Silica polyamines

Partition Chromatography. Unlike the other types of chromatography discussed thus far, this type is usually used for analytical (rather than preparative) applications. In addition, this type of chromatography is often performed in a thin-layer (rather than a column) format. The stationary phase in partition chromatography is usually a glass plate (rigid) or polyester sheet (flexible) coated with a very thin layer of the desired adsorbent. For most applications, the adsorbent is a cellulose, silica, polyamine, or aluminum oxide-based matrix. In... 

Silica Polyamine Composites Advanced Materials for Metal Ion Recovery and Remediation... 

Figure 1 Synthetic scheme for making silica polyamine composites, illustrating the key features of humidification to promote lateral polymerizan, for maximization of surface coverage.

Figure 2 The polyamines used to synthesize the silica-polyamine composites, showing structures and the available molecular weights (only values in italics were used).

Perhaps the best evidence for the superior quality of the composite comes from our comparative studies with other polyamine composites and polystyrene resins. Ramsden et al. synthesized a silica-polyamine composite by reacting 3-chloropropyl trimethoxy silane with PEI, and then reacting the resulting polyamine silane with silica gel. We reproduced this synflietic approach with the same silica used in our pro-cedme (Fig. 1). The material produced had a density of 0.31 g/mL versus 0.49 g/mL for WP-1. A scanning electron micrograph of the two materials revealed a much smoother surface for WP-1 relative to the material produced by the method of Ramsden (Fig. 4). 

Figure 6 The structure of CuWRAM, a copper-selective silica-polyamine composite, based on elemental composition and adsorption behavior.

In this section, we present the results of our studies on the recovery of copper from an actual solvent extraction raffinate from a copper mine in the United States and compare its performance to Dowex 43084 on mock ore solutions. Fourteen bed volumes of a solution containing 3000-ppm ferric ion and 1000-ppm cupric ion at pH 1.5 were passed through a 5-mL column containing CuWRAM at 2 bed volumes per minute. The experiment was repeated using the same volume of Dowex 43084 (labeled XFS, its alternative name, in Fig. 12). The contents of the sulfuric acid strip solutions reveal that the CuWRAM is more selective and has a higher flow capacity at relatively rapid flow rates. The difference in flow capacity is partially due to the difference in particle size of the two materials (100 pm for CuWRAM and 250-500 pm for XFS). However, we have previously shown that at equal particle sizes and flow rates the silica-polyamine composites have about 80% better flow capacities at 2-bed volumes per minute and at equal particle sizes (see section I.B). 2 ... 

D. Removal of Mercury from Waste Solutions Using Sulfur-Modified Silica-Polyamine Composites... 

We previously reported the synthesis of thiol-modified silica-polyamine composite using ethylene sulfide. Although the reaction of ethylene sulfide with WP-1 gave a material that had excellent mercury capture characteristics, this ligand is toxic and difficult to make and handle. In addition, ethylene sulfide polymerizes with itself in the presence of nucleophiles therefore, we could not tell if we were dealing with an amino-thiol ligand (Fig. 16 ) or a polysulfide ligand (Fig. 165).27... 

The dithiocarbamate-type ligand produced from the reaction of carbon disulfide with silica-polyamine composites represents a viable alternative to the previously reported ethylene-sulfide-modified composites. This material should prove useful for immobilizing mercury that is contained in aqueous waste streams. The resin is not going to be useful for applications requiring the regeneration and reuse of the resin. There are several other polystyrene and silica-based mercury removal resins available on the market, and it remains to be shown how these resins compare with WP-3. 

The work done so far indicates that there are distinct advantages for using silica polyamine composites over polystyrene-based resins. These advantages arise... 

D. Hagars, Performance Evaluation for Heavy Metal Ion Removal Using Silica Polyamine Composites Made with Different Silica Gels and Polyamines, Masters thesis. University of Montana, 1999. 

Robert Fischer, Development of a Copper Selective Silica Polyamine Composite, doctoral thesis, University of Montana, 2002. 

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