Two-dimensional solid-state NMR spectroscopy investigations of surface precipitation of phosphate onto calcite

Jingzhao Wang; Chao Ren; Zhen Li; Wei Li

doi:10.1016/j.scitotenv.2023.164444

Two-dimensional solid-state NMR spectroscopy investigations of surface precipitation of phosphate onto calcite

Sci Total Environ. 2023 Sep 10:890:164444. doi: 10.1016/j.scitotenv.2023.164444. Epub 2023 May 24.

Authors

Jingzhao Wang¹, Chao Ren², Zhen Li³, Wei Li⁴

Affiliations

¹ Key Laboratory of Surficial Geochemistry, Ministry of Education, School of Earth Science and Engineering, Nanjing University, Nanjing, Jiangsu 210023, China; Frontiers Science Center for Critical Earth Material Cycling (FSC-CEMaC), Nanjing University, Nanjing, Jiangsu 210023, China.
² Key Laboratory of Surficial Geochemistry, Ministry of Education, School of Earth Science and Engineering, Nanjing University, Nanjing, Jiangsu 210023, China; School of Environmental and Biological Engineering, Nanjing University of Science and Technology, Nanjing, Jiangsu 210094, China; Frontiers Science Center for Critical Earth Material Cycling (FSC-CEMaC), Nanjing University, Nanjing, Jiangsu 210023, China.
³ College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing, Jiangsu 210095, China.
⁴ Key Laboratory of Surficial Geochemistry, Ministry of Education, School of Earth Science and Engineering, Nanjing University, Nanjing, Jiangsu 210023, China; Frontiers Science Center for Critical Earth Material Cycling (FSC-CEMaC), Nanjing University, Nanjing, Jiangsu 210023, China. Electronic address: liwei_isg@nju.edu.cn.

PMID: 37236482
DOI: 10.1016/j.scitotenv.2023.164444

Abstract

The interaction of phosphate with typical soil minerals is important for understanding P cycling in natural and agricultural systems. We investigated the mechanisms of kinetics of phosphate uptake onto calcite using solid-state NMR spectroscopy. At a low phosphate concentration of 0.5 mM, the ³¹P single-pulse solid-state NMR peak revealed the formation of amorphous calcium phosphate (ACP) within the initial 30 min, which transformed to carbonated hydroxyapatite (CHAP) after 12 d. At a high phosphate concentration (5 mM), the results showed transformation from ACP to OCP, later to brushite, and eventually to CHAP. The formation of brushite is further supported by ³¹P{¹H} heteronuclear correlation (HETCOR) spectra via a correlation of δ_P-31 = 1.7 ppm and the ¹H peak at δ_H-1 = 6.4 ppm, which denotes the structure water of brushite. Furthermore, ¹³C NMR directly revealed both A-type and B-type CHAP. Generally, this work provides a detailed understanding of the aging effect on the phase transition scale of phosphate surface precipitation onto calcite in soil environments.

Keywords: ACP; CHAP; HETCOR; OCP; Phosphorus; Solid-state NMR; Sorption.

MeSH terms

Calcium Carbonate*
Carbonates*
Durapatite
Magnetic Resonance Spectroscopy
Soil

Substances

calcium phosphate, dibasic, dihydrate
Calcium Carbonate
amorphous calcium phosphate
Carbonates
Durapatite
Soil