الفهرس 
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Abstract
Phosphate ores are in high demand all over the world because they are main raw materials for production of phosphatic fertilizers and other chemicals. High percentage from phosphate rock, 95% is consumed in manufacturing of fertilizers and the production of animal feed supplements. Because of the grade of the ore is gradually falling, it is becoming an economical to mine and beneficiate many lower-grade deposits for production of phosphatic fertilizers. Since it is necessary to search for alternative efficient process and to keep lower operating costs which is bio-beneficiation, by definition, refers to selective removal of undesirable mineral constituents from an ore by utilizing bacteria as surface modifiers to enhance the separation of one mineral from another either by flotation or flocculation, thus enriching it with respect to the desired valuable minerals.
In the present study, bacterial isolates have been investigated as a flotation reagent for mineral separation. Such bacteria were isolated from the surface of phosphate rock. Samples of single minerals of apatite (P2O5), calcite (CaCO3) and quartz (SiO2) were used for studying the
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fundamental research work. Natural Phosphate Rock (Nile Valley) was used for the purpose of application the concept of selective flotation or selective bio-flotation.
The study was based on zeta potential, adhesion measurements as well as micro-flotation experiments in absence and presence of bacteria. Bacterial - mineral interactions resulted in significant changes on mineral surfaces. The changes in zeta potential, adhesion and flotation behavior of apatite, calcite and quartz particles after microbial interaction are studied. In this thesis we used single minerals of calcite, apatite and quartz in addition to phosphate rock where tests proved the purity of single minerals (28% P2O5 rates and 90.99% SiO2 and 56.5% CaO) and analysis has also shown that natural phosphate ore used has 21.89% P2O5 associated with a higher amount of calcite 48.62% CaO and lower amount of quartz 11.81% SiO2. Then followed by studying the surface properties of minerals used where results proved that the iso electric point is 4.8 for apatite and at about 1.8 for quartz. On the other hand, calcite showed positive values of zeta potential all over the pH range and started to decrease from pH 9 with no (IEP). When measuring the particle size of the minerals under study show that the d50
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of the samples are 12.29, 9.33 and 7.62 microns for each of the apatite, quartz and calcite respectively.
Two strains of bacteria were isolated and grown, which have proven they are more isolated species have effect on minerals under study where they caused a change in the surface nature of minerals , which can be relied upon in the separation process and these strains are (Bacillus cereus and Pseudomonas songnenensis) and by studying the surface properties of isolated strains by measuring the surface charge, the results have shown that iso electric point (IEP) for these strains is 2.5, and 8.5 as mentioned order.
Adhesion results indicated that the adhesion of both bacterial strains of Bacillus cereus and Pseudomonas songnenensis onto apatite and calcite surface is generally increasing with increasing conditioning time, pH and bacterial concentration. On the other hand, this effect is inversed for quartz mineral. The adhesion % values have the following order:
apatite < calcite < silica.
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The results proved that Bacillus cereus and Pseudomonas songnenensis can be used in separation of apatite from quartz and calcite.
The interactions of bacteria and their agents with minerals can be indirect, with biological products acting as surface-active agents, or direct due to microbial adhesion (or attachment) to particles bringing out surface modification. Both types of interactions can lead to alteration of mineral hydrophobicity, and in some cases cause flocculation or dispersion of mineral suspension
The FTIR of microorganisms, showed the existence of O-H, C-C, CH2, C-O, C-N and C=O bands in decreasing order. These bands reflect the general organic structure of bacteria which are mainly composed of polysaccharides and protein.
FTIR studies showed the presence of new surface groups after interaction of single minerals with Bacillus cereus and Pseudomonas songnenensis isolated bacteria and it also proved that the type of adsorption occurred is mainly chemical adsorption which makes apatite surface more hydrophilic or hydrophobic more than that of quartz and calcite and enhances its separation from both of them.
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The results of amino acid analyser and HPLC analysis of Bacillus cereus on to the surfaces of the three single minerals indicated the higher affinity of protein adsorption onto apatite surface in the order of apatite < calcite <
quartz. As, the adsorption percentage exceeds 90.6% on to apatite where 60% and 51% for calcite and quartz respectively. These results are also confirmed through SEM images.
The results of amino acid analyser and HPLC analysis for Pseudomonas songnenensis bacteria after interaction with three mineral surfaces indicated and proved the hydrophobic effect of bacterial isolate as the adsorption of polysaccharides on to mineral surfaces is much higher than protein adsorption and more specifically the adsorption % is in the order apatite < calcite < quartz with 95.96, 68.32 and 49.23% respectively which means higher affinity of flocculation of apatite using pseudomonas songnenensis bacteria rather than calcite and quartz. The results are confirmed through SEM images.
On using selective flotation technique to separate a binary mixture of apatite – quartz system by B. cereus bacteria can yield a product of about 18.5% P2O5 and 33.03% SiO2
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from a feed containing 11.56% P2O5 and 40.98 % SiO2 with a recovery of about 84.20% at optimum operating conditions. While a mixture of apatite-calcite, can yield a product containing 19.01% P2O5 and 5.01% of CaO with a recovery of about 99.9%. On applying the same conditions on flotation of low grade phosphate rock yielded concentrates containing 27.2% P2O5 with recovery of 86.64%.
Addition of pseudomonas songnenensis as a sole flotation reagent for binary mixture of apatite – quartz system can yield a product of about 19.1% P2O5 and 32.26% SiO2 from a feed containing 11.56% P2O5 and 40.98% SiO2 with a recovery of about 96.81% at optimum operating conditions. At the same time, a mixture of apatite-calcite can yield a product containing 18.5% P2O5 and 5.5% of CaO with a recovery of about 99.97% P2O5 .On applying the same conditions on flotation of low grade phosphate rock yielded concentrates containing 30.44% P2O5 with recovery of 89.51%