On the Adsorption of Heavy Metal Ions on Clay and Other Soil Constituent Minerals (2nd Report)

Abstract

The adsorption of heavy metal ions (Pb²⁺, Cd²⁺, Cu²⁺, Zn²⁺) on crystalline clay minerals, amorphous minerals and other some soil constituent minerals in acidic solution has been investigated by means of measurements of adsorption and surface area.
The adsorption speed of metal ions on the specimens was relatively high and the equilibrium condition was nearly obtained by shaking for about 5 minutes.
The adsorption was fairly affected by pH of the solution, metal ion concentration and a type of exchangeable cation in the sample. The order in which metal ions were adsorbed on the specimens was as follows; Pb²⁺>>Cu²⁺Cd²⁺>Zn²⁺.
As a result of competitive adsorption of H+, the amount adsorbed of metal ions on the clay in acidic solution had no mutual relation with the surface area. The ratio of internal surface area to total surface area of clay specimens decreased in the order of; 2;1 family clay>1;l family clay, chain structure>amorphous specimens.
In the case of montmorillonite, vermiculite, synthetic allophane and chlorite, the equilibrium data were agreement with Langmuir's adsorption formula in the whole experimental concentration ranges. But the formula was applicable in limited lower concentration ranges concerning kaolinite, halloysite and sericite.
The adsorption capacity of manganese dioxide was nearly equal to it of chlorite.