2026-03-30
Dolomite has a theoretical decomposition temperature range of 730–900°C. Between 730 and 790°C, it decomposes into free MgO and CaCO₃, while CaCO₃ decomposes at around 900°C [2]. Based on the Ca/Mg ratio, dolomite can be classified into magnesitic dolomite (1.0–1.5), dolomite (1.5–1.7), micro-calcite dolomite (1.7–2.0), calcite dolomite (2.0–3.5), and pure dolomite (1.648) [1].
Following the efficient separation of calcium and magnesium, how to convert the separated calcium resources into high-value-added calcium carbonate products with controllable morphology has become a research focus in dolomite deep processing. Currently, through processes such as carbonization, ammonium leaching, and hydrochloric acid methods, high-purity calcium carbonate products with diverse morphologies—including cubic, spindle-like, whisker-like, and vaterite forms—can be prepared from dolomite.
The carbonization method produces lightweight (nano) calcium carbonate through a "calcination-carbonization" system. Further purification yields high-quality calcium carbonate products, while the filtrate is a recoverable Mg(HCO₃)₂ solution [2]. However, since both calcium hydroxide and magnesium hydroxide participate in carbonization during preparation, simultaneously obtaining calcium carbonate and magnesium hydroxide products remains challenging [4].
Yu Feng et al. [12] used a high-concentration refined dolomite solution as raw material to prepare aragonite-type calcium carbonate whiskers with a high aspect ratio via the carbonization method. The study investigated the effects of carbonization temperature, stirring rate, CO₂ flow rate, and aging time. The resulting calcium carbonate product achieved a yield of 95%, a whisker aspect ratio of 30–35, a whisker content of 99.7%, and a whiteness of 99.9%, with uniform distribution. Mechanism analysis indicated that Mg²⁺ inhibited the growth of calcite-type calcium carbonate and promoted the growth of aragonite-type calcium carbonate, preferentially along the (120) crystal plane.
The ammonium leaching method involves reacting ammonium salts with dolomite lime to obtain a calcium salt solution, followed by introducing CO₂ to produce calcium carbonate. This method is easy to operate, involves mild reactions, and yields high-purity calcium carbonate.
Fan Tianbo et al. [9] employed a modified Solvay ammonia-soda method using dolomite as raw material without any organic additives to prepare calcium carbonate with a high vaterite content under alkaline conditions. The resulting sample had a specific surface area of 32.653 m²/g and a pore size of 2.972 nm, providing favorable space for biomolecule loading. Mechanism analysis revealed that the NH₄⁺-NH₃ buffer system not only increased the supersaturation of calcium carbonate but also improved the solution environment, with trace amounts of Mg²⁺ promoting the formation of perfect crystal morphologies.
Jia Xiaohui et al. [8] achieved controlled synthesis of metastable vaterite and aragonite calcium carbonate in a CaCl₂-NH₃-CO₂ reaction system using the obtained calcium-rich digestion solution. The vaterite content reached 97.69%, with a specific surface area of 32.653 m²/g and an average pore size of 2.972 nm.
Wu Feng et al. [2] used dolomite as raw material, hydrochloric acid as the leaching agent, and Ca(OH)₂ and NaOH as pH regulators to prepare industrial-grade lightweight calcium carbonate via the carbonization method. The results showed that calcining dolomite at 900°C for 30 min produced lightly calcined dolomite with a CaO content of approximately 64.14%. Under optimized leaching conditions (solid-liquid ratio of 1:4, stirring at 20°C for 60 min, aging for 2.0 h, adjusting pulp pH to 1.0 with 3.0 mol/L hydrochloric acid, and stirring at 80°C for 30 min), the Ca²⁺ leaching rate reached 99.38%.
A staged pH adjustment process was used to remove iron and manganese ions. The filtrate was carbonized by passing CO₂ at a flow rate of 100 mL/min under a stirring speed of 800 r/min until the slurry pH reached 7.6. This yielded lightweight calcium carbonate with a median particle size D50 of 2.404 μm, an average purity of 99.04%, and an average whiteness of 98.76. Partially replacing NaOH with Ca(OH)₂ to adjust pH effectively reduced chemical costs.
By adjusting process conditions, calcium carbonate products with various morphologies can currently be prepared from dolomite:
Spindle-like: Wang Xin et al. [11] produced calcite-type lightweight CaCO₃ with a spindle-like shape, approximately 2 μm in length and 0.6 μm in width
Whisker-like: Yu Feng et al. [12] prepared aragonite-type calcium carbonate whiskers with an aspect ratio of 30–35; Wang Dongyi et al. [10] produced calcium carbonate whiskers with an aspect ratio of 20
Cubic-like: Deng Xiaoyang et al. [7] prepared cubic-like calcium carbonate crystals with an average particle size of 5–10 μm
Vaterite: Jia Xiaohui et al. [8] and Fan Tianbo et al. [9] prepared calcium carbonate with vaterite contents of 97.69% and well-defined morphologies, respectively
Fan Yuanyang et al. [5] conducted PVC addition experiments using the prepared calcium carbonate whisker product. The results showed that the PVC material achieved a maximum tensile strain of 225% and a maximum tensile stress of 13 MPa, indicating significantly enhanced toughness and providing strong support for practical application.
Fan Tianbo et al. [9] prepared high-vaterite-content calcium carbonate with a specific surface area of 32.653 m²/g and an average pore size of 2.972 nm, offering favorable structural characteristics for biomolecule loading.
Significant progress has been made in technologies for preparing calcium carbonate from dolomite. Under laboratory conditions, calcium carbonate purity can exceed 99%, with diverse product morphologies including cubic, spindle-like, whisker-like, and vaterite forms, characterized by uniform particle size and high whiteness. The carbonization method, ammonium leaching method, and hydrochloric acid method each offer distinct features, allowing selection of the appropriate process route based on target product morphology and purity requirements. With continued advances in understanding morphology control mechanisms and optimization of process conditions, the industrial application prospects for producing high-value-added calcium carbonate products from dolomite are promising.
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