Synthesis and characterization of lanthanum-based metal organic framework decorated polyaniline for effective adsorption of lead ions from aqueous solutions

The novel La-MOF@x%PANI composite was synthesized via a two-step procedure with ultra-sonication, and the adsorption mechanism of Pb2+ ions from synthetic aqueous solutions was systematically studied. The Pb2+ adsorption on the La-MOF@x%PANI was evaluated by the Fourier transform infrared spectroscopy, powder Xray diffraction, field-emission scanning electron microscopy, energy-dispersive X-ray analysis, Brunauer-Emmett-Teller analysis, X-ray photoelectron spectroscopy, and elemental mapping analyses. The effects of the adsorption-influencing parameters, including contact time, solution pH, and co-existing cations on the maximum adsorption capacity of Pb2+ onto the prepared composite material were investigated. Moreover, the adsorption of Pb2+ ions could be eliminated with rapid adsorption kinetics using the water-stable La-MOF@x% PANI composite. The as-synthesized La-MOF@50%PANI exhibited excellent adsorption performance toward Pb2+ ions with an extraordinary adsorption capacity of 185.19 mg/g at pH 6. The Pb2+ adsorption onto the LaMOF@x%PANI composite follows the pseudo-second-order kinetics and fits well with the Langmuir isotherm model, indicating the Pb2+ adsorption depended on the solution pH as the adsorption mechanism was mainly governed by the electrostatic attraction. Notably, La-MOF@x%PANI composite possesses outstanding regeneration ability and stability after up to four successive cycles. The satisfactory findings reflect that the LaMOF@50%PANI hybrid composite holds a great promise for remediating Pb2+ ions from aqueous environments.