Scholarlink

<p>Coal gangue acid leaching residue (CG-alr) is a large solid waste generated during the extraction of aluminum-containing resources from coal gangue (CG), and its high-value-added resource utilization faces challenges. This study proposes a two-step strategy, which is high-temperature thermal alkali activation (1100&#xa0;°C&#xa0;and 0.5&#xa0;h) and low-temperature hydrothermal synthesis (95&#xa0;°C&#xa0;and 30&#xa0;h), to efficiently convert CG-alr into silicon–potassium compound fertilizer (SPCF) with a gradient structure. The system optimized three key parameters: KOH concentration, SiO<sub>2</sub>-to-K<sub>2</sub>O mass ratio, and reaction time. Under the optimal conditions (55% KOH concentrarion, SiO<sub>2</sub>:K<sub>2</sub>O=1:5, reaction time of 30&#xa0;h), a silicon conversion rate of 99.64% was achieved. X-ray diffraction (XRD) analysis confirmed that the product is mainly composed of layered potassium tetrasilicate (K<sub>2</sub>Si<sub>4</sub>O<sub>9</sub>), accompanied by a small amount of kalsilite (KAlSiO<sub>4</sub>). Scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (SEM–EDS) and X-ray photoelectron spectroscopy (XPS) revealed that for the first time, the unique gradient structure of SPCF particles: the surface is a water-soluble potassium-rich layer (K<sub>2</sub>CO<sub>3</sub>), and the bulk phase is a well-crystallized layered silicandate (K<sub>2</sub>Si<sub>4</sub>O<sub>9</sub>+KAlSiO<sub>4</sub>), which lays a theoretical foundation for the synergistic supply of potassium through “surface quick-acting &amp; bulk slow-release”. The environmental safety assessment shows that the heavy metal content in SPCF is below the detection limit and meets the national agricultural standards. This study not only provides a new approach for the efficient resource utilization of CG-alr but also reveals a gradient structure that provides a scientific basis for the development of new slow-release SPCF.</p> Graphical Abstract <p></p>

错误：搜索内容不能为空，请输入英文关键词
错误：关键词超出字数限制，请精简
高级检索

Green conversion of coal gangue acid leaching residue into a K2Si4O9 fertilizer material: a sustainable strategy for solid waste upcycling

  • 期刊论文

  • 发表日期：

    2026年5月26日

查看全文
  • Junli Zhang,
  • Zhumei Sun,
  • Yucen Gao,
  • Ying Li,
  • Rui Ma,
  • Yanfang Chai,
  • Haifang Wang

摘要

Coal gangue acid leaching residue (CG-alr) is a large solid waste generated during the extraction of aluminum-containing resources from coal gangue (CG), and its high-value-added resource utilization faces challenges. This study proposes a two-step strategy, which is high-temperature thermal alkali activation (1100 °C and 0.5 h) and low-temperature hydrothermal synthesis (95 °C and 30 h), to efficiently convert CG-alr into silicon–potassium compound fertilizer (SPCF) with a gradient structure. The system optimized three key parameters: KOH concentration, SiO2-to-K2O mass ratio, and reaction time. Under the optimal conditions (55% KOH concentrarion, SiO2:K2O=1:5, reaction time of 30 h), a silicon conversion rate of 99.64% was achieved. X-ray diffraction (XRD) analysis confirmed that the product is mainly composed of layered potassium tetrasilicate (K2Si4O9), accompanied by a small amount of kalsilite (KAlSiO4). Scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (SEM–EDS) and X-ray photoelectron spectroscopy (XPS) revealed that for the first time, the unique gradient structure of SPCF particles: the surface is a water-soluble potassium-rich layer (K2CO3), and the bulk phase is a well-crystallized layered silicandate (K2Si4O9+KAlSiO4), which lays a theoretical foundation for the synergistic supply of potassium through “surface quick-acting & bulk slow-release”. The environmental safety assessment shows that the heavy metal content in SPCF is below the detection limit and meets the national agricultural standards. This study not only provides a new approach for the efficient resource utilization of CG-alr but also reveals a gradient structure that provides a scientific basis for the development of new slow-release SPCF.

Graphical Abstract