Journal of Minerals & Materials Characterization & Engineering, Vol. 4, No.1, pp 1-10, 2005 Printed in the USA. All rights reserved
Enrichment of U, Mo, V, Ni and Ti from asphaltite ash
Işıl Aydın , Fırat Aydın , Recep Ziyadanoğulları*
Dicle University, Science and Arts Faculty,
Chemistry Department, 21180, Diyarbakir, TURKEY
In this study, the ash was sulfurized in an autoclave before flotation. The
sulfurization process was conducted at different amounts of H2S and H2O steam. The
flotation process was continued with the obtained samples. By flotation of the sample
obtained from optimum sulfurization conditions, the concentrates containing all the
uranium, molybdenum, vanadium, nickel and titanium was obtained. It was established
that the above mentioned elements were enriched 12 times more than the original ash at
the concentrate phase. The original ash was tried to enriched by flotation. How ever, the
results obtained from this study was not encouraging. Therefore, ash was sulfurized in
autoclave before flotation. In the flotation studies K-isobutylxanthate and K-
amylxanthate were used as the collectors and the Aeroflat 65 was used as the frother.
Keywords: Flotation, molybdenum, uranium, vanadium, asphaltite ash.
* For correspondance :
Fax: +90-412-2488039
Tel : +90-412-2488001/3159
Flotation has permitted the mining of low grade complex ores, which would have
been worthless if it had been necessary to rely on the time –honoured method of
gravity concentration. In addition, tailing dumps of older mines can be reclaimed. In fact,
the tailings of some previous gravity operations were higher grades than the ores being
mined in many mines of today. To the mineral world, flotation has provided millions of
tons of material that otherwise would not be economically available.
Early flotation efforts were directed primarily towards the recovery of copper,
lead, and zinc, but other materials are now recovered from other metallic ores. The great
and growing demand for molybdenum could not be satisfied without molybdenite,
produced as a by product in copper production. Other metallics recovered by flotation
include manganese, nickel, cobalt, vanadium, and bismuth [1].
In the flotation process, certain of the flotation reagents have been used for better
separation. Flotation processing involves three main steps; (i) selective chemical
modification of specific mineral surfaces to effect hydrophobicity/hydrophilicity
2Işıl Aydın , Fırat Aydın , Recep ZiyadanoğullarıVol. 4, No. 1
(flotability or nonflotability), (ii) contact between and adherence of hydrophobic mineral
particles to air bubbles, and (iii) separation of the flotable and nonflotable particles [2-5].
The Beaverlodge mill was used for flotation to remove pyrite from ground ore
prior to carbonate leaching to avoid excessive reagent consumption. Frequent efforts to
separate arsenic and nickel mineralization from uranium in Northern Saskatchewan ores,
utilizing radiometric sorting, flotation, gravity separation and screening have been
uniformly unsuccessful. These separation efforts failed because of the fine intergrowth
between arsenic/nickel minerals [ for example, millerite (NiS), niccolite(NiAs) and
gersdorffite (NiAsS) ] and uranium minerals such as uranite and coffinite [6].
The uranium ore from Jaduguda mine in India is one such deposit which needs to
be looked into from this point of view. Apart from uranium, it also contains valuable
minerals such as sulfide minerals of copper, molybdenum and nickel, as well as
magnetite and apatite. Currently, some of the minerals such as copper and molybdenum
are recovered and marketed as their concentrates. Magnetite is recovered from the ore
after uranium extraction and sold to the nearby coal washeries for use as heavy medium.
Part of the nickel sulfide minerals are recovered in the flotation stage, but not upgraded to
meet the market specifications [7].
Asphaltite ashes contain different amounts of U, Mo, V, Ni, Ti and other
transition metals depending on their formations. Main components of ash are quartz,
calcite gypsum and metal oxides. The effect of parameters such as collectors, frothers,
depressants, activators, particle size, pulp density, pH and temperature were investigated
to enrich U, Mo, V, Ni from asphaltite ashes and different minerals by flotation [8-13].
So far, it has been reported that enrichment methods performed by classical
flotation have not produced the desired results. The authors applied these classical
methods to similar samples and likewise, have not obtained good results. Therefore, the
authors have developed a new method in which surface properties were changed to
influence flotation.
To that end, asphaltite ash was reacted with H2S (g) under an autoclave, then the
samples obtained (Sulfurized sample, SS) were floated for floatability of the mentioned
elements. The main aim of this study was to determine to what extent the chemical
reaction influences flotation yield.
Material and Method
Preparation of asphaltite ash: Asphaltite sample was supplied from Silopi (in the
Southeastern Anatolia Region in Turkey ), ignited at atmospheric conditions, sieved to
-100 mesh size, roasted at 900 oC for 4 hours and again siezed to -100 mesh size, dried at
110 oC, kept in bottles and used later. The chemical analyses of asphaltite ash are given in
Vo. 4, No 1. Enrichment of U, Mo, V, Ni and Ti from asphaltite ash3
Table 1. Main components of ash not presented in Table 1 are calcide, silica and some
metal oxides (FexOy, Al2O3, MgO) which form approximately 90 % of ash.
Table 1- The chemical analysis of asphaltite ash*
Composition (%)0,330,450,600,449,472,960,05
Reagents: All the chemicals used were of analytical grade.
Apparatus: A flame atomic absorption spectrometer (UNICAM 929 Model AAS) and an
atomic emission spectrophotometer (JOBIN YVON JY 24 Model ICP-AES ) were used
for the determination of nickel and iron, and uranium, molybdenum, aluminum, titanium
and vanadium concentrations in the solution, respectively. D12 flotation apparatus,
Heraus Model Furnace and Nel 890 Model pH meter were used for flotation, roasting and
determination of pH of samples, respectively.
Flotation of Original Ash
The main aim of collective flotation is to remove Mo, V, Ni, U and Ti from the
main components of the original sample. The first flotation process was conducted by the
following conditions. The results are given in Table 2.
Table 2- Flotation of Orginal Ash*
Flotation TimeFlotation yield of the elements (%)
(Minute)Mo VUTiAlNiFe
402.85 2.48 2.21 1.77 1.702.20 2.10
Unfloated97.00 98.70 97.50 98.00 98.0097.50 98.10
Flotation conditions: Collector : potassium isobuthylxhantate (0.2 g/L) ; Frother : Aeroflat 65 (0.2 mL,
1%) ; pH : 6.5 ; Particle dimension : -100 mesh ; Stirring rate : 900 rotation / min ; Time of flotation : 40
min. , solid/liquid :100g/L
Table 2 shows that percent values of the flotation yield of the elements at 40
minutes and 21.98 g of floated was determined.
As seen in Table 2, none of the elements were collected in concentrated phase by
direct flotation of the original sample. The next flotation process was not carried out by
direct flotation of original ash.
Sulfurization of Asphaltite ash in autoclave conditions:
4Işıl Aydın , Fırat Aydın , Recep ZiyadanoğullarıVol. 4, No. 1
H2S (g)
Total flotati
Fig. 1- Effect of H2S on total flotation*
Firstly, samples of original ash were ground, sieved with 100 mesh, dried at 110
0C and then reacted at 100 0C with gas mixtures containing different amounts of H2S +
H2O for 1 hour. For this purpose, 500.00 g original ash samples were reacted separately
with mixtures of H2S and H2O to be investigated according to Table 3.
The reason for choosing the Table 3 condition was to increase the flotation yield.
This would result in a new surface and structure. The values for the sulfurization of Mo,
V, U, Fe and Ni are given in Table 3. The amounts of floated and unfloated ash of
sulfurized ash are given in Figure 1.
Table 3- The used amount of mixtures of H2S and H2O.
Experimental NoAmount of H2S (g)Amount of H2O (g)
11.09 5.0
21.36 12.5
31.64 12.5
42.05 15.0
52.18 16.0
62.46 18.0
72.73 20.0
As seen in Figure 1, it
was apparent that the lowest
amount of material was floated
for the seventh experiment
condition. At the end of the
process, the floated amount of
Mo, V, Ni, U, Al, Fe and Ti are
given in Figure 2.
The samples were
floated under the same
conditions as the original ash.
As seen in Figure 2, Mo,
V, U, Ni, and Ti were floated
with maximum yield in concentrated phase according to experiment 7 by flotation of
sulfurized ash for 40 minutes.
In order to investigate the dimension of sample on the flotation yield, the
sulfurized sample was ground, sieved (-100 , -200 and -300 mesh) and floated the same
conditions (experiment 7). The results are given in Figure 3.
In Figure 3, Mo, V, Ni, U and Ti values obtained from each sample were quite
close to each other. It was determined that, while in the flotation of the sample with -100
mesh , 11.02 g was collected, in the flotation of –200 mesh, 8.03 g was collected and in
Vo. 4, No 1. Enrichment of U, Mo, V, Ni and Ti from asphaltite ash5
Fig. 2- Effect of H2S on flotation of sulfurized asphaltite ash*.
the flotation of –300 mesh sample, 17.81 g was collected in concentrated phase. It was
found that yields in both flotations were closer. Especially, the percentages of Mo,V, Ni,
U and Ti in the sample were determined to be approximately two times greater than with
–300 mesh. It was concluded that flotation of –200 mesh particle size was suitable.
H2S (g)
% Recovery
H2S (g)
% Recovery
H2S (g)
% Recovery
H2S (g)
% Recovery
H2S (g)
% Recovery
H2S (g)
% Recovery
H2S (g)
% Recover
6Işıl Aydın , Fırat Aydın , Recep ZiyadanoğullarıVol. 4, No. 1
Size (m esh)
Recovery (%
100m esh
200m esh
300 mesh
Fig. 3- Effect of size on the flotation at sulfurized
66.577.58 8.59
Recovery (%
Mo V U Ti Al Ni Fe
Fig. 4- The Effect of pH on the Floatability of Sulfurized Samples*
*: Averages calculated for data obtained from three independent
flotation experiments
The effect of pH on
flotation was also studied.
Equilibrium pH were
adjusted as 6.2, 6.5, 7.0, 7.5,
8.0 and 8.5, respectively.
Experiments were performed
by using sulfurized –200
mesh samples, and flotation
was carried on for 40
minutes. During this time,
since substance was not
transported to foam, the
process was stopped.
Flotation yields obtained and
amount of substances are
shown in Figure 4.
As seen
in Figure 4, the
flotation yield
was reached at
pH 6.5. Yields of
Al was lowest at
this pH,
consistent with
what would be
expected. The
matter at this pH
to concentrated
phase was the
lowest, as 8.71g
as seen in Figure
4. Therefore, the pH dependent studies were carried out at above pH: 6,5. In the below
pH: 6,5, the H2S gas was produced and the flotation yield was decreased. Therefore, the
results obtained from this pH was not given. In the present study, harm to the
environment was avoided.
By keeping of experimental conditions constant in the seventh experiment,
flotation processes were conducted by changing pulp density. For this purpose, 150.0g,
200.0g, 250.0g, 300.0g of samples were put in 1000 mL of solution experiments which
were repeated twice for each. Experimental results are given in Table 4 and Table 5.
Vo. 4, No 1. Enrichment of U, Mo, V, Ni and Ti from asphaltite ash7
Table 4- The effect of pulp density on the floatability of the elements*.
Floatability of elements (%)Sample
(g) Floated amount
(g) Mo VUTiAlNiFe
150.014,22100.0 100.0 100.0
200.017,75100.0 100.0 100.0 100.08.4100.099.9
250.024,9699.0100.0100.099.0 8.9100.099.5
300.030,3599.0 9.699.799.0
350.036,0399.099.0 99.099.0 9.999.498.8
Flotation time is 40 minutes.
Table 5- Percentages of matter in concentrated phase by flotation of Sample 7*.
ElementsThe elements in the
concentrate (%)Enrich ment ratio
Mo3.73 11.30
V6.90 11.50
Ni5.42 12.04
Ti5.21 11.84
U3O80.62 12.40
Fe31.95 10.79
Al9.74 1.10
In Table 4, it is seen that despite the changes in pulp density, flotation yield did
not change. For sample 7 percent values of the elements in concentrated phase are given
in Table 5. Table 5 shows that percent values of the elements increased by 12 times,
compared to the original sample.
As seen from the results above, the transportation of matters to concentrated phase
takes 40 minutes. To reduce this duration, potassium amylxanthate was used instead of
potassium isobutylxanthate. The transportation time with potassium amylxanthate was
found to be 5 minutes and the results are given in Table 6.
Table 6- Flotation of Sulfurized Asphaltite Ash with Potassium Amylxanthate*
Flotation yield of elements (%)Floated
Material Mo VUNiTiFeAl
Concentred100.0100.0100.0 99.8 100.0 97.75.5
Non-floated---0.3 - 1.794.6
As seen in Table 6, the flotation time became shorter (5 minutes), but there were
no variations in flotation yields and collection of sample in concentrated phase. The main
points regarding the floatability of Mo, U, V, Ni and Ti in the asphaltite ash can be listed
as follows:
8Işıl Aydın , Fırat Aydın , Recep ZiyadanoğullarıVol. 4, No. 1
(i)Elements such as Mo, U, V, Ni and Ti in the asphaltite ash form complex compounds
with main components such as silica, limestone and other metal oxides of ash. It is
impossible to separate the elements above from main components of ash by direct
flotation of original ash due to homogenous dispersion of these compounds.
(ii) A concentrability method such as flotation involves separating the elements
mentioned above from asphaltite ash because the recovery of the elements are not
economical by hydrometallurgical methods.
(iii) The aim of the developed method is, as stated above, to enable a floatable surface to
form. Formation of this surface was considered to occur in solid-gas medium, thus,
process was maintained under H2S+H2O vapor medium.
(iv) Flotation of sulfurized sample carried out after these processes proved that these
elements were separated from main components and gave different compounds.
CaUO4 + 3 H2S Ca(OH)2 + US3 + 2 H2O(1)
CaMoO4 + 3 H2S Ca(OH)2 + MoS3 + 2 H2O(2)
Ca(VO3)2 + 5 H2S Ca(OH)2 + V2S5 + 4H2O(3)
FeTiO3 + H2S FeS + TiO2 + H2O (4)
FeNi2O4 + 4 H2S FeS + 2NiS + 4 H2O + S (5)
Ni2O3 + 3 H2S 2NiS + 3H2O + S(6)
Fe2O3 + 3 H2S 2 FeS + 3H2O + S(7)
Mo, U, V, Ni and Ti form free sulphides and oxides as the reactions tend to the right
slightly. These compounds are floated with anionic collectors such as xanthates, where
their surface become positive at suitable pH. Therefore, higher yields of flotation could
be carried out as the written reactions were shifted to right. When this yield is obtained,
the amount of matter collected in the concentrated phase becomes less. In this way,
concentrates containing high percentage of Mo, U, V, Ni, Fe and Ti can be obtained.
These were achieved by sulfurization under the seventh experimental condition in
Figure 5.
(v) Optimum flotation conditions are given below:
Collector: (Z5) potassium amylxhantate (0.2 g/L)
Frother: Aeroflat 65 (0.2 mL, 1%)
pH: 6.5
Particle dimension: -200 mesh
Pulp density: 250 g/l
Stirring rate : 900 rpm.
Time of flotation: 5 min.
(vi) The most suitable enrichment process was obtained for concentrate, flotation yield
and percent of elements in concentrate under conditions stated above.
Vo. 4, No 1. Enrichment of U, Mo, V, Ni and Ti from asphaltite ash9
By searching through the literature, it was found that ash samples such as coal
ash, asphaltite ash, etc.. have very low direct flotation yields. In the present study, it was
confirmed that using asphaltite ash in the flotation process does not promote the
flotation of Mo, U, V, Ni, Fe and Ti. Thus, in order to promote flotation, this new
sulfurization method was developed by the authors. To obtain the best results, the
structure and the surface should be suitable for flotation. For the sulfurization process, the
ratio of H2S and H2O is very important. This is one of the most important stages before
the flotation. In the flotation of different samples of asphaltic ashes containing various
amounts of metals, the sulfurization process, the flotation yield can be maximized [14-
Acknow l ed gment
Authors are grateful to Dicle University for financing this study [Project No:
DUAP-99-EF-378]. The authors also wish to thank anonymous reviewers for their
valuable comments.
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