Preparation of eco-friendly one-part geopolymers from gold mine tailings by alkaline hydrothermal activation

• Published in: Journal of cleaner production Vol. 298; p. 126806
• Main Authors: Liu, Qing, Li, Xiaochang, Cui, Mingyao, Wang, Junxiang, Lyu, Xianjun
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 20-05-2021
• Subjects: Alkaline hydrothermal activation; C(N)-A-S-H gel; Gold mine tailings; One-part geopolymer; Sodium aluminosilicate; C(N)-A-S-H gel; Gold mine tailings; One-part geopolymer; Alkaline hydrothermal activation; Sodium aluminosilicate
• ISSN: 0959-6526; 1879-1786
• DOI: 10.1016/j.jclepro.2021.126806

Environmental and economic issues caused by several tailings storages have attracted worldwide attention; therefore, these urgently need to be solved cost-effectively. In this study, gold mine tailings rich in Si and Al oxides were activated by an alkaline hydrothermal method for use as precursors to produce a one-part geopolymer. The results indicated that the crystalline mineral phases in tailings were partially or completely decomposed by alkaline hydrothermal activation. However, this decomposition depended heavily on the alkali content, temperature, and time. The decomposed tailings were converted to the amorphous sodium aluminosilicate reactant, thereby making tailings a reactive starting material. Subsequently, the one-part geopolymer was prepared from the activated tailings and slag by just adding water without adding any extra alkaline activator. By adding 60 wt% of slag, the one-part geopolymer with an optimum compressive strength value of 33.5 MPa at 28 days was obtained. This was much higher than that of the control sample containing raw tailings without any pretreatment. The high strength could have been because of the amorphous sodium aluminosilicate formed in the activated tailings that could dissolve in water to create alkaline conditions, which could effectively activate the pozzolanic activity of the slag. The main geopolymerization product was the glassy calcium-sodium aluminosilicate hydrate (C(N)-A-S-H) gel, which acted as a binder to closely connect the residual solid particles and form a hardened geopolymer material.
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•NaOH hydrothermally activated tailings were used as a reactive precursor.•Mineral phases in tailings were converted into the amorphous sodium aluminosilicate.•Soluble activation product could create alkaline conditions for the slag activation.•Hardened one-part geopolymer was prepared due to the formation of C(N)-A-S-H gel.