Poly(acrylic acid)-coated iron oxide nanoparticles: Quantitative evaluation of the coating properties and applications for the removal of a pollutant dye

In this work, 6–12 nm iron oxide nanoparticles were synthesized and coated with poly(acrylic acid) chains of molecular weight 2100 g mol−1. Based on a quantitative evaluation of the dispersions, the bare and coated particles were thoroughly characterized. The number densities of polymers adsorbed at the particle surface and of available chargeable groups were found to be 1.9 ± 0.3 nm−2 and 26 ± 4 nm−2, respectively. Occurring via a multi-site binding mechanism, the electrostatic coupling leads to a solid and resilient anchoring of the chains. To assess the efficacy of the particles for pollutant remediation, the adsorption isotherm of methylene blue molecules, a model of pollutant, was determined. The excellent agreement between the predicted and the measured amounts of adsorbed dyes suggests that most carboxylates participate to the complexation and adsorption mechanisms. An adsorption of 830 mg g−1 was obtained. This quantity compares well with the highest values available for this dye.

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► Iron oxide nanoparticles are synthesized and coated with poly(acrylic acid).
► Electrostatic coupling leads to a solid and resilient anchoring of the chains.
► Density of adsorbed polymers is 2 per square nanometer.
► Adsorption isotherm of methylene blue dyes reveals very high adsorption amounts.
► Quantitative comparison shows that most carboxylates participate to complexation and adsorption..