<p>A mathematical model of mass transfer and diffusion during the adsorption of the ions of heavy metals Pb²⁺, Cd²⁺, Zn²⁺, and Ni²⁺ from solutions has been developed. The isotherms and kinetic curves of adsorption of the indicated metals by natural clinoptilolite, and also the dependence of the adsorption of these ions on pH of the solution have been determined. It has been established that the process of separation is more intense at pH 6.2–7. The regularities of the influence of the concentration of the adsorptive in the solution on the total mass-transfer coefficient and the effective coefficient of diffusion in it have been determined.</p>