Effect of Calcination after NH₄NO₃ Modification of Natural Clinoptilolite on the Structural and Textural Properties

Abstract—Clinoptilolite (CLN) from Bigadiç and that of calcined forms after NH₄NO₃ modification were investigated to demonstrate their possible usability in industrial applications. ${\text{NH}}_{4}^{ + }$-modified forms were prepared using 0.2, 1.0, and 2.0 M NH₄NO₃ solutions at 90°C for 3 and 6 h, and then all samples were calcined at 400°C for 13 h. All samples were characterized using XRD, XRF, SEM and nitrogen adsorption methods. BET specific surface areas (17.8–272.9 m² g^–1) and total pore volumes (0.055–0.197 cm³ g^–1) of the clinoptilolites were calculated from nitrogen adsorption isotherms obtained at 77 K by 3Flex (Micromeritics) equipment volumetrically. After increasing the molarity and processing time of the ammonium nitrate solutions, the calcination of the samples significantly affected both morphological and textural features. Compared to starting material, XRD peaks of the samples calcined at 400°C broadened and agglomeration of clinoptilolite crystals decreased. In addition, calcined clinoptilolite samples showed different ammonia adsorption capacities (4.853–5.388 mmol g^–1).