Abstract

Objective Using magnesite as the raw material, porous magnesium hydroxy silicate with excellent adsorption performance and large specific surface area is prepared to promote the high-value utilization of magnesite resources.

Methods Magnesite was converted into magnesium bicarbonate solution (Mg(HCO₃)₂) via calcination-hydration-carbonation process to serve as the magnesium source, while tetraethyl orthosilicate was used as the silicon source. Porous magnesium hydroxy silicate with a large specific surface area was then synthesized by combining the hydrothermal method with the calcination method. This study mainly investigated the effects of the molar ratio of silicon to magnesium, hydrothermal reaction time, hydrothermal temperature, and calcination time on the microstructure, specific surface area, and pore size distribution of the products. The microstructure and adsorption performance of the prepared products were characterized by means of XRD, SEM, BET, FTIR, XPS, and ICP-AES.

Results and Discussion Using magnesite as the raw material, magnesium bicarbonate solution prepared via the calcination-hydration-carbonation process was employed as the magnesium source, while tetraethyl orthosilicate served as the silicon source. Porous magnesium hydroxy silicate was synthesized using the hydrothermal method. When the molar ratio of silicon to magnesium was 2:1, the hydrothermal reaction time was 8 h, the hydrothermal temperature was 130 ℃, and magnesium hydroxy silicate product with a specific surface area of 630.36 m²/g was obtained. Among the synthesis parameters, the molar ratio of silicon to magnesium and the hydrothermal reaction time exerted the most significant effects on the specific surface area of the magnesium hydroxy silicate. During the reaction process, the magnesium silicate initially presented as bulk solids without obvious porous structures. With a gradual increase in the content of the silicon source, primary particles were observed to gradually emerge on the surface of the bulk magnesium silicate. As the hydrothermal time increased continuously, a highly developed porous network structure was finally formed. This phenomenon could be attributed to the more complete hydrolysis of tetraethyl orthosilicate resulting from the increased silicon source and extended hydrothermal time, which provided more silanol groups for the cross-linking reaction with magnesium ions and promoted the full assembly of the porous structure. In contrast, the hydrothermal temperature exerted a relatively significant influence on the product's aggregation state. When the hydrothermal temperature was appropriate， the product existed as bulk aggregates with well-defined pore channels and uniform particles. However, when the hydrothermal temperature was excessively high, the particles grew too fast, leading to their connection into sheet-like structures, the disappearance of pore channels, and a consequent decrease in specific surface area. The final product was identified as porous magnesium hydroxy silicate crystals with a granular accumulation structure. The calcination time also showed a notable impact on the specific surface area of the magnesium hydroxy silicate. The specific surface area reached a maximum value of 706.28 m²/g after 4 h of calcination, which was 10.7% higher than that of the uncalcined sample. Calcination could induce the removal of bound water molecules from the magnesium hydroxy silicate, thereby maintaining the pore channels while forming more mesoporous and microporous structures. However, excessively long calcination time might lead to pore channel collapse, resulting in structural damage and a subsequent decrease in specific surface area. Its formation process involved three stages: the hydrolysis of tetraethyl orthosilicate to generate cyclic polysilanol intermediates rich in silanol groups； the cross-linking assembly of ions from the magnesium bicarbonate solution with these intermediates into a layered framework via Si—O—Mg bonds; and the occupation of interlayer and surface sites by hydroxyl groups, which stabilized the structure and promoted pore formation, while subsequent calcination activation induced internal dehydration of the magnesium hydroxy silicate to form new pore channels. The product adsorbed heavy metal ions through complexation reactions, with the maximum adsorption capacities of 275, 245, and 258 mg/g for Cu²⁺, Cr³⁺, and Ni²⁺, respectively. The adsorption rate was fastest and the adsorption efficiency was highest within the first 5 min, after which the adsorption reached equilibrium. Meanwhile, the pseudo-first-order and pseudo-second-order kinetic models were employed to fit and analyze the adsorption data. The fitting results showed that the adsorption of the three heavy metal ions followed a chemical adsorption process, which was consistent with the previously proposed complexation reaction mechanism for heavy metal adsorption by porous magnesium hydroxy silicate.

Conclusion Porous magnesium hydroxy silicate prepared from magnesite possesses a high specific surface area and excellent adsorption performance, enabling its application in the field of heavy metal ion adsorption from polluted water. This study not only expands the methods for preparing magnesium silicate from mineral raw materials and supplements the specific reaction conditions, but also provides theoretical support and technical reference for the high-value utilization of magnesite resources and the development of efficient and low-cost heavy metal adsorption materials.

Keywords：magnesite; magnesium hydroxy silicate; porosint; high specific surface area; adsorption

Get Citation:JIANG Jiacun， WANG Yulian， ZHAO Jing， et al. Preparation and adsorption performance of porous magnesium hydroxy silicate with high specific surface area prepared from magnesite［J］. China Powder Science and Technology，2026，32（5）：1−16.

Received: 2026-01-05, Revised: 2026-02-20, Online: 2026-04-14.

DOI：10.13732/j.issn.1008-5548.2026.05.010

CLC No:P578.955；TQ424；TB4                         Type Code: A

Serial No:1008-5548（2026）05-0001-16