Chelation adsorption

In metal chelate adsorption chromatography a metal is immobilised by partial chelation on a column which contains bi- or tri- dentate ligands. Its application is in the separation of substances which can complex with the bound metals and depends on the stability constants of the various ligands (Porath, Carlsson, Olsson and Belfrage Nature 258 598 I975 Loennerdal, Carlsson and Porath FEES Lett 75 89 1977). 

As shown in Fig. 1 biosorption comprises a variety of processes including ion exchange, chelation, adsorption, and diffusion through cell walls and membranes all of which are dependent on the species used, the biomass origin and, and solution chemistry (Gavrilescu 2004). Biosorption is a fast and reversible process for removing toxic metal ions from solution. 

Prange et al. [809,810] carried out multielement determinations of the stated dissolved heavy metals in Baltic seawater by total reflection X-ray fluorescence (TXRF) spectrometry. The metals were separated by chelation adsorption of the metal complexes on lipophilised silica-gel carrier and subsequent elution of the chelates by a chloroform/methanol mixture. Trace element loss or contamination could be controlled because of the relatively simple sample preparation. Aliquots of the eluate were then dispersed in highly polished quartz sample carriers and evaporated to thin films for spectrometric measurements. Recoveries (see Table 5.10), detection limits, and reproducibilities of the method for several metals were satisfactory. 

Gao B, An F, Tiu K. Studies on Chelating Adsorption Properties of Novel Composite Material Polyethyleneimine/silica Gel for Heavy-metal Ions. Applied Surface Science 2006 253 1946-1952. 

Ability to make metal complexes Chelating agents Immobilized metal chelate adsorption... 

Rampley, C. G. Ogden, K. L. Preliminary Studies for Removal of Lead from Surrogate and Real Soils Using a Water Soluble Chelator Adsorption and Batch Extraction, Environ. Sci. Technol. 1998, 32, 987-993. 

Liquid chromatography is rather more widely applicable than gas-liquid chromatography and in some forms has the capability to handle larger amounts of substance. All the main forms of LC are used, namely adsorption, partition, ion exchange, and gel filtration, and some newer forms of chromatography including metal-chelate adsorption, hydrophobic adsorption, and, particularly for biochemicals, affinity chromatography. 

A number of papers have appeared on the removal of heavy metals in the effluents of dyestuff and textile mill plants. The methods used were coagulation (320—324), polymeric adsorption (325), ultrafiltration (326,327), carbon adsorption (328,329), electrochemical (330), and incineration and landfiU (331). Of interest is the removal of these heavy metals, especiaUy copper by chelation using trimercaptotria2ine (332) and reactive dyed jute or sawdust (333). 

The methods which involve complexation of the metal ion with chelating agents followed by adsorption on a solid phase such as octadecylsilane (ODS) [2], Zeolite [3] or activated cai bons [4] have been reported. 

In contrast to the above resins, the chelating resin Amberlite IRC-718 is based upon a macroreticular matrix. It is claimed to exhibit superior physical durability and adsorption kinetics when compared to chelating resins derived from gel polymers and should also be superior for use in non-aqueous solvent systems. 

Addition of chelating agents to the fermentation medium may help to inhibit phage multiplication by prevention of phage adsorption to the cell wall. 

FIGURE 3-16 Accumulation and stripping steps in adsorptive stripping measurements of a metal ion (M I+) in the presence of an appropriate chelating agent (L). 

Figure 5. IR spectra of s.o. samples after various treatments. Section a after adsorption of NH3 (1 mbar) at RT Zr02 (curve 1), ZV0.58(a)pH4 (curve 2), ZV1.21(a)pH4 (curve 3). Section b ZV0.58(a)pH4 sample after adsorption of NO+O2 at 623 K (curve 1), after subsequent adsorption of NH3 (1 mbar) at RT (curve 2) and after subsequent heating at 623 K (curve 3). Bands assigned to bridged bidentate nitrates ( ) and to chelating nitrates ( ). Section c the same treatments as in section b on s.o. 1.21(a)pH4.

The precise nature of the adhesion of the polyelectrolyte cements to untreated dental enamel and dentine has yet to be established. The earliest theory was due to Smith (1968) who speculated that the polyacrylate chains of the cement formed a chelate with calcium ions contained in the hydroxyapatite-like mineral in enamel and dentine. Beech (1973) considered this unhkely since it involved the formation of an eight-membered ring. Beech studied the interaction between PAA and hydroxyapatite, identified the formation of polyacrylate and so considered that adsorption was due to ionic attraction. 

---