The fate of Cd during the replacement of Cd-bearing calcite by calcium phosphate minerals. (1st January 2023)

• Record Type: Journal Article
• Authors: Guo, Jianan; Wu, Shijun; Zhang, Xiaohang; Xie, Hong; Chen, Fanrong; Yang, Yongqiang; Zhu, Runliang
• Is Part Of: Environmental pollution. Volume 316(2023)part 1
• Publication Date: 2023-01-01
• Subjects: Cadmium -- Mineral replacement -- Calcite -- Brushite -- Hydroxylapatite; AMD Acid mine drainage -- Cd Cadmium -- CaP Calcium phosphate -- DCPD Dicalcium phosphate dehydrate -- EDS Energy dispersive X-ray spectroscopy -- EXAFS Extended X-ray absorption fine structure spectroscopy -- HAP Hydroxylapatite -- HM Heavy metal -- IARC International agency for research on cancer -- ICDD International centre for diffraction data -- OCP Octacalcium phosphate -- XRD X-ray diffraction -- PTEs Potentially toxic elements -- SEM Scanning electron microscope.; Pollution -- Periodicals; Pollution -- Environmental aspects -- Periodicals; Environmental Pollution -- Periodicals; Pollution -- Périodiques; Pollution -- Aspect de l'environnement -- Périodiques; Pollution -- Effets physiologiques -- Périodiques; Pollution; Pollution -- Environmental aspects; Periodicals; Electronic journals; 363.73
• DOI: 10.1016/j.envpol.2022.120491
• Languages: English
• ISSNs: 0269-7491

Abstract

Abstract: Carbonate-bound speciation is a critical sink of potentially toxic elements (PTEs) like cadmium (Cd) in soil and sediment. In a phosphate-rich environment, carbonate minerals could be replaced by phosphate minerals such as dicalcium phosphate dihydrate (DCPD, also known as brushite), octacalcium phosphate (OCP), and hydroxylapatite (HAP). Currently, it is unclear the migration and fate of PTEs during the replacement of PTEs-bearing carbonates by HAP and related intermediate minerals. Therefore, we synthesized Cd-bearing calcite by the coprecipitation method and converted it to DCPD, OCP, and HAP to investigate the redistribution and fate of Cd. The results showed that Cd incorporation in calcite significantly inhibited their replacement by DCPD and OCP, respectively. 1.26% of Cd in calcite was released into the solution when DCPD replaced calcite, and subsequently, most of the released Cd was recaptured by OCP. Significantly, the released Cd was below 0.05‰ when all the solid converted to HAP. These results suggested that with the application of phosphate fertilizer in alkaline soil, the secondary calcium phosphate minerals could control the environmental behavior of Cd. Graphical abstract: Image 1 Highlights: Cd in the precursors acts as an inhibitor for calcite-DCPD and DCPD-OCP replacement. Secondary calcium phosphates inherited over 98% Cd in the precursor minerals. Calcite-HAP replacement at low temperatures released more Cd than at high temperatures. One-step replacement of calcite-HAP released more Cd than multi-step replacement. Cd-bearing DCPD has a higher Cd release risk than calcite and other calcium phosphates.