粉煤灰改性及其钝化污泥与吸附水中的Cu和Zn的研究

发布时间：2018-06-04 02:02

本文选题：Cu + Zn　；参考：《哈尔滨工业大学》2016年硕士论文

【摘要】：污水处理厂产生的污泥中含有的重金属Cu~(2+)和Zn~(2+)严重超标,限制污泥利用,并且对环境危害性极大。火力发电厂燃煤后产生的固体废弃物粉煤灰的大量堆积,在占用土地资源的同时对周边环境造成了严重污染。尝试采用粉煤灰去除污水中的Cu~(2+)和Zn~(2+)以及钝化污泥中的Cu~(2+)和Zn~(2+),以达到以废治废、节约经济成本的目的。研究在“十二五”国家水专项的支持下,开展了粉煤灰的对比、改性、吸附重金属、钝化污泥以及污泥的淋滤实验的理论性研究。首先,对黑龙江省和辽宁省的粉煤灰组分进行分析,研究表明两地的粉煤灰主要含有SiO_2(石英)、Al_3Si_2O_(13)(莫来石)和SiO_2(方石英)等晶相结构,且化学组成所含比例及比表面积(~1.00m2/g)相似;表面形貌均为多孔玻璃球状且颗粒尺寸相似;两地粉煤灰表面均含有大量的C-C骨架震动峰(1087、1091 cm-1)、对称Si-O-Si弯曲伸缩振动峰(796 cm-1)、Si-O弯曲振动峰(459cm-1)。其次,采用正交实验考察不同改性方法对粉煤灰吸附重金属离子的效果,优化了酸(碱)的浓度、酸(碱)灰比、浸渍时间,或微波功率、微波时间等参数。当微波功率为400 W、辐照10 min、NaOH为6 mol/L、浸渍时间为3 h、碱灰比为5:1时,所制得的改性粉煤灰比表面积最大为21.01 m2/g,成了新的矿物质Ca2SiO4,表面激发出大量的-OH伸缩振动峰(3614 cm-1、3564 cm-1)、Si-O(661 cm-1)、-NH2(1620 cm-1)、-NH2(599 cm-1)和-CH3(2970 cm-1)等官能团,颗粒表面粗糙且吸附孔道增多,因此其钝化重金属能力明显增强,且改性粉煤灰较原状粉煤灰激发出更多的晶相物质,表面具有更多的活性基团,有利于促进Cu和Zn重金属由不稳定态向稳定态转化和吸附重金属。本研究进而通过动力学模型、热力学模型、吸附等温线等多种吸附实验确定其外在化学条件对最佳改性粉煤灰吸附Cu~(2+)和Zn~(2+)的影响。结果表明,改性粉煤灰吸附Cu~(2+)和Zn~(2+)的反应过程中,随着pH、初始离子浓度以及改性粉煤灰投加量的增加,吸附去除率越大;并且该反应符合Langmuir模型,Cu~(2+)和Zn~(2+)的理论最大吸附量分别为26.25 mg/g和22.03 mg/g;该反应符合拟二级吸附动力学模型;根据吸附热力学模型可知,该反应属于吸热的化学自发反应。最后,考察了最佳改性粉煤灰对Cu~(2+)和Zn~(2+)的钝化时间和投加量对钝化效果的影响。结果表明,随着粉煤灰的投加量增加污泥中重金属Cu和Zn的钝化效果越好,当投加量为40%时,钝化效果趋于稳定,并且改性粉煤灰对污泥中Cu~(2+)和Zn~(2+)的钝化效果优于未改性粉煤灰。当钝化时间为7d时,污泥中Cu和Zn的重金属形态已经趋于稳定化,不随时间的推移而改变其形态。研究通过土柱淋溶实验表明该改性粉煤灰钝化后的污泥,重金属固化较稳定,不随淋滤而大量析出。该改性粉煤灰钝化污泥的处理成本为(40~60)元/吨,比传统处理污泥(200~600)元/吨,更加节约经济成本
[Abstract]:The heavy metals (Cu~(2) and Zn~(2 (heavy metals) in the sludge produced by the sewage treatment plant (WWTP) exceed the standard seriously, limit the sludge utilization, and do great harm to the environment. The accumulation of fly ash, a solid waste produced by coal-fired power plants, causes serious pollution to the surrounding environment while occupying land resources. Fly ash is used to remove Cu~(2 and Zn~(2 in wastewater and Cu~(2 and Zn~(2 in passivated sludge to reduce the cost of waste treatment. With the support of the "12th Five-Year Plan" National Water Project, the theoretical study on the experiments of fly ash contrast, modification, adsorption of heavy metals, passivation sludge and sludge leaching was carried out. Firstly, the composition of fly ash in Heilongjiang Province and Liaoning Province is analyzed. The results show that the fly ash of the two places mainly contains SiOSt2 (quartz Al3Si2OSch) and SiO2 (cristobalite) crystal structure, and the proportion of chemical composition and specific surface area is 1.00m2g. The surface morphology is spherical and particle size is similar to that of porous glass, and there are a large number of C-C skeleton vibration peaks of 1087 ~ 1091 cm ~ (-1) on the surface of fly ash in both places, and a symmetrical Si-O-Si bending vibration peak of 796 cm ~ (-1) and a peak of 459 cm ~ (-1) of Si-O bending vibration. Secondly, the effects of different modification methods on the adsorption of heavy metal ions by fly ash were investigated by orthogonal experiment. The parameters such as acid (alkali) concentration, acid (alkali) cement ratio, impregnation time, microwave power and microwave time were optimized. When the microwave power is 400 W, the NaOH is 6 mol / L for 10 min, the impregnation time is 3 h, the ratio of alkali to cement is 5:1, The modified fly ash has a maximum specific surface area of 21.01 m2 / g, resulting in a new mineral Ca _ 2SiO _ 4. The surface excites a large number of -OH stretching vibrational peaks 3614 cm ~ (-1), 3564 cm ~ (-1) C ~ (-1) -O _ (1) C ~ (m-1) ~ (1) -NH ~ (2 +) ~ (1) -NH _ (599 ~ (9) cm ~ (-1) and -Ch _ (3) O _ (2970 cm ~ (-1). Therefore, the ability of passivation of heavy metals is obviously enhanced, and the modified fly ash excites more crystalline phase substances and has more active groups on the surface than the unmodified fly ash. It is beneficial to promote the conversion and adsorption of Cu and Zn heavy metals from unstable to stable. In this study, the effects of external chemical conditions on the adsorption of Cu~(2 and Zn~(2 by modified fly ash were determined by kinetic model, thermodynamic model, adsorption isotherm and other adsorption experiments. The results show that the adsorption removal rate increases with the increase of pH, initial ion concentration and the dosage of modified fly ash during the reaction of modified fly ash adsorbing Cu~(2) and Zn~(2). The theoretical maximum adsorption capacity of the reaction is 26.25 mg/g and 22.03 mg / g, respectively, which accords with the pseudo-second-order adsorption kinetic model. According to the adsorption thermodynamic model, the reaction belongs to endothermic spontaneous chemical reaction. Finally, the effects of passivation time and dosage of modified fly ash on Cu~(2 and Zn~(2) were investigated. The results showed that the passivation effect of heavy metals Cu and Zn in sludge increased with the addition of fly ash, and the passivation effect tended to be stable when the dosage was 40%. The passivation effect of modified fly ash to Cu~(2 and Zn~(2 in sludge is better than that of unmodified fly ash. When the passivation time was 7 days, the heavy metal forms of Cu and Zn in sludge tended to stabilize and did not change with time. The experiment of soil column leaching showed that the sludge after passivated by modified fly ash was stable in solidification and did not precipitate in large quantities with leaching. The treatment cost of the modified fly ash passivated sludge is 40 ~ 60 yuan / ton, which is more economical than that of the traditional sludge treatment of 200 ~ 600 yuan / ton.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：X703

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