drinking water was tested by determining the adsorption
equilibrium isotherm using a sample of actual drinking water
from the city of San Luis Potosi, Mexico. The sample was taken
from the public water system, and the sampling point was chosen
to have high fluoride concentration. All the experimental
conditions for the adsorption of fluoride from drinking water
are given in Table 2. The fluoride concentration of the drinking
water sample was 4.02 mg/L. This concentration was well above
1.5 mg/L which is the guideline value recommended by the
World Health Organization.36
The adsorption isotherm of fluoride from actual drinking
water is graphed in Figure 11 together with the adsorption
isotherms at pH 7 and 10. The adsorption isotherm of fluoride
from the actual drinking water was slightly lower than the