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Biosorption of Uranium from Uranium Conversion Waste using Aspergillus Niger Fungus

Sana, Solat | 2015

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 47426 (06)
  4. University: Sharif University of Technology
  5. Department: Chemical and Petroleum Engineering
  6. Advisor(s): Roosta Azad, Reza; Yaghmaei, Soheyla
  7. Abstract:
  8. Presence of heavy metals in industrial waste has always been a serious environmental problem. One of such metals in uranium that is used in important industries such as nuclear industry. Thus, it must be excluded from industrial waste efficiently. This research aimed to study effect of local strain of aspergillus niger in bioabsoprtion of uranium from industrial waste in which good absorption was reached and absorption of local strain was compared with that of control strain obtained from PTCC. Also, local strain was collected from uranium anomalies of Bandar Abbas Mining Site and was used to identify it with reference strains available at NCBI site using PCR and proliferation of part of sequence of small subunit of Rrna for sequencing. Based on the results, local strain (F1914) was highly similar (98%) with reference strain A. niger. Also, of three living biomass types, dried and treated (using 0.5 normal soda), were used for both local and control strain in uranium bioabsorption. Given the results, treating the biomass of local strain of A niger using soda resulted in increased uranium absorption capacity compared with living and dried biomasses of this strain respectively by 22.5±2.5 and 12.5±2.5 percent. At the same time, treating biomass of control strain of A niger using soda didn’t significantly affect such capacity compared with living and dried biomass of the same. pH is the most important parameter affecting bioabsorption and optimal pH for three types, that is, living, dried and treated biomass of local and control strains was 5, 4 and 5. Further, the equilibrium time for control strain for every said types was half as much as the same for local strain, with them being 120.60 and 240 min respectively. Concentration of biomass is another factor affecting bioabsorption. For three types of local strain, 0.2, 0.3 and 0.2 g of dried biomass per 100 ml of solution and for control strain, 0.2, 0.1 and 0.2 dried biomass per 100 ml of solution were used, respectively. Maximum absorption capacity for three types at initial concentration of 500 mg/lit of uranium was 174.11, 189.25 and 217.6 and 105.00, 107.38 and 1.9.24 mg of uranium per one gram of biomass for living, dried and treated local and control biomasses, respectively. Important point to note is that control strain was a better bioabsorber up to concentration of 50 mg per one liter of uranium, but at higher concentrations, the opposite was true. Given the results, Langmuir adsorption isotherm was well able to fit out the data obtained from living and treated biomass absorption of local and control strains; however, it was only well able to fit out data from local strain as regards dried strain. Also, absorption of dried biomass of local strain considering effective factors of single and multiple-factor mathematical models was suggested. Also, given the results in absorption bed column, height of active zone of absorption was 31.6 cm for absorption of uranium, and synthetic model of Yoon & Nelson was well able to fit out parameters related to bioabsorption by fixed bed column of dried biomass of local strains. Given the results, quasi second order synthetic model could well fit out the data related to absorption of uranium by dried biomass of local strain. Also, optimization of absorption conditions by Taguchi method showed that given the means of S/N ratio, the highest bioabsorption was obtained at of pH of about 4 with confidence of 90.5% and the best initial concentration of uranium was 10 mg/lit, and also, the proper concentration of biomass was estimated to be 0.4 g, which was consistent with the results obtained in this research. Also, given the results from absorption of cadmium and uranium and the interaction between them, it was found out the uranium had a negative effect on absorption of cadmium, while cadmium had no significant effect on bioabsorption of uranium. Therefore, local strain of A niger was more elective in bioabsorption of uranium compared to cadmium. Also, given the results from reduction of absorber local strain dried biomass, hydrochloric acid is suggested as a powerful reduction agent for separation of uranium ions from local strain dried biomasses, which resulted in recycle of uranium from local strain dried biomass at 99% at every three initial concentrations of uranium (200, 50 and 500 mg/lit)
  9. Keywords:
  10. Oranium ; Industrial Wastewaters ; Bioabsorption ; Aspergillus Niger

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