Development of citric anhydride anchored mesoporous MOF through post synthesis modification to sequester potentially toxic lead (II) from water

Here in, a post synthesis modification (PSM) approach was adopted for anchoring citric anhydride (CA) with NH2-MIL-53(Al) through covalent linkage between amino (–NH2) group of NH2-MIL-53(Al) and carboxylic group of CA to develop mesoporous amide citric anhydride [AMCA-MIL-53(Al)] metal organic framework (MOF) and its potential application in sequestering toxic lead [Pb(II)] from aqueous phase was tested. Characterization studies affirmed successful AMCA-MIL-53(Al) formation. Experimental parameters viz., pH, contact time, Pb(II) concentration, temperature, and AMCA-MIL-53(Al) dose have a profound influence on adsorption. The maximum adsorption of Pb(II) on AMCA-MIL-53(Al) was 390 mg/g, observed at 318 K. Modeling studies revealed fitting of Langmuir isotherm and Lagergren's pseudo-first-order kinetic models to experimental data. Mechanistically, the adsorption was governed by amide and carboxylate groups through coordinate and electrostatic bonds formations. Desorption studies showed 79.5% (maximum) Pb(II) recovery with 0.1 M HCl. Thus, it could be concluded that the developed AMCA-MIL-53(Al) MOF is an excellent adsorbent for an efficient and rapid Pb(II) removal and recovery.