# Synthesis of Zeolitic Material with High Cation Exchange Capacity from Paper Sludge Ash Using EDTA
## 3 Results and Discussion
As the concentration of the added EDTA increased to 1 M, the zeolitic phases in the product increased, and the CECs of the product increased from 1.2 to 3.4 mmol/g. The behavior of the CEC as the concentration of EDTA increased is associated with that of the zeolitic phase in the product because Ca masking promoted the reaction between Si and Al to synthesize zeolite crystals, which have a high CEC. These results also indicate that Ca remained in the solution after synthesis owing to Ca-masking by EDTA. Above an EDTA concentration of 1M, the zeolitic phases decreased, and the CECs of the products decreased due to the decrease in Ca-masking in the solution. These results suggest that a product with a high CEC can be synthesized in a 3 M NaOH solution containing 1 M EDTA. Figure 2: Concentrations of Si, Al, and Ca in the solution after synthesis with various concentrations of added EDTA (NaOH concentration: 3 M NaOH, Temperature: 80 \({}^{\circ}\)C, Reaction time: 24 h). The XRD patterns of PSA and the products synthesized from raw ash at various temperatures after a 24-h of reaction with or without 1 M EDTA are shown in Figure 4. PSA contains two mineral phases: gehlenite and anorthite. For the product synthesized without 1 M EDTA (Figure 4a), the anorthite peaks are less intense than those in the raw ash, indicating that a part of the anorthite dissolves in the alkali solution, whereas gehlenite does not seem to be affected at 80 \({}^{\circ}\)C. The phases formed were hydroxysodalite and zeolite-P. At 120 \({}^{\circ}\)C, anorthite was absent from the products, indicating that most of it dissolved in the alkali solution, while the gehlenite peaks were less intense than those in raw ash and the product at 80 \({}^{\circ}\)C, indicating that some of the gehlenite dissolved in the alkali solution. The phases formed were hydroxysodalite and zeolite-P. At 160 \({}^{\circ}\)C, both anorthite and gehlenite were absent, indicating that most of them dissolved in the alkali solution. The phases formed were bicroxysodalite and zoolite-P. At 160 \({}^{\circ}\)C, both anorthite and gehlenite were absent, indicating that most of them dissolved in the alkali solution. The phases formed were bicroxysodalite and zoolite-P. At 160 \({}^{\circ}\)C, both anorthite and gehlenite were absent, indicating that most of them dissolved in the alkali solution. The phases formed were bicroxysodalite and zoolite-P. At 160 \({}^{\circ}\)C, both anorthite and gehlenite were absent, indicating that most of them dissolved in the alkali solution, whereas gehlenite did not seem to be affected at 80 \({}^{\circ}\)C. The phases formed were hydroxysodalite, zeolite-P, and zeolite-A. At 120 \({}^{\circ}\)C, anorthite was absent from the products, indicating that most of it dissolved in the alkali solution, whereas the gehlenite peaks were less intense than those in raw ash and the product at 80 \({}^{\circ}\)C, indicating that some of the gehlenite dissolved in the alkali solution. At 160 \({}^{\circ}\)C, both anorthite and gehlenite were absent, indicating that most of them dissolved in the alkali solution. The phases formed at 120 \({}^{\circ}\)C and 160 \({}^{\circ}\)C were hydroxylsodalite and hydroxycanrinite, respectively. Although the dissolution behaviors of the mineral phases, gehenite and anorthite, in raw ash are almost the same, the product phases differ with EDTA addition. It should be noted that the XRD patterns of the products synthesized at 80 \({}^{\circ}\)C without EDTA in Figures 1 and 5 are almost the same regardless of stirring or standing. Figure 3: Relative crystalinities of hydroxysodalite, zeolite-P, and zeolite-A in the product, and CECs of the product after synthesis with various concentrations of added EDTA (NaOH concentration: 3 M NaOH, Temperature: 80 \({}^{\circ}\)C, Reaction time: 24 h).