Details

Autor(en) / Beteiligte

• El-Eswed, Bassam
• Dawoud, Jamal N.
• Mahmoud, Wadah F.
• Abu Salha, Yousef

Titel

Stabilization/Solidification of Wastes Containing Oxyanionic Metals: Reactions of Alkali-Activated Aluminosilicate Binders with Chromium, Arsenic, and Antimony in Comparison with Zinc

Ist Teil von

• Water, air, and soil pollution, 2022-09, Vol.233 (9), Article 367

Ort / Verlag

Cham: Springer International Publishing

Erscheinungsjahr

2022

Quelle

Alma/SFX Local Collection

Beschreibungen/Notizen

• During the last decade, alkali-activated aluminosilicates (fly ash, metakaolin, or blast furnace slag) or geopolymers have been investigated for their ability to immobilize wastes containing highly soluble oxyanionic metals of chromium (Cr), arsenic (As), and antimony (Sb). Effective stabilization of these metal anions was perceived as a challenging issue since they are not liable for precipitation or balancing the negatively charged Al tetrahedra of geopolymer. Moreover, the question about the possibility of covalent bonding of these metals to the geopolymeric aluminosilicate framework was never settled down. In the first part of the present work, the condensation reactions of oxyanionic Cr, As, and Sb species with Si were investigated using density-functional theory (B3LYP) in comparison with the reaction of Zn (cationic heavy metal) with Si and taking the reaction between Al and Si as the basic geopolymerization reaction. These calculations showed that the reaction of Si with Zn and Al species is much more favored (Δ G  =  − 67.107 and − 179.728 kJ/mol, respectively) than that of Si with Cr, As, and Sb species (Δ G  =  − 6.452, − 3.456, − 8.581 kJ/mol, respectively). For experimental verification of these results, reaction products of 30 wt% of metal salts (K 2 Cr 2 O 7 , K 2 CrO 4 , NaAsO 2 , and ZnCl 2 ) and alkali-activated metakaolin were investigated using FTIR, XRD, and SEM techniques. The results indicated that all these salts did not affect geopolymerization characters, while ZnCl 2 did. It can be concluded that wastes containing oxyanionic metals may represent a threat to our environmental even after their immobilization in geopolymer since they do not exhibit chemical bonding. However, the theoretical calculations showed that the highly alkaline or Na + -rich medium used in geopolymer preparation, which is usually thought to induce dissolution of aluminosilicate source, facilitates condensation reaction of silicate with aluminate, chromate, and arsenite species.