Substantial Copper (Cu 2+ ) Uptake by Metakaolin-Based Geopolymer and Its Resistance to Acid Leaching and Ion Exchange

• Published in: Polymers Vol. 15; no. 8; p. 1971
• Main Authors: Grba, Nenad, Grengg, Cyrill, Petronijević, Mirjana, Dietzel, Martin, Baldermann, Andre
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 21-04-2023; MDPI
• Subjects: Acid leaching; Acid resistance; Aluminosilicates; Aluminum; Aluminum silicates; Aquatic environment; Aqueous solutions; Cellulose acetate; Chemical precipitation; Chemical properties; Copper; Corrosion resistance; Efficiency; environmental protection; Environmental restoration; Experiments; Geopolymers; Granulation; green technology; Heavy metals; Ion exchange; Leaching; Metakaolin; metakaolin-based geopolymer; Sediments; Water treatment; Germany; Austria; copper; green technology; water treatment; metakaolin-based geopolymer; heavy metals; environmental protection
• ISSN: 2073-4360; 2073-4360
• DOI: 10.3390/polym15081971

Geopolymers are inorganic, chemically resistant aluminosilicate-based binding agents, which remove hazardous metal ions from exposed aqueous media. However, the removal efficiency of a given metal ion and the potential ion remobilization have to be assessed for individual geopolymers. Therefore, copper ions (Cu
) were removed by a granulated, metakaolin-based geopolymer (GP) in water matrices. Subsequent ion exchange and leaching tests were used to determine the mineralogical and chemical properties as well as the resistance of the Cu
-bearing GPs to corrosive aquatic environments. Experimental results indicate the pH of the reacted solutions to have a significant impact on the Cu
uptake systematics: the removal efficiency ranged from 34-91% at pH 4.1-5.7 up to ~100% at pH 11.1-12.4. This is equivalent to Cu
uptake capacities of up to 193 mg/g and 560 mg/g in acidic versus alkaline media. The uptake mechanism was governed by Cu
-substitution for alkalis in exchangeable GP sites and by co-precipitation of gerhardtite (Cu
(NO
)(OH)
) or tenorite (CuO) and spertiniite (Cu(OH)
). All Cu-GPs showed excellent resistance to ion exchange (Cu
release: 0-2.4%) and acid leaching (Cu
release: 0.2-0.7%), suggesting that tailored GPs have a high potential to immobilize Cu
ions from aquatic media.