Hydrophilic block copolymer-directed growth of lanthanum hydroxide nanoparticles

Bouyer, Frédéric; Sanson, Nicolas; Destarac, Mathias; Gérardin, Corine

doi:10.1039/b516368d

Cited by 61 publications

(77 citation statements)

References 66 publications

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“…In the cathodic region, the surface pH rises and extends into regions where insoluble lanthanum hydroxides form. 14 Because the pH at the electrode surface increases first, lanthanum hydroxides form on the electrode surface. Once formed, lanthanum hydroxide remains on the electrode surface until a sufficiently acidic surface pH is reached.…”

Section: Resultsmentioning

confidence: 99%

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EQCM and Surface pH Studies on Lanthanum Accumulation on Electrodes in Aqueous Solution

Babauta

Medina

Beyenal

2016

J. Electrochem. Soc.

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Lanthanum can be detected using cathodic deposition followed by anodic stripping. The deposition process controls the detection limit. In this work, lanthanum deposition was characterized using an electrochemical quartz crystal microbalance (eQCM), and surface pH near the electrode surface was quantified using microelectrodes. The eQCM was used to correlate the lanthanum mass deposited on the electrode to the applied potential. Two different lanthanum responses were identified based on pH control. In the absence of pH control, the lanthanum film remained on the electrode surface until a large anodic potential was applied (1.8 V Ag/AgCl or greater). In the presence of pH control, the lanthanum film was stripped off immediately after the applied potential was greater than −2.0 V Ag/AgCl . When we measured surface pH near the electrode surface using needle-type microelectrodes, it was found that the pH near the surface increased from 4 to above the detection limit (>10), which indicated that the surface pH was responsible for the two different observed lanthanum responses despite the bulk pH being the same. This is the first study to use eQCM and needle-type microelectrodes to correlate lanthanum deposition with surface pH rather than bulk pH. The concentrations of lanthanum and other lanthanides are typically measured by depositing them as amalgams with mercury 1 or, more recently, mercury films 2 , followed by stripping. As early as 1915 3 , mercury pools were used as cathodes that replaced platinum and copper electrodes for the electrolysis of rare earth elements. The reason for this was the fouling of the cathode with insoluble hydroxides, in which the pH at the cathode surface was thought to play a critical role. Recently, similar concerns were raised for lanthanide deposition on mercury-filmed microelectrodes. 4 The authors claimed that pH was responsible for the stability of La deposition. The effect of pH is a consequence of electrolysis or electrochemistry in aqueous solution. Considering the generation of high currents (mA/cm 2 level) on small electrodes during metal deposition, it is expected that pH changes significantly near the electrode surface. Researchers generally control bulk pH, but the pH on an electrode surface has not previously been quantified because the technology for doing this was not available until the present day. Interest in lanthanides stems primarily from electroanalysis and the need for rapid methods of detection 2 and their chemical similarity to the actinides. 5In addition, the surface pH of deposited La films needs to be characterized in order for us to understand the deposition mechanism. Often, post-treatment analysis via inductively coupled plasma mass spectrometry is used successfully to identify the composition of electrochemically deposited films 6,7 or quantify the amount of material sequestered by the electrochemical method.2 However, transient processes such as the formation of pH gradients near an electrode surface during deposition limit the usefulness of post-treatm...

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Section: Resultsmentioning

confidence: 99%

“…Thus it is expected that attempts to deposit lanthanum on electrodes immersed in simple salt solutions involve surface pH larger than 12. At these pH values, the formation of lanthanum hydroxides is prevalent 14 and becomes a complicating factor in studying lanthanum deposition in aqueous solution.…”

mentioning

confidence: 99%

EQCM and Surface pH Studies on Lanthanum Accumulation on Electrodes in Aqueous Solution

Babauta

Medina

Beyenal

2016

J. Electrochem. Soc.

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“…In addition to these template-free routes to La(OH) 3 nanostructures, the synthesis of stable La(OH) 3 nanoparticles in water by performing hydrolysis and condensation reactions of lanthanum cations in the presence of block copolymers was reported, too. The asymmetry degree of the copolymer influenced both the size and the shape of the particles [20].…”

Section: Introductionmentioning

confidence: 99%

Morphology-controlled nonaqueous synthesis of anisotropic lanthanum hydroxide nanoparticles

Djerdj

Garnweitner

et al. 2007

Journal of Solid State Chemistry

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The preparation of lanthanum hydroxide and manganese oxide nanoparticles is presented, based on a nonaqueous sol-gel process involving the reaction of La(OiPr) 3 and KMnO 4 with organic solvents such as benzyl alcohol, 2-butanone and a 1:1 vol. mixture thereof. The lanthanum manganese oxide system is highly complex and surprising results with respect to product composition and morphology were obtained. In dependence of the reaction parameters, the La(OH) 3 nanoparticles undergo a shape transformation from short nanorods with an average aspect ratio of 2.1 to micron-sized nanofibers (average aspect ratio is more than 59.5). Although not directly involved, KMnO 4 plays a crucial role in determining the particle morphology of La(OH) 3 . The reason lies in the fact that KMnO 4 is able to oxidize the benzyl alcohol to benzoic acid, which presumably induces the anisotropic particle growth in [001] direction upon preferential coordination to the ±(100), ±(010) and ±(−110) crystal facets. By adjusting the molar La(OiPr) 3 -to-KMnO 4 ratio as well as by using the appropriate solvent mixture it is possible to tailor the morphology, phase purity and microstructure of the La(OH) 3 nanoparticles. Postsynthetic thermal treatment of the sample containing La(OH) 3 nanofibers and β-MnOOH nanoparticles at the temperature of 800°C for 8 h yielded polyhedral LaMnO 3 and worm-like La 2 O 3 nanoparticles as final products.

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“…La(III) tend to bind the water molecules and the most common form obtained is [La(H2O)6] 3+ [45]. Based on hydrolysis constants of lanthanum, up to pH = 6, no hydrolysis take places and all the lanthanum would be present as La(III) ions [46]. At pH ˂ 6, strontium mainly occurs as Sr(II) and other possible form is SrOH + [47].…”

Section: Methodsmentioning

confidence: 99%

Study on adsorption behavior and separation efficiency of naturally occurring clay for some elements by batch experiments

et al. 2012

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KEYWORDSThis paper describes the versatile nature of clay that was obtained from Suez Gulf, Suez city, Egypt, as a new low cost natural resource which is non toxic to ecosystem and highly effective adsorbent material. The properties of the natural clay and its significance in removing Th(IV) and Ce(IV) as a representative of tetravalent actinides and lanthanides, respectively, La(III) as a representative of trivalent lanthanides as well as homologues of americium and Sr(II) as one of the fission products, in aqueous solutions have been studied, in order to consider its application for nuclear waste treatment. Batch experiments have been carried out to determine the effect of various factors such as initial metal ion concentration, clay dose, pH, contact time, and temperature on the adsorption process. The results have dictated that, the adsorption efficiency of the natural clay was significantly high at pH = 4. Maximum metal ion uptake capacity of clay has been obtained from batch studies was 99.24, 98.21, 77.76 and 57.94% for Th(IV), Ce(IV), La(III) and Sr(II), respectively. The thermodynamic parameters (H o , S o and G o ) have been calculated from the temperature dependent adsorption isotherms. Furthermore, separation factors () have been calculated in order to separate these elements from each other at pH = 4. Adsorption Natural clay Separation factor Radioactive waste Batch experiments Thermodynamic parameters

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Hydrophilic block copolymer-directed growth of lanthanum hydroxide nanoparticles

Cited by 61 publications

References 66 publications

EQCM and Surface pH Studies on Lanthanum Accumulation on Electrodes in Aqueous Solution

EQCM and Surface pH Studies on Lanthanum Accumulation on Electrodes in Aqueous Solution

Morphology-controlled nonaqueous synthesis of anisotropic lanthanum hydroxide nanoparticles

Study on adsorption behavior and separation efficiency of naturally occurring clay for some elements by batch experiments

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