Preconcentration of the cobalt using modified forms of the transcarpathian clinoptylolite

Neodymium sorption on the Na-form of Transcarpathian clinoptilolite

“…In more alkaline solutions, the sorption of Nd(III) decreases sharply. It is known [ 30 , 31 , 33 , 44 ] that the sorption-active centers of the Na-form of Transcarpathian clinoptilolite concerning most heavy metals are mostly surface OH groups. That is why the character of the Nd(III) sorption process can be caused by the chemical features of the Na-clinoptilolite surface and by possible forms of Nd(III) in aqueous solutions at different pH values.…”

“…The sorption properties of Na-modified Transcarpathian clinoptilolite also depend on thermal pre-treatment [ [30] , [31] , [32] , [33] , 44 ]. That is why the Na-clinoptilolite samples were heated to different temperatures for 2.5 h and after cooling in a desiccator their sorption capacity towards Nd(III) was determined.…”

“…A decrease in the sorption efficiency of Na-clinoptilolite at higher temperatures occurs due to the processes of deep dehydroxylation of the zeolite surface and its partial amorphization [ 32 ]. It is known [ 32 , 33 ] that the common lanthanide Tb is most efficiently sorbed on Na-modified Transcarpathian clinoptilolite calcined at 475–700 °C, and the sorption of the transition metal Co on the Na-form calcined at 300 °C of this zeolite is minimal. At the same time, as can be seen from Fig.…”

“…Therefore, the low-silicon calcium variety of clinoptilolite, to which Transcarpathian clinoptilolite belongs, after converting it into the sodium form, shows increased efficiency of cation exchange, in particular, increased selectivity to multi-charged cations. It is well known that Na-forms of clinoptilolite have markedly different sorptive characteristics than unmodified clinoptilolite, and they typically have a greater sorption capacity towards cations of d- and f-transition elements [ [30] , [31] , [32] , [33] , [34] , [35] , [36] ].…”