Magnetic aminated lignin/CeO₂/Fe₃O₄ composites with tailored interfacial chemistry and affinity for selective...

Phosphorus (P) has brought a series of environmental problems while benefiting mankind. To reclaim phosphorus from wastewater efficiently and conveniently, a novel magnetic adsorbent with aminated lignin/CeO₂/Fe₃O₄ composites (AL-NH₂@Fe₃O₄-Ce) possessing a high affinity to phosphate and easily separated from aqueous solutions was developed in this work. The characterization results revealed that Fe and Ce elements have been doped into the aminated lignin successfully. Batch experiment results convinced that the maximum phosphate adsorption capacity of AL-NH₂@Fe₃O₄-Ce was 183.72 mg P/g at pH = 3, which was roughly 4.5 times greater than aminated lignin and 8.5 times greater than cerium oxide, respectively. The adsorption isotherm was fitted well by the Langmuir model, and the adsorption kinetics was in line with the pseudo-second-order model. The adsorption thermodynamics indicated the adsorption process was spontaneous and naturally exothermic. Additionally, AL-NH₂@Fe₃O₄-Ce exhibited high selectivity towards phosphate over common coexisting anions (Cl^-, NO₃^-, HCO₃^-, SO₄^2- and F^-). After five consecutive cycles, the adsorption performance of AL-NH₂@Fe₃O₄-Ce decreased by only 16% compared with the fresh adsorbent, indicating that AL-NH₂@Fe₃O₄-Ce exhibited excellent recycling ability. The results of XPS analysis and batch experiments showed that the possible mechanisms were electrostatic attraction and inner-sphere complexation. The tailored interfacial chemistry affinity to phosphate as well as endowed magnetic property reveled AL-NH₂@Fe₃O₄-Ce could be adopted as an up and coming adsorbent in phosphate removal process.