Batch experiments were conducted to evaluate fluoride removal by Al,Fe,and Ti-based coagulants and adsorbents,as well as the effects of coexisting ions and formation of aluminum–fluoride complexes on fluoride removal by co-precipitation with alum(Al_2(SO_4)_3·18H_2O).Aluminum sulfate was more efficient than the other coagulants for fluoride removal in the pH range between 6 and 8.Nano-crystalline TiO_2 was more effective for fluoride removal than Al and Fe hydroxides in a pH range of 3–5.Coexisting anions in water decreased the removal of fluoride in the order:phosphate(2.5 mg/L) > arsenate(0.1 mg/L) > bicarbonate(200 mg/L) >sulfate(100 mg/L) = nitrate(100 mg/L) > silicate(10 mg/L) at a pH of 6.0.The effect of silicate became more significant at pH > 7.0.Calcium and magnesium improved the removal of fluoride.Zeta-potential measurements determined that the adsorption of fluoride shifted the PZC of Al(OH)_3 precipitates from 8.9 to 8.4,indicating the chemical adsorption of fluoride at the surface.The presence of fluoride in solution significantly increased the soluble aluminum concentration at pH < 6.5.A Visual MINTEQ modeling study indicated that the increased aluminum solubility was caused by the formation of AlF~(2+),AlF~(+2),and AlF_3complexes.The AlF_x complexes decreased the removal of fluoride during co-precipitation with aluminum sulfate. Batch experiments were conducted to evaluate fluoride removal by Al, Fe, and Ti-based coagulants and adsorbents, as well as the effects of coexisting ions and formation of aluminum-fluoride complexes on fluoride removal by co-precipitation with alum (Al 2 (SO 4) _3 · 18H_2O). Aluminum sulfate was more efficient than the other coagulants for fluoride removal in the pH range between 6 and 8. Nano-crystalline TiO_2 was more effective for fluoride removal than Al and Fe hydroxides in a pH range of 3-5. Coexisting anions in water decreased the removal of fluoride in the order: phosphate (2.5 mg / L)> arsenate (0.1 mg / L)> bicarbonate (200 mg / L) L)> silicate (10 mg / L) at a pH of 6.0. The effect of silicate became more significant at pH> 7.0. Calcium and magnesium improved the removal of fluoride. Zeta-potential measurements determined that the adsorption of phosphate shifted the PZC of Al (OH) 3 precipitates from 8.9 to 8.4, indicating the chemical adsorption of fluoride at the surface. presence of fluoride in solution significantly increased the soluble aluminum concentration at pH <6.5. A Visual MINTEQ modeling study indicated that the increased aluminum solubility was caused by the formation of AlF ~ (2 +), AlF ~ (+2 ), and AlF_3 complexes. The AlF_x complexes decreased the removal of fluoride during co-precipitation with aluminum sulfate.