UV Initiated Template Polymerization Of HACPAM And Its Performance Studying Sludge Dewatering

With the development of society and economy and the improvement of urbanization level,the burden of sewage treatment plant is gradually increasing and the output of sludge is increasing rapidly.The demand for sludge treatment is getting higher and higher.Sludge dewatering is an important link for sludge treatment and disposal.The colloid particles in the sludge and water have a strong affinity,so dewatering sludge directly is not a good idea of the effect.Therefore,it is necessary to choose reasonable chemical conditioner for pretreatment of sludge.The traditional water treatment organic flocculant is cationic polyacrylamide(CPAM).CPAM is a synthetic organic cationic polymer flocculant.CPAM has advantages of positive charge group and high molecular weight,so it has strong performance of charge neutralization and adsorption bridging.These two kinds of effects can make the destabilization and deposition of negatively charged colloidal so as to improve sludge dewatering performance.But CPAM has disadvantages of poor solubility,the high content of residual monomer and high cost at the same time.At the present stage,the wastewater quality is various,and traditional CPAM has been unable to meet the increasingly complex trentment situation.Therefore,it is of great scientific value to improve the synthesis of CPAM and modify it.This research use acrylamide(AM),acryloxyethyl trimethyl ammonium chloride(DAC)and acrylic twelve ester(LA)as monomers,and sodium polyacrylate(PAAS)as template trigger three monomer polymerization preparation for new hydrophobic modified cationic polyacrylamide(TPADL)by ultraviolet.The introduction of cationic block structure and hydrophobic monomer of TPADL enhances the viscosity,temperature resistance,salt resistance and shear resistance of TPADL.These properties make the new HACPAM have good application prospects in many fields.The main contents of this research are as follows:(1)The optimum reaction conditions is obtained through single factor and orthogonal experiments: n(PAAS): n(DAC)=1:1,UV irradiation time was 60 min,reaction pH was 4,UV light intensity was 1000 ?W·cm-2,the mass fraction of DAC was 25% and LA was 2%,mass fraction of initiator concentration and EDTA were 0.65‰ and 3%,respectively.Under these conditions,the relative molecular weight of HACPAM was 3.77 million,and the conversion rate was 98.1%.The experiment also shows that the influence of various factors on the TPADL molecular weight of the order: DAC mass fraction > pH > initiator concentration > UV irradiation time > UV irradiation time.(2)The chemical structures of TPADL and PADL were characterized by infrared spectroscopy(FTIR)and nuclear magnetic resonance spectroscopy(1H-NMR).The results showed that both of them were copolymerized by AM,DAC and LA and confirmed that TPADL forms a cationic micro block structure under the template polymerization.The thermal stability of the products can be obtained by differential thermal thermogravimetric analysis,and it is further proved that TPADL has a cationic micro block structure.(3)The properties of TPADL,PADL,TPAD and commercial CPAM were investigated by the apparent viscosity method.It can be seen from the experimental results that TPADL has a good effect of increasing viscosity,which indirectly proves that the existence of cationic micro block structure increases the tensile effect of molecular chain which further enhances the intermolecular association.Compared with other flocculants,it can be found that TPADL has better hydrophobic association and salt tolerance.(4)TPADL products were used in municipal sludge dewatering in this study.The moisture content of filter cake,the specific resistance of sludge,the supernatant turbidity and Zeta potential were used as the indexes to evaluate the performance of sludge dewatering.Cationic degree,LA content and relative molecular weight were used as variables to investigate the effect of the flocculation performance of TPADL.The experimental results showed that the optimum processing conditions: pH was 6,TPADL cation degree was 30%,the content of LA was 2%,the relative molecular weight was 377×104,the moisture content of filter cake was reduced to 64%,the specific resistance of sludge was reduced to 1.43×1012m·kg-1 and supernatant turbidity was 6.5NTU.Through the contrast experiment,it can be seen that the performance of the flocculant produced by the laboratory is better than that of the commercial CPAM and the flocculation performance of TPADL is better than that of the non template polymer PADL and non hydrophobic polymer TPAD under the same dosage.Through the analysis of Zeta potential diagram,it can be concluded that TPADL can form a cationic micro block structure,which can enhance the electrical neutralization of the polymer and make the system reach the isoelectric point quickly.Finally,according to the floc size distribution results,hydrophobic interaction can significantly improve the floc size,and the cationic block structure although contributes to increase of floc strength.The fragmentation and regeneration coefficient of the flocs were significantly improved inder the synergistic action of hydrophobic association and cationic block structure.