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Preparation of Chitosan-CdS Composite Nanoparticles by Reverse Microemulsion and Their Application in Photocatalysis

Author: HouJin
Tutor: ChenGuoHua
School: Ocean University of China
Course: Marine Chemistry
Keywords: Reverse microemulsion method Chitosan -CdS Nanoparticles Application Photocatalytic
CLC: O643.3
Type: Master's thesis
Year: 2004
Downloads: 348
Quote: 3
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Abstract

Easy to form a semiconductor material CdS adjustable nanocrystal size, but because of its poor stability, the direct use still difficult if the nanocrystals dispersed in a matrix, such as: polymer, forming an organic / inorganic iso chromatin structure; long-term stability can not only take advantage of its excellent properties, and can use a nano-material interaction with the substrate to produce new effects. In addition, the presence of organic matter can be effectively suppressed aggregation of inorganic particles, inorganic particles maintaining the unique properties of nanometer. CdS photocatalyst can be used for waste water treatment. If its functional modification, modification of the outer layer of organic compounds to become functional CdS, in wastewater treatment has more advantages than ordinary CdS. Chitosan has abundant resources, good biocompatibility, biodegradable, non-toxic, etc., is the only natural polysaccharide basic polysaccharide, is an essential element of the six life; chitosan in aqueous solution is a poly cation, the metal ion complexing with a good capacity, which makes the matrix material can be used as well to locate and control the growth of inorganic nano-particles, to prevent agglomeration. While the presence of chitosan, enhanced organic pollutants CdS photocatalytic degradation, improve the photocatalytic effect. 1. Chitosan, cadmium chloride (CdCl ₂ · 2.5H ₂ O) and thiourea ((NH ₂) ₂ CS) was synthesized through reverse microemulsion of CdS were prepared for the dispersed phase, chitosan matrix composite chitosan-CdS nanoparticles, and their spectra. A) TEM results show that: In the chitosan-CdS composite nanoparticles, CdS nanocrystals dispersed in chitosan matrix, and the presence of chitosan effectively inhibit the aggregation of CdS grains; CdS nanocrystals grain between 3 ~ 20nm in diameter. 2) XRD results show that: when CdCl ₂ and (NH ₂) ₂ CS chitosan hydrochloride solution concentration was 0.10 mol / L, were prepared containing both α-CdS and β-CdS mixed crystals of chitosan nano-CdS Nanoparticles; when CdCl ₂ and (NH _{2 ) ₂ CS chitosan hydrochloride solution concentration was 0.20mol / L or 0.30mol / L, and the aging temperature is 40 ℃, can be prepared containing only α-CdS crystals type of chitosan-CdS composite nanoparticles. Help to increase concentration and improve the aging temperature are conducive to chitosan-CdS Nanoparticles in α-CdS crystal formation. 3) fluorescence analysis results show that: when the aging temperature is lower, namely at 30 ℃, the fluorescence peaks of the blue shift, indicating that the grain size refinement occurs. 2. Chitosan-CdS Nanoparticles photocatalytic degradation of methyl orange, alizarin red and monocrotophos conducted applied research. 1) Through the photocatalytic degradation of methyl orange study showed that: the optimum conditions (eg: select sample 2, the composite nanoparticles dosage 0.30g, pH = 6), for 100mL concentration of 20mg / L of methyl orange solution of methyl orange when in 2min degradation efficiency reached 90.9%, 40min when methyl orange degradation efficiency was 94.2%; chitosan have a certain degree of methyl orange adsorption, but decolorization mainly composite nano its particle degradation of methyl orange degradation process at the maximum absorption wavelength of Ocean University of China Journal 464lun absorption peak weakened rapidly and eventually disappear; methyl orange degradation process in 258lun and 320lun at the emergence of new absorption peaks, indicating degradation of methyl orange occurred; photocatalytic degradation at pH conditions are suitable for between 6 to 8; when cdcl: and gamma HZ) Zcs chitosan hydrochloride solution concentration are o.10mol when, Preparation of Chitosan Nanoparticles a Cds photocatalytic degradation of methyl orange fastest: the aging temperature is 30 ℃ and 40 ℃, the products prepared photocatalytic degradation of methyl orange consistent; through chitosan Cds sugar a composite CdS nanoparticles and comparison of normal, indicating that the composite nanoparticles on the photocatalytic degradation of methyl orange significantly faster than ordinary CdS. 2) Through the Alizarin Red photocatalytic degradation studies showed that: the optimum conditions (eg: select a sample 21, the amount of the composite nanoparticles 0.039, pH = 6), for loomL concentration ZOm pair of alizarin red solution, Alizarin Red at Zmin degradation efficiency reached when 95.7%, 30min Alizarin red when reached 99.0% degradation efficiency: chitosan on the adsorption of alizarin red has some effect, but Alizarin red discoloration is mainly Nanoparticles it Degradation of: alizarin red degradation process at the maximum absorption wavelength of the absorption peak 26Inm weakened rapidly and eventually disappear; alizarin red degradation process and 228run at the 223lun new absorption peak appears, indicating alizarin red occurred degradation; photocatalytic degradation pH conditions at about 6:00 is more suitable; when cdC12 and (N HZ) Zcs chitosan hydrochloride solution concentration are 0.2omo ratio, the prepared chitosan nanoparticles on a CdS Composite Alizarin red degradation fastest; aging temperature at 30 ℃ 10min products prepared before the slower rate of degradation of alizarin red light, but after 10min significantly accelerate the degradation rate; through a CdS Composite chitosan nano CdS particles and comparison of normal, indicating that chitosan nanoparticles on a CdS Composite Alizarin Red photocatalytic degradation was significantly superior to ordinary CdS. 3) Through the photocatalytic degradation of monocrotophos study shows: the optimum conditions (eg: Select Sample 1, the composite nanoparticles dosage 0039, pH = 6), for 100mL volume percentage of 0.01% solution of monocrotophos in 10min and 30min, monocrotophos degradation efficiency reached 40.0% and 40.2%; chitosan adsorption of monocrotophos certain; photocatalytic degradation conditions of optimal pH of 6 or so. When CdCI: and gamma H Power CS chitosan hydrochloride solution concentrations were 0.1 omol / L, the prepared chitosan nanoparticles on a CdS Composite photocatalytic degradation of monocrotophos fastest: the aging temperature is 30 ℃, the product prepared photocatalytic degradation of monocrotophos better: through a CdS Composite Chitosan nanoparticles and ordinary Cds contrast, showed composites photocatalytic degradation of monocrotophos was significantly superior to ordinary Cds . Alizarin Red and Methyl Orange negatively charged in solution, easy for the chitosan adsorption, so photocatalytic degradation was significantly better than monocrotophos; same time as the chitosan containing free amino group under acidic conditions with a positive charge, the negatively charged organic ions electrostatic adsorption of CdS promote its photocatalytic degradation. 4) initial proposed chitosan a CdS Nanoparticles photocatalytic degradation mechanism. Adsorption is the photocatalytic degradation of the pre-steps of: the chitosan containing free amino groups with a positive charge, easy to electrostatic adsorption}

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