Superadsorbents for Strontium and Cesium Removal Enriched in Amidoxime by Homo-IPN Strategy Connected with Porous Silica Texture.

Dragan, Ecaterina Stela; Humelnicu, Doina; Ignat, Maria; Varganici, Cristian-Dragos

In light of the fact that two make more than one at a good compatibility, the homo-IPN strategy was used in this work to design novel amidoxime (AOX) interpenetrating networks into the porous silica (PSi) with the final aim to enhance the sorption performances of the composite sorbents towards Cs+ and Sr2+. To achieve this goal, the homo-IPN of poly(acrylonitrile) (PAN) was constructed first inside the channels of two kinds of porous silica, one mesoporous (PSi1) and one macroporous (PSi2), the textural properties of silica being exploited in controlling the sorption performances of the composites. The novel composites were fully characterized by thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and by the nitrogen sorption/desorption isotherms (BET analysis). The sorption properties of the PSi1/AOX and PSi2/AOX composite sorbents for Sr2+ and Cs+ were investigated in batch mode, to determine the effect of solution pH, contact time, initial metal ion concentration, temperature and the presence of competitive ions on the adsorption performances. The fast kinetics of sorption was supported by the fact that ~ 80% of Sr2+ and ~ 65% of Cs+ were adsorbed in the first 30 min, the kinetic data being better described by the pseudo-second-order kinetic model. The experimental isotherms were well fitted by the Langmuir and Sips isotherm models. The super-adsorption for Sr2+ and Cs+ is demonstrated by the values of the maximum sorption capacity of the best sorbent constructed with mesoporous silica (PSi1/IPN-AOX), which were: 344.23 mg Cs+/g and 360.23 mg Sr2+/g. The sorption process was spontaneous and endothermic for both metal ions. The presence of interfering cations (Na+, K+, Ca2+ and Mg2+), at a concentration of 10-2 M, only slightly influenced the sorption capacity for the main cation, The composite sorbents were still highly efficient after five sorption/desorption cycles.