Thermodynamic Stability of Zirconium(IV) Complexes with Hydroxy Ions

Abstract

A protometric study on the speciation of zirconium(IV) was computed and refined, by the program PROTAF, for each ionic strength. The solubility product Ks of Zr(OH) 4 was performed in an aqueous solution at 25°C in KNO 3 and four ionic strengths (0.2, 0.5, 1, and 2 mol·dm -3 ). This study calculated by taking these β mlh constants into account. . Increasing zirconium concentration induces the formation of polynuclear species outstanding resistance to corrosion, as well as to a low neutron capture cross-section. It is an essential constituent of Zr m (OH) h (4mϪh)ϩ . In accordance with studies from Zielen and Connick [2] , Johnson and Kraus [11] , and Angstadt and the core of the nuclear power station and for confining fissile materials.Tyree [12] , Baes and Mesmer conclude that the existence of a trimer, Zr 3 (OH) 4 8ϩ or Zr 3 (OH) 5 7ϩ , and of the tetramer The running of nuclear installations relies on the proZr 4 (OH) 8 8ϩ is probable. cessing of nuclear fuels and fission by-products, but also on the long-term storage, in protected sites, of confined materiAja et al. [13] also published a review concerning the aqueals which have acquired an appreciable radioactivity.ous chemistry of zirconium(IV). They principally take into In the long-term one may expect the possibility of cor-account the results obtained by Russian scientists [5] [6] [8] [14] . rosion and fissuring of the confining containers leading to They consider that the values of the formation constants of a contamination of soils and waters.the mononuclear hydroxide complexes depend little on the ionic strength and the nature of the supporting electrolyte. Modelling programs which take into account the whole For these constants, they have retained average values which local physical parameters as well as the physicochemical are very different from those given by Baes and Mesmer. data allow the quantification of these contamination risks. The values used for these simulations, especially those relatMore recently, Adair et al. [15] published an article entitled ing to zirconium, have to be as reliable as possible in order "A review of the aqueous chemistry of the zirconium-water to yield realistic estimations.system" in which they simply give the same values of conThe chemistry of zirconium(IV) in aqueous media is stants that Baes and Mesmer indicated for the mono-and dominated by the complexation of Zr 4ϩ with OH Ϫ . The polynuclear zirconium hydroxide complexes at 25°C. data currently available on zirconium hydroxide complexes In short, numerous studies deal with the formation of comes from studies carried out (essentially) before zirconium-hydrolysed complexes in aqueous solution but. The advanced species formulae many discrepancies exist from one author to another conand, above all, the values of the corresponding comcerning the major species formed and the values of the corplexation constants, seem questionable.responding constants of formation. It must be pointed that Baes and Mesmer [10] have reviewed bibliographical re-in these studies the stoi...

Preparation of palladium membrane over porous stainless steel tube modified with zirconium oxide

“…At low pH values, the monomeric form, ZrO 2 ·2H 2 O, predominates and no colloids are formed. Colloids could be found to start appearing at a pH from 3.0 to 3.5 [10]. The freshly precipitated amorphous gel is considered to be a network of zirconium tetramer unit.…”

Detection of Polynuclear Zirconium Hydroxide Species in Aqueous Solution by Desktop ESI-MS

“…In a similar manner, the dimer and trimer species shown in Fig. 1 are identified to be of [Zr 2 (OH) 5 …”

“…In the case of Zr, only mononuclear species were considered in some early studies of hydrolysis constants, 1,2) but the formation of polynuclear and colloidal species was observed in many studies. [3][4][5][6] For instance, measuring the size distributions of such species by ultrafiltration (at 3 kDa), Sasaki et al proposed that mononuclear, polynuclear, and colloidal species coexist in weakly acidic and neutral pH solutions. 7) On the other hand, Cho et al developed a method by combining laserinduced breakdown detection (LIBD) with slow coulometric titration in order to sensitively detect the formation of tiny zirconium colloids (>5 nm in size) without the ultrafiltration process.…”

Rare earths, zirconium and hafnium distribution in coastal areas: The example of Sabella spallanzanii (Gmelin, 1791)

“…On the other hand, dissolved Zr and Hf speciation is driven by the formation of hydroxyl complexes with different degrees of hydrolysis (Byrne, 2002 (Aja et al, 1995;Veyland et al, 1998;Byrne, 2002;Ekberg et al, 2004;Qiu et al, 2009). Because biological surfaces are negatively charged (Borrok et al, 2004), their larger affinity towards Hf rather than Zr can be ruled out and interactions between dissolved Zr and Hf species could occur through surface complexation.…”

“…This coherence is absent during aqueous processes due to the different grades of Zr and Hf hydrolysis and dissolved complexation in natural waters (Aja et al, 1995;Veyland et al, 1998;Byrne, 2002;Hagfeldt et al, 2004;Messner et al, 2011a;2011b;Inguaggiato et al, 2015Inguaggiato et al, , 2016Censi et al, 2017). Aqueous environments usually make Hf more surface-reactive than Zr, which changes the associated Zr/Hf with respect to the range of values recognised in rocks and minerals and provides a useful signature of solid-liquid processes.…”