Microwave promoted graft copolymerization of poly (ethylacrylate) onto k-carrageenan for removal of selected heavy metal ions from aqueous solution
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Date
2023
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The University of Dodoma
Abstract
Microwave promoted graft copolymerization of poly (ethylacrylate) onto k-carrageenan in the presence of a redox pair (potassium persulfate/ascorbic acid) led to the formation of a novel copolymer. By varying the reaction conditions such as the microwave power, reaction time, concentration of k-carrageenan, concentration of ethylacrylate, concentration of ascorbic acid and potassium persulfate concentration, copolymer samples of different grafting percentages were obtained. The copolymer sample with the highest grafting percentage was subjected to FT-IR, SEM, TGA and XRD analyses. The copolymer sample with the highest percentage of grafting was evaluated for its adsorption of Ni(II) and Cd(II) from an aqueous solution by performing batch experiments. Various adsorption parameters which include; contact time, pH, initial metal ion concentration, temperature, electrolyte strength and adsorbent dosage were varied to obtain the optimum conditions for the adsorption of metal ions. The copolymer sample was found to have high adsorption percentage at pH 8 (for Cd(II)) and pH 7 for Ni(II), temperature 35 oC { for both Cd(II) and Ni(II)}, optimum initial metal ion concentration was 100 mgL-1 and contact time of 180 min for both metal ions using 100 mg adsorbent dosage. The adsorption data obtained was studied using both Langmuir and Freundlich isotherm models. The adsorption data for both metal ions fitted with both isotherm models but a better fit was obtained with Langmuir isotherm model for both Cd(II) and Ni(II). This indicates that the copolymer surface active binding sites are heterogeneous in nature with different mechanisms of adsorption involved. Maximum adsorption capacity obtained using Langmuir isotherm model was 308.6 mgg-1 for cadmium ions and 305.8 mgg-1 for nickel ions. The adsorption of both metal ions followed pseudo second order kinetic model. The positive ΔH values endorsed the adsorption process to be endothermic in nature. The negative values of ΔG indicate the spontaneity of the adsorption process while the positive ΔS values showed that the adsorption of metal ions proceeded with increased randomness at the surface of the copolymer. High recovery percentage of the metal ions from the adsorbent indicate that the copolymer could be used for more adsorption cycles.
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Moses, M. (2023). Microwave promoted graft copolymerization of poly (ethylacrylate) onto k-carrageenan for removal of selected heavy metal ions from aqueous solution, (Master's Dissertation) The University of Dodoma.