Xianquan Wang

Mesoporous silica materials have important application prospects in the field of radioactive Cs⁺ adsorption and separation due to their ordered channel structures and high specific surface area. Understanding the microscopic adsorption and diffusion mechanism of Cs⁺ in mesoporous silica channels is key to designing efficient adsorbents. In this study; molecular dynamics simulations were employed to construct mesoporous silica models with channel widths of 2 nm; 4 nm; and 6 nm. The density distribution; radial distribution function (RDF); hydrogen-bonding network; and mean square displacement (MSD) of Cs⁺, NO₃⁻, and H₂O in the channels were systematically investigated. The results show that Cs⁺ mainly adsorbs near the channel interface. When the channel width is 2 nm; Cs⁺ is completely captured at the interface; while as the channel size increases; Cs⁺ gradually appears in the center of the channel; indicating weakened adsorption capacity. RDF analysis reveals that approximately 60% of Cs⁺ are within 0.25 nm of the surface –OH groups; forming inner-sphere complexes; while the rest are outer-sphere complexes. The RDF peak of NO₃⁻ appears at 0.4 nm; confirming its indirect adsorption via electrostatic interaction with Cs⁺. Hydrogen-bonding network analysis shows that the average number of hydrogen bonds per water molecule at equilibrium is about 3.45; which slightly decreases with increasing channel size. MSD results indicate that Cs⁺ has the weakest diffusion capacity; which increases with channel width. This study reveals the regulation mechanism of channel size on Cs⁺ adsorption and diffusion at the atomic level; providing theoretical guidance for the channel engineering design of mesoporous silica-based adsorbents.

To address the environmental threats posed by antibiotic residues in water and the engineering bottlenecks of traditional powder photocatalysts—such as high cost, complicated preparation processes—a novel Bi₂WO₆-doped geopolymer composite photocatalytic material was successfully constructed through a facile and green synthesis strategy, utilizing low-cost and readily available geopolymers as the supporting matrix. The adsorption and degradation performance of this material toward tetracycline hydrochloride (TC), a typical antibiotic in aquatic environments, was systematically evaluated under visible-light irradiation. Experimental results demonstrate that the composite system exhibits a synergistic effect of adsorption enrichment by geopolymers and in situ photodegradation by Bi₂WO₆. Under the optimized conditions of merely 4% Bi₂WO₆ loading, catalyst dosage of 1 g/L, and an initial pH of 8.0, the degradation efficiency of TC reached 82.7% after 300 min of visible-light illumination. Even in real and complex water matrices, the material maintained a stable microstructure and highly efficient targeted removal capability. Radical scavenging experiments confirmed that the highly oxidative photogenerated holes (h⁺) generated by Bi₂WO₆ and the superoxide radicals (O²⁻) derived from the reduction of dissolved oxygen are the primary active species governing the efficient decomposition of TC. This study not only ameliorates the agglomeration tendency of pure-phase Bi₂WO₆ but also, by virtue of its inexpensive raw materials, facile synthesis process, and excellent adaptability to the weakly alkaline environments of actual water sources, provides a highly feasible strategy for the future low-cost, large-scale remediation of realistic aquatic environments and the treatment of industrial antibiotic wastewater.