Preparation Of PDA Under Ultrasonic And Applications Of It For Sludge Dewatering

PDA is a linear polymer, derived from polymerization reaction occurred by AMand DMDAAC. It has the stability of the molecular structure, high charge density, goodsolubility in water, efficient, non-toxic and so on. it is able to adapt to a wide range ofpH. As early as the1960s, foreign patent report on the synthesis of PDA, in the1970s,they conducted a large-scale industrial production. Our PDA synthesis research began inthe late1980s, and now we have small-scale industrial production. However, theproduct still exist a certain gap in performance and applications, compared with similarforeign products.In aqueous media, ultrasound can generate cavitation. In the process of expansionand burst, the cavitation bubbles generated transient high temperatures and pressures,and the rapid warming of the cooling environment. This process can stimulate the watermolecules to produce a small amount of hydrogen radicals and hydroxyl radicals, andthen trigger a series of radical reactions. Therefore, the chemical reaction of theultrasonic technology can accelerate the speed of Organic Reactions, to simplify thereaction conditions. It has great potential applications in the field of organic synthesis.The paper examines the development status of the PDA and the organic polymerflocculant. Integrated ultrasonic chemical reaction mechanism, the paper determined thesynthesis method of the PDA under ultrasonic conditions. The paper went on to studythe improvement of the synthesis conditions in the PDA synthesis under ultrasonicconditions. And characterized the products obtained by various means. Analyze andverify the nature and structure of the PDA’s. Finally, the PDA was used in thedewatering of activated sludge. Cake moisture and filtrate turbidity as the marker,studied the influence of the intrinsic viscosity of PDA and the different dosage onsludge dewatering performance.The paper’s main conclusions are as follows:Firstly, under ultrasonic assisted conditions, synthesized PDA in solutionpolymerization, studied on the synthesis process conditions of PDA, determined the bestconditions of the various processes through single factor experiments. At the end,elected the optimum process conditions, namely:30%for the total monomerconcentration,30℃for reaction temperature,1h for ultrasonic time,2/8for themonomer ratio,0.4‰for the initiator concentration,0.5‰for the dosage of sodium benzoate and0.5‰for the dosage of EDTA,6for pH,0.3‰for the dosage of urea.Intrinsic viscosity of the PDA reached to14.6dL/g.Secondly, Discovered the existence of a variety of chemical bonds in the infraredspectrum, which is the characteristics of chemical bonds of AM and DMDAAC. itproves the Polymer is PDA. By DTA-TGA, found that the PDA structure is very stableat room temperature. By NMR spectra analysis, The existence of various groups in thepolymer is found, proving once again that the product is polymerization products of AMand DMDAAC. But also found that the polymer molecule chains are more evenlydistributed in ultrasonic assisted synthesis conditions. SEM analysis showed that thepolymer PDA had a unique three-dimensional network structure, which is Multi-leveland close. This makes it stronger adsorption and bridging ability than similar polymers.Its unique structure makes it can absorb the water column particulate pollutants anddissolved pollutants and so on more powerfully, to clean up pollutants in water bodiesmore thoroughly.Finally, use homemade PDA to treat Dewatering of activated sludge. study on theimpact of the intrinsic viscosity and the PDA dosage to sludge dewatering performance.The results showed that: in the viscosities of the same features, with the increase indosage, the sludge cake moisture and filtrate turbidity showed the trend which is firstdecreased and then increased. In the conditions of the same dosage, as the intrinsicviscosity increases, the optimum dosage is reduced. The experiment has been optimizedconditions for flocculation: When the intrinsic viscosity14dL/g, the dosage is1.8kg/tdry sludge. This allows the sludge cake moisture and filtrate turbidity were reduced to65%,19.7NTU. Compare the sludge dewatering effect between homemade PDA andorganic flocculants domestic sewage treatment plants commonly used. Can see thatfrom the study, sludge dewatering effect of homemade PDA is better than the other fourindustrial cationic flocculant, dosing less, but treatment effect is sound.