稻壳灰沉淀法制备白炭黑及性能研究

发布时间：2018-02-25 18:18

本文关键词： 稻壳灰白炭黑 KH570 聚乙二醇6000 碳酸钠表面改性　出处：《安徽工程大学》2015年硕士论文　论文类型：学位论文

【摘要】：我国年产稻壳(RH)约0.4亿吨,完全燃烧时具有90%左右的含硅量。目前多数作为废弃物丢弃,利用率低,并且产生的稻壳灰(RHA)也不能及时处理。本着合理利用资源,提高经济附加值和保护环境的目的,本文以发电RHA为原料,采用Na2CO3溶液沉淀法将RHA中的Si02溶出制备白炭黑,对RH资源进一步综合回收利用。本文首先对RHA中的Si02溶出工艺参数进行优化,考察反应温度、料液比、Na2CO3溶液浓度及反应时间等的参数对Si02溶出率的影响,并探索洗涤液的调节浓度对滤液循环使用的影响。然后重点探索了对白炭黑成品的KH偶联改性和在滤饼阶段的PEG6000改性,解决沉淀法白炭黑的团聚问题,用于提高产品的分散性、疏水性活化指数和DBP吸收值。主要研究内容及结论如下：从稻壳灰中采用沉淀法提取白炭黑,通过单因素实验和响应曲面法,对提取工艺进行优化,结果显示：当反应温度100℃、料液比15 g：300 mL、Na2CO3溶液浓度20wt.%、反应时间3h时,SiO2的溶出率达到92.39%。考察碳酸钠溶液循环使用情况,发现当将滤饼的洗涤液配制成10wt.%的Na2CO3溶液用于补偿反应过程中Na2CO3溶液的损失时,其他条件不变,RHA中SiO2的溶出率仍能达到90%以上,说明反应后的滤液可以循环使用,而且洗涤液和冷却用水也可回收利用,既节约成本也可减少污水排放。FT-IR光谱表明,所得产品为白炭黑,且表面存在大量羟基和吸附水,颗粒容易团聚。XRD结果表明,所得白炭黑是典型的无定形结构。SEM图片显示,产品粒子之间具有较严重的团聚现象,且粒子分布不均,单个粒子不易区分。KH570改性成品白炭黑的结果表明：当将约5g的产品分散在90 mL溶液,控制反应体系pH4-5,加入5 mL改性剂,在90℃下反应70 min,所得改性样品的疏水性活化指数达100%,产品的DBP吸收值由原来的1.97mL/g降低到1.15mL/g左右,说明产品聚集状态减弱,分散颗粒的均匀性有所提高。产品的粒度分析表明,原产品经KH570改性后,粒径总体变化不大,但团聚体更容易得到分散；FT-IR检测表明,KH570水解后的产物顺利与粒子表面-OH键合；改性前后的BJH孔径分析表明,成品白炭黑经KH570改性后,会使产品所具有的大孔和较大的比表面积遭到破坏,生长的簇团会被解离,导致改性的产品DBP吸收值大大降低,但产品的有机溶剂分散性和疏水性会得到提高。SEM显示,改性前的粒子团聚现象减弱,粒子之间更紧凑,孔隙分布更为均匀。在白炭黑滤饼阶段采用PEG 6000改性,所得工艺参数为：将滤饼用80mL水分散,加入用量15wt.%的PEG 6000、在70℃下改性2h,所得产品的DBP吸收值约3.00 mL/g。FT-IR分析表明,滤饼阶段的表面改性是可行的,PEG 6000能有效地缠绕接枝在产品表面。粒度分析表明PEG 6000吸附在白炭黑粒子表面,在促进白炭黑粒子凝聚的同时,又能阻止粒子继续团聚长大,使粒度分布更均匀,并且能有效地增加产品的孔隙率,提高产物比表面积及分散性。SEM显示产品团聚体得到释放,粒子分布更为均匀,总体分散性得到提高。同时,滤饼阶段改性处理,更容易把滤饼中包裹的杂质离子除去,也使得产品更容易干燥而不结块,产品更为疏松且容易粉碎,克服了白炭黑在干燥过程容易结晶块的问题。
[Abstract]:China's annual output of about 0.4 tons of rice husk (RH), with about 90% of the total amount of silicon containing combustion. Most discarded as waste, low utilization rate, and the rice husk ash (RHA) can not be timely treatment. The spirit of rational use of resources, protect the environment and improve the economic value added to the power of RHA as the raw material, the preparation of silica dissolution in RHA Si02 precipitation method using Na2CO3 solution of RH resources to further comprehensive utilization. Based on the RHA Si02 in the dissolution process is optimized. The effects of reaction temperature, liquid ratio, parameters of Na2CO3 solution concentration and reaction time on the dissolution rate of Si02 the effect and to explore the effect of regulating the concentration of washing liquid for recycle. And then focus on the KH coupling silica modified and refined in the cake stage of PEG6000 modification, solution precipitation method white carbon black aggregation problem for increasing production Dispersion of goods, hydrophobic activation index and DBP absorption value. The main research contents and conclusions are as follows: from rice husk ash extracted by silica precipitation method, through the single factor experiment and response surface method, the extraction process was optimized, the results show that when the reaction temperature is 100 DEG C, the ratio of material to liquid 15 g:300 mL, Na2CO3 the concentration of 20wt.%, reaction time 3h, SiO2 dissolution rate reached 92.39%. the effects of sodium carbonate solution recycling, will be found when the washing liquid cake made into Na2CO3 solution for 10wt.% Na2CO3 solution in the reaction process of loss, he keeps its condition, RHA SiO2 dissolution rate can still reach more than 90%, indicating that the reaction after the filtrate can be recycled, and the washing liquid and cooling water Recyclable utilization, thereby saving cost, reduce sewage emissions can also indicate the.FT-IR spectrum, the product is white carbon black, and there are a large number of surface hydroxyl The base and adsorbed water, particles are easy to agglomerate.XRD results show that the silica is amorphous structure of typical.SEM image display, which is a serious phenomenon of agglomeration between the particles and the particles are, the uneven distribution of individual particles are not easy to distinguish.KH570 modified silica products. The results show that when the products dispersed about 5g in 90 mL solution, reaction control system pH4-5, adding 5 mL modifier, 70 min reaction at 90 DEG C, the activation index of hydrophobic modified samples is up to 100%. The product of DBP absorption value was reduced from 1.97mL/g to 1.15mL/g, the product aggregation weakens, uniformity of dispersed particles increased product size. Analysis shows that the original product modified by KH570, the particle size changed little overall, but the aggregate more easily spread; FT-IR showed that the product of hydrolysis of KH570 particles and smooth surface of -OH bonding; BJ before and after modification The diameter of H analysis showed that the product of silica modified by KH570, the product has a large hole and a large surface area is destroyed, the growth of clusters will be led to dissociation, modified products DBP absorption value is greatly reduced, but the organic solvent dispersion and hydrophobic products will be improved.SEM showed that the modified particle weakened agglomeration between the particles is more compact, more uniform pore distribution. Using PEG 6000 modified silica phase in filter cake, the process parameters were as follows: the filter cake with 80mL aqueous dispersion, adding amount of 15wt.% PEG 6000, modified 2H at 70 DEG C, the the DBP absorption value of approximately 3 mL/g.FT-IR analysis showed that the surface of the cake stage modification is feasible, PEG 6000 winding grafting on the surface of the product effectively. Particle size analysis showed that PEG 6000 adsorbed on the silica surface, in the promotion of silica particle condensation at the same time, but also can prevent The particle to agglomerate, the particle size distribution is more uniform, and can effectively increase the porosity of the products, improve the product specific surface area and dispersion of.SEM display products aggregates to be released, the particle distribution is more uniform, the overall dispersion is improved. At the same time, cake stage modification, the impurity ions more easily wrapped cake the removal, also makes the product easier to dry without caking, products are more loose and easily broken, overcome the problem of the block easy crystallization of silica in the drying process.

【学位授予单位】：安徽工程大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ127.2

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