Red mud was also used for the removal of fluoride from aqueous
solution by C¸ engeloglu et al. ˘ [283]. They used both the original and
activated red mud forms in batch mode and found that the adsorption
capacity of activated form for fluoride was higher than that
of original form. They further reported that the maximum fluoride
removal occurred at pH 5.5. Red mud has also been used to remove
phosphate (P) from aqueous solutions by Huang et al. [284]. Acid
and acid-thermal treatments were employed to treat the raw red
mud. It was observed that the red mud with HCl treatment showed
the highest adsorption capacity among all the red mud samples,
giving adsorption capacity of 0.58 mg/g at pH 5.5 and 40 ◦C.