铝盐改性膨润土绿液除硅工艺的研究

发布时间：2018-05-13 12:34

本文选题：绿液 + 铝盐改性膨润土　；参考：《陕西科技大学》2015年硕士论文

【摘要】：本论文针对非木材纤维原料制浆厂广泛存在的“硅干扰”问题,将我国资源丰富的,易改性,膨胀性好,吸附性强的膨润土引入绿液除硅体系,制备了一种新型高效可循环的除硅剂—铝盐改性膨润土,改善了传统绿液除硅剂的除硅效率低,对绿液p H影响大,难沉降等缺点,并系统地介绍了其制备工艺,除硅工艺,脱附再生工艺。本论文以国家提出的“十二五节能减排规划”为目标,综合利用我国丰富的矿物质资源,未来可实现企业的节能减排,实现循环经济,达到环境保护的目的,具有广阔的市场应用前景。(1)铝盐改性膨润土制备工艺与机理以钠基膨润土为原料,通过添加铝盐为改性剂制备出了一种新型高效的绿液除硅剂,其硅吸附效率最高可达90%左右。以竹浆绿液的硅吸附率和p H变化为标准研究了改性膨润土的制备工艺,其最佳工艺为:钠基膨润土与铝盐的质量比为1:4,添加顺序为:先将钠基膨润土与水混合,再加入铝盐,加水量为66m L/1g钠基膨润土,搅拌时间为2h,搅拌速率为1200r/min,反应温度为室温,静置分离12h,105℃干燥,研磨,过200目筛。经过扫描电镜,X射线衍射,热分析,红外光谱分析以及粒径分布表征了铝盐改性膨润土的特征,推断其制备机理为:钠基膨润土的表面与层间分布着钠原子和一定的羟基,先向钠基膨润土中加入水搅拌,有助于打开钠基膨润土的层间,增大膨润土的层间距,有利于改性剂的引入,当钠基膨润土在水中搅拌均匀后,加入铝盐改性剂,由于铝原子亲羟基性能比钠原子强,铝盐开始进入到膨润土层间置换钠原子,钠原子从膨润土体系中游离出,并且,铝盐开始水解成为聚合羟基铝盐,当搅拌2h后,铝原子已经基本上将钠原子置换完全并且膨润土表面连接了大量的Al-OH,则铝盐改性膨润土制备完毕。(2)铝盐改性膨润土除硅工艺与机理铝盐改性膨润土除硅工艺最佳操作条件为:改性膨润土用量16g/L,搅拌时间为10 min,温度为90℃,平衡时间为5 min。通过改性膨润土对竹浆绿液(硅酸盐含量为4g/L)的吸附动力学,等温模型拟合和反应热力学的研究,可得,其吸附过程符合二级动力学模型,是物理吸附和化学吸附的共同效果。最大吸附量为252.525mg/g,与实验中得出的最大吸附量238.441mg/g相符。另外,改性膨润土的吸附过程更符合Freundlich模型,并且1/n1,可知该吸附反应容易进行,并且吸附能力强。通过简单的热力学研究发现,该吸附过程属于自发进行,不需要附加能来实现。铝盐改性膨润土吸附硅酸盐的物理吸附主要依靠膨润土层间的缝隙来实现,但吸附性能差;而化学吸附占主导因素,其吸附机理为:硅酸盐在竹浆绿液中(强碱性溶液)主要以Si-OH键的形式存在,而铝盐改性膨润土表面存在大量的Al-OH,当铝盐改性膨润土加入竹浆绿液后,Al-OH键与Si-OH键发生化学吸附反应,硅元素被吸附在膨润土表面。反应结束后,经过滤,硅元素被铝盐改性膨润土带走,成功实现除硅目的。(3)铝盐改性膨润土絮凝除硅工艺及机理的研究铝盐改性膨润土最佳絮凝除硅工艺:絮凝剂为铝盐改性膨润土-CPAM-Ca O,可以高效除硅,最高硅去除率可达99.9%,还可以降低除硅剂对绿液p H值的影响和加快硅酸盐的沉降。所以,絮凝除硅工艺是一种新型高效环保的除硅工艺。最佳条件为:铝盐改性膨润土用量16 g/L,CPAM用量15 m L/L,Ca O用量15 g/L,搅拌时间10min,澄清时间5 min。在絮凝除硅工段中,铝盐改性膨润土先与绿液中的硅酸盐充分接触,吸附。然后加入CPAM絮凝剂和Ca O助絮凝剂,CPAM趋于“环和尾”式吸附状态,充当交联架桥作用,使原来分散的吸附絮凝体,联结成缔合状聚集体,少量絮凝剂是让其到达等当点,从而形成片块状聚集体,快速下沉,使聚集体尽快脱离上层清液,加速了沉降速率,减少了澄清时间。(4)铝盐改性膨润土脱附再生工艺的研究铝盐改性膨润土脱附再生工艺可描述为将回收的使用后的铝盐改性膨润土加入到2mol/L氢氧化钠的碱性溶液中,微波中火加热4min(或者直接加热4h),连接在铝盐改性膨润土上的硅酸盐从铝盐改性膨润土上游离下来,过滤。脱附后的铝盐改性膨润土留在滤网上,硅酸盐进入绿液中,冷却,硅酸盐固体析出。过滤,干燥,硅酸盐被完整脱附出来。将脱附后的铝盐改性膨润土加入到水中,搅拌,加入铝盐改性剂,搅拌2h,静置分离,倒去上清液,干燥下浊液,研磨,过筛,就得到了再生铝盐改性膨润土。考虑成本及设备耗能等影响,建议循环2-3次使用。另外,脱附动力学研究表明铝盐改性膨润土脱附硅酸盐的过程在高强度微波下与二阶动力学模型相符,磁场力既促进了物理脱附也促进了化学脱附。其饱和脱附量为129.870 mg/g,与实验测试过程中测定出的120.948 mg/g相符。最后,通过扫描电镜,红外光谱和能谱分析对脱附物的成分进行鉴定,脱附物的主要成分为铝硅酸盐。
[Abstract]:This paper, aiming at the widespread "Silicon Interference" problem in the non wood fiber raw material pulping plant, introduces a new highly efficient and recyclable silicon removing agent, aluminum salt modified bentonite, which has rich resources, modifier, expansibility and strong adsorbability of bentonite, and improves the efficiency of removing silicon from traditional green liquid desilication agent. Low, large influence on green liquid p H, difficult to settle and other shortcomings, and systematically introduced its preparation technology, the removal of silicon technology, desorption and regeneration process. In this paper, the national "12th Five-Year energy saving and emission reduction plan" as the goal, the comprehensive utilization of China's rich mineral resources, the future can realize the enterprise energy conservation and emission reduction, the realization of the circular economy, to achieve environmental protection. The purpose of protection has broad market application prospects. (1) the preparation technology and mechanism of aluminum salt modified bentonite is made of sodium bentonite as raw material. A new type of high efficient green liquid silicon removal agent is prepared by adding aluminum salt as modifier, and its silicon adsorption efficiency is up to about 90%. The silicon adsorption rate and P H change of bamboo pulp green solution are studied as the standard. The optimum process for the preparation of modified bentonite is that the mass ratio of sodium base bentonite and aluminum salt is 1:4, and the addition order is: first mixing sodium bentonite with water, adding aluminum salt and adding 66m L/1g sodium bentonite, stirring time is 2h, stirring rate is 1200r/min, reaction temperature is room temperature, static separation 12h, 105 DEG C drying, lapping, over 200 mesh sieve. The characteristics of aluminum salt modified bentonite were characterized by scanning electron microscopy, X ray diffraction, thermal analysis, infrared spectrum analysis and particle size distribution. It was concluded that the mechanism of the preparation of sodium based bentonite was that the surface and layer of sodium base bentonite were distributed with sodium atom and certain hydroxyl group, and the sodium base bentonite was added to the sodium bentonite to stir the sodium bentonite. Between layers, increasing the spacing of bentonite is beneficial to the introduction of the modifier. When the sodium bentonite is stirred in the water, the aluminum salt modifier is added. As the aluminum atom is stronger than the sodium atom, the aluminum salt begins to go into the bentonite to replace the sodium atom, and the sodium atom is dissociated from the bentonite system, and the aluminum salt begins to hydrolyze into the sodium bentonite. After mixing 2h, the aluminum atom has basically replaced the sodium atom completely and the bentonite surface is connected with a large amount of Al-OH, then the aluminum salt modified bentonite is prepared. (2) the best operation condition of the aluminum salt modified bentonite removal process and the mechanism of the aluminum salt modified bentonite removal process is that the modified bentonite is used for 16g/L and stirred. The time is 10 min, the temperature is 90, and the equilibrium time is 5 min.. The adsorption kinetics of the bamboo pulp green solution (silicate content is 4g/L) by the modified bentonite, the isothermal model fitting and the reaction thermodynamics study. The adsorption process accords with the two stage kinetic model, which is the common effect of physical absorption and chemical adsorption. The maximum adsorption amount is 252.525m G/g is in accordance with the maximum adsorption amount of 238.441mg/g obtained in the experiment. In addition, the adsorption process of the modified bentonite is more in line with the Freundlich model, and 1/n1. It is known that the adsorption reaction is easy to carry out and has strong adsorption capacity. Through a simple thermodynamic study, it is found that the adsorption process is spontaneous and does not need additional energy to achieve. The physical adsorption of Bentonite on silicate mainly depends on the gap between bentonite layers, but the adsorption property is poor, and chemical adsorption is the dominant factor. The mechanism of adsorption is that silicate is mainly in the form of Si-OH bond in bamboo pulp green solution (strong alkali solution), and there is a large amount of Al-OH on the surface of aluminum salt modified bentonite, when aluminum salt is modified. After the bentonite is added to the bamboo pulp green solution, the Al-OH bond and the Si-OH bond have a chemical adsorption reaction, the silicon element is adsorbed on the bentonite surface. After the reaction, the silicon elements are removed by the aluminum salt modified bentonite and the silicon removal is successfully carried out. (3) the study on the process and mechanism of the flocculation and removal of silicon by aluminum salt modified bentonite is the best flocculation of the aluminum salt modified bentonite. Silicon process: the flocculant is al salt modified bentonite -CPAM-Ca O, which can remove silicon efficiently and the highest silicon removal rate can reach 99.9%. It can also reduce the effect of silicon removing agent on the P H value of green solution and accelerate the settlement of silicate. Therefore, flocculation and desilication process is a new efficient and environmentally friendly technology for removing silicon. The best condition is that the amount of aluminum salt modified bentonite is 16 g/L, CP The dosage of AM is 15 m L/L, Ca O is 15 g/L, stirring time 10min, and the time of clarification is 5 min. in the flocculating and removing silicon section. The aluminum salt modified bentonite is in full contact with the silicate in the green liquid first and adsorbed. Then CPAM flocculant and Ca O flocculant are added, and CPAM tends to "ring and tail" adsorption state and acts as crosslinking bridge to make the original dispersed adsorption. Floc forming a associative aggregate, a small amount of flocculant is to make it arrive at the same point, thus forming a lump aggregate, rapidly sinking, making the aggregate out of the upper liquid as soon as possible, accelerating the settling rate and reducing the time of clarification. (4) a study on the process of aluminum salt modified bentonite desorbing regenerative process can be traced. The recycled aluminum salt modified bentonite is added to the alkaline solution of 2mol/L sodium hydroxide. The microwave heat is heated for 4min (or directly heated to 4h). The silicate connected to the aluminum salt modified bentonite is dissociated from the aluminum salt modified bentonite and filtered. The aluminum salt modified bentonite is left on the filter net and the silicate is entered. In green liquid, cooling, silicate solid precipitation, filtration, drying, and silicate are completely removed. The aluminum salt modified bentonite is added to water, mixing, adding aluminum salt modifier, stirring 2h, statically separating, pouring the supernatant, drying turbid liquid, grinding, sifting, and obtaining the regenerated aluminum salt bentonite. Cost and equipment consumption are considered. In addition, the kinetic study shows that the process of desorption of silicate by aluminum salt modified bentonite is consistent with the two order kinetic model under high intensity microwave. The magnetic force not only promotes physical desorption but also promotes chemical desorption. The saturation desorption amount is 129.870 mg/g, and 12 measured in the test process. 0.948 mg/g coincide. Finally, the components of the desorption were identified by scanning electron microscopy, infrared spectroscopy and energy spectrum analysis. The main component of the desorption was aluminosilicate.

【学位授予单位】：陕西科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：X793

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