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<p>This study aimed to access the effectiveness of silicon (Si)-enriched biochars, derived from rice husks and wood chips through KOH and K<sub>2</sub>SiO<sub>3</sub> modification, in enhancing cadmium (Cd) stabilization in solution and paddy soil.&#xa0;The study employed isothermal and kinetic sorption experiments and soil incubation experiments to test the hypothesis that Si-enriched biochar can enhance Cd sorption, reduce bioavailability, and increase soil available Si content.&#xa0;Sorption experiments demonstrated that the KOH- and K<sub>2</sub>SiO<sub>3</sub>-modified biochars facilitated Cd sorption in solution primarily through the formation of CdCO<sub>3</sub>, with limited evidence of Cd-Si complexes. Soil incubation experiments showed that applying these modified biochars significantly reduced Cd bioavailability and mobility in paddy soil by decreasing the Cd concentration in soil pore water and exchangeable Cd, while increasing the residual Cd content. Additionally, the modified biochar increased the CaCl<sub>2</sub>-extractable Si content in the soil. However, the impact of increased soil Si content on Cd stabilization appeared to be less significant compared to the elevation of soil pH caused by biochar addition. Although the rice husks-derived biochar had a higher soil CaCl<sub>2</sub>-extractable Si content than the wood chips-derived biochar, it did not exhibit superior Cd stabilization.&#xa0;The modified Si-enriched biochars effectively stabilize Cd in paddy soils, primarily by increasing soil pH upon biochar application, which leads to reduced Cd bioavailability and increased Cd retention in soils, whereas the Si component contributed less to this immobilization compared to the pH effect.<!--Query ID="Q1" Text="Journal standard instruction requires an unstructured abstract; however, the abstract given in the manuscript was structured. Hence, the sub-headings were deleted and the paragraph was merged into one. Please check if the action made was correct and appropriate." Resolved="yes"--></p>

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Silicon-Enriched Biochar for Cadmium Stabilization in Paddy Soils: Sorption Mechanisms and Bioavailability Reduction

  • 期刊论文

  • 发表日期：

    2025年10月22日

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  • Qingyang Zeng,
  • Duoji Wu,
  • Qi Luo,
  • Jingxuan Zhang,
  • Lian Zhong,
  • Xiao Yan,
  • Jianfu Wu,
  • Zongqiang Wei

摘要

This study aimed to access the effectiveness of silicon (Si)-enriched biochars, derived from rice husks and wood chips through KOH and K2SiO3 modification, in enhancing cadmium (Cd) stabilization in solution and paddy soil. The study employed isothermal and kinetic sorption experiments and soil incubation experiments to test the hypothesis that Si-enriched biochar can enhance Cd sorption, reduce bioavailability, and increase soil available Si content. Sorption experiments demonstrated that the KOH- and K2SiO3-modified biochars facilitated Cd sorption in solution primarily through the formation of CdCO3, with limited evidence of Cd-Si complexes. Soil incubation experiments showed that applying these modified biochars significantly reduced Cd bioavailability and mobility in paddy soil by decreasing the Cd concentration in soil pore water and exchangeable Cd, while increasing the residual Cd content. Additionally, the modified biochar increased the CaCl2-extractable Si content in the soil. However, the impact of increased soil Si content on Cd stabilization appeared to be less significant compared to the elevation of soil pH caused by biochar addition. Although the rice husks-derived biochar had a higher soil CaCl2-extractable Si content than the wood chips-derived biochar, it did not exhibit superior Cd stabilization. The modified Si-enriched biochars effectively stabilize Cd in paddy soils, primarily by increasing soil pH upon biochar application, which leads to reduced Cd bioavailability and increased Cd retention in soils, whereas the Si component contributed less to this immobilization compared to the pH effect.