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The Fouling of Zirconium(IV) Hydrous Oxide–Polyacrylate Dynamically Formed Membranes during the Nanofiltration of Lactic Acid Solutions  [PDF]
Ewa Polom
Membranes , 2013, DOI: 10.3390/membranes3040415
Abstract: The results of investigations of flux decline during nanofiltration (NF) of lactic acid solutions using dynamically formed zirconium(IV) hydrous oxide/polyacrylate membranes (Zr(IV)/PAA) under conditions resulting in low and high lactic acid rejection are reported. The experimental permeate flux versus time curves were analyzed in the frame of resistance in a series model with the aim of developing the characteristic of resistances. Analysis of experimental data and results of calculations showed that the reduction of fouling effects in the investigated system could be achieved due to appropriate hydrodynamic process conditions and regular rinsing with deionized water.
Adsor??o de íons fosfato nos compósitos celulose/ZrO2.nH2O preparados pelos métodos da precipita??o convencional e em solu??o homogênea
Mulinari, D. R.;Silva, G. L. J. P. da;Rodrigues, L. A.;Silva, M. L. C. P. da;
Ceramica , 2007, DOI: 10.1590/S0366-69132007000400003
Abstract: this work describes the preparation and characterization of cellulose/hydrous zirconium oxide composites prepared by conventional precipitation (pc) and homogeneous solution (psh) from cellulose of the sugarcane bagasse and subsequent adsorption of phosphate ions. the composite obtained by the pc method was prepared using an ammonium solution as precipitating agent, whereas the composite obtained by the psh method was prepared using urea as precipitating agent. the adsorption of phosphate ions was carried out reacting a kh2po4 solution with ammonium molibdate under acid conditions to form an ammonium phosphomolybdic complex. the analyses to determine the concentration after adsorption were performed using uv-vis at 880 nm. the results were satisfactory showing that the cell/ zro2.nh2o composites obtained for both the methods presented good adsorption capacity.
Selective Sorption of Sb(V) Oxoanion by Composite Sorbents Based on Cerium and Zirconium Hydrous Oxides  [PDF]
Eva Mi?tová,Martina Telecká,Helena Parschová,Luděk Jelínek
Ion Exchange Letters , 2008,
Abstract: Composite sorbents based on hydrous oxides of cerium and zirconium were used for selective removal of Sb(V) oxoanion. The effects of pH, concentration of Sb and accompanying anions in the feed solution and kinetic of the sorption were studied. Both CeO2.nH2O/XAD-7 and ZrO-PAN sorbents showed maximum sorption of Sb(V) oxoanions at pH of 3.5. Sorbent CeO2.nH2O/XAD-7 showed higher removal efficiency than ZrO-PAN. In both cases, increased concentration of sulfates and chlorides in the feed solution caused a decrease of Sb(V) removal
Selective sorption of Sb(III) oxoanion by composite sorbents based on cerium and zirconium hydrous oxides  [PDF]
Eva Mi?tová,Martina Telecká,Helena Parschová,Luděk Jelínek
Ion Exchange Letters , 2009,
Abstract: Composite sorbents based on hydrous oxides of cerium and zirconium were used for selective removal of Sb(III) oxoanion. The effects of pH, concentration of Sb and accompanying anions in the feed solution and kinetic of the sorption were studied. Both CeO2.nH2O/XAD-7 and ZrO-PAN sorbents showed similar sorption capacity at all pH value which was studied. Sorbent CeO2.nH2O/XAD-7 showed higher removal efficiency than ZrO-PAN. In both cases, increased concentration of sulfates and chlorides in the feed solution caused a decrease of Sb(III) removal.
Estudo da adsor??o do surfatante cati?nico brometo de cetiltrimetil am?nio em diferentes matrizes inorganicas preparadas via nióbio metálico
Pereira, P. H. F.;Peixoto, A. L. C.;Silva, M. L. C. P.;
Ceramica , 2009, DOI: 10.1590/S0366-69132009000400005
Abstract: the preparation in inorganic material different from metallic niobium and its effect onto adsorption process of the cetyl trimethylammonium bromide ctabr is reported. the inorganic materials are studied niobium oxide hydrous and niobium phosphate hydrous. the niobium oxide hydrous were obtained by homogeneous solution precipitation method with thermal decomposition of (nh4)2co3 at 45 oc and 90 oc .the niobium phosphate hydrous were prepared using of metallic niobium dilution in a mixture of fluoridric/nitric (10:1) and after phosphoric acid addition. through the bet method and the sem technique it was verified that the material suffer no significant change in the physical characteristics. the langmuir and freundlich isotherms showed better result to surfactant ctabr adsorption using the material prepared at 90 oc, according to langmuir model with maximum adsorption capacity of 14.13 mg.g-1.
Adsor??o de íons sulfato em ZrO2.nH2O preparado pelo método da precipita??o convencional e da precipita??o em solu??o homogênea
Rodrigues, L. A.;Mulinari, D. R.;Silva, M. L. C. P.;
Ceramica , 2009, DOI: 10.1590/S0366-69132009000100005
Abstract: this work reports the preparation, characterization and adsorption study of sulfate on hydrous zirconium oxides prepared by conventional and homogeneous solution precipitation methods. the materials prepared were characterized by x-ray diffraction, thermogravimetric analysis, scanning electron microscopy and surface area measurements. through the q0 constant, related with the capacity of maximum adsorption, it was observed that the zro2.nh2o/psh presented better adsorption capacity than zro2.nh2o/pc. by results of δg, it was observed that sulfate ions had been adsorbed through favorable reactions for all studied concentration ranges.
Influência do agente precipitante na prepara??o do óxido de nióbio (V) hidratado pelo método da precipita??o em solu??o homogênea
Tagliaferro, Geronimo Virginio;Silva, Maria Lúcia C. P. da;Silva, Gilberto L. J. P. da;
Química Nova , 2005, DOI: 10.1590/S0100-40422005000200016
Abstract: this work reports the preparation, characterization and study of the ion exchange behavior of hydrous niobium oxide prepared by a homogeneous precipitation method. the precipitating agent was obtained in aqueous solution by thermal decomposition of urea or ammonium carbonate. the compounds were chemically and physically characterized by x-ray diffractometry, thermal analysis (tg/dtg), surface area measurements and ion exchange behavior with sodium. the materials prepared with ammonium carbonate presented a higher degree of crystallinity and better ion exchange capacity with sodium than materials prepared with urea. in the homogeneous precipitation method, materials were obtained with specific surface area of 123 - 224 m2 g-1. a variation of the preparation process produced hydrous niobium oxide with a different degree of hydration and specific surface area. this provided materials with different physico-chemical properties.
Hydrous Tantalum Phosphates for Ion Exchange Purposes: A Systematic Study
Silva, M.L.C.P.da;Silva, G.L.J.P. da;Villela Filho, D.N.;
Materials Research , 2002, DOI: 10.1590/S1516-14392002000100012
Abstract: this work describes two methods of preparation of hydrous tantalum phosphates and their characterization as ion exchangers. the hydrous metallic phosphate compounds were chemically and physically characterized by thermal gravimetric analysis, x-ray diffractometry and surface area measurements. by the first method, tantalum phosphate was prepared by alkaline fusion of ta2o5 with an excess of k2co3, followed by lixiviation of the tantalate fusion product with hot water, and precipitation with diluted h3po4. preparation ii was performed using metallic ta dissolved in concentrated hf/hno3 acidic mixture followed by hydrolysis of fluortantalic acid intermediary and precipitation with diluted h3po4. both freshly prepared materials (i and ii) were exaustively refluxed with concentrated h3po4, in its boiling point temperature, resulting respectively in ta2o5. 2.1 h2o, (ir) and ta2o5. 1.3 h2o, (iir). characterization of the prepared products have presented the following values: surface area of 108.27 ± 2.80; 220.14 ± 2.67; 117.07 ± 5.25 and 141.61 ± 0.27 m2.g-1 respectively for i, ir, ii and iir. all these materials were amorphous. the ion exchange behavior for all four hydrous tantalum phosphates was studied using na+, k+ and ba+2 as the exchanged species. the values for typical ion exchange capacity were 1.64; 1.23; 1.47 and 1.01 miliequivalent.g-1, respectively for i, ir, ii and iir products.
Hydrous Tantalum Phosphates for Ion Exchange Purposes: A Systematic Study
Silva M.L.C.P.da,Silva G.L.J.P. da,Villela Filho D.N.
Materials Research , 2002,
Abstract: This work describes two methods of preparation of hydrous tantalum phosphates and their characterization as ion exchangers. The hydrous metallic phosphate compounds were chemically and physically characterized by thermal gravimetric analysis, X-ray diffractometry and surface area measurements. By the first method, tantalum phosphate was prepared by alkaline fusion of Ta2O5 with an excess of K2CO3, followed by lixiviation of the tantalate fusion product with hot water, and precipitation with diluted H3PO4. Preparation II was performed using metallic Ta dissolved in concentrated HF/HNO3 acidic mixture followed by hydrolysis of fluortantalic acid intermediary and precipitation with diluted H3PO4. Both freshly prepared materials (I and II) were exaustively refluxed with concentrated H3PO4, in its boiling point temperature, resulting respectively in Ta2O5. 2.1 H2O, (IR) and Ta2O5. 1.3 H2O, (IIR). Characterization of the prepared products have presented the following values: surface area of 108.27 ± 2.80; 220.14 ± 2.67; 117.07 ± 5.25 and 141.61 ± 0.27 m2.g-1 respectively for I, IR, II and IIR. All these materials were amorphous. The ion exchange behavior for all four hydrous tantalum phosphates was studied using Na+, K+ and Ba+2 as the exchanged species. The values for typical ion exchange capacity were 1.64; 1.23; 1.47 and 1.01 miliequivalent.g-1, respectively for I, IR, II and IIR products.
Nanocomposites Based on Сhitozan and Сarbon Tanotubers With Iron Oxides Formed by in Situ Precipitation  [cached]
Bolbukh I.M.,Gunko G.S.,Yurkov G.Yu.,Prikhodko G.P.
Proceedings of the International Conference Nanomaterials : Applications and Properties , 2013,
Abstract: Composites which contain iron oxide nanoparticles and unmodified or aminated silica were synthesised by in situ precipitation of ferrous salts in chitozan or glucose solution. Nanocomposites based on oxidized or aminated carbon nanotubers were obtained by immobilizing oxide nanoparticles in surface layer during salt precipitation in water dispersion. The metal-containing phase was obtained by the Elmore reaction using different ratios of ferrous ammonium sulfate hexahydrate (FeSO4 (NH4)2SO4 6H2O) and ferric chloride hexahydrate (FeCl3 6H2O). The composites obtained were characterized using FTIR spectroscopy. In addition for selected samples XRD, DSC, and specific surface area measurements were carry out. The analysis results indicate that in situ co-precipitation of iron oxide precursors in chitosan or glucose allows producing Fe3O4 particles with the average size ca. 5-7 nm. The presence of silica leads to particles size decrease which can be controlled, along with iron oxide particles location, by changing the silica surface functionality. Characteristics and location of iron oxide nanoparticles in nanotubers modified layer are strongly depended from nature of the groups attached to surface.
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