الفهرس 
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Abstract
The present work has focused on the purification of Egyptian monazite isolates and then studying its sorption characteristics toward U(VI) and Th+4. Biosorbents were characterized by FTIR, XPS, EDX and SEM. The sorption characteristics for U(VI) and Th+4 ions from aqueous solutions were examined under various experimental conditions using both batch techniques. This work described suitable fungi which can efficiently remove uranium from aqueous solutions under optimized environmental conditions of pH, ions concentration, temperature, biomass dose, biomass size, contact time. This study presented a systematic detection of the biosorption properties, such as isotherm, kinetics and thermodynamics of Aspergillus nidulans biomass. The effective desorption of the metal ions was also studied and the coefficients of recovery of sorption ability were also determined. The following remarks can be drawn:
(1) Four fungal genera were isolated from Egyptian black sand monazite and other ores to accumulate uranium and thorium. All fungal isolates were able to uptake uranium and thorium from solution after 24h. But the most potent fungal isolate was identified as Aspergillus nidulans (accession number MT355567) and was found the best uranium and thorium biosorbent.
(2) Aspergillus nidulans was exposed to different physical modifications (oven drying and autoclaved biomass) and chemical modifications (using 2M hydroxylammonium sulfate and 2M hydroxylammonium sulfate+ NaOH) to enhance remove uranium(VI) and thorium(IV) from aqueous solution. Modified biomass was showed different change in texture and color. The obtained results were confirmed that the capability of oven dried and HAS+NaOH treated Aspergillus nidulans to remove U and Th from aqueous solution.
(3) The influence of different pH on metals uptake showed that the metal ion uptake by modified biomass (oven dried and HAS+NaOH) was increased with pH and was reached a maximum value at pH = 4 for U biosorption and pH = 2 for Th biosorption. Uranium (VI) removal effeciency (R%) and biosorption capacity (qe) for chemical modification were reached the maximum value (93% and 14 mg/g at pH=4.0, respectively) for HAS+NaOH modified biomass in compared to HAS modified biomass (78% and 11.9 mg/g at pH=4.0, respectively). R% and qe of autoclaved biomass were decreased (42% and 6.3 mg/g at pH= 4.0, respectively) in compared to the oven dried modified biomass which reached the maximum value (50% and 7.5 mg/g at pH=4.0, respectively). For Thorium biosorption, R% and qe for chemical modification were reached the maximum value (99% and 29.6 mg/g at pH=2.0, respectively) for HAS+NaOH modified biomass in compared to HAS modified biomass (29% and 9 mg/g at pH=2.0, respectively). R% and qe of autoclaved biomass were decreased (45% and 13 mg/g at pH=2.0, respectively) in compared to the oven dried modified biomass which reaches the maximum value (96% and 29 mg/g at pH 2.0, respectively).
(4) The removal efficiency of U was decreased with the increasing of initial concentration of uranium(VI) above 350ppm but biosorption capacity was increased with an increasing concentration of uranium. The R% and qe for oven dried (native) biomass was reached the maximum value (82% and 28.7 mg/g at 350 ppm, respectively) and for chemical (HAS+NaOH) modified biomass was reached to (89.6% and 31.4 mg/g at 350 ppm, respectively). The removal efficiency of thorium was decreased with an increasing the initial thorium concentration and biosorption capacity was increased with an increasing concentration of thorium. The R% and qe for native biomass was reached the maximum value (99.4% and 20 mg/g at 200 ppm, respectively) while for chemical modified biomass was reached to (98.7% and 29.6 mg/g at 300 ppm, respectively).
(5) The maximum U biosorption efficiency (89 % and 97 %) was achieved at a concentration of 0.4 g of dry biomass for native and chemical modified biomass, respectively. U biosorption capacities (qe) for both biomasses were reduced with further increasing concentration of biomass. The maximum Th biosorption removal rate (99 % and 99.5 %) was achieved at a concentrations of 0.05 g of dry biomass for native and chemical modified biomass, respectively. Th biosorption capacity (qe) was reduced with further increasing concentration of biomass.
(6) The maximum U biosorption efficiency (91 % and 98 %) was achieved at grain size of 0.250 mm dry biomass for native and chemical modified biomass, respectively and U biosorption capacity (qe) was increased with further increasing of grain size. The maximum Th biosorption efficiency (99.4 %) was achieved at grain size of 0.075 mm dry biomass and Th biosorption capacity (qe) was slightly constant with further increasing grain size (40 mg/g) for native biomass. For chemical modified biomass, the maximum biosorption efficiency (99.8 %) was achieved at 0.250 mm grain size and Th biosorption capacity (qe) was reached (60 mg/g).
(7) The U biosorption process was very fast, with 97 % and 98.5% of metal biosorption taking place in 16 min and 14min for native and chemical modified biomass, respectively. After this time, there was not significant change and the rate of sorption was constant. For Th biosorption, the biosorption process was very fast, with 99 % and 99.8% of metal biosorption take place in 7 min and 25 min for native and chemical modified biomass, respectively. After this time, there was not significant change and the rate of sorption was constant.
(8) Effect of temperature on the biosorption of uranium and Th was studied at 40OC, 45OC and 50oC. It can be observed that the percentage of uranium biosorption was decreased slightly with increasing temperature and the capacity of uranium biosorption was also slightly decreased with an increasing of temperature. The variety was inapparent (from 88.6 % to 86.7 % for native biomass and from 98 % to 93.8 % for chemical modified biomass). The effect of temperature on the biosorption of thorium was indicated that there is no effect of temperature on biosorption of thorium.
(9) Among the tested metal ions Mn and Fe+3 did not show any impact on uranium efficiency and biosorption capacity. For thorium biosorption, among the metal ions tested REES, U and Fe+3 were also did not show any impact on thorium removal rate and biosorption capacity.
(10) The sorption mode calculations using Langmuir and Freundlich isotherm models showed that the Langmuir model, which indicated a predominant monolayered adsorption of uranium, is better than Freundlich models to describe the adsorption isotherm of uranium by chemical modified biomass. While isotherm models showed that the Langmuir and Freundlich model, which indicated a predominant monolayered and multilayered adsorption of uranium were good models to describe the adsorption isotherm of uranium by native biomass. from the biosorption results of native and modified biosorbents to Th, the equilibrium data were fitted that the Freundlich isotherms were performed better than Langmuir, which implied that multilayer sorption for Th was involved in the adsorption process. The Freundlich model was exhibited high K and n values (n>1) indicating high biosorption volume and biosorption strength, respectively