Cadmium Recovery from HCl Solutions Using Cyanex 301 and Cyanex 302 Immobilized in Alginate Capsules (Matrix-Type vs. Mononuclear-Type Mode of Encapsulation)

Cyanex 301 and Cyanex 302 have been immobilized in alginate capsules by two methods: the matrix-type process immobilizes the extractant as homogeneous-dispersed vesicles while the mononuclear mode consists of encapsulation of the extractant drop by an alginate layer. The influence of HCl concentration on Cd(II) removal is discussed as a function of acid concentration and extractant. The sorption isotherms are fitted by the Langmuir model; maximum sorption capacities reach up to 42 mg Cd g⁻¹ in 0.1 M HCl. Uptake kinetics are controlled by resistance to intraparticle diffusion. Cadmium is desorbed using either 1 M HNO₃ or 1 M thiourea/1 M HCl solutions.