Bringing natural attapulgite into functional materials with broad applications

Attapulgite (also named as palygorskite) is a natural 2:1 layered-chain clay mineral. It is a rare non-metallic mineral and only found in a few countries in the world so far. Owing to the one-dimensional nanorod-like morphology (20~70 nm in the diameter), unique regular nanochannels (0.37 nm × 0.64 nm), structurally negative charges and abundant surface hydroxyl groups, it is irreplaceable to produce stable organic/inorganic hybrid materials (e.g., Maya blue pigments) based on the confinement effect of the nanochannels in the family of clay minerals. Its functional application has been gradually expanded from traditional fields such as activated clay, desiccants, thickening agents, soil remediation, nanofiller and fertilizer additives to high-end fields of energy storage, biomedical materials, functional coatings, healthy breeding, catalyst, etc. However, it has been recognized that the structural disaggregation of rod crystal bundles is the foundation for the high-end utilizations of attapugite. The traditional process is to down-size the mineral by mechanical milling accompanied with the damage of the rod crystal structure. According to the crystal structure and physicochemical property of attapulgite derived from different geological origins, Prof. Aiqin Wang’s team at Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, China first employed high-pressure homogenization technique to disaggregate the crystal bundles of attapulgite, which was found that the complete disaggregation of crystal bundles of attapulgite occurred after being homogenized at 30 MPa, and no obvious changes were observed for the length and crystal structure of attapulgite fibers, while the specific surface area, colloidal viscosity and suspension stability greatly increased. The introduction of high-pressure homogenization process completed the transformation of attapulgite from natural mineral material to applicable nanomaterial without structural damage. More importantly, the disaggregation of crystal bundles and surface modification could be simultaneously achieved to design functional materials by the one-step high-pressure homogenization process. However, the high-pressure homogenization process is difficult to be continuously conducted in a large scale due to the quick-wearing and high-cost of special pressurizing and sealing equipment of a high-pressure homogenizer. Thus, an energy-efficient and scale-up ultrasonic process was developed to disaggregate the aggregates of attapulgite into individual nanorods. By this process, the individually dispersed attapulgite nanorods were produced by sonication at 20 kHz, 2000 W and 30 °C for 5 minutes. This industrial ultrasonic technology could also be used to approach the effective exfoliation of two-dimensional montmorillonite and synchronous disaggregation/exfoliation of naturally mixed-dimensional clay composed of one-dimensional attapulgite and other two-dimensional clay minerals. Furthermore, natural clay or clay minerals exhibit different colors in some levels, and their color is related to the associated minerals (e.g., hematite), the adsorbed organic matters and/or the isomorphic substitutions of coloring metal ions, which directly influenced the physicochemical properties and the high-value applications. Therefore, the structural whitening is also a crucial procedure for the industrial application of clay minerals. In the case of attapulgite, different structural whitening methods have been systematically explored from a chemical perspective, including solvothermal reduction whitening, hydrothermal acid-leaching whitening, atmospheric acid-leaching whitening, semi-dried acid-leaching whitening and microwave-assisted solid-phase whitening. Among these processes, semi-dried acid-leaching whitening has achieved a continuous industrial-level production of gradient structural whitening of naturally mottled mixed-dimensional attapulgite clay to provide high-quality raw and auxiliary materials for the relevant functional applications, which also offers a technical approach for the cleaner industrial whitening of other clay minerals. The functional applications of attapulgite have been increasingly attractive since it was discovered. The applied performances of attapulgite can be summarized into four categories: adsorption, colloid, carrier and reinforcing, which are determined by the geological origins and mineralogical properties of attapulgite. To meet the major demands of application market, attapulgite-based porous adsorption materials, mycotoxin adsorbents, antibacterial nanocomposites, mineral composite nanozyme, Maya-like blue pigments, eco-friendly inorganic hybrid pigments, multifunctional superhydrophobic coatings and lithium battery separator have been designed and fabricated. Most of them have been transferred into industrialized production and served in to the national economy. During this practice, the development of green and cleaner preparation technology of functional mineral materials is one of the continuously pursued research directions, especially the mechanochemical method. From manual grinding with mortar and pestle to automated equipment of vibratory mill, planetary mill and screw extruder, the batch and continuous mechanochemical methods are investigated for the cleaner manufacturing of attapulgite-based functional materials, while organic solvents and synthetic surfactants are displaced by water and plant-derived surfactants, respectively. Meanwhile, the resource utilization of tailings and recycled mining wastes also were studied to establish an all-component comprehensive utilization system of attapulgite without the discharging of industrial wastes. Although a remarkable achievement in the research and uses of attapulgite has been made, the studies on attapulgite only experienced 50 years since 1976 in China, and there is still many challenges need to be resolved based on the interdisciplinary researches, such as artificial intelligence empowerment, layering mining and homogenization of raw ores, intelligent advanced equipment, multicomponent in-situ transformation technology, comprehensive resource utilization ratio, etc.

Bringing natural attapulgite into functional materials with broad applications

Authored by: Bin Mu, Aiqin Wang,Yushen Lu, Yongfeng Zhu, Jiang Xu, Yuru Kang, Fangfang Yang, Aiping Hui, Bowen Li

To view the past issues of the UCA magazine you must be a member of SME/UCA.

DOE’s Office of Critical Minerals and Energy Innovation Announces $29.5 Million for National Laboratory Mining Projects

AI-ready digital twin for mineral processing plants: Maximizing copper production with dynamic water management

Roundtable discussion on mine finance

DOE’s Office of Critical Minerals and Energy Innovation Announces $29.5 Million for National Laboratory Mining Projects

AI-ready digital twin for mineral processing plants: Maximizing copper production with dynamic water management

Roundtable discussion on mine finance

To view the past issues of the UCA magazine you must be a member of SME/UCA.

Rhyolite Ridge releases its 2026 report

Insights on public acceptance of major European lithium mine projects

Related Articles

How GeologicAI uses high-resolution data to reduce uncertainty in mining

AI-ready digital twin for mineral processing plants: Maximizing copper production with dynamic water management

Roundtable discussion on mine finance

Bubbles and particles for fun and profit

DOE’s Office of Critical Minerals and Energy Innovation Announces $29.5 Million for National Laboratory Mining Projects

AI-ready digital twin for mineral processing plants: Maximizing copper production with dynamic water management

Roundtable discussion on mine finance

DOE’s Office of Critical Minerals and Energy Innovation Announces $29.5 Million for National Laboratory Mining Projects

AI-ready digital twin for mineral processing plants: Maximizing copper production with dynamic water management

Roundtable discussion on mine finance

Use Single Sign On