Insight into the role of the zeolitization process in enhancing the adsorption performance of kaolinite/diatomite geopolymer for effective retention of Sr (II) ions; batch and column studies

• Published in: Journal of environmental management Vol. 294; p. 112984
• Main Authors: Salam, Mohamed Abdel, Mokhtar, Mohamed, Albukhari, Soha M., Baamer, Doaa F., Palmisano, Leonardo, Abukhadra, Mostafa R.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 15.09.2021
• Subjects: Batch adsorption; Equilibrium; Fixed bed; Geopolymer; Sr (II) ions; Zeolite; Batch adsorption; Geopolymer; Zeolite; Fixed bed; Equilibrium; Sr (II) ions
• ISSN: 0301-4797; 1095-8630
• DOI: 10.1016/j.jenvman.2021.112984

Diatomite/kaolinite-based geopolymer (GP) was synthesized and incorporated in zeolitization process (Z/GP) to investigate the role of the zeolite phases in inducing its retention capacity of the dissolved Sr (II) ions in water. The retention of Sr (II) ions using Z/GP in comparison with GP was evaluated based on both batch and fixed-bed column studies. In the batch study, the zeolitized geopolymer (Z/GP) shows enhancement in the Sr (II) retention capacity (193.7 mg/g) as compared to the normal geopolymer (102 mg/g). Moreover, the recyclability studies demonstrate higher stability for Z/GP than GP with a retention percentage higher than 90% for five reusing runs. The kinetic and the equilibrium properties of the occurred Sr (II) retention reactions follow the assumption of the Pseudo-Second order model (R2 > 0.96) and Langmuir model (R2 > 0.97), respectively. The Gaussian energies (15.4 kJ/mol (GP) and 11.47 kJ/mol (Z/GP)) related to retention mechanism of chemical type and within the suggested range for the zeolitic ion exchange processes. The Sr (II) retention reactions by GP and Z/GP are of spontaneous and exothermic properties which qualifies the products to be used at low-temperature conditions (20 °C). The column studies also declared higher performance for the Z/GP fixed bed as compared to the normal GP bed considering the total Sr (II) retention percentage (72.9%), treated volume (8 L), saturation time (1620 min), and a maximum capacity of Z/GP particles in the bed (567.6 mg/g). •Zeolitized geopolymer product was synthesized for enhanced retention of Sr (II).•The qmax of the geopolymer and the zeolitized product are 102 mg/g and 193.7 mg/g.•The retention reactions of Sr (II) follow Langmuir and Pseudo-Second order models.•The retention process occurred by chemical, exothermic and spontaneous reactions.•The column tests show higher retention by the zeolitized product than geopolymer.