CO2-assisted ‘Weathering’ of Steel Slag-Derived Calcium Silicate Hydrate: A Generalized Strategy for Recycling Noble Metals and Constructing SiO2-Based Nanocomposites

• Published in: Journal of colloid and interface science Vol. 622; pp. 1008 - 1019
• Main Authors: Sun, Lingmin, Wu, Junshu, Wang, Jinshu, Yang, Yunfei, Zhou, Wenyuan, Yang, Yilong, Du, Yucheng, Hu, Peng, Li, Yongli, Li, Hongyi
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 15.09.2022
• Subjects: adsorbents; Adsorption; calcium; calcium silicate; Calcium silicate hydrate; carbon dioxide; carbonation; Decalcification; hazardous waste; nanocomposites; nanocrystals; nanopores; pollution; Recycle; steel; toxicity; Decalcification; Calcium silicate hydrate; Adsorption; Recycle
• ISSN: 0021-9797; 1095-7103; 1095-7103
• DOI: 10.1016/j.jcis.2022.04.182

[Display omitted] •1. Amorphous calcium silicate hydrate (CSH) is prepared using steel slag.•2. CSH shows superior adsorption properties towards metal ions.•3. CO2 decalcification of spent CSH adsorbent is realized via carbonation process.•4. Noble metals are recycled by the adsorption-decalcification process.•5. The decalcification shows a wide adaptability for constructing SiO2-based composites. The spent adsorbent loaded by toxic metals is a solid hazardous waste which could cause significant secondary pollution due to potential possible additional release of metal ions. Therefore, the main subject is direct reutilization of spent adsorbents which can further economically and realistically offer new features, like recycling metal adsorbed, or formation of functional SiO2-based nanocomposites. The nanoporous structure and negative surface charges enable steel slag-derived amorphous calcium silicate hydrate (CSH) to retain effectively the incoming metal ions (e. g. Au3+, Ag+, Pd2+, Fe3+, Co2+, Ni2+, Cu2+, Zn2+, Ce3+, Y3+, and Gd3+) by chemisorption. Sparked by natural carbonation ‘weathering’, which ultimately sequestrates atmospheric CO2 by alkaline silicate minerals to leach calcium from mineral matrix, the decalcification reactions of metal-bearing CSH results in successful recovery of noble metals (Ag, Au, Pd) upon NaOH etching the resultant SiO2 support. Further, SiO2-based heterostructures, containing nanocrystalline metals (e. g. Au0, Ag0, Pd0, Fe0, Co0, Ni0, Cu0, and Zn0) or rare-earth oxides (e. g. CeO2, Y2O3, and Gd2O3), are formed after reduction in H2/Ar (5 vol% H2) flow, which is also very important for the multipurpose immobilization of diverse hybrid materials on SiO2 surface (e. g. Cu0-Ag0@SiO2, Cu0-CeO2@SiO2, and Cu0-Ag0-CeO2@SiO2).