| Liquor pollution load, high colour, high toxicity and processing difficulty of APMP pulping effluent, which limits the development of papermaking industry in our country. Lignin degradation products, low molecular organic acid and chitosan degradation products is the main source of pollution load and toxicity. In this thesis, typical wastewater samples were collected in each chemical soak section which simulated pulping process of the unique North fast-growing poplar in laboratory scale. Several key factors that influence degradation of organic pollutes in the APMP wastewater are carefully investigated using Fenton process, to reveal mechanism and kinetics of the organic pollutants degradation. These results can off era theoretical guidance and support for the poplar APMP pulping wastewater treatment in practice application.Single factor method was used to identify dissolution concentration of lignin and sugarin the wastewater. Results show that concentration of both lignin and sugar are the key factors for the pollutant load in the wastewater. The contribution order of each pulping process factors to the pollution load in the wastewater is as follows:NaOH dosage> H2O2 dosage>reaction temperature> reaction time>Na2SiO3 dosage. In the subsequent Fenton treatment process, the degradation of both sugar and lignin is the key to reduce the pollutants concentration in the wastewater.The wastewater treatment produced from the pulping process was conducted by Fenton pretreatment experiment. The influence of various reaction conditions on CODcr and chroma removalin poplar APMP pulping wastewater pretreatment was discussed, the optimum conditions for the Fenton pretreatment are proposed as follows:Initial pH:4, reaction time:30 mins, H2O2 dosage:2.0 mL/L, FeSO4 dosage:2.4 g/L. Under this optimum condition, removal efficiency of CODcr and color are 38.7% and 65.4%, respectively. However, the CODcr’s value of the wastewater is still as high as 13000 mg/L This requires to be further biologically treated after mixing with the wastewater with low organic pollutes concentration, such as cooking squeeze grind wastewater, and washing wastewater.Fenton degradation of lignin is mainly controlled by reaction temperature, initial pH, initial concentration of lignin, initial concentration of Fe2+ and initial concentration of H2O2. Under the condition of the fixed initial pH and temperature, the chemical reaction dynamics model of Fenton degradation was established. The Fenton oxidative degradation of lignin follows this reaction rate equation: The reaction order of the Fenton degradation of lignin is 1.53. The reaction rate is mainly affected by the concentrations of the reactant, followed by Fe2+, and then H2O2. Xylose containing hydroxyl can accelerate the degradation of lignin because Xylose becomes easy to react with the branch on the lignin benzene by Fenton porcess. Under the fixed lignin of 1.0 g/L, the removal of CODcr in the lignin and xylose-mixed wastewater increases with the increasing of xylose concentration. This indicates the existence of xylosesynergistic effect on the lignin degradation.FT-IR spectrum analysis shows that various functional groups derived from lignin and sugar were found in the wastewater, which become the main source of the wastewater pollution load. The chemical soaking process leads to the dissolving of polysaccharide and lignin. After Fenton pretreatment of lignin in the wastewater, the absorption band of methoxybelonging to lignin disappears, which suggests the degradation of lignin and anew matter formationwith a conjugated structuredue to the reaction between phenyl ring and benzene ring of lignin. TGA analysis shows that after Fenton pretreatment, part of lignin, LCC, etc. macromolecular organics in the wastewater degrades into smaller molecular organics. In addition, CHNS elemental analysis reveals that both C and H content decreasesin the Fenton pretreated wastewater. This result suggests that a deep degradation of organics in the wastewateroccurs and leads to the production of CO2 and H2O.GC-MS spectrum shows that the number of VOC pollutants in the wastewater increases from 21 to 28 after Fenton pretreatment. The relative content of allbenzene ring organic substances increases from 79.6% to 84.2%. Among them, the relative contentof two benzene rings increases from 38.8% to 44.8%, which increase the whole organics concentration because of their poor degradation performance under Fenton treatment conditions. Instead, the short-chain (C<8)organics in the treated wastewater aids the degradation process while its relative content increases from 1.0% to 7.8%.The breaking off of some substituent groups and/or the ring opening ofbenzene rings substanceto short-chain organics can improve the biodegradabilitythus leading to a cost cut off to the further treatment of Fenton pretreated waste water. |
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