Effective removal of phosphate from aqueous solution using humic acid coated magnetite nanoparticles. (15th October 2017)

• Record Type: Journal Article
• Authors: Rashid, Mamun; Price, Nathaniel T.; Gracia Pinilla, Miguel Ángel; O'Shea, Kevin E.
• Is Part Of: Water research. Volume 123(2017)
• Page Start: 353
• Page End: 360
• Publication Date: 2017-10-15
• Subjects: Humic acid coated magnetite nanoparticles -- Adsorption -- Magnetic separation -- Phosphate; Water -- Pollution -- Research -- Periodicals; 363.7394
• DOI: 10.1016/j.watres.2017.06.085
• Languages: English
• ISSNs: 0043-1354

Abstract

Abstract: Effective removal of excess phosphate from water is critical to counteract eutrophication and restore water quality. In this study, low cost, environmentally friendly humic acid coated magnetite nanoparticles (HA-MNP) were synthesized and applied for the remediation of phosphate from aqueous media. The HA-MNPs, characterized by FTIR, TEM and HAADF-STEM showed the extensive coating of humic acid on the magnetite surface. The magnetic nanoparticles with diameters of 7–12 nm could be easily separated from the reaction mixture by using a simple hand held magnet. Adsorption studies demonstrate the fast and effective separation of phosphate with maximum adsorption capacity of 28.9 mg/g at pH 6.6. The adsorption behavior follows the Freundlich isotherm suggesting the formation of non-uniform multilayers of phosphate on the heterogeneous surface of HA-MNP. The adsorption kinetic fits the pseudo-second order model well with rate constants of 0.206 ± 0.003, 0.073 ± 0.002 and 0.061 ± 0.003 g mg −1 min −1 for phosphate (P) concentrations of 2, 5 and 10 mg/L respectively. The removal of phosphate was found higher at acidic and neutral pH compared to basic conditions. The nanoparticles exhibit good selectivity and adsorption efficiency for phosphate in presence of co-existing ions such as Cl −, SO4 2− and NO3 − with some inhibition effect by CO3 2− . The effect of temperature on the adsorption reveals that the process is endothermic and spontaneous. HA-MNPs are promising, simple, environmentally friendly materials for the removal of phosphate from aqueous media. Graphical abstract: Image 1 Highlights: HA-MNPs effectively removes phosphate with maximum adsorption capacity of 28.9 mg/g. Adsorption of phosphate on HA-MNP mainly follows the mechanism of chemisorption. The phosphate removal works better at acidic to neutral pH and at high temperatures. After the treatment, HA-MNPs can be easily separated by using a simple magnet.