| The diatomaceous earth is a silicastone with biogenic origin,it has the advantages of high adsorption,high porosity,large surface area,and stable chemical properties etc.,thus the diatomaceous earth as well as the modified diatomaceous earth have great utilization potentiality in the fields of adsorbing and removing of toxic gas and solid materials,coating industry,food industry as well as sewage treatment.The copolymer(that is anionic polyacrylamide,APAM)of acrylamide(AM)and acrylic acid(AA),as a water-soluble polyelectrolyte,is widely applied in many fields such as petroleum,papermaking,food chemistry,and water treatment etc.Due to the high level of cost performance,APAM is one of the most widely used flocculating materials currently for in the water treatment industry.However,since the linear macromolecular chain of APAM tends to coil and tangle etc.in the electrolyte solution,it could lead to the decline of flocculation efficiency.To solve this issue,we produced a series of organic/inorganic hybrid flocculation composite by adopting the method of surface grafting of AM/AA copolymer onto diatomaceous earth.Due to the unique macromolecule grafting structure of flocculation composite material,it keeps great configuration stability in the electrolyte solution,which greatly improves the flocculating performance of the flocculating material.This article produces a series of composite flocculant(PAAD series)by the methods of aqueous solution polymerization,dispersion polymerization,and emulsion polymerization etc.1.The aqueous solution polymerization has the advantages of simple procedure,less environmental pollution,and low cost etc.In this research,we use the free radical aqueous solution polymerization method to synthesize the anionic composite flocculant(abbreviation: S-PAAD)and confirm the optimal reaction conditions for the synthesis.The sedimentation time is just 3.31 s,while the commercial flocculant needs 9.12 s to settle,the settling rate of the new flocculant is three times faster than the commercial flocculant.The transmittance measurement of the liquid supernatant,we found that the transmittance of the new flocculant is higher than the commercial flocculant by 8%.2.The dispersion polymerization in saline medium is a new type of polymerization for water-soluble polymer,the saline is used as the dispersion medium to avoid the using of organic solvent.The product can be diluted directly for usage with the advantage of rapid dissolving.The dispersing type of anionic flocculating composite materials presents flocculating performance that is more effective,when the salt concentration reaches 21wt%,the system viscosity is relatively appropriate,after fixing the salt concentration,change the stabilizer content to 14wt%,and confirm the optimal formulation.A great flocculation effect is achieved by just adding 10 ppm of this product.Its flocculation rate is 2 times faster than the traditional product,the transmittance reaches 92.41%,while the transmittance of the traditional flocculant is less than 90% at its optimal dosage.3.The emulsion polymerization has the advantages of rapid reaction rate,low viscosity of the polymerization system,rapid heat dissipation,and high molecular weight etc.,thus we adopt the emulsion polymerization method to produce the composite flocculant.In the research,we take W/O emulsion stability and flocculating performance as the main indexes to optimize the reaction parameters and confirm the optimal reaction conditions in the end.The results of the flocculating performance test show that: As the content of flocculant increasing,the flocculating performance gradually increases,the flocculation rate is accelerated;when the adding amount is over-dose,the system transmittance gradually decreases,the sedimentation time gradually slows down,the sewage system tends to be stable afterwards,the transmittance as well as the sedimentation time don't have much variances.When the dosage is optimal,the transmittance reaches up to 94.6%,the sedimentation time is 14 s. |
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