Modelling the Effects of Competing Anions on Fluoride Removal by Functionalized Polyacrylonitrile Coated with Iron Oxide Nanoparticles

Abstract

Fe₂O₃ nano particles supported on functionalized poly-acrylonitrile was prepared. PAN-oxime-nano Fe₂O₃ was characterized by XRD, FTIR andTEMand used for fluoride adsorption. The adsorption capacity increased with increasing initial fluoride concentration and reaction time. Fluoride-removal performance of PAN-oxime-nano Fe₂O₃ was also tested in the presence of various competing anions usually found in drinking water. Competitive sorption between fluoride and competing anions showed a minimum preference for chloride counterions. Carbonate was the greatest competitor for fluoride removal followed by phosphate and sulphate. Counterion presence decreased fluoride adsorption capacity in order of CO₃²⁻> PO₄³⁻> SO₄²⁻> Cl⁻. The presence of anions at various concentrations decreased fluoride adsorption capacity on PAN-oxime-nano Fe₂O₃ by 1.22 to 6.51 mg g^–1. Effects of each two anions exist simultaneously in aqueous solution on fluoride adsorption was investigated using Tukey’s test (called also a pairwise comparison). Tukey’s HSD results indicate that the differences between various pairs of anions are significant (P < 0.05), except for chloride–sulphate (P = 0.08). In the design of PAN-oxime-nano Fe₂O₃ for environmental applications, the strong influence of the counter ions must be considered.

KEYWORDS Fluoride, PAN-oxime- nano Fe₂O₃, counterion, adsorption.