Key Takeaways & Executive Findings
- •• Hydroxamic acid adsorption on malachite is highly anisotropic across different exposed crystal surfaces, with the (100) surface showing the greatest competitive advantage over water molecules. • Surface energies of malachite crystal faces follow the order (201)>(100)>(110)>(001)>(010)>(201), revealing significant anisotropy in surface stability. • Water molecules hinder hydroxamic acid adsorption to varying degrees, with minimal interference on the (100) surface, making it the most favorable for flotation separation. • First-principle DFT calculations provide theoretical guidance for the precise design of flotation reagents and optimization of mineral surface interfaces to enhance copper oxide ore recovery.
Abstract
The intricate grinding process exposes various cleavage surfaces of mineral particles. This paper systematically investigates the structural characteristics of exposed malachite crystal surfaces and the adsorption behavior and mechanism of hydroxamic acid and water molecules using first-principle density functional theory. The study reveals anisotropic surface energies among crystal surfaces, ranked as (201)>(100)>(110)>(001)>(010)>(201). The adsorption of hydroxamic acid and water molecules on malachite surfaces also exhibited anisotropy. The difference in adsorption strength between hydroxamic acid and water molecules on the six exposed surfaces followed the order of (110)>(100)>(010)>(001)>(201)>(201), and the resistance of water molecules to the adsorption of hydroxamic acid on the six exposed surfaces was (110)>(201)>(010)>(201)>(001)>(100). It indicates that the reagent exhibits a strong competitive advantage in adsorption on the (100) surface, and the hindrance of water molecules to reagent adsorption is relatively small, which is favorable for flotation. This study provides theoretical references and innovative insights for the precise design of flotation reagents, as well as for the meticulous optimization of mineral surface interfaces, with the objective of enhancing flotation separation.
1. Introduction
Copper is one of the most widely used non-ferrous metals, a sulfurophilic element primarily found in sulfide ore and oxidized ore. With the depletion of high-quality copper sulfide resources, the development and utilization of oxidized ore resources have gained increasing attention [1]. Currently, there are two strategies for the flotation of copper oxide minerals. The first strategy is surface sulfidization flotation, which uses a sulfidizing agent to treat the surface of copper oxide minerals, forming a sulfide layer similar to that of sulfide minerals. This process allows for the use of sulfide mineral flotation reagents for flotation collection [2 −4]. The second strategy is direct flotation, where an oxidized mineral collector is used for the flotation of copper oxide minerals [5−7]. The (201) surface of malachite is the main cleavage surface, which has been studied extensively [8−10]. However, the random nature of the grinding process exposes malachite to different crystal surfaces. As a result, it is important to systematically study the behavior and adsorption differences of flotation reagents and water molecules on these exposed crystal surfaces.
A comprehensive investigation into the diverse surface properties and adsorption behaviors of mineral crystal surfaces is essential for understanding the interfacial interactions among minerals. The complex and random grinding process will cause mineral particles to expose different cleavage surfaces, so the active particle distribution, broken bond and surface energy of different crystal faces will be different, which will
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ZHANG Chen-yang, LIU Si-yuan, JIANG Wan-yao, ZHANG Hong-liang, WU Lin-lin, RAO Xin, SUN Wei, ZOU You, PEI Yong (2025). Insights into the anisotropy in hydroxamic acid adsorption on different exposed crystal surfaces of malachite from first-principle calculations. Journal of Central South University. https://doi.org/10.1007/s11771-025-5991-6
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Frequently Asked Questions
What is the main finding about malachite crystal surfaces and adsorption?
The study reveals that both surface energy and hydroxamic acid adsorption on malachite are anisotropic across different exposed crystal faces. The (100) surface exhibits the strongest competitive adsorption advantage for hydroxamic acid over water, making it the most favorable for flotation.
How does water molecules affect the adsorption of hydroxamic acid on malachite?
Water molecules interfere with hydroxamic acid adsorption to different extents depending on the crystal surface. On the (100) surface, this hindrance is relatively small, which enhances the reagent's adsorption efficiency and is beneficial for flotation separation.
What method was used in this study?
The researchers employed first-principle density functional theory (DFT) calculations to systematically investigate the structural characteristics and adsorption behavior of hydroxamic acid and water molecules on six exposed malachite crystal surfaces.
Why is it important to study different crystal surfaces of malachite?
Grinding processes randomly expose various cleavage surfaces of mineral particles. Understanding the anisotropic adsorption behavior on these surfaces is crucial for optimizing flotation reagent design and improving the efficiency of copper oxide ore recovery.
What are the practical applications of this research?
The findings provide theoretical references for the precise design of flotation reagents and for the meticulous optimization of mineral surface interfaces, ultimately aiming to enhance flotation separation in copper oxide mineral processing.
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