Study On The Treatment Of Dye Wastewater By Adsorption-Microwave Catalytic Method

In this dissertation, the current treatment technologies of dye wastewater and the application microwave technology in environmental protection field are reviewed. The principles and characteristics of microwave technology for the pollutants degradation are discussed. On the basis of microwave degradation principles, several new methods for degradation of dye wastewater by adsorption--microwave irradiation have been developed. The results of the research were presents as follows. 1. Six dyes were selected as simulating dye wastewater, and their characteristics (including maximal wavelength of the adsorption, working curve equation and CODCr value) were determined. 2. Preliminary experiments were carried out to find out the appropriate adsorption—catalysts. Six kinds possible materials (including transitional element oxides, loaded macroporous resin, zeolite, loaded zeolite, steel wire brush, coke and iron scraps) were tested. The results showed that coke and iron scraps were economical and efficacious adsorption—catalysts. Under microwave irradiation, coke and iron scraps produce high heat, and the dyes were degraded on the surface of coke and iron scraps respectively. Therefore, coke and iron scraps were used throughout the experiments as adsorption—catalysts. 3. Three dyes, orange X-GN, brilliant green and nile blue sulfate were chosen as model pollutants. Coke was employed as adsorption—catalyst. Under microwave irradiation, adsorption of dyes on coke was accelerated. When 3 g coke and 100 % microwave power were utilized to 24 ml dye solution, decolorization rates of orange X-GN, brilliant green and nile blue sulfate reached 97.51 %, 99.80 % and 99.30 % after irradiated 14 min, 7 min and 1.5 min respectively. The used coke was irradiated with different microwave power and reused in next cycle. The results indicated that the regenerated coke remained high efficiency after 10 cycles. Comparing the UV-Visible spectra of the treated and untreated dye solution, it was found that the dye has been removed from the solution after microwave irradiation in the presence of coke. Based on the experiments results, the mechanism of dyes removal can be concluded as follows: Firstly, microwave irradiation accelerated adsorption speed of regeneration of coke was obtained simultaneously. 4. Iron scrap was employed as adsorption—catalyst to degrade three dyes chosen as model pollutants under microwave irradiation. When 2 cm3 iron scrap and 100 % microwave power were utilized to 24 ml dye solution, decolorization rates of crystallized purple, reactive light yellow X-7G and nile blue sulfate reached 99.88 %, 99.81 % and 99.38 % after irradiated 2.5 min, 1.5min and 2.0 min respectively. The COD removal rates of three dye solutions were 95.32 %, 67.25 % and 94.77 % respectively. Iron scrap remained high efficiency after 8 cycles. A co-operative mechanism of adsorption -microwave irradiation -internal-electrolysis has been proposed for the degradation of dyes. 5. With the homemade fix bed microwave reactor, dynamic experiments were carried out. When 10 cm3 padding of iron scrap and 480 W microwave power were used, decolorization rates of nile blue sulfate, malachite green and crystallized purple solutions (400 mg/l) within 3 min were 92.51 %, 99.97 % and 94.22 % respectively. After used 3 h, the activity of iron scrap remained unchanged. High decolorization rates and COD removal rayes were achieved. During the whole process, the stability of reacting system was satisfactory.