while it was 157.7, 165.9, and 171.8 Cmol/kg for the synthesized zeolites. In general, the synthesis of zeolite from these rocks is recommended as a suitable method for waste management in the stone industry with considering the economic aspects.
