Evaluation of the selectivity of Ag(I) extraction on thiosemicarbazone-silica gels

Abstract

The preparation of a series of new functionalised silica gels with fixed thiosemicarbazone fragments by the reaction of aldehyde silica gels with thiosemicarbazide in an ethanol medium in the presence of a catalytic amount of hydrochloric acid is described. The materials were characterized by thermogravimetric analysis and infrared spectroscopy. The choice of unified conditions for concentration and separation is substantiated using the example of silver (I) ions, which allows for comparison of modified materials with different functional capacities. Sorption isotherms of silver (I) ions were obtained and the values of the maximum sorption capacity of materials were calculated. The distribution of silver (I) in two-phase systems modified silica gel - solution for model systems containing equimolar ratios of silver (I) ions and functional groups, as well as two-, three-, five- and ten-fold excesses of the analyte, was studied, distribution coefficients were calculated. Multicomponent systems were simulated under conditions of 10 and 100 times the molar excess of aluminium (III), cadmium (II), nickel (II), zinc (II), iron (III), copper (II) ions relative to the analyte. It has been shown that for systems containing silver (I) ions at levels of 1/100 and 1/10 of the maximum capacity of the material, the nature of the change in the distribution coefficient is similar to systems containing equimolar amounts of functional groups and analyte. The distribution and selectivity coefficients were calculated. The similarities and differences in the sorption extraction of Ag(I) by organomineral materials with the same complex-forming functional group from multicomponent systems have been revealed.