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Fabrication and Characterization of a Hydrogel Absorbent for the Simultaneous Removal of Dye and Heavy Ion Metal From Water

Ahmadi Bonakdar, Arezoo | 2025

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 58066 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Pircheraghi, Gholamreza
  7. Abstract:
  8. In recent years, environmental concerns regarding the removal of pollutants such as organic dyes and heavy metals from water sources have increased significantly. In this regard, hydrogels based on natural polymers have attracted considerable attention for water treatment applications due to their biodegradability, low toxicity, and desirable stability. Hydrogel beads, with their highly porous structure, provide high adsorption capacity and rapid adsorption kinetics. In this study, hydrogel beads based on alginate and polyvinyl alcohol (PVA) polymers were fabricated as mixed and hybrid composites in the presence of zeolitic imidazolate framework (ZIF-8) and diatomite fillers. For this purpose, ZIF-8 nanoparticles were synthesized using a wet chemical method, and the ZIF-8-diatomite hybrid was prepared via in-situ synthesis. Structural characterization, swelling percentage, mechanical stability, and the individual and simultaneous adsorption of Cu²⁺ ions and methylene blue dye were investigated. The evaluations revealed that the specific surface area of ZIF-8 was 2246.9 m²/g, diatomite had 6.2 m²/g, and the ZIF-8-diatomite hybrid exhibited 36.3 m²/g. Scanning electron microscopy (SEM) images confirmed the presence of ZIF-8 on the disk-like plates of diatomite in the hybrid sample. The mixed and hybrid ZIF-8-diatomite composite hydrogel beads maintained high swelling percentages (above 100%) while improving mechanical stability compared to pure polymer beads. In individual adsorption tests, the hybrid hydrogel beads demonstrated the highest methylene blue removal (95%) due to the significant enhancement in surface area and ion-exchange properties from hybridization, as well as the higher weight fraction of diatomite. For copper adsorption, the mixed composite beads performed better due to the uniform distribution of particles and the higher weight fraction of ZIF-8. Under simultaneous presence of methylene blue and copper ions, diatomite and hybrid beads showed better dye adsorption (80% and 69%, respectively). However, the hybrid hydrogel beads achieved comparable adsorption efficiency (91%) to pure polymer beads by preserving more active sites on the polymer matrix and creating new active sites in the hybridized particles. The adsorption kinetics of the selected hybrid sample followed a pseudo-first-order model for methylene blue and a pseudo-second-order model for Cu²⁺ ions. The results of this study demonstrate that developing alginate/PVA-based hydrogel beads reinforced with hybrid nanoparticles can effectively remove organic dyes and heavy metal ions from water
  9. Keywords:
  10. Methylene Blue ; Water Treatment ; Purification ; Zeolite Imidazolate Framework ; Copper (II) Ion ; Diatomite ; Simultaneous Adsorption ; Hydrogel Beads ; Heavy Metals Removal

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