Dear Dr. Af:

See, it is necessary to check if you have an niobium oxide or an niobium oxide with some hidratation degree. The dissolution process to retrive niobium cations is well distinct depending on the oxide or oxide.nH2O.

Being the oxide Nb2O5, it is possible that HF exhibits some difficulty. See, let's suppose that the intention be the development of a source of niobium, that not a derived of clore, thus the ideal is use a further precursor for niobium cation, as NH4H2(NbO(C2O4)3).2H2O a complex salt, water soluble. Consider to access the site follow:

http://www.cbmm.com/us/p/108/niobium-technology-supplier.aspx

click products

verify ammonium niobium oxalate

Please, consider the solicitation of a free sample for investigative procedures. A priori, this a international company where no restrictions to sample access are common.

It is possible that you interested in some kind of chemical analysis and necessitate develop a standart, in this sense there is a route disponible from Abstract book from "7o Encontro Nacional of Química Analítica", where a process devepoled by Jovino A de Souza is reported. As this material is in brazilian portuguese, I will translate for you, perhapz would be usefull:

- The solubilizing of sample  was carried out via oxidant fusion method with K2S2O7 at 450 oC.

- After cooling, the mass resulting of fusion was treated with oxlic acid 4%, 4 g in 100 ml de water.

- In the sequence, the niobium cations form a complex by adding of a solution of pyrogallol sulfite.

- This complexation gives a solution with color yellow-orangedish, allowing an spectroscopic analysis from color (Lambert-Beer Law).

Kind regards

Marcos Nobre

I guess so, but why HF? have you tried aqua regia? or concentrated nitric acid?

 You can dissolve (i.e. etch) Nb2O5 with (hot) H2SO4 + HCl or with HF + HNO3.

thank you very much; i will try

Dear Dr. Af:

See, it is necessary to check if you have an niobium oxide or an niobium oxide with some hidratation degree. The dissolution process to retrive niobium cations is well distinct depending on the oxide or oxide.nH2O.

Being the oxide Nb2O5, it is possible that HF exhibits some difficulty. See, let's suppose that the intention be the development of a source of niobium, that not a derived of clore, thus the ideal is use a further precursor for niobium cation, as NH4H2(NbO(C2O4)3).2H2O a complex salt, water soluble. Consider to access the site follow:

http://www.cbmm.com/us/p/108/niobium-technology-supplier.aspx

click products

verify ammonium niobium oxalate

Please, consider the solicitation of a free sample for investigative procedures. A priori, this a international company where no restrictions to sample access are common.

It is possible that you interested in some kind of chemical analysis and necessitate develop a standart, in this sense there is a route disponible from Abstract book from "7o Encontro Nacional of Química Analítica", where a process devepoled by Jovino A de Souza is reported. As this material is in brazilian portuguese, I will translate for you, perhapz would be usefull:

- The solubilizing of sample  was carried out via oxidant fusion method with K2S2O7 at 450 oC.

- After cooling, the mass resulting of fusion was treated with oxlic acid 4%, 4 g in 100 ml de water.

- In the sequence, the niobium cations form a complex by adding of a solution of pyrogallol sulfite.

- This complexation gives a solution with color yellow-orangedish, allowing an spectroscopic analysis from color (Lambert-Beer Law).

Kind regards

Marcos Nobre

your process is interesting, but I do not have the means to achieve it 

For guidance please see the article below:

K.C. Nathsarma and B.B. Nayak. Purification of niobium oxide by

dissolution and solvent extraction. MINERALS & METALLURGICAL PROCESSING. November 2011 • Vol. 28 No. 4

thanks for all,itried many processes but Nb2O5 didnt dissolved

I try HF,HNO3+HCl,H2SO4,NaOH.........

Dear Dr. Ehya;

Your result is a fact. It is impossible use a acids mixture at room temperature or hot that dissolve Nb2O5.

with best regards

Marcos Nobre

It seems that there many attempts to dissolve Nb2O5. I do dissolve Nb2O5 not hydrated, using 20-30%aqueous HF solution. It won't dissolve instantly rather you may have to put the Nb2O5 -HF mixture solution in water bath with occasional stirring for several hours depending on how much Nb you want to dissolve at a time. It is better to attempt with small amount e.g., 1gm may be until the process is standardized.

Dear all:

The purity of Nb2O5 is very important. An oxide exhibiting high purity tends to be much more stable. This is a characteristic of anhydrous oxide. However, hydrated oxide are slight soluble, HF or aqueous HF, after very long time. In this sense, it is necessary to ponder cost/benefit/risk of the process. It’s important verifies the name and its correlation with X-ray diffraction and infrared characterization. Also, a general name can occur, as an example the hydrated niobium oxide is commonly termed niobium acid Nb2O5.nH2O.

with best regards

Marcos Nobre

DEAR ALL:

HOW can i dissolved this problems?HOW COULD DISSOLVED THIS OXIDE?

Dear Dr. Ehya:

I find a recent description of the classic sequence of Nb2O5 dissolution. I don’t make this rote but seems a viable way. See, I think that a solution of Nb cation cannot be reached, I don´t know, but a solution of niobium ions, as one provide by the niobium oxalate is viable. If hepl you, see below from steps sequence:

Fusion step:

In a hot platinum crucible, Nb2O5 and KHSO4, 1:7, should be fused, the temperature of fusion depend on the purity of Nb2O5 and average crystallite size, then fusion can be carried out since in Bunsen burner up to furnace, at around 600 oC. Liquid state formation is reached.

Solidification step:

In a crucible, hard porcelain, put liquid to attain father solidification.

Crushing step;

The solidified liquid (Nb2O5 dissolved in KHSO4) should be crushed, a priori, this material is fragile and crushing process can be manual with help of a pistile, fine powder are desired.

Washing step:

In a very very pure hot water, not boiling, sufficient to dissolve the fine powder crushed at 85 oC during 1 hour, with stirring. Age of solution by sufficient time, 12 hours as example. Separation is via vacuum filtering. With very very pure hot water, wash several times up to absence of K trace, dry. The material resultant is Nb2O5.nH2O.

As function of “n” is important to make a Thermogravimetric analysis to know the real amount of Nb2O5 that will be in fact manipulated.

Using Nb2O5.nH2O, Niobium salts soluble in water or alcohol, as niobium oxalate can be synthesized. See, it is possible have in hands (solution) ions niobium, but not Nb cations. There are a great number of methods to niobium salts synthesis that can be synthesized as oxalates, citrates, oxi-oxalates of ammonium…

with best regards

Marcos Nobre