Comparison of the Capacity of Fluoride Adsorption and Recycling Ability of Al(OH)3-Coated Iron Oxide Nanoparticles Prepared by Different Methods

Abstract

Removal of fluoride from wastewater is crucial to avoid excess accumulation of fluoride in the environment, which causes harm to humans. In this work, we performed a comparison study in which four different core–shell magnetic nanoadsorbents of fluoride ions were synthesized, characterized, and tested: NP1@Al(OH)3AQ, NP1@Al(OH)3ORG, NP2@Al(OH)3AQ, and NP2@Al(OH)3ORG. NP1 and NP2 stand for iron oxide nanoparticles prepared via the co-precipitation method and via thermal decomposition of organic precursors, respectively. AQ and ORG refer to the aqueous or organic media employed for the synthesis of the Al(OH)3 shell. Although the nanomaterials containing the NP2 core showed higher adsorption capacity, a result in line with the higher content of Al(OH)3 of these NPs, NP1@Al(OH)3AQ were the only nanoparticles which could be regenerated and reused after fluoride desorption in alkaline medium. Pre-incubation of HepG2 cells exposed to fluoride ion with NP1@Al(OH)3AQ and NP2@Al(OH)3AQ produced a further recovery of cell’s viability. Cell viability tests performed with both NPs after 1, 2, or 3 uses showed a decrease in protection with increasing number of uses. In addition, NP1@Al(OH)3 responded better to cellular protection, in good agreement with results obtained in vitro in the absence of biological material.