“…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.…”