الفهرس 
Production of PhosphogypsumOnly 14 pages are availabe for public view
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Abstract
Bioremediation of radioactive waste or bioremediation of radionuclides is an application of bioremediation based on the use of biological agent’s bacteria, plants and fungi (natural or genetically modified) to catalyze chemical reactions that allow the decontamination of sites affected by radionuclides. Biosorption is a physiochemical process that occurs naturally in certain biomass which allows it to passively concentrate and bind contaminants onto its cellular structure. Removing toxic heavy metals from industrial wastewater and aid in environmental remediation. Bioaccumulation refers to the accumulation of substances, in an organism. Bioaccumulation occurs when an organism absorbs a - possibly toxic - substance at a rate faster than that at which the substance is lost by catabolism and excretion.
Biosorption suggests many advantages than other techniques for the removal of metal ions as:
1. Rich sources and chemically stable.
2. A high surface area (porous).
3. High efficiency to treat low concentrations of heavy metals.
4. Easy to produce high concentrations of metal ion adsorption active groups.
5. Easy to make chemical modification.
This thesis aims to minimize the content of radioactive elements from phosphogypsum (PG) which is a by-product during phosphoric acid manufacture to be safely used. This study has been summarazied in the following results:-1- Using yeast as Saccharomyces cerevisiae in different environmental media in terms of the type of carbon source, a source of nitrogen and different types and concentration of organic acids with PG. The effect of all these factors on the process of interaction of yeast on PG which contains elements and ionic components that decreased or increased.
By using different carbon sources (glucose, sucrose, fructose, lactose, maltose and starch) when cultivated Saccharomyces cerevisiae which is a good biosorbent for U and Th. starch gave highest biosorption capacity of U and Th reached to 62.8% (13 ppm) and 64.7% (6 ppm) respectively.
2- By using this starch in media with different nitrogen sources namely ammonium nitrate, potassium nitrate, sodium nitrate, ammonium chloride and peptone results showed that KNO3 and peptone was the best nitrogen sources for reducing U and Th % reached for 62.8% (13ppm) and 82.3% (3 ppm) respectively.
3- By fixing pepton as nitrogen source and starch as carbon source for the media of Saccharomyces cerevisiae and using different organic acids namely (salicylic acid, citric acid, oxalic acid and boric acid) with different concentrations (5, 10, 15, 20 gm). from the result, 5gm of oxlaic acid yielded biosorption efficiency for uranium 51.4% (17 ppm) and thorium 58.8% (7 ppm). While 20 gm of citric resulted biosorption efficiency 54.2% (16 ppm) for uranium and 70.5% (5 ppm) for thorium. At 5gm of citric acid, the biosorption efficiency was obtained 42.8% (20 ppm) for uranium and 82.3% (3 ppm) for thorium. At 10 gm of boric acid gave 37.1% (22 ppm) and 35.2% (11 ppm) for uranium and thorium respectively. With 10gm of salicylic acid, the biosorption efficiency was 60% (14ppm) for uranium and 64.7% (6 ppm) for thorium.compering with control sample 35,17ppm for U and Th respectively.
4- Algae serve as good biosorbant due to their abundance in seawater, fresh water, cost effectiveness, reusability and high metal sorption capacity.
Many current and potential uses of algae have been identified and these have been separated into (1) agriculture, horticulture and agronomy (2) uses in animal aquaculture, (3) aesthetics, (4) cosmetics, (5) environmental health, monitoring and remediation, (6) food, (7) health,thalassic and wellness, (8) industry.
Using different types of algae: chlorophyta (green algae) include (Caulerpa prolifera and Ulva lactuca), two types of Phaeophyta (Brown algae) include (Cystosira myrica and Sargassum detifolium) and one type of Rhodophyta (Red algae) (Sarconema filiformis) with different concentrations of PG (50,100,150,200 and 250 gm) to focuse on the change in values of radioactive elements within PG sample and the extent of the change in composition of algae used it self by following up functional groups.
(A) By applying chlorophyta (green algae) (Caulerpa prolifera and Ulva lactuca) the data showed that at 50gm of PG the biosorption effieciency of U and Th reached for 51.4% (17ppm), 52.9% (8ppm) by dealing with Caulerpa prolifera while with Ulva lactuca at 100gm of PG the biosorption effieciency of U and Th reached for 42.8% (20ppm) and 44.1% (9.5ppm) respectively.
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(B) By using Phaeophyta (Brown algae) include (Cystosira myrica and Sargassum detifolium) the most percent of U and Th recoreded 48.5% (18ppm) and 29.4% (12ppm) at 50gm of PG which deal with Sargassum detifolium while Cystosira myrica at 50gm of PG showed the best U and Th biosorption capacity represented by 80% (7ppm) and 82.3% (3ppm).
(C) By dealing with Rhodophyta (Red algae) represented by Sarconema filiformis the most percent of U and Th recoreded is 68.5% (11ppm) and 58.8% (7ppm) biosorption effeciancy at 50gm of PG.
Conclusion
from the results, we consider that,
- The preferred biosorption conditions for the treatment of phosphogypsum by using Saccharomyces cerevisiae were found that, the greatest biosorption efficiency was 60% (14 ppm) for uranium in the present of 10 gm of salicylic acid while 82.3% (3 ppm) for thorium by applying 5 gm citric acid in presence of pepton and starch as the best nitrogen and carbon sources respectively.
- For the algae used, the best biosorption efficiency of U and Th results gave 80% (7ppm), 82.3% (3ppm) respectively at 50gm of PG with Cystosira myrica.
(PG) is used as:
A daily cover for landfills which are under increased demand each year
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A soil additive (sometimes called land plaster) to improve the soil’s workability and receptivity to moisture, and to overcome the corrosive effect of alkalinity. Phosphogypsum specifically benefits some crops where substantial amounts of sulfate sulphur are required. A road base that is cheaper than traditional materials used as a road base. A food, drugs and cosmetics industry. Positive reproductions or replicas of oral structures in dentistry. A primary ingredient in toothpaste. In conclusion, phosphogypsum radioactive elements could be enhanced by applying microorganisms which is cheap and more environmentally friendly methods. The current work indicates the great effect of biological mediated phosphogypsum samples in decreasing the level of some toxic and radioactive elements especially uranium and thorium..