الفهرس 
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Abstract
Summary and Conclusion
Rare earth elements are collection of seventeen chemical
elements in the periodic table, specifically the fifteen
lanthanides plus scandium and yttrium. REEs are widely used
in industry, agriculture, and medicine. REEs can enter the food
chain, resulting in their intake by human. Thus, it has become
increasingly important to know the behavior of these elements
in the environment.
The present study is stressed on samples from Magharet
El Meyiah Formation of early Carboniferous age in
southwestern Sinai. A total of (16) representative samples
were collected to represent the lithologic variations from north
(Budaa), middle (El Gor) and south (G. Farsh El Azraq)
localities.
This work aims to study the effects of fungal biomass on
the solubilization of REEs, selective leaching and precipitation
of some of trace elements, the effect of the REEs on the
physical and chemical properties of the bio-cell walls and
attempt to visualize if there is contribution of the isolated
biomass on the concentration of the REEs in the study samples.
To study the bioleaching of REEs from the collected
rock samples in different localities, it is very important to
identify and discuss the results and distributions of major,
trace, rare earth and radioactive elements.
Chemical analyses of the three carbonaceous shale
samples from Budaa, El Gor and G. Farsh EL Azraq localities
showed high content of SiO2 which represented by (av.=
51.1%, 66.3% and 62%) respectively , and moderate content of
Al2O3 were recorded as (av. = 13.9%, 14.5% and 15.1%)
respectively.
The well noticed thing is the high loss on ignition for
samples of the studied localities. The highest loss on ignition
(61.1%) was recorded in Budaa (sample B.8). This high loss on
ignition was found to affect on the process of bioleaching of
the REEs as will be seen later. All the studied samples are
generally depleted in their Pb and Ga contents and have
moderate contents of (Ni, Cu, Zn, Rb, Y, Sr, V and Nb) which
are lower than 100 ppm and high values of Zr content in El
Gor, G. Farsh EL Azraq and Budaa localities (av. = 938, 921
and 560 ppm) respectively are attributed to the presence of
zircon mineral. All studied samples of the examined localities
are characterized by very high values of Ba content. The
average values of this element are 2454, 2121 and 2604 ppm in
the studied Budaa, El Gor and G. Farsh EL Azraq localities
respectively. The whole studied samples are generally similar
in their Cr and Rb contents. Carbonaceous shales show REEs
content ranging between 200 ppm and 581 ppm with an
average 366 ppm. The average of activity concentrations of
238U, 226Ra, 232Th radionuclides in the three localities are higher
than that reported in UNSCEAR (2000) but have lower 40K
contents. The 238U/235U ratios are nearly within the natural ratio
(21.7) for investigated samples from the three localities. The
238U/226Ra and 238U/232Th ratios indicate U-migration-in these
sedimentary rocks.
Eight fungal genera were isolated from the studied
samples. The most dominant were Aspergillus and Penicillium.
The Aspergillus (A.) was identified as A. niger, A. flavus, A.
terreus and A. ficuum whereas, Penicillium (P.) was P.
aeruginosa, P. oxalicum, P. cyclopium and P. diversum. All of
the tested fungi could grow in the presence of 1% ore
concentration of the studied Budaa locality samples (B.4, B.8
and B.3). It was found that direct bioleaching process of REEs
from the tested samples was more effective than indirect
process for all tested microorganisms. The bioleaching
percentages of REEs from the tested samples by Aspergillus sp.
were more than Penicilium sp. whereas; A. niger was the
superior followed by A. flavus. The obtained results showed
that as the concentrations of REEs in the original samples
decrease the bioleaching efficiency in the whole fungi increase.
The reverse case was in the growth of fungus which increases
with the increase of REEs concentrations except in A. terreus
and P. oxalicum. The growth of Penicillium sp. in the presence
of carbonaceous shale samples was higher than A. niger
followed by A. flavus. The best leaching efficiency of REEs
was occurred only when the final pH of the media became
more acidic which reached to 4.24 for A. niger and 4.64 for A.
flavus.
Aspergillus niger and Aspergillus flavus were selected to
study the factors affecting the bioleaching efficiency of REEs
from the studied sample B.3, B.4 and B.8 from Budaa locality.
The maximum leaching of REEs was obtained using
1% sample concentration by A. niger and followed by A. flavus
reached to 86% and 60% respectively from the studied sample
B.3. The bioleaching efficiency was observed to decrease by
increasing the sample concentration in the growth medium. An
important note was that at 1%, 5% and 7% ore concentrations
and high REEs content for sample (B.4), the bioleaching
efficiency of A. flavus was higher than that of A. niger. This
means that A. flavus can work under stress of REEs content
than A. niger.
The maximum bioleaching efficiency of REEs using A.
niger and A. flavus was obtained at 7 days of incubation and
rapidly decreased after these days. The behavior deviated
something from this result especially with A. flavus in the
samples (B.8) with high carbon content which plays essential
role in the leaching efficiency. A very important notice is that
the A. niger did not affected by the high content of carbon in
this sample, while A. flavus was affected as noticed after
sample roasting at 1000 oC.
The best leaching efficiency of REEs from ore samples
by A niger and A. flavus was occurred at 30 oC. It was noticed
that at lower temperature (20°C) or higher temperature (40°C
and 45°C) the fungal bioleaching was highly decreased.
The bioleaching efficiency was highly affected by initial
pH of growth medium. However, the bioleaching of REEs was
optimum at pH value 4.
Optimum conditions of REEs bioleaching by A. niger
and A. flavus on Budaa sample (B.3), reached 86% and 73%,
respectively, were found at (1%) ore concentration, (7 days)
incubation period, (30 °C) temperature and pH (4). The resulted
optimum conditions for REEs solubilization by A. niger and A.
flavus were applied on samples from the other studied locations
having different REEs concentrations. The best bioleaching
efficiency (91%) of REEs is found in El Gor sample (G.1)
which has the lowest content of REEs concentrations.
By using HPLC, the concentration of oxalic, citric and
formic acids in the fermented liquor by A. niger were 1.068,
12.876 and 8.887 mg/ml, respectively whereas being oxalic
(3.054) and citric (8.456) mg/ml for A. flavus. from the
previous results it can be deduced that the citric and oxalic
acids contents produced by A. niger was higher than that
produced by A. flavus often at 7 days incubation period. This
explains the higher REEs bioleaching efficiency of A. niger
than A. flavus. With pulp density 1%, citric and oxalic acid
concentrations increased to 21.844 and 28.967 mg/ml for A.
niger and 6.688 and 23.683 mg/ml for A. flavus, while with
increasing pulp density to 7%, the citric and oxalic acid
concentrations decreased to 16.379 and 2.077 mg/ml for A.
niger and 3.767 and 16.818 mg/ml for A. flavus.
For REEs recovery, the oxalic acid was used for
precipitation then the precipitate was analyzed by ESEMEDAX
analysis. It is clearly evident that the total REEs
concentrate includes La, Ce and Nd assays and 9.29, 39.06 and
16.58 %, respectively, while Pr and Sm assay 6.18 and 5.49 %,
respectively. The product from bioleaching process of REEs by
A. niger indicate selective nature of the fungi where the
dissoluted and precipitated elements represent only the LREEs
except Eu which is very low in the original sample. The XRD
pattern of the precipitated REEs showed the presence of the
chemical compound sodium neodymium carbonate hydrate
NaNd(CO3)26H2O associating with other compound named
Vanadyl phosphate ethanol (C4H12O2VOPO4). The last
compound considered as an evidence for the reactions between
fungi media and original sample. Vanadium is coming from the
original sample which has 201 ppm.
To optimize the relevant biosorption factors during
bioleaching process by A. niger and A. flavus for the studied
sample
B.3. The highest biosorption efficiency of REEs obtained from
5% ore concentration of Budaa (B.3 sample) by A. flavus
followed by A. niger reached to 21 and 18% respectively. A
well noticed point is that the efficiency of A. flavus is higher
than that of A. niger. This means that A. flavus can work under
stress of REEs content than A. niger. The final pHs were
increased with increasing concentrations in the growth media.
Biosorption of REEs by both tested fungi was highly affected
by contact time. The results showed the rapid increase of
biosorption efficiency of REEs with time. However, best
accumulation of REEs occurred at nine days of incubation for
A. flavus and A. niger reached to 24 and 20% respectively. The
biosorption of REEs by fungal biomass was slightly affected by
different temperature from 37-45 oC, but lowest biosorption of
REEs was occurred at 20 oC 12 and 9% respectively, while at
40 oC biosorption was reached to the highest value. At this
temperature, A. niger biosorbed 20% from the total amount of
REEs found in B.3 sample. On the other hand, A. flavus
biosorbed 24% from the total amount of REEs found in B.3
sample. After 40 oC the amounts of REEs accumulation
decreased. The pH seems to be the most important parameter in
the biosorption process. The maximum REEs uptake wa
observed at initial pH 7 for dry biomass of A. niger and A.
flavus 20 and 24% respectively.
The important morphological changes of A. niger were
investigated by using microscopic examination which showed
that the vesicle diameter of A. niger was decreased with
increasing ore concentration in the growth media. Also, the
primary stigmata appeared shorter than the control, whereas the
secondary stigmata were found to disappear with increasing ore
concentration. The conidial heads reduced in size and carrying
little number of conidia which appear thicker than control in
1% and 7% ore concentration.
Transmission electron microscope (TEM) analysis of A.
niger grown on Dox agar media contains (0, 3, 5 and 9 %) ore
concentration of B.3 showed that elements were accumulated
and precipitated around cell wall and therefore it formed a
black dense area around it. This dense area was increased with
increasing ore concentration in the growth media. The
thickness of cell walls was markedly increased at 5% ore
concentration when compared to control. At 9 % ore
concentration cell wall start to hydrolysis and cell large
vacuole was formed due to metal ions entrance at (3% - 9%)
ore concentration.
The adsorption efficiency for different elements at 3%
ore concentration can be arranged in descending order as
follow Al ˃ Fe ˃ Si ˃ Ca ˃ Mn ˃ P ˃ U ˃ Co ˃ Cu ˃ S ˃ Ce ˃
K ˃ Ni ˃ Cl ˃ Zn whereas at 7% the adsorption efficiency
arranged as follow Mn ˃ Fe ˃ K ˃ Co ˃ Ce ˃ P ˃ Ni ˃ Si ˃ Al
˃ Zn ˃ Na ˃ Ca ˃ Cu ˃ U. The adsorption efficiency for
different elements at 3% ore concentration by A. flavus can be
arranged in descending order as follow Fe ˃ Al ˃ Si ˃ Mn ˃ Na
˃ Zn ˃ Co ˃ Ni ˃ K ˃ U ˃ P ˃ Ca ˃ Ce ˃ Cu whereas at 7%
the adsorption efficiency could be arranged as follow Fe ˃ Mn
˃ Al ˃ Ce ˃ Si ˃ P ˃ Zn ˃ K ˃ Co ˃ Nb ˃ Ca ˃ Ni ˃ S ˃ U ˃
Cu ˃ Cl.
The main achieved goal in this work is the selectivity of
Ce from REEs being in both fungal, whereas A. niger and A.
flavus in 7% ore concentration adsorbed 6.84% and 7.01% of
Ce, respectively.
5.2 Conclusion
1- Bioleaching and biosorption are two processes occur
together at the same time with different optimum
conditions.
CHAPTER 5 Summary and Conclusion
203
2- The variation in the amount of leachability of REEs was
depending on geochemical features and concentration of
REEs in the ore.
3- The high loss on ignition is negatively affecting on the
process of bioleaching of the REEs.
4- Acidolassies is the principal mechanism in the bioleaching
of metals by microorganisms which produced organic acids
such as citric and oxalic.
5- Some elements were leached from tested ore and affect on
the soluble of REEs due to the toxic effect on the activate
microorganisms.
6- The product from bioleaching process of REEs by A. niger
indicate selective nature of the fungi where the dissoluted
and precipitated elements represent only the LREEs.
7- Biosorption on the external cell surface is biomass defense
system against toxic metals with producing an external
polymeric layer to avoid metal penetration through the cell
wall and still a life.
8- The Biosorption process of REEs by A. niger and A. flavus
indicate selective nature of Ce from REEs being in both
fungus.