Role of Post-Exposure Time in Co(II) Sorption of Higher Concentrations on Electron Irradiated Sheep Wool.

Sorption of Co(II) was investigated on natural as well as accelerated electron beam modified sheep wool involving low and high concentrations up to 200 mmol·dm-3. The sorption experiments confirmed the dependence of the sorption capacity not only on sorbate concentration and absorbed dose of energy, but also on post-exposure time. Post-exposure heating to accelerate transformation of the wool structure was of no effect on the sorption comparing with a simple storage for a period of 100 days. Under all tested conditions, the sorption maximum was measured for Co(II) concentration of 125 mmol·dm-3 and that was assigned to form a Co(II) complex with keratin. This assumption was tested on visible spectra of mixed solutions of Arginine and Co(II) to be a simplified model of Co(II) interaction with keratin. The sorption decrease is associated with generation of cross links between macro-chains through ligands of the Co-complex. The nodal points are a hindrance to diffusion of next ions into the fibers. Also, pH variations of aqueous extracts from the wool samples depending on absorbed dose and post-exposure time indicate complexity of the structural transformation being specific for each dose applied.

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.

The Effect of High-Energy Ionizing Radiation on the Mechanical Properties of a Melamine Resin, Phenol-Formaldehyde Resin, and Nitrile Rubber Blend.

Irradiation by ionizing radiation is a specific type of controllable modification of the physical and chemical properties of a wide range of polymers, which is, in comparison to traditional chemical methods, rapid, non-polluting, simple, and relatively cheap. In the presented paper, the influence of high-energy ionizing radiation on the basic mechanical properties of the melamine resin, phenol-formaldehyde resin, and nitrile rubber blend has been studied for the first time. The mechanical properties of irradiated samples were compared to those of non-irradiated materials. It was found that radiation doses up to 150 kGy improved the mechanical properties of the tested materials in terms of a significant increase in stress at break, tensile strength, and tensile modulus at 40% strain, while decreasing the value of strain at break. At radiation doses above 150 kGy, the irradiated polymer blend is already degrading, and its tensile characteristics significantly deteriorate. An radiation dose of 150 kGy thus appears to be optimal from the viewpoint of achieving significant improvement, and the radiation treatment of the given polymeric blend by a beam of accelerated electrons is a very promising alternative to the traditional chemical mode of treatment which impacts the environment.