| Cationic polyacrylamide（CPAM）is an organic polymer flocculant,which is widely used in sewage treatment and sludge dewatering because of its advantages such as lower dosage of flocculant,higher flocculation efficiency and stronger stability performance.In the process of flocculation,negatively charged pollutant particals can be destabilized to lose their stability under the effect of charge neutralization,and then aggregate together to form large flocs under the effect of adsorption and bridging.finally,the large flocs can be removed from the water by precipitation.In general,initiation method is critical to the synthesis of CPAM,However,traditional initiation methods such as thermal initiation is limited in the preparation of CPAM because of its disadvantages such as longer initiation time,lower polymerization efficiency and higher cost.Therefore,It is necessary to find a new kind of initiation method to prepare CPAM with excellent performance.Surface photocatalysis is widely used in the catalytic degradation of organic wastewater.In recent years,it has been used for the synthesis of composite materials and polymers as a result of its faster reaction speed,higher polymerization efficiency and lower cost.Under the irradiation of photons with high-energy,the photocatalysts can generate a large number of hydroxyl radicals to initiate the copolymerization of monomers.At present,this method of initiation is rarely used in the synthesis of CPAM,therefore,it is of great significance to investigate the synthesis of CPAM through photocatalytic surface initiation.In this study,a cationic polyacrylamide flocculant NT-P（AM-DMC）（NT-PAD）was synthesized through photocatalytic surface initiation using AM and DMCas monomers,nano-Ti O2 as an initiator and urea as solubilizers,at the same time,the characteristics of NT-PAD was discussed through a series of characterization methods.Finally,flocculation treatment of kaolin wastewater and dewatering application of municipal domestic sludge were carried out to evaluate the flocculation performance of NT-PAD.The main content and conclusions of this thesis are as follows:（1）In the synthesis of NT-PAD through photocatalytic surface initiation,the initiation mechanism of Nano-Ti O2 was analysised.The factors affecting the polymer intrinsic viscosity and conversion were investigated to optimize polymerization conditions,including the concentration of Nano-Ti O2,the total monomer mass fraction,the DMC monomer mass fraction,the system p H,the initiation time and the urea concentration.In addition,The response surface analysis method was used to study the effect of the four major factors and their interactions on the intrinsic viscosity,and then,the preparation conditions were optimized.（2）The functional group structure of NT-PAD was anaysised by FTIR and 1H NMR,the results showed that the functional groups of the relevant monomers were appeared in the polymer,which indicated that the AM and DMC were successfully polymerized.TG/DSC analysis showed that NT-PAD had good thermal stability.SEM analysis revealed that NT-PAD had void structure and a large specific surface area.（3）NT-PAD was applied to the treament of kaolin suspension synthesis wastewater in this study.The turbidity removal rate was used as an index to evalute the effect of flocculant intrinsic viscosity,dosage and suspension p H on the flocculation performance.The results showed that with a rational range,the higher the intrinsic viscosity of the flocculant are,the better flocculation performance are.NT-PAD can get better flocculation results with a lower dosage in a wider p H range of 3.0～11.0.The analysis of Zeta potential showed that NT-PAD has stronger electrical neutralization and patching capabilities.Compared with commercially organic/inorganic flocculants,the results showed that NT-PAD can achieve better results with lower dosage.Finally,the possible flocculation mechanism was inferred according to the influence of various factors on the turbidity removal rate of kaolin suspension.（4）NT-PAD was applied to the treament of sludge dewatering and flocculation.The FCMC of sludge,the turbidity of supernatant,the SRF of sludge after dewatering and the Zeta potential were uesd as indicators to evaluate the performance of sludge dewatering.The intrinsic viscosity of NT-PAD,flocculant dosage and p H of the sample sludge were used as variables to investigate the effect of the Sludge dewatering performance of NT-PAD.The results showed that optimal p H value of sludge dewatering performance was6.0～7.0,within this range,sludge dewatering performance would get better with less dosage of NT-PAD.The analysis of Zeta potential showed that NT-PAD has stronger electrical neutralization and patching capabilities.Compared with commercially organic flocculants,NT-PAD was more effective in the sludge dewatering flocculation,and the particle size of the sludge after flocculation was studied.Finally,the possible flocculation mechanism was inferred according to the influence of various factors on the performance of sludge dewatering. |
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