(A) study on the treatment of radioactive waste water by use of organic-inorganic composite resin

Abstract

In this study, a series of stepwise procedures to prepare a new organic-inorganic composite magnetic resin with phenolsulphonic-formaldehyde and freshly formed iron ferrite was established, based upon wet-and-neutralization method for synthesizing iron ferrite and pearl-polymerization method for synthesizing rigid bead-type composite resin. The PSF-F (phenolsulphonic formaldehyde-iron ferrite) composite resin prepared by the above method shows stably high removal efficiency (maximally over 3.1 meq./g-resin) to Co(II) species from wastewater in a wide range of solution pH. The wide range of applicable solution pH (i.e. pH 4.0 to 10.3) implies that the PSF-F composite resin overcomes the limitations of the conventional ferrite process which is practically applicable only to alkaline conditions. It has been found that both ion exchange (by the organic resin constituent) and surface adsorption (by the inorganic adsorbent constituent) are major reaction mechanisms for removing Co(II) from wastewater, but surface precipitation results in the high sorption capacity to Co(II) beyond normal ion exchange capacity of the phenolsulphonic-formaldehyde resin. Standard enthalpy change derived from van’t Hoff equation is $32.0 kJmol^{-1}$ conforming to the typical range for chemisorption or ion exchange. In a wide range of equilibrium Co(II) concentration, the overall isotherm is qualitatively explained by the generalized adsorption isotherm concept proposed by McKinley and Alexander. At the experimental conditions where the PSF-F composite resin shows equivalent selectivity to Co(II) and other competing reagents (i.e. EDTA and Na), the ratios of Co(II) to other chemicals turn out to be 2:1 and 1:221, respectively. In addition, the selectivity of the PSF-F composite resin to Co(II) species is very high (about 72% of Co(II)-removal efficiency) even when the molar ratio of Co(II) to Ca(II) is 1:30. It is anticipated that the PSF-F composite resin can also be ...