Modelling the effects of competing anions on fluoride removal by functionalized polyacrylonitrile coated with iron oxide nanoparticles

Fe2O3 nano particles supported on functionalized poly-acrylonitrile was prepared. PAN-oxime-nano Fe2O3 was characterized by XRD, FTIR and TEM and 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 CO24- > PO34- >SO24- Cl3-. 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.