Cancrinite synthesis from natural kaolinite by high pressure hydrothermal method: Application to the removal of Cd2+ and Pb2+ from water

Véronique Wernert (1, 2) , Oliver Schaef (2) , Lobna Aloui (2) , Carine Chassigneux (2) , Fadhila Ayari (3) , Dalila Ben Hassen Chehimi (3) , Renaud Denoyel (2)

1 AMU - Aix Marseille Université
2 MADIREL - Matériaux divisés, interfaces, réactivité, électrochimie
3 LACReSNE - Laboratoire des Applications de la Chimie aux Ressources et Substances Naturelles et à l'Environnement

Zeolites were synthesized from natural Tunisian clay by hydrothermal treatment under high pressure (100 MPa H 2 O pressure) at different gradients of temperature in high pressure autoclaves. The natural clay was first heated at 650 � C (HC-heated clay) and then transformed to an amorphous phase at 650 � C by adding different amount of NaOH. By increasing temperature and NaOH content, low-density frameworks zeolites like faujasite are transformed into more stable zeolites having higher density frameworks like cancrinite due to dissolution and recrystallisation steps. Cancrinite (Na 8 (H 2 0) 2 CO 3 [Al 6 Si 6 O 24 ]) (IZA-code: CAN) was successfully synthesized with a good purity. The synthesized CAN was characterized by X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM). The removal performance of heavy metal ions (Cd 2þ , Pb 2þ) from solution by pure CAN and clays has been studied. The kinetics of adsorption of Cd 2þ and Pb 2þ are very fast: equilibrium is reached within 2 min at 298 K. The capacity of adsorption of CAN is higher for Pb 2þ (192 mg g À 1) than for Cd 2þ (68 mg g À 1). Adsorption equilibrium of Cd 2þ and Pb 2þ on CAN were well represented by Langmuir equation although the thermodynamic study reveals a more complex mechanism: thermodynamic parameters, such as equilibrium constant, free energy, entropy and enthalpy for adsorption were obtained from the experimental data, including adsorption microcalorimetry.

Keywords: High pressure hydrothermal synthesis; Metakaolinite; Cancrinite; Heavy metals; Cadmium; Lead; Adsorption; Calorimetry

Domains: Chemical Sciences; Material chemistry

Véronique Wernert, Oliver Schaef, Lobna Aloui, Carine Chassigneux, Fadhila Ayari, et al.. Cancrinite synthesis from natural kaolinite by high pressure hydrothermal method: Application to the removal of Cd2+ and Pb2+ from water. Microporous and Mesoporous Materials, 2020, 301, pp.110209. ⟨10.1016/j.micromeso.2020.110209⟩. ⟨hal-03220980⟩