Adsorption of La(III) in aqueous systems by N-(2-hydroxyethyl) salicylaldimine-functionalized mesoporous silica

• HESI-SBA-15 as a new adsorbent was synthesized for the first time.
• This adsorbent was selective for lanthanum ion removal in presence of other ions.
• The factors that affected adsorption of La(III) in aqueous solution were studied.
• La3+ uptake process was according to pseudo-second-order kinetic model.

In this work, a novel modified SBA-15 with covalently bonded N-(2-hydroxyethyl) salicylaldimine Schiff base as a ligand (HESI-SBA-15) was successfully synthesized, characterized and used as a selective absorbent for lanthanum ions removal from water systems. The structure and physicochemical properties were identified by elemental analysis, X-ray diffraction, nitrogen adsorption–desorption, thermogravimetric analysis and FTIR spectroscopy, scanning electron microscopy, BET surface area and BJH pore size. These techniques have confirmed that the Schiff base ligand was successfully grafted on the SBA-15 surface and ordered arrangement of the silica support was preserved under functionalization. The effect of pH, adsorbent dose, contact time, ionic strength and initial metal ions concentration were studied by using a batch method. This new adsorbent showed high adsorption capacity and selectivity for lanthanum in the presence of other ions. The adsorption process was exactly according to the pseudo-second-order kinetic model. The adsorbent showed a good reusability after four cycles recovery.

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