Zirconyl salts

Hydrazine and substituted-hydrazine complexes of the type ZrOX2(NH2NHR)4 (R = H, Me or Ph X = Cl, Br, I, NCS or N03) have been synthesized by addition of six equivalents of the hydrazine to an ethanol solution of the appropriate zirconyl salt. An IR band at —970 cm-1 assigned to v(N—N) indicates the presence of bidentate chelating or bridging hydrazine ligands these complexes may be polymeric since they are insoluble in common organic solvents.56... 

Treatment of a hot methanol solution of appropriate zirconyl salts with 1,10-phenanthroline mono-Af-oxide (phenNO) yields the oxozirconium(IV) complexes [ZrO(phenNO)X2] (X = Cl, Br, N03 or NCS), [ZrO(phenNO)2]I2 or [Zr0(phenN0)3][Q04]2.697 These compounds are analogues of the 2,2 -bipyridine-l,l -dioxide complexes discussed in Section 32.4.4.1. 

Another preparative method in which the rate of precipitation is slow involves slow decomposition of zirconium fluoro complexes [14], These are first prepared by adding an appropriate amount of hydrofluoric acid (HF) to the zirconyl salt and these complexes are decomposed in the presence of phosphoric acid, with a slow stream of nitrogen or water vapor passing through the system. The rate of precipitation of zirconium phosphate is controlled by the rate of removal of HF from the system, and when this is very slow, a highly crystalline a-ZrP is obtained. The gamma form of the metal phosphate differs significantly from the alpha and current discussion will be concerned with the latter phase. 

Aqueous solutions of zirconium or hafnium compounds may be obtained by dissolving the conesponding hydrous dioxide in the appropriate strong acid. Because zirconium and hafnium oxides are such weak bases, these aqueous solutions tend to hydrolyze, with formation of zirconyl salts such as Zr0(N03)2. 

The most important zirconyl salt is ZrOCI2-8H20 which crystallizes from dilute hydrochloric acid solutions and contains the ion [Zr4(0H)8-(H20)i6]8 +. Here the Zr atoms lie in a distorted square, linked by pairs of hydroxo bridges, and also bound to four water molecules so that the Zr atom is coordinated by eight oxygen atoms in a distorted dodecahedral arrangement.14... 

The authors described the hydrolysis of dissolved zirconium and zirconyl salts as an isopolybase characterised by an increase of polymerisation with increasing pH, by slow aggregation rates of polymeric species, by the coexistence of species of different degrees of hydrolysis and polymerisation, by the effect of the initial Zr concentration on the dominant solution species and by influence of the nature of the anion (nitrate vs. perchlorate) on the hydrolysis process. The authors evaluation of their results assumes that the zirconyl ion predominates in aqueous solution, a hypothesis that is invalid [62SOL/TSV]. 

Zirconium forms only one important oxide, zirconia Zr02, which is amphoteric in character. The normal zirconium salts, like ZrC, are readily hydrolysed in solution giving rise chiefly to zirconyl salts, containing the divalent radical ZrO. The zirconates, e.g. Na2Zr03, are best produced from Zr02 by fusion methods. Zirconium also readily forms complex ions like hexafluorozirconate(IV) [ZrF ] , produced by heating zirconia with potassium hydrogen fluoride. 

The current synthetic technologies for the preparation of zirconia are generally based on precipitation with suitable bases fixim soluble forms of Zr ion. The traditional me od starting from aqueous solutions of zirconyl salts (nitrate, chloride, sulfate) leads to very small primeiry particles that upon drying coalesce into cakes with poor mechanical stability, eventually leading to very fine powders (< 100 jon) [6], The major drawback of this procedure is the near impossibility of obtaining the final particles with proper shapes and diameters in the 0.5-2 mm range. 

Another self-assembly approach to form noncentrosymmetric multilayers has been reported by Katz et al. [165]. The donor and acceptor phosphonate-substituted azo chromophores and zirconyl salts were alternatively deposited in up to 32 layers from aqueous solutions. Good structural regularity was suggested by the linear increase of with increasing numbers of layers. The SHG signal of this material was stable up to 150°C, at which point chromophore decomposition occurred. 

The chemistry of aqueous solutions of zirconium salts (does the zirconyl ion exist ). A. S. Solovkin and S. V. Tsvetkova, Russ. Chem. Rev. (Engl. Transl), 1962,31, 655-669 (161). 

From 1958 to 1970 inorganic salts such as CaCl2(53,55,56), MgCl2(57), KC1(55-58), hydroxyaluminum chloride(59-63), and zirconyl chloride(64-67) were introduced and found acceptance as clay protection additives. Each salt has its own peculiar set of advantages and disadvantages. It is now routine to include 2% KC1 by weight of water as a clay treatment chemical in nearly all fracture waters. 

The salt, zirconyl perchlorate , explodes if heated rapidly. Later work suggests alternative formulations for the salt. 

Zirconium tetrabromide is a white microcrystalline salt which is very hygroscopic. It dissolves in water with the liberation of heat, forming zirconyl bromide. The tetrabromide is also soluble in certain organic solvents, such as alcohol and ether. It reacts with ammonia at low temperature to form ammines. 

The resistance of cellulose to microbial attack when it was treated with resins was attributed to chemical bonds formed between the fiber and the resin this was ascertained by treating cotton with a variety of phosphonium salt-resin compositions having different degrees of cross-linking and homopolymerization (127). Some of the more recent approaches for producing antimicrobial fibers include the use of reactive dyes (128) and mixtures of zirconyl and copper salts (15) on cotton and the bromination of jute (129). 

SYNS DISULFATOZIRCONIC ACID SULFURIC ACID, ZIRCONIUM(4+) SALT (2 1) ZIRCONYL SULFATE... 

Kaneko et al. employed a coprecipitation method, which involved a base-catalyzed procedure that precipitated irregular particles of zirconia-silica mixed oxides. Specifically, a zirconium salt (zirconyl chloride octahy-drate) was added to an acidified solution of sodium me-tasUicate ennehydrate. The solution was made alkaline... 

The individual elements produced various results. Additions of antimony oxide, tin(ll) oxide, and samarium oxide gave no evidence of reactions with the nitrate melt or solubility. The addition of zirconyl nitrate resulted in the evolution of nitrogen dioxide from the melt and the formation of a white insoluble precipitate. Addition of palladium nitrate to the melt produced a black melt and black insoluble solids. Dissolution of the cooled and solidified salt cake with distilled water indicated that a palladium mirror had formed at the meniscus of the melt. Niobium was added as potassium hexaniobate, KgNb Oj I6H2O. 

Pillared zirconium clay modified by sulfate constitutes a new class of materials. Nevertheless, the classical procedure consisting of impregnating these solids with sulfate solutions presents some disadvantages such as low surface area and a poor sulfur thermal stability. In a previous work, we have developed a new in situ sulfation preparation method using zirconyl chloride as zirconium precursor. However, the use of this salt gives an intercalation solution with a very low pH which can affect the clay layers. Furthermore, the addition of sulfate ions to the ZrOz solution is limited by Hauser salt or polymeric phase precipitation. 

Aqueous Chemistry and Complexes. Zr02 is more basic than Ti02 and is virtually insoluble in an excess of base. There is a more extensive aqueous chemistry of zirconium because of a lower tendency toward complete hydrolysis. Nevertheless hydrolysis does occur and it is very doubtful indeed if Zr4 + aquo ions exist even in strongly acid solutions. The hydrolyzed ion is often referred to as the zirconyl ion and written Zr02 +. However, there is little, if any, reliable evidence for the existence of such an oxo ion either in solution or in crystalline salts,12 although the infrared spectrum of one form of ZrOCl is reported to have a band at 877 cm-1, perhaps indicative of a Zr=0 group.13 No such group has ever been directly identified by diffraction methods. 

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