Effects of experimental variables on phosphate adsorption on bentonite

The adsorption process of phosphate ions on a bentonite from Almería (East‐Andalucía, Spain) was studied at 30°C over a range of experimental conditions such as saline (0.1 M KCl) or non‐saline medium, natural or calcium homoionic bentonite and different pH values. In order to calculate the adsorption capacities ( X m ) of the samples, the experimental data points were fitted to the Langmuir equation. X m values ranged from 0.42 μg P g −1 for the natural sample in non‐saline medium to 0.74 μg P g −1 for the same sample in saline medium, the X m value corresponding to the calcium homoionic bentonite sample being intermediate. At different pH conditions, X m increased from 0.28 μg P g −1 at a pH of 1.3 to 1.53 μg P g −1 at a pH of 4.4, and then decreased to 0.42 μg P g −1 at a pH of 8.7.