磁改性农用秸秆吸附联用反硝化脱氮去除水源水中硝酸盐的研究

发布时间：2018-05-15 16:08

本文选题：小麦秸秆 + 吸附　；参考：《济南大学》2017年硕士论文

【摘要】：硝酸盐大多数为离子型化合物,是无机污染物的一类,极易溶解在水体当中。硝酸盐影响人体血液输送氧的能力,严重危害人体健康。在众多水处理工艺中,单一的水处理方法很难做到对硝酸盐的彻底无害化处理。本研究利用吸附法高效吸附水源水中的硝酸盐并结合微生物反硝化使硝酸盐转化为N2释放从而实现无害化处理。选用农作物小麦秸秆作为吸附剂原料,通过乙二胺交联法和共沉淀法制备出磁改性小麦秸秆吸附剂,并对其进行物化表征来探究改性效果及吸附机制。通过静态吸附和动态吸附试验来探究不同吸附条件对吸附效果的影响并分析吸附机理。针对硝酸根的可生物还原特性,驯化培养反硝化菌对饱和吸附剂进行再生处理,探讨吸附剂反硝化再生的可行性。主要结论如下:(1)以小麦秸秆为原料,利用乙二胺交联法成功制造出改性小麦秸秆吸附剂,通过对不同实验因素的分析,确定乙二胺改性小麦秸秆吸附剂最佳合成条件为:小麦秸秆投加量2g;乙二胺用量3mL;N,N-二甲基甲酰胺(DMF)用量10mL;三乙胺用量10mL;醚化过程时间60min,温度90℃;催化过程时间60min,温度90℃;接枝反应过程时间90min,温度90℃。(2)对原小麦秸秆(WS)、附磁小麦秸秆(MWS)、乙二胺改性小麦秸秆(AWS)、磁改性小麦秸秆(M-AWS)四种秸秆吸附剂吸附效果进行对比,发现原小麦秸秆(WS)、附磁小麦秸秆(MWS)对硝酸根基本没有吸附效果,而乙二胺改性小麦秸秆(AWS)、磁改性小麦秸秆(M-AWS)对硝酸根有很好的去除效率。本实验最终确定选择磁改性小麦秸秆作为吸附剂,吸附完成后可以在外加磁场作用下快速分离出来,在回收利用方面比单纯乙二胺改性小麦秸秆有优势。(3)未处理的小麦秸秆等电点pHpzc为2.1,而通过乙二胺交联法和共沉淀法制备的磁改性小麦秸秆吸附剂的等电点pHpzc为7.1;通过X-射线粉末衍射(XRD)和红外光谱表征(FTIR)分析磁改性小麦秸秆吸附剂引入大量带正电荷的季胺基官能基团,从而导致小麦秸秆的表面发生了非常明显的电荷变化;改性后制备得到的磁改性小麦秸秆吸附剂表面负载了大量季胺基官能团和Fe3O4粒子,因此吸附剂表现出较高的正电荷性,有利于去除水溶液中的硝酸根。(4)磁改性小麦秸秆吸附硝酸根反应过程非常快,一般在20min内就能完成;反应过程受pH影响,pH在4-10范围内,吸附剂对硝酸根有较高的去除率;受水环境温度影响不大,温度为20,30和40℃时,磁改性小麦秸秆对NO3-的吸附容量分别为54.5mg/g,51.7mg/g和49.8mg/g;该吸附剂吸附硝酸根的吸附等温线符合Langmuir吸附等温线模型;伪二级动力学模型能够很好地描述磁改性小麦秸秆吸附剂对硝酸盐的整个吸附过程,其拟合曲线基本不会与吸附数据发生偏移,相关系数(R2)较高,为0.998-0.999,说明吸附过程是化学吸附而且是一个限速吸附过程。(5)培养驯化反硝化菌5d以后,活性污泥基本上适应了本实验的培养环境;15d-22d左右,活性污泥的生长速率明显加快;22d-30d,活性污泥的生物量基本上达到稳定状态。经过培养驯化,本实验的活性污泥成功富集了一定数量的硝酸根还原菌,通过对菌群DNA的提取和菌群DGGE基因片段的分析可知反硝化菌成为优势菌群,微生物群落适用于硝酸根的还原。(6)磁改性小麦秸秆吸附剂对硝酸根吸附的动态实验,填柱高度、过柱流速、初始硝酸根浓度、pH等因素对过柱实验的影响较大。填柱高度大,能够吸附更多的硝酸根,但是并没有增加磁改性小麦秸秆吸附剂对硝酸根的吸附效率;进入吸附柱的硝酸根浓度高,则吸附柱内的吸附剂很快被进水中硝酸根占据,因此吸附柱在很短时间内就达到饱和状态;控制过柱流速,延长接触时间在一定情况下可以增加吸附效率,但时间过长也会影响实际工艺过程。因此,选择恰当的过柱条件可以有效提高过柱效率。(7)对硝酸根吸附饱和的磁改性小麦秸秆进行微生物反硝化再生,结果表明静态吸附后,驯化后的厌氧型微生物对磁改性小麦秸秆吸附剂的一次还原效率约为93%,二次还原效率约为89%,第五次还原效率80%左右;动态吸附硝酸根后,通过一次和二次穿透点的不同,计算可知反硝化微生物对磁改性小麦秸秆吸附剂的一次还原效率约为89%,二次还原效率约为83%;吸附联用微生物还原后可以达到硝酸根的彻底无害化处理。
[Abstract]:Most of the nitrate is ionic compound, which is a kind of inorganic pollutant. It is very easy to dissolve in water. Nitrate affects the ability of human blood to transport oxygen and seriously endangering human health. In many water treatment processes, a single water treatment method is difficult to do the thorough and harmless treatment of nitrate. This study uses adsorption method efficiently. The nitrate was adsorbed in water source water and combined with microbial denitrification to make nitrate conversion to N2 release to achieve the harmless treatment. The wheat straw was selected as the absorbent material, the magnetic modified wheat straw adsorbent was prepared by the ethylamine crosslinking method and the coprecipitation method, and its physicochemical characterization was carried out to explore the modified effect and adsorption. Mechanism. Through the static adsorption and dynamic adsorption tests to explore the effects of different adsorption conditions on the adsorption effect and analyze the adsorption mechanism. In view of the bioreducibility of nitrate, the domesticated culture denitrifying bacteria regenerated the saturated adsorbent and discussed the feasibility of the denitrification regeneration of the adsorbent. The main conclusions are as follows: (1) wheat straw Straw was used as raw material to make the modified wheat straw adsorbent successfully. Through the analysis of different experimental factors, the optimum synthesis conditions of the modified wheat straw sorbents were: 2G of wheat straw, 3mL of ethylenediamine, N, N- two methyl formamide (DMF) dosage 10mL; three ethylamine dosage 10mL; etherification process. 60min, temperature 90 C; catalytic process time 60min, temperature 90 C; grafting reaction time 90min, temperature 90. (2) of wheat straw (WS), magnetic wheat straw (MWS), ethylenediamine modified wheat straw (AWS), magnetic modified wheat straw (M-AWS) four straw adsorbents adsorption effect was compared, found the original wheat straw (WS), magnetic wheat straw attached to the wheat straw. MWS has no adsorption effect on nitrate, while ethylene diamine modified wheat straw (AWS), magnetic modified wheat straw (M-AWS) has a good removal efficiency to nitrate root. Finally, the magnetic modified wheat straw was selected as an adsorbent. After the adsorption, it can be quickly separated under the effect of external magnetic field. The pure ethylenediamine modified wheat straw has advantages. (3) the pHpzc of the untreated wheat straw is 2.1, and the isoelectric point pHpzc of the magnetically modified wheat straw adsorbent prepared by the ethylenediamine crosslinking method and the coprecipitation method is 7.1; the magnetic modified wheat straw adsorbent is introduced by the X- ray powder diffraction (XRD) and the infrared spectrum characterization (FTIR). With the positive charge of Ji Anji functional group, the surface of wheat straw has a very obvious charge change, and the surface of the magnetic modified wheat straw adsorbent is loaded with a large number of Quaternary functional groups and Fe3O4 particles, so the adsorbent shows a higher positive charge and is beneficial to the removal of the nitrate in the aqueous solution. (4) (4) the reaction process of magnetic modified wheat straw adsorbed nitrate root is very fast and can be completed in 20min. The reaction process is affected by pH, and the adsorbent has a high removal rate of nitrate in the 4-10 range; the temperature is not affected by the temperature of water environment, the temperature is 20,30 and 40 C, the adsorption capacity of magnetic modified wheat straw to NO3- is 54.5mg, respectively. /g, 51.7mg/g and 49.8mg/g, the adsorption isotherm of adsorbent adsorbed nitrate conforms to the Langmuir adsorption isotherm model, and the pseudo two stage kinetic model can describe the whole adsorption process of the magnetic modified wheat straw adsorbent for nitrate, and the fitting curve will not offset the adsorption data, and the correlation coefficient (R2) is higher, which is 0.998. -0.999 shows that the adsorption process is chemical adsorption and a speed limiting adsorption process. (5) after the cultivation of the acclimated denitrifying bacteria 5D, the activated sludge basically adapts to the culture environment of this experiment. The growth rate of activated sludge is obviously accelerated at about 15d-22d, and the biomass of activated sludge is basically stable. After cultivation and domestication, A certain number of nitrate reducing bacteria were enriched in the activated sludge in this experiment. By the extraction of DNA and the analysis of the DGGE gene fragment of the bacteria group, the denitrifying bacteria became the dominant bacteria group, and the microbial community was suitable for the reduction of nitrate. (6) the dynamic experiment of the adsorption of nitrate on the magnetic modified wheat straw adsorbent, the height of the column and the height of the column. The column flow rate, the initial nitrate concentration, pH and other factors have great influence on the column experiment. The height of the column is large and it can absorb more nitrate, but it does not increase the adsorption efficiency of the magnetic modified wheat straw adsorbent to the nitrate root; the adsorbent in the adsorption column is quickly occupied by the nitrate root in the suction column. Therefore, the adsorption column is saturated in a very short time; controlling the flow velocity of the column and prolonging the contact time can increase the adsorption efficiency in a certain condition, but the time is too long will also affect the actual process. Therefore, the selection of proper column conditions can effectively improve the efficiency of the column. (7) the magnetic modified wheat straw saturated with nitrate is adsorbed. Microbial denitrification was carried out. The results showed that after the static adsorption, the first reduction efficiency of the anaerobic microorganism was about 93%, the two reduction efficiency was about 89%, and the fifth reduction efficiency was about 80%. After the dynamic adsorption of nitrate, the denitrification was calculated by the difference of the first and two penetration points. The one time reduction efficiency of microorganism to magnetic modified wheat straw adsorbent is about 89%, and the two reduction efficiency is about 83%, and the adsorption combined with microorganism can achieve the thorough innocuous treatment of nitrate.

【学位授予单位】：济南大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU991.2;X712

【参考文献】