Preparation And Modification Of Green Synthesized Fe₃O₄ Nanoparticles To Remove Ammonia And Phosphate In Aqueous Solutions

The green synthesis of magnetite nanoparticles ?MNP? using plant extracts have attracted much attention due to its eco-friendly route, simple operation, low cost and can realize large-scale production. However, Fe₃O₄ nanoparticles easily tend to aggregate into large particles, leading to reduce reactivity and limit its application. In this study, ionic surfactants such as cationic surfactant ?cetyltrimethylammonium bromide ?CTAB?? and anionic surfactant ?sodium dodecyl sulfate ?SDS?? as surface modification were investigated in green synthesis of Fe₃O₄ NPs to understand the effect of ionic surfactants on the dispersity and stability of Fe₃O₄ NPs. The results of characterizations indicated that the as-prepared EL-MNP, EL-MNP@CTAB, EL-MNP@SDS were uniform in shape and spherical morphology with average diameter of-180nm,-90 nm,-60nm respectively. It showed that EL-MNP@CTAB was best with removal efficiency of 97.3% when the phosphate initial concentration was 10 mg/L. The removal mechanism based on chemisorption of ligand exchange, electrostatic attraction between CTA+ and negatively charged phosphate, and hydrogen-bond interaction was proposed, which was associated with the biomolecules containing functional groups such as carboxyl and phenolic hydroxyl group capping on the surface of EL-MNP. Besides, zeolite was employed as the supporting material to prepare zeolite supported Fe₃O₄ NPs ?EL-MNP@zeolite? to improve the removal of mixed NH₄⁺-PO₄^3- contaminants using EL-MNP or EL-MNP@CTAB. The removal efficiency of NH₄⁺ and PO₄^3- by EL-MNP@zeolite were 43.32% and 99.84% respectively at room temperature. This study demonstrates that ionic surfactants as the modifier can not only improve the dispersity and stability of green synthesized Fe₃O₄ NPs, but also enhance the removal efficiency of mixed contaminant such as NH₄⁺-PO₄^3-. Moreover, the study also in green nanotechnology from both fundamental research to applied research provides a new insight on the use of surface modification to improve the function of Fe₃O₄ NPs and its removal for mixed containment.