Eco − utilization of silicon − rich lye: Synthesis of amorphous calcium silicate hydrate and its application for recovering heavy metals

• Published in: Separation and purification technology Vol. 282; p. 120092
• Main Authors: Qi, Fang, Zhu, Ganyu, Zhang, Yimin, Hou, Xinjuan, Li, Shaopeng, Yang, Chennian, Zhang, Jianbo, Li, Huiquan
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.02.2022
• Subjects: Calcium silicate hydrate; Causticization; Heavy metals; Recovery; Silicon−rich lye; Silicon−rich lye; Calcium silicate hydrate; Causticization; Recovery; Heavy metals
• ISSN: 1383-5866; 1873-3794
• DOI: 10.1016/j.seppur.2021.120092

•Nano-crystalline C − S − H is synthesized from SRL by mild causticization and crystallization strategy.•High-efficiency separation of Na/Si components and alkali recycling can be collaboratively achieved from SRL.•C-S-H presents amorphous honeycomb porous structure and activity ions exchange sites.•Amorphous C − S − H exhibits quickly recovery performances to heavy metals Cu (II), Zn (II), and Cr (III).•Heavy metal recovery mechanisms are cations exchange and interlayer bonding proved by DFT simulation. During sustainable high-value utilization of coal-based solid wastes, a kind of characteristic silicon-rich lye (SRL) generated, and its comprehensive recovery and recycling remains an important subject. Through a simple and facile strategy of mild caustic-crystallization method, SRL was favorably utilized through calcium silicate hydrate (C − S − H) synthesis with silicon conversion efficiency over 97.33%. The micro-morphology of C − S − H presented a typical “honeybee hive”−like porous structure with numerous exchangeable activity cations and combination sites in the silicate chain structure. The amorphous C − S − H products possessed marvelous recovery abilities for typical heavy metals as Cu (II), Zn (II), and Cr (III) in industrial wastewater with recovery efficiency all above 99.6% in quite a short period. The recovery mechanism of C − S − H toward heavy metals was revealed as calcium ions exchange and interlayer structure combination with SiO4 and AlO4 tetrahedron through the analysis of characterization technologies and DFT simulation calculation. C − S − H synthesized in SRL contributes to achieving valuable resources conversion and recycling for guiding sustainable development of coal-based solid waste comprehensive utilization.