Enhanced Fenton-like catalytic activity and stability of g-C3N4 nanosheet-wrapped copper phosphide with strong anti-interference ability: Kinetics and mechanistic study.

Metal-based Fenton-like catalysts usually activate H2O2 to produce free radicals (•OH and O2•-) for the degradation of organic pollutants. However, a catalytic reaction dominated by free radicals is easily interfered with by various inorganic anions and water matrices. Herein, g-C3N4-wrapped copper phosphide (CuxP), as a highly efficient Fenton-like catalyst, was successfully synthesized by a simple low-temperature phosphidation method. The CuxP/g-C3N4 catalyst exhibited excellent catalytic ability for the removal of various organic contaminants over a wide pH range of 3-11. In addition, the catalyst exhibited strong anti-interference ability toward various inorganic anions (Cl-, SO42-, NO3-, F-, H2PO4-, HCO3- and CO32-) and water matrices (lake water, river water, tap water and simulated water matrix). The reasons for this performance were analyzed by verifying the mechanism of the catalytic reaction. Compared to the pure CuxP catalyst, the CuxP/g-C3N4 composite possessed good catalytic stability. The enhanced and deactivated mechanisms of the CuxP/g-C3N4 catalyst were systematically analyzed by a series of characterization techniques. A possible reaction mechanism was also proposed based on the experimental results. This work provides new insights into designing highly efficient metal-based Fenton-like catalysts with strong anti-interference ability to practically treat wastewater.

Firmness evaluation of melon using its vibration characteristic and finite element analysis.

The "Huang gua" melons were measured for their physical properties including firmness and static elastic modulus. The vibrational characteristics of fruits and vegetables are governed by their elastic modulus (firmness), mass, and geometry. Therefore, it is possible to evaluate firmness of fruits and vegetables based on their vibrational characteristics. Analysis of the vibration responses of a fruit is suggested for measuring elastic properties (Firmness) non-destructively. The impulse response method is often used to measure firmness of fruits. The fruit was excited using three types of balls (wooden, steel and rubber) and the vibration is detected by an accelerometer. The Instron device was used to measure the static elastic modulus of the inner, middle and outer portions of melon flesh. Finite element (FE) technique was used to determine the optimum excitation location of the chosen measurement sensor and to analyze the mode shape fruits. Four types of mode shapes (torsional or flexural mode shape, first-type, second-type spherical mode and breathing mode shape) were found. Finite element simulation results agreed well with experimental results. Correlation between the firmness and resonant frequency (r2=0.91) and between the resonant frequency and stiffness factor (r2=0.74) existed. The optimum location and suitable direction for excitation and response measurement on the fruit were suggested.