| As one of the main pollution sources of waters, pulping and papermaking effluent has become a bottleneck in the development of papermaking industry. This kind of wastewater has characteristics of high concentration organic substance, abundant lignin and other polyphenols which are difficult to be decomposed by microbe. Therefore it is very hard to treat with conventional methods for wastewater treatment, such as physical or chemical or biological treatment. By now, there is not very effective technology of treating pulping and papermaking wastewater, especially for middle-scale factories, because of the non-wood fiber material, low technology and small scale. In this paper, a novel biomimetic flocculation method was developed. It was confirmed that the biomimetic oxidation could degrade lignin model. The biomimetic flocculation was also used to treat wastewater of paper mill, and it obtains great success.In this paper, a model compound ofβ-O-4 type lignin model compound (i.e. guaiacyglycerol-β-guaiacyl ether) was synthesized with a modified method. The synthesis method of an impant intermediate,i.e. 4-(α-bromoactyl)-guaiacol was improved, Its yield reached 80%. The combination of infrared spectra, 1H-NMR analysis was used to identify the chemical structure of the product and related precursors.The lignin model compound of guaiacylglycerol-β-guaiacyl ether was treated with a Fe-carboxyl acid complexes (Fe-CA)/H2O2 biomimetic system. The reaction products were analyzed by 13C-NMR and GC-MS. The mechanism of the biomimetic degradation of thisβ-O-4 structure was also explored. It was found there were a lot of carbonyl, carboxyl and hydroxyl groups in the degraded products. It was proved that the following three types of reaction were caused by the Fe-CA/H2O2 system:β-aryl ether cleavage, Cα-Cβcleavage, Cβ-Cγcleavage. It was found that Fe-CA/H2O2 biomimetic system could deeply degrade MWL from Eucalyptus globules. Carboxyl, carbonyl and hydroxyl group increased significantly. That can increase the proximity between degraded lignin and cationic inorganic or organic flocculate. As a result wastewater COD will be decreased greatly.A stable and high efficiency Fe2+-carboxyl acid complexes (Fe-CA) which could simulate the lignin peroxidase to treat the paper mill wastewater by quickly oxidation and flocculation treatment. As compared with Cu-pyridine biomimetic system and Cu-amine biomimetic system, the Fe-CA biomimetic system was more effective. Furthermore effect of biomimetic dosage, pH, temperature on wastewater treatment was investigated respectively. According to the experimental results and condition of a middle-scale paper mill, an integrated treatment process was designed and optimized. The optimal coagulant and its actual application parameters of coagulation for the wastewater were acquired by pilot experiment. The optimal condition was as follow. Fe-CA 0.02mol/m3; H2O2 150g/m3; Al2(SO4)3(18H20) 300g/ m3; CPAM 5g/m3; 30min reaction time and 6h sedimentation.Based on the results stated above, a mill scale Fe-CA biomimetic flocculation process was developed for the mixed wastewater treatment of a paper mill in Shandong Provice. The design of the biomimetic flocculation system was also carried out in our research group. After one month continual operation, very good COD and SS elimination effect was achieved. The elimination rate of main pollutant such as CODCr and SS reached above 55%, 60% respectively. Through lignin massive removing, the effect of subsequent biochemical was also enhanced. The process have merit of simple equipment, easy operation and low cost. It is also suitable for treatment of heavly duty effluent.
|
PDF Full Text Request