Synthesis And Performance Evaluation Of Weakly Cross-linked Cationic Polymer Flocculant

Flocculation is widely used and plays an important role in many wastewater treatment technologies.At present,the traditional cationic polymer flocculant is easy to crimp in high salt concentration sewage due to its linear structure.Especially in the stage of oil field sewage flocculation treatment,its high salinity makes the conformation of flocculant molecules change,the main chain curl deformation,and the sewage treatment effect is reduced.In order to ensure that flocculant molecules will not crimp and deform in high salt concentration wastewater and improve the treatment effect of cationic flocculant wastewater.In this paper,a kind of cationic flocculant with molecular structure as a net was prepared by means of light crosslinking,the synthetic conditions were optimized and its structure was characterized.The removal effect of pollutants in simulated sewage and car washing wastewater was compared and discussed.The mechanism of action of the flocculant was analyzed and summarized.The relative molecular mass and conversion rate of the polymerization products were used as the optimization indexes.A series of net cationic flocculants were synthesized by aqueous solution polymerization,the influence of each factor on the polymerization was investigated,the experimental results show that:At the reaction temperature of 20℃,the mass fraction of the total monomer is 40%,and the molar ratio of monomer AM to DMC is 5:1,the dosage of crosslinking agent was 5ppm,and the dosage of solvent was 3%of the monomer mass,the addition amount of V-50 is 0.02%of the mass of monomer,and the addition amount of REDOX initiator is 0.06%of the mass of monomer in the complex initiator system,the pH value of the reaction system was 6.5 and the reaction time was 3h,the weak crosslinked cationic polymer flocculant with good treatment effect can be obtained.The structure and composition of the flocculant were characterized by IR,NMR and SEM,and the thermal stability of the product was analyzed.The synthetic reticulated cationic flocculant and two kinds of linear cationic flocculants were applied to the removal of sodium bentonite suspension.The effects of flocculant dosage,molecular weight and cation degree,sewage pH value and salt concentration on the transmittance,Zeta potential and flocculation sedimentation rate of supernatant after flocculation treatment were compared and discussed,the results show that the self-made mesh flocculant can achieve the treatment effect of less dosage,wider pH applicable window and higher superfine liquid transmittance.The study on pollutant removal of car washing wastewater from a car washing shop in chengdu city was carried out by the application of net cationic flocculant and two kinds of linear cationic flocculant in the market,the removal effects of flocculant dosage and wastewater pH value on three pollution indexes of CODcr,LAS and turbidity were compared and discussed,and the flocculant PAC was combined with three cationic flocculants to treat car washing wastewater.The results show that the self-made flocculant has the best treatment effect when it is treated separately and in combination.By analyzing the treatment effects of various flocculants at different salt concentrations and the particle size changes of floc treated by different flocculants before and after crushing,It was found that the net cationic flocculant had better anti-salt flocculation effect,the flocculant molecules and their flocculations are more resistant to shear interference,the flocculation mechanism of reticulated cationic flocculant was summarized.