The Dissolution Behavior of Feldspar Minerals in Various Low-Molecular-Weight Organic Acids

Shao-Min Lin; Ya-Ling Yu; Ming-Feng Zhong; Huan Yang; Chen-Yang Zhang; Zhi-Jie Zhang; Yun-Ying Wu

doi:10.3390/ma16206704

The Dissolution Behavior of Feldspar Minerals in Various Low-Molecular-Weight Organic Acids

Materials (Basel). 2023 Oct 16;16(20):6704. doi: 10.3390/ma16206704.

Authors

Shao-Min Lin¹, Ya-Ling Yu¹, Ming-Feng Zhong², Huan Yang¹, Chen-Yang Zhang^{1

3}, Zhi-Jie Zhang², Yun-Ying Wu^{3

4}

Affiliations

¹ School of Materials Science and Engineering, Hanshan Normal University, Chaozhou 521041, China.
² School of Materials Science and Engineering, South China University of Technology, Guangzhou 510641, China.
³ Chaozhou Branch of Chemistry and Chemical Engineering Guangdong Laboratory, Chaozhou 521041, China.
⁴ Guangdong Chaoshan Institute of Higher Education and Technology, Chaozhou 521041, China.

Abstract

Feldspar is a high-abundance mineral in the earth's crust, and its natural weathering and dissolution processes are an important phenomenon on the earth's surface. This study focused on the dissolution behavior of silicon (Si) and aluminum (Al) in feldspar minerals (microcline and albite) when exposed to low-molecular-weight organic acids (LMWOAs). Various analytical techniques, including atomic absorption spectrophotometer, X-ray diffraction, scanning electron microscope, and Fourier-transform infrared spectroscopy, were employed to investigate these processes. The results revealed that the concentration of Si and Al released from alkali feldspar increased after treatment with LMWOAs, exhibiting non-stoichiometric dissolution. The Si/Al release ratio from feldspar deviated from the expected value of three. Among the LMWOAs tested, oxalic acid was found to be more effective in dissolving aluminum, while citric acid showed greater efficacy in dissolving silicon. Notably, the composite acid demonstrated the highest capacity for feldspar dissolution, with values of 538 μM (Si) and 287 µM (Al) after treatment for 720 h, respectively. The dissolution data for Si and Al in the organic acid solution was fittingly described by a first-order equation, with high correlation coefficients (R² ≥ 0.992). The characterization of feldspar powders indicated that the (040) crystal plane of feldspar was particularly susceptible to attack by organic acids. In the presence of these acids, the chemical bonds Si (Al)-O, Si-Si(Al), and O-Si(Al)-O shifted to higher wavenumbers. Additionally, the surface corrosion morphology of feldspar exhibited distinct nanostructures, which became more pronounced with increasing exposure time. It was also observed that the reactivity of feldspar increased over time. These findings provide valuable insights into the natural dissolution process of feldspar and offer a new perspective for the study of this phenomenon.

Keywords: crystal plane; dissolution; feldspar; low-molecular-weight organic acids; nanostructures.

Abstract

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