Synthesis of a clinoptilolite–Fe system with high Cu sorption capacity

An iron oxide–clinoptilolite system was synthesized by adding natural clinoptilolite in an iron nitrate solution under strongly basic condition. The newly synthesized material has a red–brown color. A combination of XRD, FTIR and EPR spectroscopies, as well as specific surface area measurements and TG/DSC thermal analyses provided information on the type of Fe species located on the zeolite surface. Clinoptilolite seems to maintain its structure, while Fe3+ species are in a symmetric environment (Th or Oh). The new material has a noteworthy high value of specific surface area (151 m2 g−1) and is fully iron exchanged (Fe/Al = 1.23). Differences in FTIR and TG/DSC spectrograms between the Fe–Clin system and untreated Clin were reported and explained. According to Cu adsorption/desorption experiments, carried out after the synthesis and characterization procedures, the Fe–Clin system is a promising new material since it adsorbs significantly larger Cu concentrations than clinoptilolite. This fact is owed to its high specific surface area and to its high negative surface charge. Desorption of Cu was also examined and it was observed that the Fe–Clin system desorbs smaller Cu amounts than untreated clinoptilolite.