Bidentate-mononuclear

Surface complex formation with ligands that form bidentate, mononuclear surface complexes, e.g., oxalate, salicylate, citrate, diphenols, etc. 

Bidentate complexes Refers to Stem inner-sphere bidentate-mononuclear or bidentate-binuclear complexes. 

Bidentate-mononuclear complex A Stem inner-sphere adsorption complex that consists of two atoms bridging between an atom of the adsorbed species and an adsorbent metal atom. Commonly, two oxygens may bridge between an iron atom in the adsorbent and adsorbed arsenate (see Chapter 2). 

Inner-sphere complex A type of Stern layer, where a chemical species bonds directly onto the surface of a solid material (adsorbent) in an aqueous solution. The formation of inner-sphere complexes is called chemisorption. Stern inner-sphere adsorption complexes are further divided into monodentate, bidentate-mononuclear, and bidentate-binuclear types (compare with outer-sphere complex). 

Rapid formation of a (hypothetical) bidentate, mononuclear surface complex is the important first step followed by photoexcitation of this surface complex and subsequent electron transfer to Fe(III) with formation of an oxalate radical and Fe(II). The oxalate radical undergoes a rapid decarboxyla-... 

The various elementary steps involved in the surface photoredox reaction, leading to dissolution of hematite in the presence of oxalate, are outlined in Figure 12.10. The two-dimensional stmcture of the surface of an iron(III) hydroxide given in this figure is highly schematic. The charges indicated correspond to relative charges. An important step is the formation of a hypothetical bidentate, mononuclear surface complex. With pressure jump relaxation technique, it has... 

Figure 24. Possible stable Co2+ surface complexes on the (A) (001) and (B) (110) surfaces of rutile indicated by the GI-EXAFS data of Towle et al. (1999). In (A), site (1) is a bidentate polynuclear complex, while site (2) is a bidentate mononuclear complex. In (B), site (1) is a monodentate complex, while site (2) is a bidentate binuclear complex.

FIGURE 9.17 Calculated Zn(II)-Ti02 surface complexes from density functional theory (a) dissolved Zn(II) with six outer-sphere water molecules (b) monodentate mononuclear (c) bidentate binuclear (BB) (d) bidentate mononuclear (BM). Gray, black, large white, and small white circles denote Zn, O, Ti, and H atoms, respectively. (Reprinted with permission from He et al. 2011, 1873-1879. Copyright 2011 American Chemical Society.)... 

The effect of pH on heavy metal ion adsorption capacity was studied by previous researchers using the shake flask experiments. Eric and Roux used the shake flask experiment to study the influence of pH on the heavy metal ion binding onto a fimgus-derived bio-sorbent in the year, 1992. Also the evaluation of the effect of the hydrochloric acid concentration on the adsorption of platinum group metal ions onto chemically modified chitosan was done by Inoue et al., using the shake flask experiment [85]. Depending upon the type of P complexation with the surface such as monodentate, bidentate mononuclear, and bidentate binuclear the phosphorus desorption is potentially controlled. These complexes can be either non protonated or protonated depending on the suspension pH [184]. 

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