Date of Defense
22-4-2025 1:00 PM
Location
F1 Building , Room 1117
Document Type
Thesis Defense
Degree Name
Master of Science in Water Resources
College
College of Engineering
Department
Civil and Environmental Engineering
First Advisor
Dr. Mohamed Hamouda
Keywords
Geopolymer; Taguchi method, TOPSIS, fly ash, slag, sorption, performance evaluation, solution characteristics, operational conditions.
Abstract
Reducing the levels of heavy metals in water is crucial, given their severe environmental and health impacts. Various methods exist for heavy metals removal. Yet, they mostly come with multiple drawbacks, such as costly treatments and limited efficiency. Previous studies have found geopolymer to be a promising sorbent because it is synthesized using by-product materials, making it an eco-friendly and economically sustainable alternative. Limited studies explored the sorption potential of fly ash-slag blended geopolymers; none examined the effect of mix design factors synergically on sorption, mechanical properties, and durability, and few considered solution characteristics and operating conditions simultaneously. Therefore, this thesis aims to develop and evaluate a fly ash-slag blended geopolymer sorbent for heavy metals removal from wastewater under varying conditions. The work was implemented through two main phases. In the first phase, an initial study was conducted to design 16 geopolymer mixes and select the optimum mix. In phase two, the impact of various parameters on the lead (Pb2+) uptake capacity of the selected optimum geopolymer mix was examined. In phase one, single and binary fly ash and slag blends were utilized as the binding material. The geopolymer composite was activated using either sodium hydroxide solely or in combination with sodium silicate. The Taguchi method was employed to design geopolymer mixes, having four factors, each with four levels of variation. These factors included the fly ash-to-slag ratio (FA), binder content (BC), the molarity of the sodium hydroxide solution (M), and the sodium silicate-to-sodium hydroxide ratio (SS/SH). The performance of the geopolymer sorbent was rigorously assessed against a comprehensive set of responses categorized into synthesis and performance criteria. The TOPSIS methodology was applied to aggregate the response criteria and determine the optimal mix for superior performance. A sensitivity analysis was performed to study the sensitivity of the results to the weights assigned for each criterion. In this phase, the results showed that the optimum mix consisted of an FA of 33%, BC of 1050 kg/m3, M of 10, and SS/SH of 3. Phase two investigated the impact of various parameters on the Pb2+ uptake capacity of the selected optimal geopolymer mix. These parameters include changes in solution characteristics and variations in operational conditions. Furthermore, the impact of introducing a foaming agent to the optimum mix was examined. The results demonstrated that the removal efficiency increases with increasing geopolymer dosage, contact time, temperature, and the decrease of geopolymer particle size and Pb2+ initial concentration. Moreover, it has been observed that adding a foaming agent to the geopolymer mix enhances the removal efficiency. The optimum removal efficiency was obtained at a final pH of 5. The kinetic data were found to fit the pseudo-second-order kinetic model. Also, the sorption isotherm study indicated that the experimental data showed a high nonlinearity, and the Langmuir model fits the data better than the Freundlich model. This study demonstrated the potential of using geopolymer as a sorbent in removing heavy metals from water, addressing a critical environmental concern with great implications for practical applications. Future studies should focus on investigating the performance of geopolymer composites in large-scale productions and industrial real-life wastewater instead of synthetic wastewater. Additionally, further exploration into the valorization and regeneration of geopolymer composites and sustainable final disposal strategies should be performed. Moreover, expanding the environmental and cost-benefit analyses conducted in this study by including a life cycle assessment to evaluate the geopolymer performance as a sorbent compared to traditional sorbents is recommended.
Included in
DESIGN AND EVALUATION OF GEOPOLYMER COMPOSITE AS A POTENTIAL SORBENT OF HEAVY METALS FROM WATER
F1 Building , Room 1117
Reducing the levels of heavy metals in water is crucial, given their severe environmental and health impacts. Various methods exist for heavy metals removal. Yet, they mostly come with multiple drawbacks, such as costly treatments and limited efficiency. Previous studies have found geopolymer to be a promising sorbent because it is synthesized using by-product materials, making it an eco-friendly and economically sustainable alternative. Limited studies explored the sorption potential of fly ash-slag blended geopolymers; none examined the effect of mix design factors synergically on sorption, mechanical properties, and durability, and few considered solution characteristics and operating conditions simultaneously. Therefore, this thesis aims to develop and evaluate a fly ash-slag blended geopolymer sorbent for heavy metals removal from wastewater under varying conditions. The work was implemented through two main phases. In the first phase, an initial study was conducted to design 16 geopolymer mixes and select the optimum mix. In phase two, the impact of various parameters on the lead (Pb2+) uptake capacity of the selected optimum geopolymer mix was examined. In phase one, single and binary fly ash and slag blends were utilized as the binding material. The geopolymer composite was activated using either sodium hydroxide solely or in combination with sodium silicate. The Taguchi method was employed to design geopolymer mixes, having four factors, each with four levels of variation. These factors included the fly ash-to-slag ratio (FA), binder content (BC), the molarity of the sodium hydroxide solution (M), and the sodium silicate-to-sodium hydroxide ratio (SS/SH). The performance of the geopolymer sorbent was rigorously assessed against a comprehensive set of responses categorized into synthesis and performance criteria. The TOPSIS methodology was applied to aggregate the response criteria and determine the optimal mix for superior performance. A sensitivity analysis was performed to study the sensitivity of the results to the weights assigned for each criterion. In this phase, the results showed that the optimum mix consisted of an FA of 33%, BC of 1050 kg/m3, M of 10, and SS/SH of 3. Phase two investigated the impact of various parameters on the Pb2+ uptake capacity of the selected optimal geopolymer mix. These parameters include changes in solution characteristics and variations in operational conditions. Furthermore, the impact of introducing a foaming agent to the optimum mix was examined. The results demonstrated that the removal efficiency increases with increasing geopolymer dosage, contact time, temperature, and the decrease of geopolymer particle size and Pb2+ initial concentration. Moreover, it has been observed that adding a foaming agent to the geopolymer mix enhances the removal efficiency. The optimum removal efficiency was obtained at a final pH of 5. The kinetic data were found to fit the pseudo-second-order kinetic model. Also, the sorption isotherm study indicated that the experimental data showed a high nonlinearity, and the Langmuir model fits the data better than the Freundlich model. This study demonstrated the potential of using geopolymer as a sorbent in removing heavy metals from water, addressing a critical environmental concern with great implications for practical applications. Future studies should focus on investigating the performance of geopolymer composites in large-scale productions and industrial real-life wastewater instead of synthetic wastewater. Additionally, further exploration into the valorization and regeneration of geopolymer composites and sustainable final disposal strategies should be performed. Moreover, expanding the environmental and cost-benefit analyses conducted in this study by including a life cycle assessment to evaluate the geopolymer performance as a sorbent compared to traditional sorbents is recommended.