# Synthesis of Zeolitic Material with High Cation Exchange Capacity from Paper Sludge Ash Using EDTA
## 2 Materials and Methods
### Experimental Method  
To investigate the effect of the addition of EDTA on zeolite synthesis, 10 g of PSA was added to 100 mL of 3 M NaOH solution with an EDTA concentration ranging from 0 to 2 M in a 200 mL Erlenmeyer flask fabricated from polymethylpentene (TPX) and was heated at 80 \({}^{\circ}\)C for 24 h in a water bath to synthesize zeolitic material. After heating, the resulting solid was filtered, washed with distilled water, and dried in an oven at 60 \({}^{\circ}\)C overnight to obtain the product. The mineralogical composition of the product was identified by X-ray powder diffraction (XRD) (Rigaku, XRD-DSC-XII, Tokyo, Japan) using CuK\(\alpha\) radiation (30 kV, 15 mA) over the 2\(\theta\) range of 5-55\({}^{\circ}\) (scan speed of 5\({}^{\circ}\)/min and step scan size of 0.02). The morphologies of the products were observed using a scanning electron microscope (SEM) (JEOL, JSM-6510A, Tokyo, Japan) under a vacuum pressure of 1 \(\times\) 10\({}^{-6}\) Pa and an accelerating voltage of 15 kV. The concentrations of Si, Al, and Ca in the filtrate after synthesis were analyzed using inductively coupled plasma spectrometry (ICP) (Shimadzu, ICP-7500, Kyoto, Japan) (RF power: 1150 W; peristaltic pump speed: 50 r/min; auxiliary gas flow rate: 0.5 L/min; atomizer gas flow rate: 0.7 L/min). The CECs of the product were measured using the method reported by [PERSON] et al. [51], as follows. The product was immersed in 1 M ammonium acetate solution, and the solution was shaken for 20 min to replace NH4+ in exchangeable sites in the product. It was then centrifuged, and the supernatant was removed by decantation. This procedure was repeated three times. The sample was then washed with 80% EtOH for subsequent replacement. The NH4+ in the product was replaced by K+ using a 10% KCl solution in a procedure that was repeated three times, and the NH4+ content in the supernatant was measured. The CEC was calculated using the following equation:  
\[\text{CEC}(\text{mmol}/\text{g})=\frac{C_{Am}\cdot V}{w}, \tag{1}\]  
where \(C_{Am}\) is the NH4+ concentration in the supernatant (mmol/L), \(V\) is the volume of the supernatant solution (L), and \(w\) is the weight of the sample (g). To investigate the effect of temperature on zeolite synthesis, 1 g of PSA was added to 10 mL of 3 M NaOH solution with or without 1 M EDTA in a 50 mL pressure vessel, and the vessel was heated at 80, 120, and 160 \({}^{\circ}\)C for 24 h in an electric furnace. After heating, the vessel was quenched with tap water, and the solid product was filtered, washed with distilled water, and dried overnight in an oven at 60 \({}^{\circ}\)C. The mineralogical composition of the product was identified by XRD, and the CEC of the product was measured. The morphologies of the products were observed by SEM. The concentrations of Si, Al, and Ca in the filtrate after synthesis were analyzed using ICP. The zeolitization processes of PSA with and without EDTA were compared to determine the differences in the reaction processes. PSA (100 g) was added to 1 L of 3 M NaOH solution with or without 1 M EDTA in a 1 L Erlenmeyer flask (made of polymethyl pentene) equipped with a dimroth condenser, and the mixture (slurry) was continuously stirred at 80 \({}^{\circ}\)C for 24 h. Five milliliter aliquots of the slurry were removed at varying time intervals to monitor the reaction process. The aliquots were filtered, and the filtrates were analyzed by ICP to determine the concentrations of Si, Al, and Ca during the synthesis reaction. The solid product was washed with distilled water and dried overnight at 60 \({}^{\circ}\)C. The products were analyzed by XRD and SEM to identify the zeolite phases, and the CECs of the products were measured.