Performance of surfactant-modified *BEA-type zeolite nanosponges for the removal of nitrate in contaminated water: Effect of the external surface.

Hierarchical *BEA-type nanosponges zeolite with a high external surface area (116 m2.g-1) and small crystal size, synthesized in the presence of a dual-porogenic organic compound, were modified with a cationic surfactant (HDTMA+Br-: hexadecyltrimethyl ammonium bromide) in order to create a new anion exchanger system: the surfactant-modified zeolite nanosponges (SMZNS). For comparison, two other surfactant-modified *BEA-type zeolite materials, SMZMC and SMZNC, were obtained by modifying the synthesized conventional micron-size microcrytals and nanocrystals *BEA-type zeolite with HDTMA+Br-, respectively. Textural and structural properties were determined for the three prepared materials using N2 adsorption/desorption analysis, XRD, SEM, and TEM. Nitrate adsorption isotherms were drawn in a large concentration range [0.8-24.2 mmol.L-1] and fitted with Langmuir isotherm model. The maximum nitrate removal capacity (1338 mmol.Kg-1/83 mg.g-1) was obtained for SMZNS material. This value is the highest ever observed for nitrate removal using surfactant-modified zeolite. The nitrate removal kinetics were fitted with the pseudo second-order model for both materials SMZNS and SMZNC.