الفهرس 
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Abstract
Hazardous metals pollution is one of the most important environmental problems today, especially in relation to water contamination. Several industries and radiochemical activities produce wastes and wastewaters that are discharged in water sources threatening the ecosystems and ultimately human health. Therefore, removal of toxic heavy metals and radioactive ions to an environmentally safe level in a cost effective and environment friendly process assumes great importance. The utilization of biosorption technology for the treatment of wastewaters contaminated with heavy metals and radioactive ions has become an alternative method to conventional treatments. Biosorption utilizes various natural materials including; algae, fungi, yeast and bacteria to sequester hazardous ions from aqueous solution. The present study aimed to isolate bacterial species from hazardous liquid wastes at Hot Laboratory Centre able to stand for heavy metals and radioactive ions. The isolated bacteria species were identified as; Bacillus pumilus and Bacillus licheniformis and investigated for cesium and strontium removal. The effect of washing with distilled water and pretreatment with various concentrations of HCl and NaOH solutions of 0.01, 0.025, 0.05 and 0.1N on the biosorption of free bacterial biomass of B. pumilus and B. licheniformis was studied to achieve the maximum biosorption of cesium and strontium ions from liquid solutions. The results showed that washing of B. pumilus biomass with NaOH increased its biosorption capacity and the best NaOH concentration was 0.05N for cesium and 0.025N, for strontium. In contrast, washing B. licheniformis with 0.025N HCl achieved the maximum biosorption for both Cs and Sr ions. The immobilization studies were conducted using different immobilization matrices namely; Calcium alginate (CA), Polyvinyl alcoholalginate (PVA/CA) and Chitosan-alginate (CTS-CA). The biosorption ability of the immobilization matrices beads for the studied metals ions (Cs and Sr) were examined using different bead sizes of; small (1 - 1.5 mm), medium (2 - 2.5 mm) and large (3.5 4 mm). The results showed that the small bead sizes achieved the highest removal efficiency and the order of Cs removal was PVA/ where, 38.7, 33.8 and 9.7 mmol were removed per gram dry weight, respectively. However, the order of Sr CTS/CA where, 194.7, 152.1 and 44.7 mmol were removed per gram dry weight, respectively. The effect of the environmental factors on the biosorption of the studied metal ions (Cs and Sr) was investigated using CA-immobilized pretreated biomass of B. pumilus and B. licheniformis where, 0.25 g of the pretreated biomass was mixed with 5 ml of the studied gel. The effect of different bead sizes showed that the maximum uptake of Cs (55.2 and 56%) was obtained by CA- immobilized B. pumilus and B. licheniformis, respectively using small bead sizes. On the other hand, the maximum uptake of Sr (88%) was obtained by CA- immobilized B pumilus and B. licheniformis using small bead sizes. The effect of the pH on the biosorption was investigated at different pH values of 2, 4, 5.5, 8 and 10, at fixed other conditions. The maximum uptake percent of Cs ions was showed at pH 5.5 for control CA-beads and CA-immobilized B. pumilus and B. licheniformis beads, while, the maximum uptake of Sr was showed at pH 5.0. It was found that, the biosorption process reached equilibrium after two hours of the beginning of the experiments, where 32, 55.2 and 56% of Cs ions was removed from 250ppm cesium solution by small beads for control CA-beads and CA-immobilized B. pumilus and B. licheniformis, respectively. However, 76.8, 88 and 88% of Sr ions was removed from 250 ppm strontium solution by small beads for control CA- beads and CAimmobilized B. pumilus and B. licheniformis, respectively. Results showed that the optimum weight of B. pumilus and B. licheniformis to be immobilized was o.25g per 5ml sodium alginate gel for Cs and Sr removal. The effect of temperature was studied at different temperature of 15, 25, 37 and 45 ºC. The results showed that the maximum uptake of cesium and strontium by CA-immobilized B. pumilus and B. licheniformis was obtained at 25 ºC after two hours. The biosorption of cesium and strontium ions by CA-immobilized B. pumilus and B. licheniformis was studied at different concentrations of, 50, 100, 150, 200 and 250 ppm. The results cleared that the maximum uptake percent 100 % of Cs and Sr by CA-mmobilized B. pumilus was observed at ion concentrations of 50, 100 and 150 ppm after two hours. On the other hand, the maximum uptake percent by CA-immobilized B. licheniformis were 90, 99.6 % for Cs and Sr, respectively, at ion concentration 50 ppm after two hours. The biosorption of Cs and Sr ions from binary solution with final concentration 250 ppm for each metal ion was studied and compared with the biosorption of the metal ion from single element solution. The obtained results indicated that the uptake of both Cs and Sr ions from binary solution is lower than that from single ion solution for CA-immobilized B. pumilus and B. licheniformis beads. Also, results cleared that the uptake of Cs in binary solution by CA-immobilized B. pumilus was higher than that of CAimmobilized B. licheniformis. On the other hand, the uptake of Sr in binary solution by CA-immobilized B. licheniformis was slightly higher than that of CA-immobilized B. pumilus. The biosorption efficiency of PVA/CA-immobilized beads was investigated to compare with CA-immobilized beads. The important experimental conditions namely; the effect of biomass treatments, the effect of immobilized weight and the effect of bead sizes were studied. The effect of biomass pretreatment was studied using the same pretreatment solutions as in CA-beads studies. The obtained results indicated that the order of Cs and Sr ions removal by the different beads was as follow; PVA/CA-immobilized treated B. pumilus and B. licheniformis PVA/CA- -immobilized non- treated B. pumilus and B. licheniformis. The same as CA-immobilized beads, it was found that 0.25 g of biomass weight achieved the maximum removal percent. The effect of different bead sizes for; small (1 1.5 mm), medium (2 - 2.5 mm) and large (3.5 4 mm) showed that the maximum uptake of Cs was 44, 52 and 52 % by small beads of control PVA/CA and PVA/CA- immobilized B. pumilus and B. licheniformis, respectively. The maximum uptake of Sr 81.6, 81.6 and 84 % was obtained by control PVA/CA, PVA/CA- immobilized B. pumilus and B. licheniformis, respectively, using small beads. Batch experiments were conducted using control CTS/CA-beads and CTS/CA-immobilized B. pumilus and B. licheniformis beads to determine the maximum uptake of Cs and Sr ions. The effect of washing the free biomass on the uptake capacity was studied, where the same pretreatment solutions were used as CA and PVA/CA immobilization system. The obtained results indicated that same pattern of the two immobilization system was detected. The order of Cs and Sr ions removal was CTS/CA-immobilized treated biomass beads CTS/CACTS/ CA-immobilized non- treated biomass beads. Results showed that 0.25g of immobilized B. pumilus and B. licheniformis was chosen as optimum biomass weight for maximum uptake percent. The effect of different bead sizes showed that the maximum uptake of Cs 10.4, 14.4 and 20 % was obtained by small beads of; control CTS/CA, CTS/CAimmobilized B. pumilus and B. licheniformis, respectively. The maximum uptake of Sr 20, 32 and 28 % was obtained by small beads of; control CTS/CA, CTS/CA-immobilized B. pumilus and B. licheniformis, respectively. The uptake of active cesium by studied immobilization matrices and the isolated bacterial strains (free or immobilized) was investigated. The uptake percent of 137Cs by CA and PVA/CA beads were the higher removal percent 72.4 and 72.3 %, respectively. On the other hand, 17.2 % were removed by CTS/CA. The biosorption of 137Cs by different weights of 0.25 and 0.5 g for the free bacterial cells was done under optimum experimental conditions showed that, the increase in cell weight for the same solution of 137Cs (10 ml) resulted in slightly increase in uptake percent for B. licheniformis (48.9 and 57.1 %). However, the increase in free biomass weight of B. pumilus showed no effect on the uptake percent. While the biosorption capacity decreased with the increase in biomass weight for both bacterial strains. The biosorption of 137Cs by CA-immobilized B. pumilus and B. licheniformis was investigated by studding the effect of beads number, the immobilized biomass weight and the effect of different 137Cs activities under optimum environmental conditions. The effect of different beads numbers was investigated using 50 and 250 beads prepared using 0.25 g biomass / 5 ml sodium alginate gel. It was found that the increase in beads numbers increased the uptake percent. Different weights 0.25, 0.5 and 1g of B. pumilus and B. licheniformis were immobilized using 5 ml sodium alginate to investigate the best weight per 250 beads. The results showed that the increase in the immobilized weights for B. pumilus resulted in decrease the uptake percent and the best immobilized weight was 0.25 per 5 ml gel. While, for B. licheniformis, it was found that the increase in biomass weight from 0.25 to 0.5g increased the uptake percent from 73.9 to 81.9, then further increase in biomass decreased the uptake percent. The effect of different activities was studied using the best immobilized weight for B. pumilus (0.25 g) and for B. licheniformis (0.5 g). Results indicated that the increase of activity increased the uptake percent and the uptake capacity for B. pumilus where, 67.1, 76.6 and 77.7 % were removed from 5000, 8000 and 15000 Bq/ml 137Cs solution. However, the increase in activity decreased the uptake percent of B. licheniformis. Although, the uptake of 137Cs by control PVA/CA- beads showed nearly the same biosorption capacity of control CA-beads, the PVA/CAimmobilized B. pumilus and B. licheniformis exhibited lower 137Cs removal percent 65.5 and 60.4 %, respectively, than that for CA-immobilized B. pumilus and B. licheniformis 76.6 and 81.9 %, respectively. The ability of reusing the biosorption system and its efficiency for removing 137Cs was studied for three cycles. The beads were washed after each cycle with 0.1N HCl for 10 minutes. Results showed that the biosorption percent in the three cycles for CA-immobilized B. pumilus were 77.9, 22.7 and 46.9 % and the elution was 37.4, 100 and 100 % for the three cycles. Results obtained for the CA-immobilized B. licheniformis showed the same pattern where, 81.9, 20.7 and 41.6 % were removed for the three cycles and the elution was 39.4, 100 and 100%.