The different composition of the natural clays requires an optimization of NaOH concentration for each source of kaolin reported in the literature for the synthesis of zeolite A. A screening from 1 M to 4 M NaOH was tested to produce zeolite A in the treatment of the metakaolin both from raw and mechanically purified kaolin. As can be observed in the XRD profiles showed in Fig. 3, the appearance of the characteristic peaks of zeolite A occurs at 2.5 M NaOH with a perfect matching with the characteristic peaks of standard zeolite A and the literature value [17]. However, the optimum crystallinity is obtained with 3 M NaOH and further alkalinity, 3.5 and 4 M NaOH, does not yield any improvement. Alkan et al. reported zeolite A synthesized from natural kaolin with the optimized alkali concentration of 4 M and solid/liquid ratio of 1.25 g/25 ml [18]. For these experiments, the synthesis timewas set at 3 h at 100 C with no gel aging time taken into account. Prolonged reaction time to 6 h resulted in the partial transformation from zeolite A to the more thermodynamically stable sodalite phase although Novembre et al. [19] reported this transformation occurs after 8 h of crystallization time (Fig. 4). The ICP elemental analysis collected in Table 2 show a Si/Al ¼ 1 in good agreement with the standard zeolite A (SZA).