Effect of grain size and interfering anion species on the removal of fluoride by hydrotalcite-like compounds

Nickel and magnesium hydrotalcite-like compounds (NiAlHT, MgAlHT) were investigated to remove fluoride ions from aqueous solutions in batch system. F− ions were determined in the remaining solutions using a fluoride ion selective electrode. Kinetic of the fluoride sorption from aqueous solutions by nickel hydrotalcite-like compound with different grain size were determined as well as the effects of Cl−, SO42− and As(V) on the sorption kinetic. It was found that the adsorption rate is the highest using grains samples of 25–50 mesh and in about 600 min the equilibrium was reached in all systems; the results were best fitted to the Elovich rate model equation which indicates that the sorption mechanism is trough a chemisorption process. Other anions interfere on the F− adsorption from bicomponent aqueous solution by NiAlHT and MgAlHT. NiAlHT is more efficient than MgAlHT to remove fluoride from the aqueous solutions.

► The grain size influence the adsorption rate of fluoride ions by hydrotalcites.
► The interference of other anions on fluoride sorption by NiAlHT is SO42− > As(V) > Cl−.
► The interference of SO42−, As(V) and Cl− on fluoride sorption by MgAlHT is similar.
► NiAlHT is more efficient than MgAlHT for fluoride removal by chemisorption process.