Preparation of recyclable magnetic palladium nanocatalysts by dispersion strategy based on sodium alginate for reduction of p-nitrophenol and Suzuki-Miyaura coupling.

Palladium (Pd) has excellent catalytic performance, its application is seriously limited by low atomic utilization and weak recovery capacity. To solve these problems, we report a universal palladium nanocatalysts preparation strategy by taking advantage of the rich chemistry of sodium alginate (SA). SA units not only self-assemble into a cross-linked porous carboxyl and hydroxyl framework but also can coat different substrates. Benefiting from the distinguished chelation of SA, metallic nanocatalysts can be achieved. As a proof-of-concept demonstration, Pd loading on nano-Fe3O4 modified with SA and investigated their catalytic capabilities. The catalyst was Fe3O4 nanoparticles encapsulated by SA film loaded with 0.4 wt% of Pd. It has a particle size around 100 nm and has good superparamagnetism with a saturation strength of 76.26 emu/g. It exhibited good catalytic activity at TOF = 660 h-1 and TOF = 4311 h-1 in typical Suzuki-Miyaura coupling reaction and the reduction of p-nitrophenol, respectively, and showed appreciable recyclability in the test of recyclability. Thus, our findings demonstrate that recyclable magnetic palladium nanocatalysts have several attractive features, such as easy preparation, outstanding catalytic activity and reusability. This work lays the foundation for the preparation of palladium nanocatalysts and the potential application of SA in the field of catalysts.

Spatio-Temporal Variation Characteristics of PM2.5 in the Beijing-Tianjin-Hebei Region, China, from 2013 to 2018.

Air pollution, including particulate matter (PM2.5) pollution, is extremely harmful to the environment as well as human health. The Beijing-Tianjin-Hebei (BTH) Region has experienced heavy PM2.5 pollution within China. In this study, a six-year time series (January 2013-December 2018) of PM2.5 mass concentration data from 102 air quality monitoring stations were studied to understand the spatio-temporal variation characteristics of the BTH region. The average annual PM2.5 mass concentration in the BTH region decreased from 98.9 µg/m3 in 2013 to 64.9 µg/m3 in 2017. Therefore, China has achieved its Air Pollution Prevention and Control Plan goal of reducing the concentration of fine particulate matter in the BTH region by 25% by 2017. The PM2.5 pollution in BTH plain areas showed a more significant change than mountains areas, with the highest PM2.5 mass concentration in winter and the lowest in summer. The results of spatial autocorrelation and cluster analyses showed that the PM2.5 mass concentration in the BTH region from 2013-2018 showed a significant spatial agglomeration, and that spatial distribution characteristics were high in the south and low in the north. Changes in PM2.5 mass concentration in the BTH region were affected by both socio-economic factors and meteorological factors. Our results can provide a point of reference for making PM2.5 pollution control decisions.

Recyclable ferromagnetic chitosan nanozyme for decomposing phenol.

Decomposing phenol and phenolic compounds to purify the environment is a focus of social attention. The use of ferromagnetic nanoparticles (MNP) to degrade phenol and phenolic compounds possesses many advantages and has received extensive attention. However, the unsatisfied catalyst activity and stability of MNP hamper its industrial applications. To improve MNP's properties, a ferromagnetic chitosan nanozyme (MNP@CTS) was synthesized via an improved hydrothermal method and molecular self-assembly technology. Its particle size was 11.76 nm, polydispersity index (PDI) was 0.073, surface zeta potential was 40.34 mV, saturation magnetization value was 35.28 emu g-1 and coercivity value was 17.56 Oe. The catalytic condition was extensively optimized among a range of pH and temperature, as well as initial concentrations of the substrate and H2O2, and MNP@CTS removed over 95% phenol from an aqueous solution within 5 h under the optimum conditions. Moreover, MNP@CTS was stable and could be regenerated for reuse for at least ten rounds. Thus, our findings open up a wide spectrum and lay a foundation of environmental friendly applications of MNP@CTS, showing several attractive features, such as easy preparation, low cost, excellent catalytic activity, good stability and reusability.

Recyclable magnetic carboxymethyl chitosan/calcium alginate - cellulase bioconjugates for corn stalk hydrolysis.

The use of cellulase hydrolysis of straw to produce fermentable sugars has many application prospects. However, cellulase is very expensive, which hampers its industrial applications. To improve cellulase's catalytic activity and reduce the enzyme cost, magnetite carboxymethyl chitosan/calcium alginate - cellulase bioconjugate (MCCCB) was synthesized via an improved hydrothermal method, molecular self-assembly technology, physical absorption, embedding and covalent bonding. Its loading capacity was 3.95mg/mL, and the catalytic activity increased to 267.18%. We decreased the release rate, improved the reusability, and enhanced the stability of MCCCB. Corn stalk hydrolysis also greatly improved, and the overall yield of fermentable sugars increased by 698.26%. All of these results indicate that MCCCB could significantly improve the efficiency of cellulase, greatly reduce the cost of enzyme, and effectively promote the production of fermentable sugars.

Synthesis of superparamagnetic carboxymethyl chitosan/sodium alginate nanosphere and its application for immobilizing α-amylase.

In order to improve catalytic activity, increase recycling times, reduce use cost for enzyme, superparamagnetic carboxymethyl chitosan/sodium alginate nanosphere (SM/CMC/SA) has been synthesized via an improved hydrothermal method, molecular self-assembly technology, electrostatic interaction and amide linkage. Its mean diameter was 65nm, zeta potential was -36.9mV and BET was 53.8m(2)/g. α-Amylase was selected as a simulation object to manufacture an immobilized enzyme (SM/CMC/CA/α-Amy), and its catalytic activity, release behavior, reusability and stability were researched. Immobilization increased 4.67 times to catalytic activity, slowed down release rate and improved reusable performance. SM/CMC/CA/α-Amy showed higher activity over a wider pH range, especially in strong acidic and alkaline environments. The thermal stability and storage stability were improved remarkably too. All these results indicated that SM/CMC/SA was an ideal carrier for immobilizing enzyme.

Photocatalytic inactivation efficiency of anatase Nano-TiO(2) Sol on the H(9) N(2) avian influenza virus.

This study was conducted to investigate efficiency of TiO(2) nanomaterial as a novel environment-friendly disinfectant to control avian influenza (AI) by its photochemical sterilization ability. Anatase nano-TiO(2) sol, a neutral, viscous aqueous colloid of 1.6% TiO(2) , was synthesized from peroxotitanic acid solution according to the Ichinose method. Transmission electron microscope images showed that the TiO(2) particles were spindle-shaped with an average size of 50 nm. X-ray diffraction patterns revealed that the crystal phase of TiO(2) particles was anatase type with photocatalytic effect. A photocatalytic film of nano-TiO(2) sol was tested as a means of inactivating H(9) N(2) avian influenza virus (AIV). Inactivation capabilities were examined with 365nm ultraviolet (UV) radiation under black light by adjusting the UV intensity, the UV irradiation time and the quantity of AIV. The titer change of AIV was determined by hemagglutination tests. Cytopathic effect of Madin Darby canine kidney (MDCK) cells was monitored by inverted fluorescence microscope. The results showed that anatase nano-TiO(2) sol significantly inactivated AIV under UV irradiation of 365nm. The inactivation of AIV viruses reached up to 100%. Therefore, anatase nano-TiO(2) sol is a potentially environment-friendly antivirus agent to prevent AI.