STUDIES ON ULTRASONIC DEGRADATION AND BLOCK COPOLYMERIZATION OF POLYACRYLAMIDE AND POLY(ETHYLENE OXIDE)

The kinetics of ultrasonic degradation of aqueous solution of polyacrylamide（PAM）and poly（ethyleneoxide）（PEO）as well as ultrasonic block copolymerization of aqueous solution of the mixture of PAM/PEOwere studied respectively.The degradation reaction of PEO follows a linear relationship between（P1-P∞）-1and irradiation time,while that of PAM follows a linear relationship between（P1-P∞）-1/2and irradiation time.The structure of the copolymer was identified by IR,NMR and DTA,and the copolymer prepared is a blockone.The copolymer formed by irradiating 1% aqueous solution of PEO/PAM mixture（1:1）for a period of40min.at 18.2 kHz with a sonic intensity corresponding to 2.OA input current on the reversed main circuitamounts to 61.8%.

Ultrasonic Degradation of Biosynthetic Poly (3-Hydroxybutyrate-co-Hydroxyvalerate)

In this article, ultrasonic degradation of copolymers--poly (3\|hydroxybutyrate\|co\|hydroxyvalerate) (PHBV) was first re ported. Effect of reaction conditions on the degradation rate was investigated. By ultrasonic irradiation w e find that copolymers with narrower molecular weight distributions and higher purity can be obtained in a s hort time and chain cleavage takes place at HV block.

Numerical simulation of acoustic field under mechanical stirring

The present study analyzes the effect of stirring on ultrasonic degradation experiments through acoustic field distribution,which provides a guidance for further improvement of the degradation rate of organic solutions.It is known that in order to eliminate the standing wave field formed by ultrasonic radiation in the water tank,the liquid in the water tank needs to be stirred and the corresponding distribution of acoustic field is simulated by using the finite element method(FEM).The standing wave leads to an uneven distribution of the acoustic field when it is not stirred,and disappears after being stirred,which increases the cavitation area in the ultrasonic cleaning tank.Then,the degradation experiment with agitation is carried out.The experimental results show that the degradation rate of the solution is higher than that when there is no agitation,which confirms the importance of the acoustic field distribution to ultrasonic degradation.In addition,it is clear that with the increase of the stirring speed,the degradation rate increases first and reaches a maximum at 600 rpm before decreasing.Finally,the distribution of flow field is simulated and analyzed.

Ultrasonic preparation of nano-nickel/activated carbon composite using spent electroless nickel plating bath and application in degradation of 2,6-dichlorophenol

Ni was effectively recovered from spent electroless nickel （EN） plating baths by forming a nano-nickel coated activated carbon composite. With the aid of ultrasonication, melamine- formaldehyde-tetraoxalyl-ethylenediamine chelating resins were grafted on activated carbon （MFT/AG）. PdC12 sol was adsorbed on MFT/AC, which was then immersed in spent electroless nickel plating bath; then nano-nickel could be reduced by ascorbic acid to form a nano-nickel coating on the activated carbon composite （Ni/AC） in situ. The materials present were carefully examined by Fourier transform infrared spectroscopy, X-ray diffraction, field emission scanning electron microscopy, X-ray photoelectron spectroscopy and electro- chemistry techniques. The resins were well distributed on the inside and outside surfaces of activated carbon with a size of 120 ± 30 nm in MFT/AC, and a great deal of nano-nickel particles were evenly deposited with a size of 3.8 ± 1.1 nm in Ni/MFT. Moreover, Ni/AC was successfully used as a catalyst for ultrasonic degradation of 2.6-dichloronhenol.

Progress in sonochemical fabrication of nanostructured photocatalysts

In recent years,nanostructured photocatalysts have become the research focus due to their immense potential application in environmental purification and energy conversion.The photocatalytic performance of photocatalysts is closely related to their synthesis methods.High-intensity ultrasound irradiation could provide a unique tool for fabrication of photocatalysts with novel nanostructures.Ultrasound induces acoustic cavitation which generates unique physicochemical conditions,e.g.,hot spot（5000℃）,high pressure of 100 MPa,fast rate of heat conduction（〉〉1×10^10℃·s^-1）.These unique physicochemical conditions allow for the synthesis of various nanostructured photocatalysts.This review summarized the recent development in fabrication of photocatalysts with special nanostructures and their applications.The typical sonochemical reactors and parameters in sonochemical synthesis are introduced and discussed.Sonochemically prepared structures including nano-/microspheres,one-dimensional（1D） nanorods,two-dimensional（2D） nanosheets（nanoflakes,nanosquares）,noble metal nanoparticle（NP）-deposited and element-doped photocatalysts are described and summarized.It is believed that sonication is a green methodology,and it holds greatpotential in the near future for nanostructured photocatalyst fabrication.