Insights into the adsorption mechanism of malachite green on Mn7SiO12 synthesized using manganese acetate and sodium silicate

Synthetic dye pollution, particularly from cationic dyes such as Malachite Green (MG), was recognized as a serious risk to both the environment and human health owing to its toxic nature and durability. To provide a high-performance and easily prepared adsorbent, a template-free hydrothermal route was developed for the synthesis of Mn 7 SiO 12 (HMS) with Na 2 SiO 3 9H 2 O and Mn(CH 3 COO) 2 ·4H 2 O serving as precursor materials. HMS possessed a large specific surface area of 530.16 m 2 /g and exhibited a strong affinity toward MG, enabling rapid adsorption of 683.79 mg/g within 5 min. Analysis of equilibrium and kinetic data confirmed that MG removal was governed by monolayer adsorption accompanied by a chemisorption-controlled rate process. Zeta potential measurements further revealed that HMS remained negatively charged over a wide pH range, which facilitated the selective capture of cationic dye molecules. FTIR characterization, combined with mesopore structural features, indicated that MG adsorption was primarily dominated by electrostatic attraction, hydrogen bonding, and mesopore confinement. With its straightforward synthesis and excellent adsorption performance, HMS was identified as a potential material for practical applications in dye-contaminated wastewater. • Template-free hydrothermal synthesis of Mn 7 SiO 12 (HMS) using Na 2 SiO 3 9H 2 O and Mn(CH 3 COO) 2 ·4H 2 O as precursors. • HMS exhibited a high specific surface area of 530.16 m 2 /g and rapidly adsorbed 683.79 mg/g of Malachite Green within 5 minutes. • Adsorption mechanism dominated by monolayer chemisorption, driven by electrostatic attraction, hydrogen bonding, and mesopore confinement. • The adsorption of Malachite Green on HMS followed the Langmuir model and pseudo-second-order kinetics.