Investigation of Improving Amino Content on Hybridized Polyamine Silica Composites

Abstract

The aim of the present study was to improve amino content on the surface of polyamine silica composites. Results showed that amino contents of PAA/SiO 2 and EDA/SiO 2 prepared by surface substitution reaction were 1.491 mmol Á g À1 and 1.415 mmol Á g À1 , and there were many residual chloropropyl groups on their surfaces. To increase amino contents, a technology of two-step reaction, first adding PAA for 10 h and adding EDA 14 h later, was established to prepare PAA-EDA/ SiO 2 . Comparing with those of PAA/SiO 2 and EDA/SiO 2 , adsorption capacity and amino content of PAA-EDA/SiO 2 were improved significantly and reached up to 2.170 mmol Á g À1 and 0.724 mmol Á g À1 , respectively. 1838 INTRODUCTIONRecently, polyamine silica materials, which show excellent adsorption properties and mechanical stability due to a large number of amino groups loading on the surface of silica gel, are widely used in the field of separation, enrichment of heavy metal ions and environmental protection [1][2][3][4][5] . The materials, such as polyethyleneimine silica composites and poly(allylamine) silica composites which showed excellent adsorption properties for Cu(II), Zn(II), Ni(II), Pb(II) and so on [6,7] , were synthesized by surface grafting method. And then their selectivities for the specific ions were improved through further functional group modification [6,8] or surface ion imprinting [9][10][11] .For example, poly(allylamine) was immobilized on the surfaces of silica gel by the surface grafting and imprinting manner. The imprinted cavities in the thin polymer layer of the ion-imprinted poly(allylamine)-silica composites were of great advantage to the fast binding of the template Cu(II) with the recognition sites [7,9] . In a word, the materials prepared by surface grafting and surface ion imprinting method have many advantages: high selectivity, more accessible group sites, fast adsorption and desorption kinetics, and more homogeneous. In the references of involving polyamine silica composites, there are several aspects which have attracted extensive research interest.One aspect of these studies is to improve the functional group content of the polyamine silica composites, so that the adsorption capacity for metal ions could be increased through concentration effect of the functional groups [6][7]12] . Another aspect is to improve the adsorption selectivity of the composites for specific metal ions through further functional group modification or surface ion imprinting [9][10][11] . In addition, the polyamine silica composites with good adsorption properties have increasingly attracted extensive interest due to the potential applications in many scientific and industrial fields, such as separation, chromatography stationary phases, catalysis and environmental protection. However, the raw polyamine materials are usually expensive, which would lead to higher application costs. Therefore, the polyamine materials substituted for the inexpensive surface modifier have become a key focus of research recently [13][14] .In our previ...