Optimization of Fe3O4/SiO2/N-TiO2/Ag/AgCl core-shell nanomaterial and its properties, repeatability and photocatalytic mechanism

Aspergillus oryzae β-D-galactosidase immobilization on glutaraldehyde pre-activated amino-functionalized magnetic mesoporous silica: Performance, characteristics, and application in the preparation of sesaminol

Aspergillus oryzae β-D-galactosidase (β-Gal) efficiently hydrolyzes sesaminol triglucoside into sesaminol, which has higher biological activity. However, β-Gal is difficult to be separate from the reaction mixture and limited by stability. To resolve these problems, β-Gal was immobilized on amino-functionalized magnetic nanoparticles mesoporous silica pre-activated with glutaraldehyde (Fe3O4@mSiO2-β-Gal), which was used for the first time to prepare sesaminol. Under the optimal conditions, the immobilization yield and recovered activity of β-Gal were 57.9 ± 0.3 % and 46.5 ± 0.9 %, and the enzymatic loading was 843 ± 21 Uenzyme/gsupport. The construction of Fe3O4@mSiO2-β-Gal was confirmed by various characterization methods, and the results indicated it was suitable for heterogeneous enzyme-catalyzed reactions. Fe3O4@mSiO2-β-Gal was readily separable under magnetic action and displayed improved activity in extreme pH and temperature conditions. After 45 days of storage at 4 °C, the activity of Fe3O4@mSiO2-β-Gal remained at 92.3 ± 2.8 %, which was 1.29 times than that of free enzyme, and its activity remained above 85 % after 10 cycles. Fe3O4@mSiO2-β-Gal displayed higher affinity and catalytic efficiency. The half-life was 1.41 longer than free enzymes at 55.0 °C. Fe3O4@mSiO2-β-Gal was employed as a catalyst to prepare sesaminol, achieving a 96.7 % conversion yield of sesaminol. The excellent stability and catalytic efficiency provide broad benefits and potential for biocatalytic industry applications.

Enhanced catalytic sulfamethoxazole degradation via peroxymonosulfate activation over amorphous CoSx@SiO2 nanocages derived from ZIF-67

In this work, the amorphous CoS_x@SiO₂ nanocages were hydrothermally synthesized by sulfurizing ZIF-67@SiO₂ in the presence of thioacetamide (TAA). The catalytic performances of CoS_x@SiO₂ nanocages as heterogeneous catalysts to activate peroxymonosulfate (PMS) for the sulfamethoxazole (SMX) degradation were systematically investigated. 100% SMX was degraded within 6 min in CoS_x@SiO₂/PMS system, indicating that the amorphous CoS_x@SiO₂ nanocages exhibited outstanding sulfate radical-advanced oxidation process (SR-AOP) activity toward SMX degradation due to the regeneration of Co²⁺ by surficial sulfur species like S^2-/S₂^2-. The effects of PMS dosages, initial pH, SMX concentrations and co-existing ions on SMX degradation efficiency were explored in detail. The SMX removal efficiency was obviously improved in the simulated wastewater containing chloride ions (Cl^-) and low-concentration bicarbonate ions (HCO₃^-). The residual PMS and the generated sulfate radical (SO₄·^-) were determined quantitatively in CoS_x@SiO₂/PMS system. A possible mechanism in CoS_x@SiO₂/PMS system was proposed based on the results of quenching experiments, X-ray photoelectron spectroscopy (XPS) analysis, electrochemical tests, and electron spin resonance (ESR). The CoS_x@SiO₂ exhibited good stability and reusability, in which 100% SMX removal was achieved even after five consecutive cycles. This work provided a strategy for regulating the stability of cobalt-based catalyst for efficient pollutant degradation by PMS activation.