Citrate Stabilized Magnetic Nanoparticles (Fe3 O4 ) for the Removal of Pb 2+ Ions in Wastewater

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Addis Ababa University


Water contaminations by heavy metals are a major environmental problem due to their acute toxicity and their accumulation in food chains. One of such toxic heavy metals is Pb 2+ ions. In this study the synthesis of bare magnetite nanoparticles (B-MNPs), and citric acid coated magnetite nanoparticles (Cit-MNPs) to remove heavy metal Pb Page IV 2+ ions from wastewater is reported. The Fe 3 O 4 MNPs were synthesized using standard coprecipitation methods. The as such prepared MNPs were characterized by AAS, XRD, FTIR, BET, and Zetasizer. Citric acid was used as surface coating and functionalization of MNPs to increase the selectivity of the magnetic MNPs towards Pb 2+ ions. Using a permanent magnet, the Cit-MNPs were easily separated from the mixture after adsorption of Pb 2+ ions. The adsorption of Pb 2+ ions from synthetic wastewater was tested using a batch experiment to assess the feasibility of the prepared MNPs. The main operational parameters namely pH, adsorbent mass, initial Pb 2+ ions concentration, and contact time were investigated to understand the optimal experimental conditions for removal of Pb 2+ ions. The adsorption efficiency was highly pH-dependent. The maximum removal efficiencies of Pb 2+ ions on Cit-MNPs and B-MNPs were over 96.1% and 83.3%, using adsorbent dose: 0.1 g/L , at pH: 5, contact time: 60 minutes, initial metal ions concentration: 50 mg/L, shaker speed: 200 rpm, and temperature: normal, respectively. The sorption of Pb 2+ ions onto nanoadsorbents obeyed the Freundlich adsorption isotherm model. The maximum adsorption capacity achieved by Cit-MNPs is about 200 mg/g, which is higher than B-MNPs, i.e., 111.1 mg/g. A kinetic study confirms more the pseudo-second-order model with R 2 = 0.99. The first-order rate constant of K 1 and second-order rate constant of K 2 were found to be, K 1 = 1.1x10 -2 minute -1 , K 2 = 1.3x10 -2 minute -1 for B-MNPs and K 1 = 1.9x10 -2 minute -1 , K 2 = 1.4x10 -2 minute -1 for Cit-MNPs, respectively. This result confirmed that the synthesized MNPs nanoadsorbents are considered the most promising sorbent with high efficiency and more feasible to remove Pb 2+ , a heavy metal ions from synthetic wastewater.



Magnetite nanoparticles, Citric acid, Wastewater, Lead ions, Adsorption