Synthesis of novel CO32−/Cl−-bearing 3(Mg + Zn)/(Al + Fe) layered double hydroxides for the removal of anionic hazards

• New eco-friendly and cheap layered double hydroxides (LDH’s) compositions were synthesized.
• The anionic heavy metal complex dye Isolan Dark Blue 2SGL-01 and CrO42− ion were removed.
• High adsorption capacities were obtained.
• Magnetic separation of as-synthesized or loaded Fe-LDH’s is available.

The new CO32−/Cl− layered double hydroxides (LDHs) (Mg(3−3v)Zn3v)/(Al(1−w)Few) were synthesized and calcined at 450 °C (CLDH), where v and w = 0, 0.1, 0.2, and/or 1, as adsorbents to remove anionic hazards such as Isolan Dark Blue 2SGL-01 (IDB) and CrO42− from polluted wastewater. The products were characterized by powder X-ray diffractometry, Fourier transform infra-red spectra, thermogravimetric analysis, elemental analysis, scanning electron microscope, magnetic susceptibility and specific surface area measurements. The effect of composition of LDH’s on their uptake capacities (qe) for IDB and chromate ions were studied. CLDH’s were more effective in removing anionic hazards than LDH, in particular with IDB and for v and w = 0.1 and/or 0.2. High adsorption capacities were obtained up to 438 and 46.3 mg g−1 (30.1 and 15.7% of the theoretical capacities), for IDB and chromate, respectively. Fe-containing LDHs could be magnetically separated either as-synthesized or loaded.

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