Wensheng Zhang

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.

The uniaxial tensile properties of multi-scale fiber-reinforced cementitious material (MSFRCM) with steel and polyvinyl alcohol (PVA) fibers and calcium carbonate whisker (CW) were studied. The results showed that CW improved the uniaxial tensile stiffness, strength, peak strain, and toughness of the steel-PVA hybrid fiber-reinforced cementitious material. The CW not only played a role in the small deformation stage but also improved the load holding capacity and toughness of the hybrid fiber-reinforced cementitious material during the large deformation stage. Computational models to assess the uniaxial tensile strength and toughness of the MSFRCM were established. Microstructure observations showed that the steel and PVA fibers formed a weak interfacial transition zone (ITZ) due to the “wall effect.” The CW effectively optimized the structure of the ITZ of the steel and PVA fibers through physical and chemical effects, such as filling, bridging, improving Ca(OH)2 orientation, and chemical effects. The steel fibers, PVA fibers, and CW in the MSFRCM bridged cracks at the macro, mesoscopic, and microscopic levels, respectively. As a result, we observed a fiber chain effect that improved the positive hybrid effect between the multi-scale fibers.

Sodium aluminate (NaAlO ₂ ) can be used to accelerate hydration of Portland cements. Here, we compare the use of NaAlO ₂ solutions with deionized water on the hydration of Al‐doped β‐C ₂ S. The microstructure development of hydration product C‐S‐H obtained from hydrated Al‐doped β‐C ₂ S was investigated. NaAlO ₂ significantly improved the hydration kinetics of Al‐doped β‐C ₂ S due to the enhancement in the precipitation of calcium hydroxide and stimulation of C‐(A)‐S‐H nucleation and increased the early‐age mechanical strength of Al‐doped β‐C ₂ S pastes. NaAlO ₂ promoted the incorporation of Al in the C‐(A)‐S‐H structure and accelerated the formation of C‐(A)‐S‐H phases containing tetra‐, penta‐ and hexa‐coordinated Al in its composition. The alkali cations modified the electrostatic equilibrium of the C‐(A)‐S‐H, thus promoting the development of the nano‐mechanical properties.