【作者】 袁林；

【导师】 刘敏； 罗先华；

【作者基本信息】 四川大学 ， 环境工程（专业学位）， 2021， 硕士

【摘要】 随着城镇污水总磷排放标准的提高,迫切需要开发更加高效的除磷材料。为弥补现有纳米纤维素材料的不足,本研究使用聚酰胺环氧氯丙烷树脂（Polyamide Epichlorohydrin Resin,PAE）和聚乙烯醇（Polyvinyl Alcohol,PVA）交联纳米纤维素（CNFs）,随后负载氢氧化铁,制备两种新型复合材料,即CNFs-PAE-Fe和CNFs-PVA-Fe。并对两者的除磷性能进行探究,其结果如下:PAE对纳米纤维素的交联效果优于PVA,CNFs-PAE-Fe的最佳制备条件如下:将CNFs在转速20000 rpm下均质30 min,并在搅拌过程中按质量比m（PAE）:m（CNFs）=0.6:1加入PAE,随后再按质量比m（Fe（OH）₃）:m（CNFs）=1.5:1加入三氯化铁（Fe Cl₃）和氢氧化钠（Na OH）。反应完成后用水稀释至0.5 wt%,并超声10 min（40 k Hz,120 W）制成均质原浆材料,最后进行冷冻干燥获得颗粒状改性纳米纤维素材料。在该条件下制备所制备的CNFs-PAE-Fe具有较好的稳定性,吸附除磷反应结束后,材料形貌依然保持完整,无破碎现象。通过扫描电镜（SEM）、能谱仪（EDS）和比表面积孔径分析仪（BET）分析发现,氢氧化铁成功负载在改性后的纳米纤维素上,且改性后比表面积显著增大。CNFs-PAE-Fe对磷的吸附容量随磷初始浓度的增加而增加,其对磷的最大吸附容量为16.48 mg/g。此外,本研究还考察了初始p H（3.0-12.0）对CNFs-PAE-Fe除磷的影响。结果表明,在p H=4.0时吸附容量最高,其对溶液中磷的去除率可达91.70%;在初始p H=7.0时,去除率为87.70%,仅下降了8.78%。可见,CNFs-PAE-Fe在中性时也具有较好的吸附效果。最后,本研究探讨了不同吸附时间对CNFs-PAE-Fe除磷性能的影响。结果表明,吸附时间的延长有利于CNFs-PAE-Fe对磷的吸附;其在24 h时能达到最佳吸附状态。当洗脱液按V（Na Cl）:V（Na OH）=3:2进行配比时,其对磷的解吸效果最佳。解吸后使用冷冻干燥的干燥方式使材料在再生5次后形貌依旧保持完整。实际废水的动态吸附结果表明,A厂和B厂的二沉池出水在经过100 min和220 min的动态吸附后,出水磷浓度均低于0.30 mg/L,均能达到沱江和岷江流域的总磷排放标准（DB51/2311-2016）（<0.30 mg/L）。可见,CNFs-PAE-Fe在实际生活污水的深度除磷方面具有良好的应用前景。为分析CNFs-PAE-Fe的除磷机理,本研究使用四种吸附动力学模型（准一级、准二级、Elovich和M-W内扩散）和四种等温吸附模型（Langmuir、Freundlich、Temkin和Toth）对CNFs-PAE-Fe的除磷过程进行了拟合。结果表明,准二级动力学模型（R²=0.995）和Langmuir模型（R²=0.963）具有较好的拟合能力;这表明材料是以化学吸附为主的单分子层吸附。此外,通过傅里叶红外光谱仪（FTIR）和X射线光电子能谱仪（XPS）的表征结果也发现,静电引力和配体交换作用是CNFs-PAE-Fe除磷的主要原因,且吸附后磷主要以Fe₂（HPO₄）₃和Fe（H₂PO₄）₃的形式存在于CNFs-PAE-Fe上。更多还原

【Abstract】 With the improvement of the total phosphorus discharge standard for urban sewage,there is an urgent need to develop more efficient phosphorus removal materials.To make up for the shortcomings of existing nanocellulose materials,this study uses polyamide epichlorohydrin resin（PAE）and polyvinyl alcohol（PVA）to cross-link nano cellulose（CNFs）,and then load hydrogen.Iron oxide,to prepare two new composite materials,namely CNFs-PAE-Fe and CNFs-PVA-Fe.And the phosphorus removal performance of the two is explored,and the results are as follows:The crosslinking effect of PAE on nanocellulose is better than that of PVA.The best preparation conditions for CNFs-PAE-Fe are as follows:homogenize CNFs at a speed of 20000 rpm for 30 min,and press the mass ratio m（PAE）:m（CNFs）=0.6:1 add PAE during the stirring process.Then add ferric chloride（Fe Cl3）and sodium hydroxide（Na OH）according to the mass ratio m（Fe（OH）3）:m（CNFs）=1.5:1.After the reaction is complete,dilute with water to 0.5 wt%,and ultrasonicated for 10 min（40k Hz,120 W）to make a homogeneous original slurry material,and finally freeze-dried to obtain a granular modified nano-cellulose material.The CNFs-PAE-Fe prepared under this condition has good stability.After the adsorption and dephosphorization reaction is completed,the morphology of the material remains intact and there is no fragmentation.Through scanning electron microscopy（SEM）,energy spectrometer（EDS）and specific surface area pore size analyzer（BET）analysis,it was found that ferric hydroxide was successfully loaded on the modified nanocellulose,and the specific surface area increased significantly after modification.The adsorption capacity of the CNFs-PAE-Fe for phosphorus increases with the increase of the initial concentration of phosphorus,and its maximum adsorption capacity for phosphorus is 16.48 mg/g.In addition,this study also investigated the effect of initial p H（3.0-12.0）on CNFs-PAE-Fe phosphorus removal.The results show that the adsorption capacity is the highest at p H=4.0,and its removal rate of phosphorus in the solution can reach 91.70%;at the initial p H=7.0,the removal rate is87.70%,which is only a decrease of 8.78%.It can be seen that CNFs-PAE-Fe also has a better adsorption effect when it is neutral.Finally,this study explored the effect of different adsorption times on the performance of CNFs-PAE-Fe phosphorus removal.The results show that the extension of the adsorption time is beneficial to the adsorption of CNFs-PAE-Fe to phosphorus;it can reach the best adsorption state at24h.When the eluent is proportioned according to V（Na Cl）:V（Na OH）=3:2,its desorption effect on phosphorus is the best.After desorption,freeze-drying is used to keep the material intact after 5 times of regeneration.The results of dynamic adsorption of actual wastewater show that the effluent phosphorus concentration of the secondary sedimentation tanks of Plant A and Plant B is less than 0.30 mg/L after dynamic adsorption for 100 min and 220 min.Both can reach the total phosphorus emission standards in the Tuojiang and Minjiang river basins（DB51/2311-2016）（<0.30 mg/L）.It can be seen that CNFs-PAE-Fe has a good application prospect in the deep dephosphorization of actual domestic sewage.To analyze the dephosphorization mechanism of CNFs-PAE-Fe,this study used four adsorption kinetic models（quasi-first,quasi-two,Elovich and M-W internal diffusion）and four isotherm adsorption models（Langmuir,Freundlich,Temkin and Toth）Fitting the dephosphorization process of CNFs-PAE-Fe.The results show that the quasi-second-order kinetic model（R2=0.995）and the Langmuir model（R2=0.963）have good fitting ability;this indicates that the material is a monolayer adsorption dominated by chemical adsorption.In addition,through the characterization results of Fourier Infrared Spectroscopy（FTIR）and X-ray Photoelectron Spectroscopy（XPS）,it is also found that electrostatic attraction and ligand exchange are the main reasons for CNFs-PAE-Fe phosphorus removal,and the phosphorus after adsorption,It mainly exists on CNFs-PAE-Fe in the form of Fe₂（HPO₄）₃ and Fe（H₂PO₄）₃.更多还原