Effect of calcium ions on the interaction of alkaline minerals with dissolved organic matter: Implications for organic carbon sequestration in bauxite residue

• Published in: Plant and soil 2024-04, Vol.497 (1-2), p.79-91
• Main Authors: Xue, Shengguo, Zhang, Yufei, Jiang, Jun, Li, Feng, Chen, Chaorong, Guo, Xuyao, Chen, Qi, Zhu, Feng, Chen, Hualin, Wu, Yujun
• Format: Article
• Language: English
• Subjects: Adsorption; Agriculture; Atomic force microscopy; Bauxite; Bayer process; Biomedical and Life Sciences; Calcium; Calcium ions; Carbon sequestration; Chemical composition; Dissolved organic carbon; Dissolved organic matter; Ecology; Electrostatic properties; Emission analysis; Emission spectra; Excitation spectra; Fourier transforms; Functional groups; Immobilization; Infrared analysis; Infrared spectroscopy; Ions; Life Sciences; Minerals; Plant Physiology; Plant Sciences; Polysaccharides; Red mud; Research Article; Residues; Revegetation; Sodalite; Soil Science & Conservation; Spectrum analysis; Surface chemistry; Thermogravimetric analysis
• ISSN: 0032-079X; 1573-5036
• DOI: 10.1007/s11104-023-06009-3

Purpose The interaction of minerals and organic matter significantly affects the stability of organic carbon, which is key to the rehabilitation of bauxite residue. However, due to the microscopic structure of minerals and the chemical composition of dissolved organic matter (DOM), the interaction mechanism between alkaline minerals and DOM in the presence of calcium ions that are widely used as amendments is still poorly understood. Methods In this work, the mechanism of adsorption and immobilization of organic matter by sodalite and cancrinite in the presence of calcium ions was investigated at the microscopic scale, using Fourier transform infrared spectroscopy (FTIR), excitation-emission matrix fluorescence (EEM) spectra, thermogravimetric analysis (TG) and atomic force microscope (AFM). Results The calcium ions can act as bridges to connect the negative sites on the mineral surface with the polysaccharide functional groups of organic matter, thus promoting organic carbon sequestration via ligand exchange and/or electrostatic interactions. Furthermore, DOM located in the structure within the cancrinite surface may be better protected due to physical isolation. The 3D view of the interacted minerals-organic matter assemblages provided visual evidence that the adsorption sites distributed on the surface of cancrinite increased by the action of calcium ions, with different adsorption capacities of individual sites for DOM. Conclusions The calcium ions enhance the ability of alkaline minerals to trap dissolved organic carbon, and the work highlighted the significance of organo-mineral associations in the microscopic mineral structure for the organic carbon sequestration in the revegetation process of bauxite residue disposal areas.