| When the dye wastewaters, often with compositions complicated, colorful, and high chemical oxygen demanding, flow into natural waters, they will significantly pollute the water environment and are bad for people. Therefore, a comprehensive treatment of dye wastewaters has become urgent and necessary. Polypropylene nonwoven fabrics have been found wide applications due to their high mechanical properties, porosity, chemical stability, low cost and so on. After UV-initiation graft modification, polypropylene nonwoven fabrics endow a good adsorption toward dyes and demonstrate membrane-like separation. In addition, while the grafted fabric was used in the electrochemical oxidation device, it reduced the COD of dye wastewaters, improved the treatment efficiency.In this thesis, the simulated dye wastewaters of the cationic red X-GRL and the weak acid red RN were handled in two different ways. First, anionic monomer acrylic acid(AA) and cationic monomer methacrylamido propyl trimethyl ammonium chloride(MAPTAC) were grafted onto polypropylene nonwoven fabric under UV irradiation respectively, and this process supplied the fabrics with adsorptive function toward cationic and acid dyes. The static dye adsorption and desorption characteristics, as well as the 10-time dynamic adsorption and desorption cycles were investigated in detail. Second, electrochemical oxidation was used to treat dye wastewater, in order to overcome a secondary pollution of desorption and limitations of removing single dye in the first method. In these experiments, the effects of different conditions were briefly studied. Then the adsorption and electrochemical oxidation were investigated systematically in the presence of ion exchange polypropylene nonwovens and ion exchange resin. The main results and conclusions are listed as follows:The major results and conclusions are listed as follows:(1) The cationic dye adsorption of PP-g-AA follows both the Lagergren’s pseudo-second order kinetic equation and the double exponential model. The higher the initial concentration, the faster the rate of adsorption. The adsorption equilibrium time is generally 60 min.(2) The ultrasonic desorption of adsorbed PP-g-AA fabric was carried out in a mixed solvent of anion surfactant, ethanol and water with optimized desorption solution components of 5% sodium dodecyl benzene sulfonate and ethanol: water = 3: 7(v/v). The desorption time was about 60-90 min. The ultrasonic desorption process follows the Lagergren’s pseudo-second order kinetics. At different initial adsorptions, the desorption amount and rate were firstly increased and then decreased with time and the initial adsorption amount. The ethanol was evaporated under vacuum and the surfactant was removed with foam separation for the treatment of the desorption wastewater. The ultrasonic desorption of adsorbed PP-g-MAPTAC fabric shared the similar behavior of desorption of adsorbed PP-g-AA fabric except for cationic surfactant 1427.(3) The two grafted fabrics have good adsorption properties, the maximum adsorption capacity of PP-g-AA to cationic red X-GRL was 122.38mg/g while that of PP-g-MAPTAC to weak acid red RN was 230.36mg/g.(4) The 3-column permeation experiment was run with source solution of 3L 10mg/L cationic dye wastewater and then desorption was done with 300 m L under ultrasonication. The process of permeation-and-desorption cycle was repeated over 10 times. Each of dye removal was more than 96% and the maximum desorption rate reached 89.08%. Under the operation pressure 37.1k Pa, the water flux of PP-g-AA fabric can be up to 38.6L/(m2 h), showing an excellent characteristics of filtration separation and recycling properties. The similar operation was done for PP-g-MAPTAC fabric except the 2-column permeation and the cationic surfactant desorption solution were employed. Each of dye removal was over 79%, and the maximum desorption rate was up to 98.43%. Under the operating pressure 40 k Pa, the water flux of PP-g-MAPTAC film can reach 20.1L/(m2 h).(5) In the electrochemical oxidation treatment of cationic red X-GRL dye wastewaters without filling ion exchange materials in the dilute chamber, the decolorization and the CODcr removal rates were increased with the increase of the applied voltage while decreased with the increase of the dye water velocity if the 0.1M Na Cl solution was used as electrolyte. The decolorization and CODcr removal rates was 100% and over 70% respectively for dye concentration 30mg/L at the inlet flow rate 750 m L/h and the voltage of 30 V. In addition, the electrochemical oxidation of the electrolyte of Na Cl was stronger than that of Na2SO4.(6) However, in the electrochemical oxidation treatment of dye wastewaters with filling ion exchange resin and textile in the dilute chamber, the decolorization and the CODcr removal rates were 96% and 70% for cationic dye wastewater at inlet flow rate 1250 m L/h and the voltage of 10 V, while those were 100% and 76% for acid dye wastewater at inlet flow rate 750 m L/h and the voltage of 25 V.The feature and innovations of this thesis are as follows:(1) The adsorptive filtration and separation of both cationic and acid dye wastewaters with laboratory-made grafted polypropylene nonwoven fabrics were done, and the results showed the volume ratio of purified water to regeneration solution reached 10, and the permeation-and-desorption cycle repeated over 10 times, the ethanol, surfactant and dye in the desorption wastewater were regenerated with vacuum distillation and foam separation.(2) Based on electrochemical oxidation principle, the electrodeionization technique was used to handle dye wastewater issue, and the decolorization and CODcr removal rates were reached high. |
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