Sorption kinetics of copper, nickel and cobalt ions under their compresence from aqueous solutions by zeolites

Abstract

The mutual influence on the kinetics of the sorption of copper (II), nickel (II) and cobalt (II) ions (under their compresence) by natural zeolite of Yagodninsky deposit (Kamchatka) was experimentally investigated. Mineral composition of the zeolite tuffs of the Yagodninsky deposit of the Kamchatka Krai are represented by clinoptilolite (up to 70%) and mordenite (up to 10%). Cristobalite, quartz, mica and clay minerals account for up to 20%. Clinoptilolite of the Yagodninsky deposit is represented by a polycationic Na-K-Ca-form. The dominant replaceable cations in clinoptilolite are alkali metals: Na⁺ and К⁺. Mordenite is characterized by the predominance of Ca²⁺ ions. The natural form of zeolite is not only homogeneous single crystals, but also aggregates in the form of mineral grains intergrowths.

The value of sorption capacity, the coefficient of internal diffusion, the rate constant of exchange reaction according to the models of pseudo-first and pseudo-second order were calculated for each ion. The calculated diffusion coefficients, reaction rate constants k₁ (pseudo-first-order model, с^-1) and k₂ (pseudo-second-order model, g·mmol-eq^-1·s^-1), high correlation coefficients confirm that the diffusion of exchangeable ions in the crystal lattice of minerals is the limiting factor.

The sorption capacity of zeolite from individual solutions decreases in the series Cu> Ni> Co and it is 31.7, 27.0, 23.0 mmol-eq/kg, respectively. The presence of copper (II) ions in the solution affects much on the sorption of nickel and cobalt from aqueous solutions of complex composition. It is, probably, connected with the crystal-chemical radius of copper (II) ion. Compared to nickel (II) ions and cobalt (II) ions it is the largest.