介孔硅酸钙及其与氧化石墨烯、纳米零价铁复合材料的制备及吸附性能研究

发布时间：2018-05-04 21:32

本文选题：介孔硅酸钙 + 复合材料　；参考：《湖南科技大学》2017年硕士论文

【摘要】：重金属废水和有机染料废水已成为目前水体污染的两大难题。与传统处理方法相比,吸附法操作简单,成本较低,适于各类废水处理,在实际应用中具有巨大潜力。而选择一种性能优良的高效吸附剂是采用该方法取得良好处理效果和经济效益的关键。本文以介孔硅酸钙为研究对象,采用模板法和水解法制备介孔硅酸钙,再由介孔硅酸钙分别负载氧化石墨烯和纳米零价铁制备成复合材料,考察了介孔硅酸钙负载氧化石墨烯复合材料对重金属离子的吸附性能,探讨吸附作用机理;同时考察了介孔硅酸钙负载纳米零价铁复合材料对重金属和有机染料甲基橙的去除效果。(1)以四水硝酸钙和九水硅酸钠为原料,十六烷基三甲溴化铵为模板剂,采用模板法制备介孔硅酸钙,考察了模板剂的去除方法对其结构、形貌等的影响,并用红外光谱、X射线衍射、扫描电镜和BET表面分析等对其结构进行了表征。结果表明,采用水洗法去除模板剂所制备的介孔硅酸钙比表面积较大,为244.32 m~2/g,且孔道丰富、清晰,但水洗过程较为繁琐,烧制法去除模板剂会影响其孔道结构,生成大孔,且比表面积仅为7.31 m~2/g。以正硅酸乙酯和四水硝酸钙为原料,采用水解法制备介孔硅酸钙。该方法操作简单,制备出的介孔硅酸钙比表面积较大,为206.17 m~2/g,且表面孔道丰富呈现花状。两种硅酸钙晶型均为水化硅酸钙。(2)考察了上述两种方法制备的介孔硅酸钙对Cu~(2+)、Zn~(2+)、Cd~(2+)、Mn~(2+)和Ni~(2+)等5种重金属离子的等温吸附、热力学和动力学特征,探讨了吸附剂对重金属离子的吸附机理以及吸附剂的选择性吸附和再生性能。结果表明,水解法制备的介孔硅酸钙对Cu~(2+)、Zn~(2+)和Cd~(2+)的吸附符合Langmuir模型,是较为理想的单分子层化学吸附,吸附容量大小为Cu~(2+)Cd~(2+)Zn~(2+);而模板法制备的介孔硅酸钙对Mn~(2+)和Ni~(2+)的吸附更符合Freundlich模型,为非均匀表面吸附,吸附容量大小为Ni~(2+)Mn~(2+)。动力学研究表明,两种介孔硅酸钙对重金属离子的吸附情况均更符合准二级吸附动力学模型,升高温度有利于反应进行;一般均能在75 min内对重金属离子达到吸附平衡。热力学研究表明,上述几种重金属离子的吸附过程△H0、△G0,为吸热反应,自发进行的过程,主要为“熵推动”效应。水解法介孔硅酸钙的吸附机理研究表明,当p H为6时对Cu~(2+)、Zn~(2+)和Cd~(2+)的吸附效果最好;酸性会影响吸附剂的孔道结构,碱性条件会使金属离子水解沉淀;吸附过程中存在金属离子与钙离子的交换作用,且钙离子的交换量与吸附剂对重金属离子的吸附能力大小成正比。介孔硅酸钙对Cu~(2+)、Cd~(2+)、Zn~(2+)的吸附存在一定的选择性,选择性强弱为:Cu~(2+)Cd~(2+)Zn~(2+),与吸附容量大小一致,说明吸附容量的大小可在一定程度上反映吸附选择性的强弱。两种材料均具有优良的再生性能。(3)以水解法介孔硅酸钙为载体,与氧化石墨烯复合制备复合吸附材料,考察了对Cu~(2+)的吸附性能。经红外、X射线衍射、扫描电镜和BET表征,氧化石墨烯不均匀穿插在介孔硅酸钙孔道中,孔径均主要分布为10-30 nm,属介孔材料,相比于原始硅酸钙比表面积有所降低。复合材料对Cu~(2+)的吸附在293 K的条件下,添加量为0.01 g、0.02g和0.03 g的GO与介孔硅酸钙复合材料的平衡吸附量依次为7.03 mmol/g、7.11 mmol/g和6.91 mmol/g。在此温度下的平衡吸附量均高于原始硅酸钙的6.81 mmol/g,且随着GO添加量的增多,对Cu~(2+)的吸附量先增加后减少,最适添加量为0.02 g。吸附过程以化学吸附为主,吸附过程是比较理想的单层吸附,符合Langmuir模型。其吸附动力学研究表明,准二级吸附动力学模型更适于描述介孔吸附剂对重金属离子的吸附情况,且升高温度有助于吸附速率的提高。较原始硅酸钙能更快达到平衡,为60 min。复合材料对Cu~(2+)的吸附热力学研究则表明吸附过程为吸热反应,是熵增自发进行的过程。复合材料的再生性能较强,经过6次的洗脱循环,去除率仅下降了6.8%。(5)以硫酸铁为原料,用Na BH_4还原制备纳米零价铁,再负载到介孔硅酸钙上,制备成复合材料,经X射线衍射和扫描电镜和透射电镜等表征,所制备的纳米零价铁成功负载到介孔硅酸钙上,且能均匀分散在载体的孔道上。从经济和效果两种因素分析,介孔硅酸钙负载纳米零价铁要优于纳米零价铁和介孔硅酸钙,零价铁与硅酸钙的最佳质量比为1:10,反应温度为293 K和p H为中性时对甲基橙的去除效果较好。此种比例的复合材料在处理铜和甲基橙及锌和甲基橙复合污染时,不仅效果优于原始硅酸钙对单一重金属离子的吸附效果,还能保持良好甲基橙的去除效果。本课题着重于吸附材料对重金属和有机染料的吸附性能研究,制备出具有优良效果的吸附剂,为材料的实际应用提供了大量的基础数据,是一类极具开发价值的新型吸附剂。
[Abstract]:Heavy metal wastewater and organic dye wastewater have become the two problem of water pollution at present. Compared with the traditional treatment methods, the adsorption method is easy to operate and is low in cost. It is suitable for all kinds of wastewater treatment, and has great potential in practical application. In this paper, mesoporous calcium silicate was used as the research object. Mesoporous calcium silicate was prepared by template method and hydrolysis method, and then the mesoporous calcium silicate loaded graphene oxide and nano zero valent iron were prepared. The adsorption properties of mesoporous calcium silicate loaded graphene oxide composite on heavy metal ions were investigated. At the same time, the removal effect of mesoporous calcium silicate loaded nano Zero Valent Iron Composites on heavy metals and organic dye methyl orange was investigated. (1) four calcium nitrate and nine sodium silicate were used as the raw material and sixteen alkyl trimethyl ammonium bromide as a template. The template method was used to prepare mesoporous calcium silicate, and the structure of the template was investigated. The structure was characterized by infrared spectroscopy, X ray diffraction, scanning electron microscopy and BET surface analysis. The results showed that the surface area of mesoporous calcium silicate prepared by water washing method was 244.32 m~2/g, and the pore was rich and clear, but the process of water washing was more complicated. The pore structure is influenced by the formation of a large pore, and the mesoporous calcium silicate is prepared by hydrolysis of ethyl orthosilicate and four calcium nitrate. The method is easy to operate, the surface area of the mesoporous calcium silicate is larger, the surface area is 206.17 m~2/g, and the surface pore is rich in flower shape. Two kinds of calcium silicate crystals are all water. Calcium silicate. (2) the isothermal adsorption of 5 heavy metal ions, such as Cu~ (2+), Zn~ (2+), Cd~ (2+), Mn~ (2+) and Ni~ (2+), prepared by the two methods, were investigated. The mechanism of adsorption and adsorption of adsorbents on heavy metal ions and the selective adsorption and regeneration of adsorbents were investigated. The results showed that the hydrolysis method was used. The adsorption of mesoporous calcium silicate on the adsorption of Cu~ (2+), Zn~ (2+) and Cd~ (2+) conforms to the Langmuir model. It is an ideal single molecular layer chemical adsorption. The adsorption capacity is Cu~ (2+) Cd~ (2+) Zn~ (2+) Zn~. It is Ni~ (2+) Mn~ (2+). The kinetic study shows that the adsorption of heavy metal ions by two mesoporous calcium silicate is more in line with the quasi two stage adsorption kinetic model, and the increase of temperature is beneficial to the reaction. The adsorption equilibrium of heavy metal ions can be reached within 75 min. Thermodynamic study shows the adsorption process of the heavy metal ions above Delta H0, Delta G0, which is a spontaneous process for endothermic reaction, is mainly a "entropy driven" effect. The adsorption mechanism of calcium silicate by hydrolysis method shows that when p H is 6, the adsorption effect of Cu~ (2+), Zn~ (2+) and Cd~ (2+) is the best. Acidity will affect the pore structure of adsorbents, alkaline conditions will make metal ions hydrolyze and precipitate; and the adsorption process is stored. The exchange of metal ions with calcium ions is proportional to the adsorption capacity of the adsorbents on heavy metal ions. The adsorption of Cu~ (2+), Cd~ (2+) and Zn~ (2+) on the adsorption of mesoporous calcium silicate is selective. The selectivity is: Cu~ (2+) Cd~ (2+) Zn~ (2+), which is consistent with the size of adsorption capacity, indicating the size of adsorption capacity. To a certain extent, it can reflect the strength of adsorption selectivity. The two materials have excellent regeneration properties. (3) the composite adsorbents were prepared by the hydrolysis of mesoporous calcium silicate and the compound of graphene oxide. The adsorption properties of Cu~ (2+) were investigated by infrared, X ray diffraction, scanning electron microscopy and BET, and the unevenly interspersed of graphene oxide. In the mesoporous calcium silicate channel, the pore size is mainly distributed at 10-30 nm, which is a mesoporous material, and the specific surface area of the calcium silicate is lower than that of the original calcium silicate. The adsorption amount of the composite material to Cu~ (2+) is 0.01 g, and the equilibrium adsorption capacity of GO and mesoporous Calcium Silicate Composites of 0.02g and 0.03 G is 7.03 mmol/g, 7.11 mmol/g and 7.11 mmol/g. The equilibrium adsorption capacity of 6.91 mmol/g. at this temperature is higher than that of 6.81 mmol/g of the original calcium silicate, and with the increase of GO addition, the adsorption amount of Cu~ (2+) is increased first and then decreased, and the optimum addition amount is 0.02 g. adsorption process mainly by chemical adsorption. The adsorption process is an ideal monolayer adsorption, which is in accordance with the Langmuir model. The adsorption kinetics study The study shows that the quasi two stage adsorption kinetic model is more suitable for describing the adsorption of heavy metal ions by mesoporous adsorbents, and the increase of temperature is helpful to increase the adsorption rate. The adsorption process is faster than that of the original calcium silicate. The adsorption thermodynamics of the 60 min. composite material to Cu~ (2+) shows that the adsorption process is an endothermic reaction, which is entropy increasing spontaneously. The regeneration performance of the composite is strong. After 6 times of elution cycle, the removal rate is only reduced by 6.8%. (5) with ferric sulfate as raw material. The nano zero valent iron is prepared by Na BH_4 reduction and then loaded onto the mesoporous calcium silicate, and the composite is prepared by X ray diffraction and scanning electron microscope and transmission electron microscope. Iron is successfully loaded on the mesoporous calcium silicate and can be evenly distributed on the channel of the carrier. From two factors of economic and effect, the mesoporous calcium silicate loaded nano zero valent iron is superior to nano zero valent iron and mesoporous calcium silicate. The optimum mass ratio of zero valent iron to calcium silicate is 1:10, and the reaction temperature is 293 K and P H is neutral to methyl orange. The effect of the composite is better than that of copper and methyl orange and zinc and methyl orange. The effect is better than the adsorption effect of the original calcium silicate on the single heavy metal ion, but also the removal effect of the good methyl orange. The research focuses on the adsorption properties of adsorbents on heavy metals and organic dyes. The adsorbent with excellent effect provides a lot of basic data for the practical application of materials, and is a new type of adsorbent with great development value.

【学位授予单位】：湖南科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TB33;O647.3

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