Huijuan Guan

PtNi nanoparticles embedded in porous silica microspheres as highly active catalysts for p -nitrophenol hydrogenation to p -aminophenol

AbstractSupported Pt-based alloy nanoparticles have attracted greater attention in catalysis due to their high activity, reduced cost, and easy recycling in chemical reactions. In this work, mesoporous SiO2 microspheres were employed as support to immobilize PtNi alloy nanocatalysts with different mass ratios of Pt and Ni (1:0, 3:1, 1:1, 1:3 and 0:1) by a facile in situ one-step reduction in the absence of any capping agent. SEM, EDS, TEM, FTIR, XRD, ICP-AES, XPS and nitrogen adsorption/desorption analysis were employed to systematically investigate the morphology and structure of the obtained SiO2 microspheres and SiO2/PtNi nanocatalysts. Results show that uniform PtNi nanoparticles can be homogeneously and firmly embedded into the surface of SiO2 microspheres. When the as-prepared SiO2/PtNi nanocatalysts were used in the reduction process of p-nitrophenol to p-aminophenol, the nanocatalyst with Pt and Ni mass ratio of 1:3 showed the highest catalytic activity (TOF of 5.35 × 1018 molecules⋅g−1⋅s−1) and could transform p-nitrophenol to p-aminophenol completely within 5 min. The SiO2/PtNi nanocatalyst can also maintain high catalytic activity in the fourth cycle, implying its excellent stability during catalysis. Graphical AbstractPtNi was embedded into mesoporous SiO2 surface to avoid its aggregation and loss in catalysis. SiO2/PtNi(1:3) catalyst can be used/reused as efficient catalyst with high activity and stability.

Immobilization of laccase onto porous polyvinyl alcohol/halloysite hybrid beads for dye removal

Laccase was immobilized in polyvinyl alcohol beads containing halloysite nanotubes (PVA/HNTs) to improve the stability and reusability of enzyme. The porous structure of PVA/HNTs beads facilitates the entrapment of enzyme and prevents the leaching of immobilized laccase as well. Halloysite nanotubes act as bridge to connect the adjacent pores, facilitating the electron transfer and enhancing the mechanical properties. PVA/HNTs beads have high laccase immobilization capacity (237.02 mg/g) and activity recovery yield (79.15%), indicating it can be used as potential support for laccase immobilization. Compared with free laccase, the immobilized laccase on hybrid beads exhibits enhanced pH tolerance (even at pH 8.0), good thermal stability (57.5% of the initial activity can be maintained at 75 °C), and excellent storage stability (81.17% of enzyme activity could be retained after storage at 4 °C for 5 weeks compared with that for free enzyme of 60%). Also, the removal efficiency for reactive blue can reach as high as 93.41% in the presence of redox mediator 2,2-azinobis(3-ethylbenzthiazoline-6-sulfonate), in which adsorption and degradation exist simultaneously. The remarkable pH tolerance, thermal and storage stability, and reuse ability imply potential application of porous PVA/HNTs immobilized enzyme in environmental fields.