الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
 |  | from | 209 |  |  |
| | | from | 209 | | |
Abstract
Heavy metal pollution causes severe damage to all life forms. Cadmium is introduced to the environment by many industrial wastewaters. Algal biomasses are used to absorb cadmium as they are economical, eco-friendly and more effective than bacteria and fungi. Therefore, this study investigated the ability of algal biomasses to remove cadmium ion from aqueous solution. The following results were obtained from our results:
1- Six algae obtained from Abu Quir beaches at Alexandria city, Suez Bay shore at Suez city and Phycology laboratory, Botany Department, Faculty of Science, Tanta University, Egypt. They were identified as Corallina officinalis, Ulva fasciata, Corallina mediteranea, Pterocladia capillacea, Ulva lactuca and Chlorella vulgaris.
2- Biomasses of Ulva fasciata, Pterocladia capillacea, Chlorella vulgaris and Ulva lactuca biomasses were the most effective for Cd (II) biosorption from aqueous solution.
3- Kuhl’s medium was the best medium for biomass production of Chlorella vulgaris as compared with Allen, BG-11, Bold and Chu-10 media.
4- The highest optical density, cell count, chlorophyll-a content of Chlorella vulgaris were obtained by using ammonium chloride as nitrogen source at pH 12 as compared with a control. The highest biomass production was recorded by using aerated culture and natural sunlight.
5- The Cd (II) biosorption by different algal biomasses was affected by different conditions such as biomass particle size, pH, initial metal concentration, biosorbent dose, temperature, agitation speed 137
and time. The maximum Cd (II) biosorption efficiency of Chlorella vulgaris, Ulva lactuca, Ulva fasciata and Pterocladia capillacea biomasses were obtained by using 0.125 mm particle size. The optimum conditions for Ulva fasciata for maximum biosorption capacity were at pH 4, initial Cd (II) concentration was 20 mg/ L, biomass dosage was 0.06 g/ 50 ml metal solution, temperature was at 30 ͦC, agitation speed was 250 rpm and agitation time was 30 minutes.
The optimum conditions for maximum bio sorption capacity for Pterocladia capillaceous were at pH 7, initial Cd (II) concentration was 30 mg/ L, biomass dosage was 0.08 g/ 50 ml metal solution, temperature was at 30 ͦC, agitation speed was 250 rpm and agitation time was 30 minutes.
The optimum conditions for maximum biosorption capacity for Chlorella vulgaris, were at pH 6, initial Cd (II) concentration was 75 mg / L, biomass dosage was 0.08 g/ 50 ml metal solution, temperature was at 25 P C, agitation speed was 250 rpm and agitation time was
30 minutes.
The optimum conditions for maximum biosorption capacity for Ulva lactuca, were at pH 7, initial Cd (II) concentration was 30 mg/ L, biomass dosage was 0.1 g / 50 ml metal solution, temperature was at 20 PC, agitation speed was 200 rpm and agitation time was 30
minutes.
6- The maximum Cd (II) biosorption efficiencies which were obtained under optimum conditions for each alga were 98.607, 95.860, 95.667 and 91.923% for Chlorella vulgaris, Ulva fasciata, Ulva lactuca and Pterocladia capillacea, respectively. 138
7- Different chemical and physical pretreatment methods were used to enhance the biosorption efficiency and capacity by different algal biomasses. Among these methods, acetic acid pretreated Chlorella vulgaris and Ulva lactuca were found to be effective whereas autoclaved pretreated Ulva fasciata and Pterocladia capillacea were found to be effective as compared with heat dried biomasses. The biosorption efficiencies of acetic acid pretreated Chlorella vulgaris and Ulva lactuca were 99.346 and 99.203%, respectively. Also, the biosorption efficiencies of autoclaved pretreated Ulva fasciata and Pterocladia capillacea were 99.727 and 96.047%, respectively.
8- Different weights of pretreated Chlorella vulgaris, Ulva fasciata, Pterocladia capillacea and Ulva lactuca biomasses were immobilized into Ca- alginate and the formed algal beads were tested for their ability to absorb cadmium from aqueous solution. The results showed that the highest biosorption efficiencies were obtained by using 0.025, 0.05, 0.1 and 0.15 g for Chlorella vulgaris, Ulva fasciata, Pterocladia capillacea and Ulva lactuca, respectively as compared with a control (beads only).
9- Fourier Transform infrared analysis for dry (unloaded and loaded) algal biomasses and pretreated (unloaded and loaded) algal biomasses suggested that hydroxyl, amide with hydrogen bond and carbonyl stretching in carboxyl groups played an important role in Cd (II) ions biosorption.
10-Analyzing the morphology of calcium alginate beads showed the porosity of their surface.
11- Scanning electron microscopy elucidated the absorption of Cd (II) ions by immobilized pretreated Chlorella vulgaris, Ulva fasciata, Pterocladia capillacea and Ulva lactuca biomasses as these 139
biomasses had morphological changed such as irregular surface and shrinking after biosorption process.
12- Finally, the Cd (II) biosorption was also confirmed by EDX analysis which showed the presence of cadmium ion signal at 3.1 Kev after biosorption process.