Preparation of amine-modified silica foams and their adsorption behaviors toward TNT red water

Secondary and primary amines containing silica foams (F–SiO 2 ) were prepared by using silane coupling agents, (3-aminopropyl) triethoxysilane (KH-550) and bis(3-triethoxysilicyl propyl)-amine (KH-270), as modifiers. Not only Brunauer–Emmett–Tell (BET) surface and pore size of F–SiO 2 are greatly reduced after modification, but also increased chemical oxygen demand (COD) removal efficiency to trinitrotoluene (TNT) red water is obtained. Among the series of F–SiO 2 , the secondary amine modified silica foams possess higher COD removal capacity. Controlled experiments indicate the adsorption mainly derives from the attraction of amine groups toward the negative organic pollutants in TNT red water rather than the effect of the large BET surface and hydroxyl groups on the surface of F–SiO 2 . The adsorption model studies show the pseudo-second-order dynamic adsorption model and Langmuir isotherm model well fit the experimental data. The prepared amine-modified F–SiO 2 is an efficient adsorbents of organic pollutants in TNT red water.