| The treatment of dye wastewaters is an important and difficult task due to the complexity, high color, potential toxicity, and heary environmental impact. Various techniques and method have reported to disposal dye wastewaters. Usually, complicated interaction mechanisms are included in the treatment processes. The knowledge about the interaction mechanisms is helpful to understand the treatment process and improve the removal efficiency. In this thesis, chemometrics methods were employed to analyze the spectrometric data in the decolorization processes of simulated dye wastewaters. The detailed information about residual color was obtained. After the optimization of operational conditions, the removal efficiency in treatment of dye wastewater is improved.1. Process analysis in the oxidation of simulatd dye wasterwaterThe oxidation processes of simulatd dye wasterwater by Fenton's reagent and and F, Ce-doped PbO2 /Ti anode were tested. Cationic dye (Safranine) and anionic dye (Tracid orange GS, Reactive Violet K-3R, and Orange G) were used as the model dyes. The spectrometric data in the oxidation precesses were analyzed by a multiple linear regression method. The operational conditions were optimized. In oxidation process by Fenton's reagent, the light scattering from the particles and colored intermediates change the shape of the asorption spectrum of the reaction mixture. Consequently, large systemic error was added in the values of color removal efficiency and rate constant estimated by the traditional spectricmetric method. In the degradation of Safranine using Fenton oxidation process, free dye, two colored intermediates and the light scattering from the floc particles were the four origins of the residual color in the reaction mixture. In the early oxidation stage, free dye is the main contributor for the residual color. As the oxidation progresses, the proportion of colored intermediates and light scattering in the residual color increases. In the later oxidation stage, the residual colur is mainly from the light scattering of floc particles. F and Ce-doped PbO2 /Ti modified electrode was prepared by high temperature thermal oxdation. The prepared PbO2 /Ti modified electrode has high electric catalytic activity to Tracid orange GS, Reactive violet K-3R, and Orange G as well as COD. The electrode offers the advabtage of stable and durable performance. The influence of current density and salt concentration on the removal efficiency was tested.2. Decolorization of simulated dye wastewaters by chemical flocculationPolyaluminium chloride (PAC) and epicholorohydrin-dimethylamine polymer (EPI-DMA) were chosen as the model flocculants. Direct fast scarlet 4BS and Tracid orange GS were used as the model dyes. According to the analysis for the specrpmetric data, free dye, complex of dye and flocculant, and the light scattering from the particles are the three components that are related directly to the decolorization efficiency in single dye simulated wastewater. In the region of insufficient dosage of flocculant, the residual color in the samples is mainly due to free dye. When the flocculant is over dosed, the residual color in the samples is mainly from the re-stabilized complex of dye and flocculant. In addition, the light scattering from the particles is one of the reasons for the lower decolorization efficiencies. In flocculation in binary dye mixture, five components are related to the the residual color of the samples. Because of the difference in the binding ability of dyes to the flocculants, the decolorization curves are different for each dye. In the region of insufficient dosage of flocculant, higher decolorization efficiencies are obtained for the dye with greater binding ability to flocculant. The harmless treatment for the floc from flocculation by high temperature was tested. The residua was used as adsorbent for dye adsorption. The floc of PAC-dye was calcined in muffle. The prepared aluminium residua was used as adsorbent to Direct fast scarlet 4BS。The floc of EPI-DMA-dye was heated by microwave radiation. The prepared carbon residua show high adsorption capacity to dyes.3. Combination of chemical flocculation and photocatalytic degradationDye watewaters contain complexied components and have high color. There are many methods employed in dye wastewater treatment. These methods have different advantages and disadvantages. Generally, the removal efficiency by one mehod is limited. For example, in flocculation by EPI-DMA in mixture of Active red purple X-2R and nonionic surfactant (OP-10), the color reval efficiency is high while the removal of OP-10 is low. Ifhe flocculant is over dosed, EPI-DMA is added as in water as a new pollutant and increases the value of chemical oxygen demand (COD). TiO2 nanoparticles is an excellent photocatalyzer in degradation COD. But its photocatalytic performance is limited in solution of high color because the parts of photons are absorbed by color solution. In the combination of chemical flocculation and photocatalytic degradation processes, the removal efficiency is much improved. At first, chemical flocculation is used to remove dye. The influence of high color on photocatalytic degradation is eliminated. The residual COD is reduced by TiO2 photocatalytic degradation in a deep treatment process. Hence, the removal efficiency for color and COD is improved.4. Adsorption of methylene blue and brilliant green on activated carbon derivedfrom peanut hull and treatment of real dye wastewater Activated carbon was prepared from peanut hull using chemical activation by phosphoric acid. The prepared activated carbon, a cheap and excellent adsorbent with specific surface area of 215 m2/g, was used for the adsorption of dyes from solutions. The adsorption capacity to methylene blue (MG) and brilliant green (BG) are 596 and 528μmol/L, respectively. The adsorption of MG and BG obeys Langmuir adsorption isotherm. The adsorption equilibrium constants are 0.328 and 0.103L/mol for MG and BG, respectively. The adsorption processes follow the pseudo-second order kinetic model. In mixed solution of MG and BG, MG is preferentially adsorbed in the case of insufficient dosage of adsorbent. The total amount of dye adsorbed vs to residual dye concentration obeys Langmuir adsorption isotherm, too. With increasing concentraton of MG to BG, the total adsorption equilibrium constant and capacity increase. The loaded activated carbon was regenerated by microwave radiation. Finally, the treatment of a real dye wastewater was tested by the methods used in this thesis.
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