Study On The Degradation Performance Of PAM-PAFC In Printing And Dyeing Wastewater

Dyeing wastewater is one of the main sources of water pollution,which is characterized by complex components,high content of organic matter,deep chromaticity and great variation of water quality and quantity,it belongs to the industrial wastewater which is difficult to be treated.The traditional biological and physical methods can not achieve efficient removal.In contrast,chemical coagulation has a good application prospect,and the choice of coagulant is very important.Polyaluminium ferric chloride（PAFC）is a kind of inorganic polymer flocculant,which has the advantages of both polyaluminum and polyferric,such as high utilization efficiency,wide source of raw materials,low price and so on.In order to further improve the flocculation performance of PAFC and the treatment effect of dyeing wastewater,in this paper,the PAFC was prepared from aluminium trichloride and iron trichloride,and the preparation conditions were optimized to decolorize the simulated dyeing wastewater.Then,the self-made PAFC was combined with organic polymer flocculant PAM to decolorize the simulated dyeing wastewater,on the one hand,it can reduce the amount of inorganic coagulant,reduce the water pollution that may be caused by the amount of organic coagulant,on the other hand can increase the flocculation effect.The main research contents and results are as follows:（1）Polyaluminium ferric chloride（PAFC）with different alkalization degree,preparation temperature and Al/Fe molar ratio was prepared by single factor method.The decolorization of reactive red 2 and reactive blue 19 simulated dyeing wastewater was used as indexes to carry out flocculation test,and the flocculation performance of PAFC composite flocculant was investigated.On the basis of single factor study,orthogonal experiment was used to optimize the influencing factors.The results showed that the activity of PAFC was higher under the conditions of alkalization degree of 1.5,preparation temperature of 70°C and Al/Fe molar ratio of 9:1,and the decolorization effect of reactive red 2 and reactive blue 19 was the best.（2）The morphology and crystal structure of PAFC were observed by SEM,XRD and FT-IR.SEM showed that the self-made PAFC had high molecular density,long chain formed by the combination of molecules,and the macromolecule with high degree of polymerization formed by interlacing with each other,and the structure of PAFC was regular;XRD showed that the self-made PAFC flocculant has achieved good modification on the basis of maintaining the original morphology of Al,the more Al content is,the stronger its flocculation performance is;FT-IR showed that the peaks at 3416cm^-1are both strong and wide,which was composed of Fe-OH,Al-OH and H-OH.（3）The decolorization of reactive red 2 and reactive blue 19 by self-made PAFC and market-made PAFC was compared and analyzed.When the dosage was250mg/L,the decolorization rate of reactive red 2 with self-made PAFC and market-made PAFC was 84%and 78%,respectively,the decolorization rate of reactive blue 19 with self-made PAFC and market-made PAFC was 88%and 81%.The results showed that the flocculation effect of self-made PAFC was better than market-made PAFC under the same conditions.（4）The decolorization effect of reactive red 2 and reactive blue 19 in different p H,temperature,dosage of PAFC and PAM was studied by single factor.The results showed that the decolorization rate of reactive red 2 was 89.1%when the p H of raw water was 6,the temperature was 40°C,the dosage of PAFC was 180 mg/L and the dosage of PAM was 10 mg/L;When the p H of raw water was 7,the temperature was40°C,the dosage of PAFC was 200 mg/L,and the dosage of PAM was 10 mg/L,the decolorization rate of reactive blue 19 was 95.5%.The decolorization rate of reactive red 2 and reactive blue 19 with PAM coagulant is about 10%higher than that without PAM coagulant at the same p H,temperature and PAFC dosage.Under the same condition of decolorization rate,the dosage of PAFC coagulant with PAM coagulant is less than that without PAM coagulant.（5）On the basis of single factor test,the key process parameters are optimized by response surface method,the validity of the quadratic polynomial mathematical model and the interaction of each factor with the decolorization rate of reactive red 2and reactive blue 19 were established and analyzed by Box-Behnken.The results showed that for reactive red 2,the effects of four factors on the decolorization rate was as follows:temperature>p H>PAM dosage>PAFC dosage,under the optimum conditions of p H was 6.3,PAFC dosage was 172mg/L,PAM dosage was 10mg/L and temperature was 41°C,the decolorization rate predicted by the model was 90.04%,and the actual decolorization rate was 91.15%;The effects of four factors on the decolorization rate were as follows:p H>temperature>PAFC dosage>PAM dosage.The optimum technological parameters were as follows:p H was 6.5,PAFC dosage was 196mg/L,PAM dosage was 11mg/L and temperature was 44°C,the model predicted the decolorization rate to be 95.58%and the actual decolorization rate to be96%.The regression model has good prediction performance and can be used to guide production practice.（6）After a series of chemical reactions such as polymerization and hydrolysis of A1³⁺and Fe³⁺,the physical and chemical properties of the obtained polymers are changed and a new copolymer is formed.The new copolymer has longer and more stable molecular chain,and has the functions of adsorption bridging,electric neutralization,compressing double electric layer,net trapping and sweeping in the coagulation reaction,which is more beneficial to the aggregation of colloid.After the addition of organic coagulant PAM,the synergistic effect was increased.The long molecular chain of PAM improved the bridging and netting effect and increased the coagulation effect.