Hydroxyethylethylenediaminetriacetic

The lanthanides form many compounds with organic ligands. Some of these compounds ate water-soluble, others oil-soluble. Water-soluble compounds have been used extensively for rare-earth separation by ion exchange (qv), for example, complexes form with citric acid, ethylenediaminetetraacetic acid (EDTA), and hydroxyethylethylenediaminetriacetic acid (HEEDTA) (see Chelating agents). The complex formation is pH-dependent. Oil-soluble compounds ate used extensively in the industrial separation of rate earths by tiquid—tiquid extraction. The preferred extractants ate catboxyhc acids, otganophosphoms acids and esters, and tetraaLkylammonium salts. 

Wood and Higginson " have made a detailed study of the kinetics of oxidation of Fe(ll) by a number of complexes of Co(IIl) with ethylenediaminetetraacetic acid (H4Y = EDTA) and hydroxyethylethylenediaminetriacetic acid (H3YOH = HEDTA). Rate data and activation parameters are quoted (Table 21) for the... 

The reaction between two polydentate complexes of Cu(II), CuY (YjH4 = ethylenediaminetetraacetic acid, Y2H4 = hydroxyethylethylenediaminetriacetic acid) and thiourea to give a Cu(I) complex of thiourea (this product was not identified), follows kinetics ... 

The most important ferrous developers, however, are the complexes with ethylenediaminetetraacetic acid (EDTA) and related ligands, such as diethylenetriaminepentaacetic add (DTPA), nitrilotriacetic add (NT A) and JV-hydroxyethylethylenediaminetriacetic add (HETA). Complexes... 

Versenol 120 [Dow], TM for the trisodium salt of IV-hydroxyethylethylenediaminetriacetic acid (C10H15O7N2Na3). 

HEDTA (hydroxyethylethylenediaminetriacetate) chelate Fe(III) so eflFectively that upon base hydrolysis only one coordination position is available for bridging, and dimers of the type (EDTA Fe)20 and (HEDTA Fe)20, but no higher polymers, form 12, 13, 14). As a result, EDTA and HEDTA are excellent solubilizing agents for Fe(III) over a wide pH range extending to very basic solutions. 

N-Hydroxyethyl-1,2-ethanediamine. See Aminoethylethanolamine Hydroxyethyl ether cellulose. See Hydroxyethylcellulose N-(2-Hydroxyethyl)-N-ethylaniline. See Phenylethylethanolamine Hydroxyethyl ethylcellulose (INCI). See Ethyl hydroxyethyl cellulose Hydroxyethylethylenediamine N-(2-Hydroxyethyl) ethylenediamine N-(P-Hydroxyethyl) ethylenediamine. See Aminoethylethanolamine Hydroxyethyl ethylenediamine triacetic acid N-(2-Hydroxyethyl) ethylenediamine triacetic acid N-(P-Hydroxyethylethylenediamine)-N,N, N -triacetic acid. See HEDTA Hydroxyethylethylenediaminetriacetic acid, trisodium salt. See Trisodium HEDTA (N-Hydroxyethylethylenedinitrilo) triacetic acid. See HEDTA... 

Chelating agents that contain amino and carboxyl groups mask metal ions effectively. Chemical compounds of this type are nitrilotriacetic add (NTA), ethylene-diaminetetraacetic add (EDTA), diethylenetriaminepentaacetic add (DTPA), and hydroxyethylethylenediaminetriacetic add (HEEDTA). Other complexing agents include the soluble salts of oxalic add, dtric acid, tartaric acid, gluconic add, amines, and ammonia. 

Fig. 8.9 Correlation of stability constants with number of available coordination sites 1, iminodiacetic acid 2, N-hydroxyethyliminodiacetic add 3, nitrilotriacetic acid 4, N-hydroxyethylethylenediaminetriacetic acid 5, ethylenediaminetetracetic acid 6, diethylene-triaminepentaacetic acid 7, triethylenetetraaminehexaacetic acid 8, diaminocyclohexcme-tetraacetic acid [3].

The electrochemical properties of the W /V -NTA (nitrilotriacetic acid) system have been studied [1]. From the Ei/j value and Nernst equation, Meier et al. evaluated the formation constant for V(II)NTA(H20). Kato et al. [2] studied the polarographic behaviour of V(III)-HEDTA (N-hydroxyethylethylenediaminetriacetic acid). They proposed the electrode mechanisms for V(III)-HEDTA and calculated the equilibrium constants by a curve fitting method. Jung et al. [3] studied reduction mechanism of VO" -DTPA (diethylenetrlaminepentaacetlc acid) at a mercury electrode in aqueous solution. They proposed that reduction reactions of the VO " -DTPA system occurred through an ECE reaction sequence. 

HsiHEDTA), hydroxyethylethylenediaminetriacetic acid, and the lighter Ln(HEDTA) chelate species are more soluble in water than H4(EDTA) and the HLa(EDTA)-7H20, HLa(EDTA) H20, HCe(EDTA) H20 and HPr(EDTA) H20 species. This permits ammonium HEDTA to be used as the eluant with H -ion retaining beds at all temperatures and greatly simplifies reagent recovery. Even the effluent water can be reused. Table 22.6 lists the separation factors available with HEDTA at 92°C, as well as at 25°C. 

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