Copper and cadmium extraction from highly concentrated phosphoric acid solutions using calcium alginate gels enclosing bis(2,4,4‐trimethylpentyl)thiophosphinic acid

Abstract

The availability of alginate gels enclosing Cyanex 302 [bis(2,4,4-trimethylpentyl)thiophosphinic acid] for the uptake of cadmium and copper from highly concentrated solutions of industrial phosphoric acid wet process phosphoric acid (WPA)] was studied. For this purpose, beads of alginate gels enclosing microdrops of kerosene solutions of the industrial extractant Cyanex 302 at different concentrations were prepared. The experimental procedure gives rise to a composite bead in which alginate is the continuous phase and the organic extractant forms the discrete homogeneously distributed phase within the bead. The equilibrium in this three-phase system (phosphoric acid-extractant solution-alginate gel) was modelled in terms of the corresponding distribution factors, the main chemical reactions and their equilibrium constants. Retention isotherms of both metal ions were obtained experimentally at four concentrations (1.0, 2.5, 5.0 and 7.5 mol L −1 ) of pure phosphoric acid. High metal removal efficiency, due to liquid-liquid extraction processes, was observed even in the most acidic conditions. High values of the extraction constants were estimated, with the distribution coefficients between aqueous and alginate phase being near unity. Finally, the results obtained with industrial WPA are in close agreement with those predicted by the physicochemical model developed in synthetic media.

Kinetic analysis of metal uptake by dry and gel alginate particles

“…Several alginate-based sorbents have been evaluated for metal uptake from aqueous solutions for possible application in water treatment processes. The most common preparations are calcium alginate gel beads, plain or with other metal binding-sorbents entrapped in the gel matrix [7][8][9][10][11][12][13][14][15]. Some authors use dry beads prepared by drying the conventional gel beads to produce a material easier to manipulate and with improved sorption properties [16][17][18][19].…”

Encapsulation of Cyanex 302 with Alginate for Palladium Recovery

“…This study focuses on the encapsulation of Cyanex 302 (bis(2,2,4‐trimethylpentyl) monothiophosphinic acid) in mononuclear (N) calcium alginate gel beads. The conventional process (matrix‐type encapsulation, M) consists of the mixing of the extractant with alginate solution making an emulsion before dropping the mixture into an ionotropic gelation solution (i.e., CaCl 2 , for example) . Various shapes of microcapsules such as granules, fibers and films have been prepared .…”

“…The conventional process (matrix-type encapsulation, M) consists of the mixing of the extractant with alginate solution making an emulsion before dropping the mixture into an ionotropic gelation solution (i.e., CaCl 2 , for example). [15,[19][20][21][22] Various shapes of microcapsules such as granules, fibers and films have been prepared. [23] Moreover, alginate microcapsules were prepared by coating of fresh alginate microcapsules with chitosan or polyethyleneimine (PEI).…”

Extractant Immobilization in Alginate Capsules (Matrix- and Mononuclear-Type): Application to Pb(II) Sorption from HCl Solutions

“…However, new processes have been recently developed for the immobilization of extractants and ionic liquids. The extractant is encapsulated in a polymer or a biopolymer matrix [ 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 ]. In this case, the extractant is generally immobilized in the matrix of the polymer by emulsification and subsequent polymerization or jellification (for example, ionotropic gelation of alginate in the presence of calcium ions), the so-called matrix-type encapsulation process (M).…”