Magnetic sorption materials for recovery of organic anions from aqueous solutions

Layered double hydroxides (LDHs) belong to the class of two-dimensional anionic clays with a layered structure similar to brucite. The combination of sorption and magnetic properties of layered materials is promising. In this work, magnetic materials based on LDHs (MLDHs) were synthesized and their sorption and magnetic properties were studied. The synthesis of LDHs was carried out by a co-precipitation method followed by calcination. Intercalated Mg, Fe(III)-, Mg, Fe(III), Al-and Mg, Al-LDHs were prepared using LDHs by rehydration in solutions of iron(III) citrate (Cit) or oxalate (Ox) followed by the calcination at 400°C for 2-4 h. LDHs and their thermal decomposition products were characterized by FTIR spectroscopy, laser and X-ray diffraction and thermogravimetry. The sorption experiment was carried out under static conditions using glutamic acid (Glu) as a model organic compound. The maximum sorption capacity of Mg, Fe(III)-LDH and Mg, Al-FeCit-LDH calcined at 400°C was 6.6 and 8.8 mg/g Glu, respectively. The sorption kinetics of intercalated and calcined Mg, Al-and Mg, Fe(III), Al-LDH and calcined at 500º C Mg, Fe(III)-LDH was described by the pseudo-second order model. The magnetic properties of the LDHs and thermal decomposition products were retained after the adsorption of glutamic acid, making it possible to easily separate these MLDHs from the solution by magnetic field