Synthesis of a novel macroporous silica-based polymeric material containing 4,4′,(5′)-di(tert-butylcyclohexano)18-crown-6 functional group and its adsorption mechanism for strontium

A novel, specific macroporous silica-based 4,4',(5')-di(tert-butylcyclohexano)-18-crown-6 (DtBuCH18C6) chelating polymeric material (DtBuCH18C6/Si-polymer) was synthesized by impregnating DtBuCH18C6 molecule into the Si-polymer particles that was prepared by a series of polymerization reactions between similar to50 mum SiO2 and a mixture of m/p-divinylbenzene, alpha,alpha-azobisisobutyronitrile, 1,1-azobiscyclohexane-1-carbonitrile, m/p-formylstyrene, methyl benzoate and diotylphthatate at 90 degreesC. This hydrophilic material exhibited the much higher adsorption ability for Sr(II) than that of a commercial Sr-resin, an inert conventional polymer-based adsorbent. The complex composition between DtBuCH18C6/Si-polymer and Sr(II) was determined as 1:1 type by investigating the influence of the concentrations of DtBuCH18C6, Sr(II), H+ and NO3- on the adsorption of Sr(II) onto DtBuCH18C6/Si-polymer. The adsorption equilibrium equation was described as follows Sr-(aq)(2+) + 2NO(3(aq))(-) + DtBuCH18C6/Si-polymer((re)) <----> Sr(NO3)(2) (.) DtBuCH18C6/Si-polymer((re)) The apparent adsorption equilibrium constant was calculated to be log K-ad = 2.21 +/- 0.15 at 2.0 M HNO3 at 25 degreesC. The monolayer molecule adsorption mechanism was determined by examining the relationships between -ln(1 - F) and t and lnt, respectively. The corresponding adsorption equations at different temperatures were obtained. The chelating effect of the DtBuCH18C6/Si-polymer adsorbent for Sr(II) was considered as the mainly adsorptive pathway. (C) 2004 Elsevier B.V. All rights reserved.