Ultraviolet-initiated Synthesis Of APAM And Applications For Removal Of DEHP From Water

Dioctyl phthalate (C24H38O4, DEHP, MW=390.57) made of octanol or isooctylalcohol (2-EH) and phthalic acid is a phthalic acid ester, commonly called DEHP. Thephthalic acid esters (PAEs) compounds is a kind of important chemical raw material,and it is widely used in rubber, plastic, etc. However, PAEs is able to cause a pollutionto aquatic environment containing the lakes and rivers, posing a potential threat tohuman health, thus indicating that a timely and effective control measures need to bestudied for the control of the PAEs. The DEHP removal by coagulation-flocculationprocess in this study was investigated in which the coagulants that plays an core role inreducing the hazardous materials need to be studied further.Anionic polyacrylamide (APAM) that is polymerized with anionic monomer andacrylamide is a water-soluble polymer. There is a carboxylic acid polar (—COOH)functional groups in the structure of APAM, which makes the APAM has a goodadsorption and bridging ability. APAM has been wildely used in the fields of watertreatment, chemical industry, oil recovery and mineral beneficiation. However, usingcoagulation-flocculation process to remove PAEs has not been well understood. In thisstudy, the synthetic flocculant with high intrinsic viscosity and low dissolution time wasused in removing organic pollutant PAEs from water.The main contents in this research were as follows:①The synthesis and optimization of anionic polyacrylamide: Fistly, with anexisting technique for the synthesis of anion polyacrylamide (APAM), an excellentanionic polyacrylamide flocculant P(AM/AA/NaOH) was synthesized using acrylamide(AM), acrylic acid (AA) and sodium hydroxide (NaOH) under ultraviolet (UV)irradiation. During the synthesis, parameters affecting performance of APAM wasstudied in detail. By single factor experiment and orthogonal experiment, the optimalconditions obtained in this study indicated that the monomer mass ratiom(AM):m(AA):m(NaOH) is7:2:1, the total monomer mass fraction is35%, the initiatorconcentration is0.15%, and the illumination time is50min. Prepared under theconditions, the anionic polyacrylamide had a molecular weight of16.94million, whichshowed a good solubility.②The structural characteristics of the copolymer P (AM/AA/NaOH): the Analyticresults showed that a variety of chemical bonds belonging to the AM and AA monomers were found in the APAM through fourier transforms infrared spectroscopy (FTIR)analysis, confirming that the polymer was prepared successfully. TG-DTA analysisindicated that the structure of APAM is very stable at room temperature. The scanningelectron microscopy (SEM) analysis showed that the surface of APAM was net structure,having a large number of layered microporous, which made the specific surface area ofpolymer greatly increased. The ultraviolet spectrum analysis demonstrated that themonomers AM and AA did occur the polymerization reaction and produced a newpolymer. Finally, the nuclear magnetic resonance (NMR) spectrum analysis showed thatthe proton peaks originate from AM and AA appearred in spectra of APAM, thusindicating that the APAM were the co-polymer of the monomers AM and AA.③Removal of DEHP from water through flocculation process by APAM: Theeffects of dosage, pH and stirring time on the removal of DEHP were investigated.Through the single factor experiment, it was found that the removal efficiency of DEHPwas up to82.8%with a dosage, pH, mixing time and settling time of7.5mg/L,2.0,4.0min and120min, respectively. The results of orthogonal optimization experimentindicated that with a dosage of7.5mg/L and mixing time of4.0min at pH2.0, theremoval efficiency of DEHP of82.8%was achieved. Compared with two commercialanionic polyacrylamide flocculants, the self-prepared APAM had a better effect onremoval of DEHP with less dosage used.