Complexation Sorbents and Applications

Theoretical and applied aspects of microwave heating, as well as the advantages of its application are discussed for the individual analytical processes and also for the sample preparation procedures. Special attention is paid to the various preconcentration techniques, in part, sorption and extraction. Improvement of microwave-assisted solution preconcentration is shown on the example of separation of noble metals from matrix components by complexing sorbents. Advantages of microwave-assisted extraction and principles of choice of appropriate solvent are considered for the extraction of organic contaminants from solutions and solid samples by alcohols and room-temperature ionic liquids (RTILs). 

Sorbents and separations based on 7r-complexation have also found use in other possible applications. Ag+ ion-exchanged X or Y zeolites showed an excellent capability for purification of olefins by removing trace amounts of corresponding dienes. This has been demonstrated for the butadiene/butene system (Padin, Yang, and Munson, 1999). 

Based on the principles of n-complexation, we have already developed a number of new sorbents for a number of applications. These include sorbents for (a) olefin/paraffin separations [9-12], (b) diene/olefin separation or purification (i.e., removal of trace amounts of dienes from olefins) [13], and (c) aromatics/aliphatics separation and purification (i.e., removal of trace amounts of aromatics from aliphatics [14]. Throughout this work, we have used molecular orbital calculations to obtain a basic understanding for the bonding between the sorbates and sorbent surfaces, and further, to develop a methodology for predicting and designing n-complexation sorbents for targeted molecules (e.g. Ref 11). 

Molecularly imprinted solid-phase extraction (MISPE) is widely used for selective extraction of pharmaceuticals in variety of matrices (Rao et al, 2011 Javanbakht et al, 2010). The potential value of MISPE lies in the ability to selectively isolate specific compounds or their structural analogues from a complex matrix. The application of MIPs as sorbents allows not only preconcentration and cleaning of the sample but also selective extraction of the target analyte, which is important, particularly when the sample is complex and impurities can interfere with the quantification. 

Modeling of contaminant leaching is a complex and diverse discipline. From simplified to more comphcated models there are several options available. The selection of the appropriate model is based on the needs and most importantly on the resources available such as data, sorbent and sorbate characteristics, and reaction constants, among others. The literature review presented in this chapter includes a wide range of applications for contaminant leaching from natural systems that have been contaminated to engineered systems where a byproduct needs to be evaluated for potential reuse as opposed to disposal. 

The w-complexation bond is typically a weak bond that can be formed between the sorbent and sorbate. The sorbents that are used for separation and purification based on w-complexation are called w-complexation sorbents. Development of r-complexation sorbents began only recently. A number of such sorbents have already been used commercially, and tremendous potential exists for future applications in separation and purification, both for the chemical/petrochemical industry and environmental applications. For this reason, jr-complexation sorbents are discussed in a separate chapter. 

For the reasons above, the w-complexation sorbents hold a tremendous potential for future applications in purification, some of which will be inclnded for discnssion. The removal of dienes from olefins by AgY and CuY has already been demonstrated and applied in the field (Padin et al., 2001). Other promising applications inclnde ... 

---