Changes in the acid-base properties of hydrogels of metal oxide hydroxides induced by aging in solutions of electrolytes

Pechenyuk, S. I.; Matveenko, S. I.

doi:10.1007/bf02495071

Cited by 3 publications

(2 citation statements)

References 6 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…To prepare each sample of the ferrogel, the initial solution (5 mL) was diluted before precipitation to 50 mL, i.e., 0.01 moles of the oxyhydroxide (1.06 g of Fe(OH) 3 ). Zirconogels (7•10 -3 -8•10 -3 mol) were synthesized by the dis solution of ZrO(NO 3 ) 2 •2H 2 O (2.19 g) in water (50 mL) fol lowed by neutralization with a 2 M solution of NaOH.…”

Section: Methodsmentioning

confidence: 99%

Estimation of the specific content and nature of sorption sites of iron(III) and zirconium(IV) oxyhydroxides

2005

Self Cite

View full text Add to dashboard Cite

The sorption of anions H 2 PO 4 -, HPO 4 2-, PO 4 3-, [Fe(CN) 6 ] 3-, and [Fe(CN) 6 ] 4-from aqueous solutions on the surface of Fe III and Zr IV oxyhydroxide hydrogels freshly precipitated at pH 4-13 was studied. The region of sorbate concentrations was from 0.00025 to 0.06 mol L -1 . The plots of the anion uptakes vs. their equilibrium concentrations are represented by iso therms of the first type, which are well described by the Langmuir equation if the quantity of the amount adsorbed is expressed as mol site g -1 . The maximum uptakes and constants of the Langmuir equation were calculated. The phosphate anions occupy the same number of sorp tion sites on the sorbents precipitated at different pH. The average specific content of sorption sites for the ferro and zirconogels in the metastability period is independent of the pH of their precipitation, being 3.1•10 -3 and 3.2•10 -3 mol site g -1 , respectively. The [Fe(CN) 6 ] 3-and [Fe(CN) 6 ] 4-anions are sorbed only on the positively charged sites of the hydrogels and occupy not more than 2•10 mol site g -1 in the studied interval of pH of precipitation.Freshly precipitated gels of metal oxyhydroxides, in particular, of Fe III and Zr IV , prepared by the fast alkaline hydrolysis of salt solutions, being washed off from the mother liquor and stored in water, exist as metastable phases. Their composition and acid base and sorption properties remain virtually unchanged for a time period from several days to several weeks. 1-5 Some published data 5 suggest that the specific surfaces of the hydrogels obtained by the alkaline hydrolysis of aqueous solutions of metal salts, such as Fe III , Zr IV , Ti IV , Cr III , and In III salts, are independent of the pH of precipitation. There fore, the interaction with protons, hydroxyl groups, and sorbate ions during the metastability period can be re duced to the recharge of the surface.In several cases, the sorption isotherms of hydro phosphate anions by the ferrogels precipitated at a con stant pH of precipitation (pH pr ) are dome shaped. 6 The sorption of phosphate anions on the ferrogels does not increase with an increase in the anion concentration, un like the sorption on goethite, 7 but somewhat decreases, and the initial regions deviate from the ordinate more strongly than those in the Langmuir isotherms. 8 This char acter of the isotherms can be explained 8,9 by different forms in which the sorbate exists in solutions.When the positive charge of the surface decreases, the uptake of several anions (sulfate, chromate, oxalate) on goethite and other crystalline oxyhydroxide sorbents 7,10 in the region of the negatively charged surface decreases to zero. For the sorption of hydrophosphate anions on the ferrogels, a change in the surface charge does not notice ably change the uptake value.It was supposed 8,9,11-13 that the character of sorption processes is also affected by the heterogeneous nature of sites on the oxyhydroxide surface.In this work, we attempted to reveal the regularities of sorption on the oxyhydroxide hyd...

show abstract

Section: Methodsmentioning

confidence: 99%

Estimation of the specific content and nature of sorption sites of iron(III) and zirconium(IV) oxyhydroxides

2005

Self Cite

View full text Add to dashboard Cite

show abstract

“…1 Hydrogels of tri and tetra valent metal oxohydroxides (MOH) are interesting repre sentatives of these systems. 2- 6 The study of the rheologi cal properties of freshly prepared monolith gels, 7-10 whose three dimensional framework retained, suggests that the MOH hydrogels possess noticeable shear strength. They are continuous polymeric matrices in which liquid crys talline phases consisting of fragments with unstable struc ture can be formed.…”

mentioning

confidence: 99%

Determination of particle size in aqueous suspensions of hydrogels of iron(III), indium(III), aluminum, chromium(III), titanium(IV), and zirconium(IV) oxohydroxides

2005

Self Cite

View full text Add to dashboard Cite

Dispersion of hydrogels of Fe III , In III , Al III , Cr III , Ti IV , and Zr IV oxohydroxides in an aqueous medium was studied by sedimentation analysis. The hydrogel dispersion depends on the metal nature, pH of precipitation, and suspension concentration. The systems are predomi nantly polydisperse, and the gel particle size ranges from 2 to 140 µm. The data obtained suggest that the gel particles are formed by three dimensional networks consisting of polymeric chains metal-oxygen and contain cavities filled with water.The role of nanoparticles in the genesis of gel systems has intensely been studied. 1 Hydrogels of tri and tetra valent metal oxohydroxides (MOH) are interesting repre sentatives of these systems. 2-6 The study of the rheologi cal properties of freshly prepared monolith gels, 7-10 whose three dimensional framework retained, suggests that the MOH hydrogels possess noticeable shear strength. They are continuous polymeric matrices in which liquid crys talline phases consisting of fragments with unstable struc ture can be formed. It remains unclear how far these conclusions can be extended to suspensions of gels ob tained by the fast alkali hydrolysis of aqueous solutions of the corresponding metal salts with continuous stirring in a vortex mode followed by washing from a mother liquor by multiple centrifuging and repulping. 3 In this work, we attempted to reveal the state of the MOH gels in suspensions using sedimentation analysis, which is widely used to determine the fractional composi tion of microheterogeneous systems. There are many vari ants of apparatus equipment and mathematical methods for processing results of sedimentation analysis, 11-15 which is poorly used for studying hydrogels. 13, 14 We have previously found that the properties of ob jects called MOH hydrogels change remarkably due to the interaction with electrolyte solutions. This concerns acid base and sorption characteristics, 5,6 consistency, and even color of the hydrogels. Due to partial crystallization, the concentrations of impurity ions and intramicellar water 4 and sedimentation rate change. We succeeded to develop a method for determination of the specific surface S sp of the oxohydroxide hydrogels from the limiting amount adsorbed of the OH groups 16 and showed that the S sp values for the freshly prepared MOH are independent of the pH of their precipitation. The S sp values of Fe III , Cr III , Zr IV , and In III oxohydroxides are equal to 585, 930, 420, and 240 m 2 g -1 , respectively.In this work, we studied the freshly precipitated at different pH and washed Fe III , In III , Al III , Cr III , Ti IV , and Zr IV oxohydroxides. The dispersion of their suspensions was studied by the sedimentation method in a gravitation field at different suspension concentrations in water and in an electrolyte (NaCl and Na 2 SO 4 ) solution. We at tempted to determine how the S sp values of the MOH hydrogels depend on dispersion. ExperimentalThe method of fast alkali hydrolysis of metal salt solutions was used to obtain MOH hydrogels...

show abstract

Synthesis of zirconia sol stabilized by trivalent cations (yttrium and neodymium or americium): a precursor for Am-bearing cubic stabilized zirconia

et al. 2010

View full text Add to dashboard Cite

Recent concepts for nuclear fuel and targets for transmuting long-lived radionuclides (minor actinides) and for the development of innovative Gen-IV nuclear fuel cycles imply fabricating host phases for actinide or mixed actinide compounds. Cubic stabilized zirconia (Zr, Y, Am)O(2-x) is one of the mixed phases tested in transmutation experiments. Wet chemical routes as an alternative to the powder metallurgy are being investigated to obtain the required phases while minimizing the handling of contaminating radioactive powder. Hydrolysis of zirconium, neodymium (a typical surrogate for americium) and yttrium in aqueous media in the presence of acetylacetone was firstly investigated. Progressive hydrolysis of zirconium acetylacetonate and sorption of trivalent cations and acacH on the zirconia particles led to a stable dispersion of nanoparticles (5-7 nm) in the 6-7 pH range. This sol gels with time or with temperature. The application to americium-containing solutions was then successfully tested: a stable sol was synthesized, characterized and used to prepare cubic stabilized zirconia (Zr, Y, Am)O(2-x).

show abstract

Changes in the acid-base properties of hydrogels of metal oxide hydroxides induced by aging in solutions of electrolytes

Cited by 3 publications

References 6 publications

Estimation of the specific content and nature of sorption sites of iron(III) and zirconium(IV) oxyhydroxides

Estimation of the specific content and nature of sorption sites of iron(III) and zirconium(IV) oxyhydroxides

Determination of particle size in aqueous suspensions of hydrogels of iron(III), indium(III), aluminum, chromium(III), titanium(IV), and zirconium(IV) oxohydroxides

Synthesis of zirconia sol stabilized by trivalent cations (yttrium and neodymium or americium): a precursor for Am-bearing cubic stabilized zirconia

Contact Info

Product

Resources

About