Comparative Study between Commercial Charcoal and Asphodelus ramosus Tuber Derived Activated Carbons for Adsorption of Heavy metals from Aqueous Solution
Date
2017-06-15
Authors
Mahameed, Abdullah
Journal Title
Journal ISSN
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Publisher
An-Najah National University
Abstract
In this project Asphodelus ramosus Tuber was subjected to several in-vitro investigations to show its antioxidant, and anti-obesity using different solvents for extract preparation . Activated carbon was prepared from this tuber tissues by different methods then to set up kinetic study of some heavy metals adsorption from aqueous solution onto this activated carbon to evaluate the power of this plant tubers to environmental purification from these harmful heavy metals and compared it with commercial activated carbon.
The results of phytochemical screening tests showed that Asphodelus ramosus tuber methanolic extract was rich in phytochemical compounds like Flavonoid, glycosides, phenols, alkaloids, proteins, carbohydrates, tannin while antioxidant activity evaluated by using 2, 2-diphenyl-1-picryl-hydrazyl-hydrate assay also showed that methanolic extract was the best one in its antioxidant activity with IC50=13.8µg/ml which is close to IC50= 2.08µg /ml for Trolox ( the standard reference compound).So these tubers can be a good candidate of manufacturing biological and pharmacological active pharmaceuticals, cosmeceuticals and nutraceuticals formulations as it has good antioxidant effect. On the other hand anti lipase investigation showed that the methanol extract had the least value of the half maximal inhibitory concentration IC50 which was 63.09 then aqueous extract with IC50 value =79.43, while higher values for IC50 were obtained for both acetone and n-hexane extracts which were 316 and 630 respectively. Comparing these results with orlistat IC50 which was 12.3 both acetone and n-hexane extracts seems to be not active as lipase enzyme inhibitors. while the methanol extract was the most potent one as natural anti-lipase inhibitor .
Adsorption capacity of AAC for heavy metals from aqueous solution was expressed using Freundlich and Langmuir models to study adsorption isotherm at equilibrium. In order to determine whether the adsorption process is chemical or physical, two kinetics models were used.
Results also showed that the activated carbon produced from Asphodelus ramosus tubers showed largest Surface area that determined by iodine number was 506.5mg/g using zinc chloride as activating agent.
Results showed that Percentage removal of all heavy metals Cr(III), Cu(II), pb(II)and Cd(II) increases with increasing in both temperature and pH value as optimum adsorption occur at 45ºC and pH=12 .
The effect of heavy metal concentration on adsorption by CAC and AAC has also been investigated in the range of ( 5-80 ppm) . The results indicated that the best adsorption capacity occur at low concentration as when 5ppm was used the %Removal reach 99.7%, 92.9%, 91.1% and 57.06% for pb(II), Cr(III), Cu(II) and Cd(II) respectively.
The equilibrium adsorption time for all investigated heavy metals was 7hr for both Asphodelus ramosus tuber and commercial activated carbon , but most of the adsorption attained within the first 30 min
Freundlich model describe adsorption isotherm of all screened heavy metals more efficiently onto AAC with n ranging between 1 to 10 that indicated favorable adsorption. This finding validated the assumption of multilayer physical adsorption process of heavy metal ions on activated carbon.