Preliminary Research On Flocculation Performance And Mechanism Of The Simulated Reactive Dye Wastewater

In this paper, the effect of different flocculant dosages on the flocculation decolorization efficiency of simulated reactive dyeing wastewater with single component was studied by using beaker flocculation method, and the flocculation mechanism has been discussed.By using4kinds of inorganic flocculants, namely PAC, PFS, AS and FS, and3kinds of cationic homopolymer, namely PDAC, PDMC and PDM as well as cationic copolymer P(DAC-AM), the jar tests were used to treat three kinds of simulated dyeing wastewater with single component, namely reactive red3BF, yellow3RF and brilliant blue KN-R respectively. The influences of flocculant dosages on the decolorization rate, the CODcr removal rate and the suspended particles Zeta potential were also tested. The sedimentation velocity of floccules and their infrared spectrum were also detected. On this basis, the effects of the inorganic flocculants kinds, pH of wastewater, the intrinsic viscosity of homopolymer and copolymer with different cationic degree and the electric charge of the dyes on maximal decolorization rate were analyzed. The corresponding mechanism of flocculation decolorization was preliminary discussed.The results showed that the decolorization rate and CODcr removal rate of the simulated dyeing wastewater increased at first and then gradually declined with the increase of the flocculant dosages, while the Zeta potential of suspended particles increased with the increase in the flocculant dosages. And the result of data analyses showed that PAC had both a wider dosage range and pH adaptation scope than the other3kinds of inorganic flocculants under their respective selected coagulation condition. By increasing the intrinsic viscosity of PDMC, PDAC, PDM from1.84,0.84and0.57dL·g-1to6.16,6.88and2.98dL·g-1respectively, there was no significant difference on the best decolorization rate. By increasing the intrinsic viscosity of P(DAC-AM) with cationicity50%from4.90dL·g-1to12.61dL·g-1or increasing the cationicity of P(DAC-AM),whose intrinsic viscosity is about7.5dL·g-1,from30%to100%, there was a growth in the best decolorization rate,but a growth of cationic degree narrowed the maximal decolorization range. Besides, the bigger the relative molecular mass of the dye was, the more sulfonic acid groups on the dye there were, the easier the their simulated wastewater could be decolorized. An analyses of the Zeta potential of suspended particles and the sedimentation velocity of floccules showed that through the electrical neutralization and adsorption bridging, the inorganic polymer PAC and PFS could form a larger flocs with dye rapidly, while the low molecular AS, which only has the electrical neutralization, needs more time for flocculation sedimentation. Homopolymer PDMC had better desoluion to the active dye molecules than others, due to hydrophobic methyl groups in PDMC, thus its flocculating settling time is significantly less than PDAC and PDM. The charge analysis showed that quantity of electrostatic charge of flocculants was about20percent less than that of the dye when reaching maximal decolorization rate. Infrared spectrum showed that chemical interaction was observed between the quaternary ammonium group in flocculants and sulfonic acid group in dye, leading to the formation of insoluble dye-ammonium salt macromolecule.Therefore, the flocculants kinds and the pH of wastewater had a remarkable effect on maximal decolorization rate. The intrinsic viscosity of homopolymer flocculants had no significant effect on the decolorization rate. The maximal decolorization rate was significantly affected by the intrinsic viscosity and cationicity of copolymer flocculants and the structure of the dye.The completed researches above offered a feasible foundation for systematic research of the simulated dyeing wastewater with multicomponent and the actual dyeing wastewater.