Anion-induced exchange interactions in binuclear complexes of Cu(II) with flexible hexadentate bispicolylamidrazone ligands

Competitive Adsorption of Cr(III) and Cu(II) on Electron Beam-Irradiated Sheep Wool from Binary Solutions Can be Controlled by the Absorbed Dose

Sheep wool irradiated by an electron beam was tested for adsorption of Cr(III) and Cu(II) from binary solutions within the same concentration of each cation from 15 to 35 mmol·dm^-3. The wool sorptivity examination was aimed at searching the effect of the dose absorbed by wool on simultaneous sorption of these cations due to surface and bulk changes. The partners affected each other under these conditions. In the whole concentration range, the sorptivity of nonirradiated wool (0 kGy) for Cu(II) fluctuated within the range of 14.5-20.7 mg·g^-1, while sorptivity for Cr(III) ranged from 14.8 to 7.5 mg·g^-1. However, sorptivity for Cu(II) was always superior to Cr(III). At a 24 kGy dose, the wool sorptivity for both cations decreased approximately by half and tended to converge, whereby at 20 mmol·dm^-3, a slight predominance for Cr(III) was already observed. However, the sorptivity of 100 kGy dosed wool acquired a clear predominance for Cr(III) over Cu(II) in the entire concentration range, showing some leveling around 14.5 mg·g^-1. Sorptivity for Cu(II) was suppressed and increased nonlinearly with concentrations from 1.7 to 10.2 mg·g^-1. It was concluded that optimally dosed wool could provide a special adsorbent suitable to control preferential sorption of some cations from binary solutions.

Why Natural or Electron Irradiated Sheep Wool Show Anomalous Sorption of Higher Concentrations of Copper(II)

Sorption of higher concentrations of Cu(II) solution onto natural sheep wool or wool irradiated by an electron beam was studied. Sorption isotherms were of unexpected character, showing extremes. The samples with lower absorbed doses adsorbed less than non-irradiated wool, while higher doses led to increased sorption varying with both concentration and dose. FTIR spectra taken from the fibre surface and bulk were different. It was concluded that there was formation of Cu(II)-complexes of carboxylic and cysteic acids with ligands coming from various keratin macromolecules. Clusters of chains crosslinked through the ligands on the surface limit diffusion of Cu(II) into the bulk of fibre, thus decreasing the sorption. After exhausting the available ligands on the surface the remaining Cu(II) cations diffuse into the keratin bulk. Here, depending on accessibility of suitable ligands, Cu(II) creates simple or complex salts giving rise to the sorption extremes. Suggestion of a mechanism for this phenomenon is presented.