Preparation Of PDA And Applications Of It For Removal Of Organic Pollutants In Water

Phthalate esters （PAEs） is such an important chemical raw material that is commonly present in environmental medium, which is also called endocrine disruptors or environmental hormones. Although the PAEs has been widely used in many fields, the material has posed a potential threat to human or animal endocrine systems, and thus a toxic to reproduction and development. Furthermore, continuing pollution of the urban source water from PAEs has also posed a lot of attention. Because PAEs was generally characterized by stability, cumulative, durability and resistant to degradation under common condition, we should carry out more effective measures on preventing the urban source water from PAEs pollution. Humic acid is an important class of natural organic matter in water, and also an important component of natural organic matter, due to its unique physical and chemical properties, It could affect Human and aquatic life, so it is essential to do the research for removing it.In this study, firstly, coagulation-flocculation experiments were carried out in an attempt to obtain higher removal efficiency of phthalate esters in water. Secondly, the organic coagulant diallyl dimethyl ammonium chloride and acrylamide （PDA） was grafted by free radical polymerisation of acrylamide monomer （AM） onto the cationic monomer dimethyl diallyl ammonium chloride （DMDAAC）. Thirdly, the synthesized PDA was characterized and the properties of which were analyzed. Fourthly, a new method to detect the residual monomers AM concentration in PDA was proposed using PDA near infrared spectroscopy. Lastly, coagulation-flocculation process was applied to the removal of PAEs and Hunic Acid in water with the prepared product, which also included the investigation of the coagulation-flocculation mechanism, and parameters affecting the coagulation-flocculation behavior.The main conclusions and contents in the study were as following:（1） Coagulation-flocculation process was carried out for the removal of the PAEs containing dimethyl phthalate （DMP） and diethyl phthalate （DEP） in water, and a comparison was made using the polymeric aluminum chloride （PAC）, polymeric ferric sulfate（PFS）, poly diallyl dimethyl ammonium chloride（PDMDAAC） and industry CPAM. In addition, parameters affecting the coagulation-flocculation process such as coagulant dosage, pH, mixing and settling time, were investigated. The results showed that the organic coagulant PDMDAAC, industry CPAM and self-made CPAM exhibited higher coagulation efficiency than inorganic coagulant: PAC and PFS. In addition, the composite coagulant （PDMDAAC/CPAM） presented better coagulation effect on treatment efficiency than individual coagulant （PDMDAAC）. Effects of the operational variables on the treatment efficiency follow dosage were > pH > mixing time > settling time order using the principal component analysis.（2） Cationic polyacrylamide （PDA） was prepared by the copolymerization of a cationic monomer dimethyldiallylammonium chloride （DMDAAC） with acrylamide （AM） through inverse emulsion polymerization, where Span-80 and Tween-80 were used as emulsifier and liquid paraffin respectively with stage addition into the reaction system. The effect of reaction variables such as oxidant/reductant （NaHSO₃/K₂S₂O₈） and DMDAAC /AM mass ratio, pH value, dosage of EDTA, temperature, reaction time, nitrogen blowing time were investigated in detail. The optimum conditions used as followed: the NaHSO₃/K₂S₂O₈ mass ratio was 5:3, the DMDAAC /AM was 2:8, the pH value was was 8.0, the dosage of EDTA was 0.6mL, the reaction time was 5.0h, nitrogen blowing time was 40.0min.（3） Near infrared reflectance spectroscopy（NIRS） was used as a rapid and accurate method to determine the residul of acrylamide monomer in the product of diallyl dimethyl ammonium chloride and acrylamide. 38 of samples were self-prepared in the laboratory and their near infrared spectroscopy were scanned, among which, seven bands were investigated and the characteristic peak intensity in each band was as the independent variables, where the residual AM concentration was considered as the dependent variable. Also, partial least squares （PLS） method was used to establish the NIRS calibration modeling. The characteristic peaks and the entire spectrum segment as the input layer neurons in radical basis function （RBF） were investigated for establishing the mathematical conversion NIRS calibration modeling. For reducing the NIRS spectrum noise, the wavelet analysis was used as pre-treatment process. The measured value was determined by using precipitation titration and a comparison was made between the simulated and measured value. The result showed that the calibration model: PLS modeling and （RBF neural network） established in this paper exhibited a remarkable feasibility to predict the cationic degree of PDA based on the near infrared spectroscopy.（4） Coagulation-flocculation was carried out for treatment of water containing the phthalic acid ester（PAEs） using the organic coagulant PDA. Parameters affecting the coagulation-flocculation process such as coagulant dosage, pH value, mixing and settling time, were measured. The result showed that PDA has better flocculation efficiency in comparison to inorganic coagulant.（5） Humic acid in water was treated with PDA. The results suggested the impact of some factors on the treatment efficiency of humic acid. In addition, the fractal dimension of the flocs generated after the coagulation-flocculation was investigated. In general, the fractal dimension ranges from 1.10 1.55. The flocs’ structure presented the same fractal characteristics with strong self-similarity. It showed a positive correlation between the humic acid removal and the fractal dimension of the formed flocs.