Coal-Based Fertilizer Helps Clean Lead-Contaminated Soil and Releases Nutrients

Jenn Hoskins
11th August, 2024

Coal-Based Fertilizer Helps Clean Lead-Contaminated Soil and Releases Nutrients

Image Source: Natural Science News, 2024

Key Findings

  • Researchers from Taiyuan University of Technology found that coal slime-based silica fertilizer (CSF) can improve soil quality and reduce lead contamination
  • CSF increases the availability of essential nutrients like silicon, calcium, and potassium for plants
  • In lead-contaminated soil, CSF reduces the bioavailability of lead and enhances plant growth, increasing biomass and nutrient levels
High-ash coal slime-based silica fertilizer (CSF) has emerged as a promising solution for both the coal industry and agriculture. Researchers from Taiyuan University of Technology, China, have investigated the potential of CSF to provide essential mineral nutrients and mitigate lead (Pb) contamination in soil[1]. This study highlights the performance and mechanisms of CSF, which primarily contains potassium tobermorite and potassium silicate, in improving soil quality and ensuring sustainable agricultural practices. The study conducted by Taiyuan University of Technology focused on several key aspects of CSF's effectiveness. Leaching experiments revealed that low-crystalline muscovite was the only crystalline phase present during CSF etching. The silicon (Si), calcium (Ca), and potassium (K) in CSF showed significant solubility in citric acid, indicating their availability for plant uptake. Soil cultivation and planting trials demonstrated CSF's ability to neutralize soil acidity, enhance available soil Si and K, and increase exchangeable Ca content. Additionally, CSF reduced the bioavailability of Pb, decreasing exchangeable Pb by 19-75% and carbonate-bound Pb by 6-18%, while increasing residual Pb content. The impact of CSF on plant growth was also significant. In Pb-contaminated soil treated with 0.4% CSF, the Pb content in Chinese cabbage (Brassica rapa) was reduced by 25%. Moreover, plant biomass, Ca, and K levels increased by 37%, 36%, and 4%, respectively. Soil pH also rose by 0.58, and residual Pb content increased by 5%. The dominant form of Pb in CSF-treated soils was lead silicate, which is more stable than other Pb compounds like lead carbonate and lead sulfate. First-principle calculations confirmed that Pb3Si2O7, formed by CSF passivation, had greater stability in the soil compared to PbCO3 and PbSO4, with cohesion energies of -1.98 eV, -1.38 eV, and -1.41 eV, respectively. This study builds on previous research and provides a comprehensive understanding of CSF's potential in soil remediation and agricultural enhancement. For instance, a survey conducted in Ulaanbaatar, Mongolia, highlighted the issue of metal pollution in urban soils, particularly the elevated levels of arsenic (As) and Pb[2]. The sources of this pollution were identified as coal combustion in power plants and the use of leaded fuel. The findings of the current study suggest that CSF could be an effective measure to mitigate Pb contamination in such urban environments. Furthermore, the concept of using silicate materials for soil improvement and CO2 capture has been explored in earlier studies[3]. The addition of crushed silicate rocks to croplands has been proposed as a strategy to enhance soil fertility, improve crop production, and sequester CO2. The current study's findings on the solubility and availability of Si, Ca, and K in CSF align with these earlier suggestions, reinforcing the idea that silicate-based amendments can offer multiple environmental benefits. Additionally, research on Si/Al-based adsorbents for capturing heavy metals in incineration flue gases has shown that materials like kaolinite and montmorillonite have strong adsorption capacities for Pb and Cd[4]. The current study's focus on the formation of stable lead silicate compounds in soil further supports the effectiveness of silicate-based materials in immobilizing heavy metals and reducing their bioavailability. In summary, the research conducted by Taiyuan University of Technology demonstrates the promising application of coal slime mineral fertilizers for soil improvement and lead passivation. By providing essential nutrients and stabilizing Pb in soil, CSF offers a sustainable solution for enhancing agricultural productivity and mitigating metal contamination. The study's findings contribute to a growing body of evidence supporting the use of silicate-based materials for environmental remediation and sustainable agriculture.

AgricultureEnvironmentSustainability

References

Main Study

1) Performance of coal slime-based silicon fertilizer in simulating lead-contaminated soil: Heavy metal solidification and multi-nutrient release characteristics.

Published 8th August, 2024

https://doi.org/10.1016/j.jhazmat.2024.135453

Related Studies

2) Assessment of metals contamination of soils in Ulaanbaatar, Mongolia.

https://doi.org/10.1016/j.jhazmat.2010.08.106

3) Farming with crops and rocks to address global climate, food and soil security.

https://doi.org/10.1038/s41477-018-0108-y

4) Experimental and theoretical studies on the adsorption characteristics of Si/Al-based adsorbents for lead and cadmium in incineration flue gas.

https://doi.org/10.1016/j.scitotenv.2022.159895


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