Kinetics Processes Of Oxidation And Electro-coagulation In The Simulated Wastewater

Usually,single dye is chosen as the model for simulated wastewater in most of refferences in color removal of dye wastewaters. The investigation related to the removal of dyes in mixed dye simulated wastewater is rare. The color removal efficiency, which is estimated according to the absorbance at the wavelength of the maximum absorption of the dye, has limited information about the composition of the solution. On the other hand, the color removal efficiency estimated by this indicator may have large systemic error. In this thesis, spectrophotometric data of simulated wastewaters of single and mixted dyes during oxidation or electro-coagulation processes were analyzed a chemometrics. The residual color profiles, color removal efficiencies and kinetics in single dyes and mixed dyes simulated wawater were obtained.1. Influence of particle light scattering and color intermediate on data analysis in decolorization of simulated dye wasterwater using Fenton oxidation processAcid scarlet GR (AS-GR), Reactive violet K-3R (K-3R), Direct fast scarlet 4BS (DFS-4BS), Orange G (O-G), and the mixture of DFS-4BS and O-G were used as the model. It was shown that the presence of light scattering of particles and color intermediates caused large systemic error on the estimations of color removal efficiency and rate constant in decolorization of dye using Fenton oxidation process by spectrometric method. In oxidation of a single dye by Fenton's regent, free dye, color intermediate and the light scattering from the floc particles were the three origins of the residual colorof the solution. The contribution of the three color components to the total residual color profile in the Fenton oxidation process were simultaneously determined by employing a multiple linear regression (MLR) method. In the initial stage of oxidation, the free dye was the main body of residual color. As the oxidation progressing, the residual color from free dye decreased while the influence of light scattering from floc particles and color intermediate enhanced. In the later oxidation stage, the residual color was mainly due to the light scattering effect and residual color intermediate. The presence of the light scattering and color intermediate resulted in positive error in dye concentration that is determined by using the absorbance at the maximum wavelength of the dye. By using the MLR method, the influence of light scattering and color intermediate in estimation of the oxidation kinetics and efficiency was corrected. Complete oxidation of dye was achieved and the color removal of dye was found to follow first order kinetics. The effect of the initial experimental conditions included pH, concentrations of dye, ferrous ions and hydrogen peroxide on color removal kinetics was investigated.2. The investigation of the oxidation process of malachite green and crystal vilote by electro-Fenton techniqueThe electrodes used in electro-Fenton were Ti anode and active carbon felt cathode. Malachite green and crystal vilote were used as the model dye. The change in the shape of the absorptive spectrum of the mixture was observed during the electro-Fenton process. In the presence of light scattering of particles and color intermediates, there are large difference among the value of rate constant and color removal monitored by different indicators. The effect of the initial experimental conditions included pH, concentrations of dye, ferrous ions and current density on color removal kinetics was investigated. The kinetics for color removal of single dye was found to follow first order model. By using the MLR method, residual color profiles in binary dye mixture of malachite green and crystal vilote were determinated. It was shown that malachite green was oxidated preferentially to crystal vilote in the binary mixture due to competitive oxidation. The investigation of oxidation of mixed dye is helpful to understand the removal mechanism of dye wastewaters.3. The investigation of of electro-coagulation processes of dye simulated wasterwaterIron was used as electrode in electro-coagulation treatment for dye simulated wasterwater. The electro-coagulation processes of AS-GR, O-G and Direct vilote (DV) were used as modle. The mechanism of color removal is based on the coagulation between the dye and colloid particles from the electrode reaction. The influence of light scattering form floc on the spectrum of dye is severe. This kind of influence can not be eliminated even by a centrifugal separation or filtration. By using MLR method, the concentration of the components of the mixed dye system, the residual color of each color species were determinated simultaneously. In binary bye of AS-GR and O-G, AS-GR was removed preferentially. In ternary mixture of dye, the remval rate is in the order of DV >AS-GR> O-G. The effect of operation parameters on removal efficiency was investigated.