Removal of fluoride from aqueous solution onto Zr-loaded garlic peel (Zr-GP) particles

Garlic peel, as the raw material, was modified by loading with zirconium(IV), exhibiting quite good uptaking behaviour for fluoride anion. The adsorption experiments were carried out in batch shaking vessels, and the process was strongly dependent on the pH value. The adsorption fits Langmuir model well, and the maximum adsorption capacities at equilibrium pH 2 and 6 are evaluated to be 1.10 and 0.89 mol(fluoride)/kg of Zr-loaded garlic peel gel, respectively. The evaluation of effects of coexisting anions such as nitrate, sulfate and phosphate shows that nitrate and sulfate have no negative effect on the adsorption of fluoride, while phosphate has a little effect. Adsorption kinetics of fluoride is well described by pseudo-second-order rate equation, and the corresponding adsorption rate constant is calculated to be 3.25×10−3 g/(mg·min).