Preparation Of Chitosan-CdS Composite Nanoparticles By Reverse Microemulsion And Their Application In Photocatalysis

The size of CdS nanocrystal as semiconductor is easy to control, however, its stability is bad. So it is difficult to utilize it directly. If it's dispersed equality in some matrix (polymeric compound, et al.) to form organic/inorganic heterojunction structure, its excellent characteristic, and new effects which come from interaction of nanomaterial and matrix, can be utilized life-term. In addition, organic can restrain effectively inorganic particles from gathering and maintain their peculiar nanocharacteristic.CdS can be utilized as pholocatalyst for waste water treatment. If functional modification is made, i.e., organic is modified on the surface to form functional CdS, it is more superior than common CdS in waste water treatment. Chitosan is rich in nature, kind for biology compatibility, easy for biodegradation and innoxious, et al. It is only one alkalescence polysaccharide in natural polysaccharides and a necessary one of six life elements for human body. Chitosan is an aggregate positive ion in solution and its coordination and complex with metal ion is good. It is possible for chitosan to decide location, control grow of inorganic nanoparticles and prevent agglomeration. The results of photocatalysis and photocatalytic degradation of organic-contaminant by CdS are improved since the existence of chitosan.Chitosan-CdS composite nanoparticles (CdS is disperse phase and chitosan is matrix) are prepared by reverse microemulsion with chitosan, cadmiun chloride (CdCl2 ?2.5H2O) and sulfocarbamide ((NH2)2CS), and characterization is made.The results of TEM show that CdS nanocrystal disperses in chitosan matrix uniformly, and chitosan prevents them from aggregating effectively and the sizes are around 3~20nm.The results of XRD show that nanomixed crystals of a -CdS and -CdS are prepared when the concentration of CdCl2 and (NH2)2CS chitosan chloride solution is 0.10mol/L, and single crystal of a -CdS is prepared when the concentration is 0.20mol/L or 0.30mol/L and maturing temperature is 40 . It is beneficial for a -CdS to generate with increasing concentration and maturing temperature.The effects of fluorescence spectrum show that blue-shift occurs at fluorescence peak. This means that the sizes of particles become fine.The application of chitosan-CdS composite nanoparticles is researched on photocatalytic degradation of methyl orange, alizarin red and monocrotophos.In optimum condition (for example, sample 2, the amount of composite nanoparticles is 0.30g, pH=6), the degradation efficiency of methyl orange reaches 90.9% in 2min and 94.2% in 40min when the concentration is 20mg/L in 100mL solution. Chitosan has sorption to methyl orange in a certain degree, but the decolour of methyl orange mainly comes from the degradation by compositenanoparticles. The absorption peak becomes weak rapidly and disappears finally at maximum absorption wavelength 464nm, and the new absorption peaks appear at 258nm and 320nm during the degradation of methyl orange. So the degradation of methyl orange occurs. The suitable condition of pH is among 6-8 for photocatalytic degradation.The rate of photocatalytic degradation of methyl orange is fastest when composite nanoparticles are made from the concentration of 0.10mol/L, and the effect on photocatalytic degradation of methyl orange is in accord basically when the maturing temperature is 30 and 40 , and composite nanoparticles is superior to common CdS by contrast.In optimum condition (for example, sample 21, the amount of composite nanoparticles is 0.03g, pH=6), the degradation efficiency of alizarin red reaches 95.7% in 2min and 99.0% in 30min when the concentration is 20mg/L in l00mL solution. Chitosan has sorption to alizarin red in a certain degree, but the decolour of alizarin red mainly comes from the degradation by composite nanoparticles. The absorption peak becomes weak rapidly and disappears finally at maximum absorption wavelength 261nm, and the new absorption peaks appear at 223nm and 228nm during the degradation of alizarin red. So the degradation of al...