1. Overview of Attapulgite
Attapulgite (Mg₅Si₈O₂₀(OH)₂·4H₂O) is a clay mineral with a nanorod crystal morphology. Its length is about 0.5-5 μm, the diameter is about 20-70 nm, with regular nanoscale channels of 0.37 nm × 0.64 nm. It is a hydrous magnesium aluminum silicate clay mineral with a layered chain structure. Epic Powder Machinery specializes in jet pulverization technology. Jet Mill MQW40 by Epic Powder ensures the efficient processing of attapulgite powder pulverization.
Attapulgite possesses a large specific surface area, surface charge, and cation exchange capacity. This makes it widely used in the preparation of adsorbents, adhesives, desiccants, catalysts, food additives, and functional composites. It plays an irreplaceable role as a base material in fields such as chemical engineering, catalysis, environmental protection, and new materials. Attapulgite pulverization is a crucial pretreatment step aimed at increasing its specific surface area to enhance adsorption capacity.
Basic structural parameters, scanning electron microscope (SEM) images.
Transmission electron microscope (TEM) images.
2. Physicochemical Properties and Surface Modification of Attapulgite
2.1 Adsorption
The significant channel cross-sectional area and unique crystal structure of attapulgite contribute to its adsorption properties. Its adsorption mechanisms mainly include physical and chemical adsorption. Physical adsorption occurs through van der Waals forces. While chemical adsorption forms covalent bonds when Si-O-Si oxygen bridges break, allowing for the attachment of adsorption molecules. Surface modification of attapulgite can enhance its adsorption performance.
Attapulgite effectively removes impurities such as metals, sulfur, and asphalt from petroleum hydrocarbons, as well as color and harmful components from fats, mineral oils, and vegetable oils. It also shows excellent adsorption capabilities for heavy metals (e.g., Cr³⁺, Hg²⁺). It’s widely used as a deodorant, filtering aid, purifier, and decolorizer in the environmental protection industry. The process of attapulgite pulverization typically involves mechanical crushing and grinding to achieve the desired particle size distribution.
2.2 Catalysis
As a naturally occurring nanomaterial with a nano-channel structure, attapulgite features nanoparticles and a high aspect ratio. It provides numerous nanosized channels and active centers. Therefore, it can function both as a catalyst and as a catalyst support.
2.3 Colloidal and Suspensive Properties
Under shear forces, attapulgite can disperse into a chaotic three-dimensional network structure in water and other media. At lower concentrations, attapulgite colloids exhibit high viscosity and maintain a high degree of suspension stability in saline solutions, alongside good salt resistance, alkali resistance, thermal stability, and rheological properties. Thus, it is used as a circulating drilling mud in oil fields and as an additive in coatings.
2.4 Other Properties
Attapulgite has a very large specific surface area and some ion exchange capacity, making it widely utilized as a desiccant, moisture-absorbing agent, adsorbent, catalyst support, and antimicrobial agent. Due to its special needle-like and fibrous crystal structure, it is non-toxic, odorless, non-irritating, chemically stable, easy to dry, and has low hardness, making attapulgite an excellent filler for polymer materials. Effective attapulgite pulverization can partially break its rod-like crystal bundles, thereby exposing more active sites.
2.5 Modification of Attapulgite
The unique structure and properties of attapulgite offer significant application value. However, its crystal structure limits its adsorption performance. Therefore, after purifying attapulgite, surface modification is necessary to further increase its specific surface area, surface charge, and channel size to enhance its adsorption and support properties.
Modification Methods for Attapulgite
| Modification Method | Primary Principle | Application Direction |
| Thermal Treatment | Attapulgite loses adsorbed, zeolitic, crystalline, and structural water upon heating; specific surface area increases, nanochannel diameter expands, enhancing adsorption performance. | Filler materials, heat treatment processing |
| Acid Modification | Acid treatment replaces cations in the structure; octahedral sheet cations dissolve, replaced by hydrogen ions; generates broken bonds, increasing specific surface area and activity. | Water treatment, decolorizing agents |
| Alkali Modification | Alkali treatment alters the crystal phase structure, causing transformation; metal cations are corroded, increasing surface negative charge and active sites; nanochannels widen, specific surface area increases. | Water treatment, ion adsorption |
| Salt Modification | Salt treatment increases exchangeable cations, alters surface charge, increases internal nanochannels, and enhances adsorption. | Water treatment, ion adsorption, soil purification |
| Combined Modification | Combined use of acid, alkali, salt, etc., to improve adsorption performance. | Water treatment, carrier materials, soil purification |
| Organic Modification | Organic treatment forms an organic monolayer on the surface, imparting organic-inorganic dual characteristics, altering hydrophilicity/lipophilicity, and expanding application range. | Surfactants, coupling agents |
Currently, the primary modification processes include thermal modification, inorganic modification (acid, alkali, salt modification), and organic modification. Among these, acid modification is the most common. Many researchers employ acid treatment on attapulgite, while research on salt modification is relatively limited. Salt modification is more environmentally friendly than acid modification and could be explored further in the future due to its low carbon footprint. Organic modification also has clear advantages over inorganic methods, with surfactants and coupling agents being the most commonly used. Most studies still focus on single modification methods, which are now quite mature. Therefore, considering combined modifications that leverage the benefits of multiple methods could improve modification effectiveness. The efficiency of subsequent modifications, such as acid or heat treatment, is highly dependent on the degree of attapulgite pulverization.
3. Applications and Research Progress of Attapulgite
3.1 Drug Carrier
Due to attapulgite’s large specific surface area and strong adsorption abilities, it is widely used as a carrier for high-concentration pesticide powders. As a matrix for granules. Particularly for liquid pesticides, processing into high-concentration powders or wettable powders using attapulgite as a carrier can adjust the flowability and dispersibility of the formulation. The rheological and thickening properties of attapulgite make it widely used as a thickening agent in pesticide suspensions.
Preparation Process for High-Performance Pesticide Carrier from Attapulgite
A two-step deactivation method yields high-performance clay products. After inert modification, the surface acidity of attapulgite increases from pKa < 1.8 to pKa > 3.3, with little change to the specific surface area. The modified attapulgite can be used as a pesticide carrier. Stability tests indicate that its performance is comparable to that of silica carriers. While maintaining the strong adsorption properties of attapulgite, thus addressing issues such as narrow application scope and short storage life.
In addition to smart slow-release pesticides, attapulgite is also used in the production of medications for human consumption. It serves as an adsorbent, suspending agent, and excipient in various drugs. National standards exist for attapulgite, and it is recognized as a safe pharmaceutical material.
3.2 Catalytic Carrier Materials
With its porous structure, attapulgite accelerates reaction rates when reactants are adsorbed in its internal channels. As reactants diffuse out of these channels, the crystal lattice of attapulgite remains intact, making it an ideal load-type catalytic carrier material. High-catalytic-performance metals, metal oxides, and metal salts can be uniformly loaded onto attapulgite, facilitating the full exposure of active centers and the transfer of active substances, significantly enhancing catalytic activity. Currently, attapulgite is widely used in catalytic nitrogen fixation, degradation of pollutants in water, removal of atmospheric pollutants, and oxygen evolution reactions. In composite material preparation, controlled attapulgite pulverization ensures its uniform dispersion within the polymer matrix.
3.3 Energy Storage Carrier Materials
Attapulgite itself is non-conductive and cannot be directly used as an electrochemical energy storage material. However, existing technologies such as templating and melt diffusion methods can introduce electroactive materials into attapulgite, allowing its application in the field of electrochemical energy storage. Commercial lithium-ion battery anode materials primarily consist of carbon-based materials, which have low specific capacity. Attapulgite can be reduced through aluminum thermite reactions to produce attapulgite-derived silicon (SiATP), which can replace carbon as an anode material in batteries.
3.4 Colloidal Materials
When dispersed in water or other low-concentration solutions, attapulgite forms individual rod crystals or smaller bundles, which then intertwine under van der Waals forces to create a network structure, resulting in a high-viscosity suspension. This demonstrates excellent colloidal properties, making attapulgite an important component in thickeners, drilling muds, and coating applications.
3.5 Beverage Clarifying Agents and Cosmetic Additives
Food Industry: Attapulgite acts as a decolorizing and clarifying agent, achieving over 70% decolorization and 90% clarification for edible oils and beverages.
Cosmetic Industry: It functions in UV protection, oil control, and skin repair products.
3.6 Environmental Adsorbent Materials
Currently, it actively removes heavy metals, organic dyes, antibiotics, and other pollutants from wastewater. Recent exploratory studies have also investigated its use for adsorbing or enriching radioactive materials in the nuclear industry. With significant progress in modification research, the types of pollutants that attapulgite can adsorb are continuously expanding. Attapulgite pulverization enhances the removal efficiency of pollutants by creating more accessible pores and channels for diffusion.
Main Adsorption Mechanisms for Pollutants
| Pollutant Type | Metal Ions | Dye Molecules | Non-metallic Ions | Radioactive Metal Ions |
| Main Adsorption Mechanisms | Electrostatic interaction, Chemical complexation, Cation exchange, Surface precipitation | Pore adsorption, Electrostatic interaction, Hydrogen bonding, Chemical complexation | Pore adsorption, Electrostatic interaction | Electrostatic interaction, Chemical complexation |
3.7 Antimicrobial Materials
Although attapulgite does not have high antibacterial activity, its pore structure and surface activity can load active antibacterial agents to create composite antibacterial materials. On one hand, attapulgite can physically adsorb bacteria, affecting cell membrane permeability and inhibiting normal material exchange with the environment. On the other hand, the rod-like crystals of attapulgite exhibit a needle-puncture effect. It can damage bacterial cell walls and membranes, rendering bacteria inactive.
Construction of Antibacterial Metal Composites: Attapulgite has regular nanoscale channels and surface functional groups. Due to the isomorphous substitution phenomena during its formation, attapulgite carries permanent negative charges and forms numerous defects or residual bonds within its structure. This demonstrates strong adsorption capabilities for pigment molecules, heavy metal ions, dyes, and antibiotics.
Attapulgite carrying dodecyltrimethylammonium bromide extends antibacterial efficacy with low biotoxicity.
The bismuth vanadate/attapulgite photocatalyst degrades antibiotics 1.4 times faster than pure bismuth vanadate.
In addition to the aforementioned antibacterial materials, attapulgite shows good application potential in composite scaffold materials and wound healing materials. However, the actual application of attapulgite in biomedicine is still relatively limited, necessitating the acceleration of the development of attapulgite-based medical products. Rapid hemostatic gauze utilizies attapulgite’s high adsorption capacity and orthopedic or dental substitutes that leverage its antibacterial properties and biocompatibility. In the feed industry, attapulgite pulverization is essential for achieving the fine particle size required for effective toxin adsorption and mixing uniformity.
3.8 Attapulgite Filling Materials
The unique fibrous morphology of attapulgite not only gives it the special properties of nanomaterials but also excellent filling capabilities. It makes it applicable in polymer reinforcement and papermaking. Unlike traditional fillers like calcium carbonate, kaolin, and talc widely used in papermaking, fibrous attapulgite exhibits better compatibility with plant fibers. In plastic processing, attapulgite’s filling performance is significantly superior to other inorganic fillers. It improves the mechanical, thermal, and crystallization properties of plastics. Optimizing the parameters of attapulgite pulverization, including time and energy input, is key to balancing production costs and performance enhancement.
3.9 Friction Materials
Phenolic resin (PF), as a typical thermosetting resin, is widely used in friction materials due to its high heat resistance, excellent mechanical properties, and good processing performance. However, the low toughness and high friction coefficient of pure PF limit its applications in solid lubrication. Molecular structure modification, rubber particle doping, and fiber reinforcement can optimize the tribological properties of PF composites. Research indicates that one-dimensional attapulgite (AT) nanofibers exhibit a significant synergistic enhancement effect when used in combination with high-modulus microfibers (CF, GF) in PF composites. When attapulgite makes up 20% of the mass fraction, the compressive strength of the multi-nano composite materials GF/AT/PF and CF/AT/PF exceeds 400 MPa. This demonstrates extremely high load-bearing capacity.
3.10 Animal Production Materials and Feed Additives
In animal production, attapulgite can be an adsorbent to capture heavy metals, mycotoxins, bacteria, and bacterial toxins, thereby maintaining the integrity of the animal intestinal mucosal barrier. Furthermore, both inorganic and organic modification treatments can enhance its biological activity, with modified attapulgite exhibiting good antibacterial properties. Studies have found that adding attapulgite to feed can enhance intestinal mucosal immunity and antioxidant functions. It can also regulate intestinal microbial balance, improve intestinal mucosal morphology, promote animal growth and development, and enhance production performance. Attapulgite can also effectively mitigate pathogen-induced damage to the animal intestinal barrier.
Given its numerous benefits, attapulgite can serve as a pellet binder, a carrier for trace elements, and an adsorbent for heavy metals in feed.
Functional Performance of Attapulgite in Feed
3.11 Lithium Battery Material Additives
In recent years, researchers have extensively explored clay minerals represented by attapulgite in the battery sector, discovering that attapulgite inhibits lithium dendrite growth, providing a new approach to the protection of lithium metal battery anodes.
Research has shown that loading attapulgite onto fiber membranes can be effective for lithium metal battery anode protection. Symmetrical batteries and lithium iron phosphate full batteries were assembled for electrochemical testing. Research indicates that fiber membranes containing attapulgite effectively suppress lithium dendrite growth. The a polarization voltage of only 83.2 mV after 500 hours of cycling at a deposition capacity of 1 mA·h/cm² and a current density of 2 mA/cm². The full battery with added attapulgite fiber membranes maintained a discharge capacity of 84.92 mA·h/g after 1,000 cycles at 1C rate.
Conclusie
In recent years, the unique rod structure and channel architecture of attapulgite have garnered attention for the precise and targeted construction of novel nanofunctional materials. These products are expected to meet application demands in adsorption, catalysis, and composite materials. As foundational and applied research continues to deepen, the application process of attapulgite in nanofunctional applications will advance. It promotes the high-end development of mineral functional materials and continuously enhancing product added value. This progress will drive the upgrade of the attapulgite industry chain and contribute to sustainable industrial development.
About Epic Powder
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