A study on the adsorption of lead (Pb) ions on clay from South Africa was done in a batch
adsorber with pH as a determining factor. The saturation capacity of lead ions on clay was
62.1 mg g-1 which increased with increasing the pH of the system.
Also, lead ions adsorption on kaolinite clay from Nigeria at different initial concentrations and temperatures showed that the adsorption capacity increased from 3.94 to 8.85 mg g-1 by increasing the solution temperature. This suggested that the adsorption of lead ions on kaolinite clay is an endothermic. The adsorption of lead ions on phosphatic clay from USA using batch equilibrium technique was 32 mg g-1. The effect of changing pH of solution on
Pb ion adsorption by tripolyphosphate-impregnated kaolinite clay (where kaolinite from Nigeria)
indicated that the adsorption depends on the pH of the solution. For example, at pH= 4 and the
concentration as 500 ppm, the adsorption capacity was 24.7 mg g-1.
Hectorite clay from USA and vermiculite clay from Spain were converted to functionalized hectorite and functionalized vermiculite using thiol groups and used to adsorb lead ions from aqueous solution. The maximum adsorption capacity of functionalized vermiculite clay for lead ions was 33 mg g-1 and higher than the functionalized hectorite of 10 mg g-1. Three types
of Saudi natural clays (namely Tabuk, Baha and Khaiber) were used to adsorb lead ions from
wastewater. The maximum adsorption capacity of these clays was 30, 25 and 10 mg g-1 for Tabuk,
Baha and Khaiber clay, respectively