农业秸秆活性炭改性及处理含汞废水的研究

发布时间：2018-04-21 10:58

本文选题：含汞废水 + 秸秆活性炭　；参考：《四川师范大学》2016年硕士论文

【摘要】：含汞废水是很多工业生产过程排放的一类重金属废水,其危害早已被人们所认识,并开发出多种物理、化学和生物处理方法。然而,现有的方法由于存在许多弊端而制约了广泛的工程应用,含汞废水仍然是目前环境的重要汞污染源之一。随着国际、国内对环境汞排放标准限值的进一步收严,大量的含汞废水处理越来越需要开发高效、低耗、低成本的处理材料、处理工艺和技术,确保含汞废水的达标排放。本文以农业作物秸秆制备的秸秆活性炭为材料,通过改性,研究改性活性炭对溶液中汞的吸附特性、吸附机制及影响因素,探索改性活性炭处理含汞废水的工艺参数,为开发出低成本、高效、环境友好的汞吸附材料提供科学依据。研究的结果表明:1.改性条件影响活性炭的吸附性能。在600℃、800℃和1000℃的温度条件下制得的改性活性炭对Hg(Ⅱ)的吸附率有明显差异,温度条件为1000℃得到的改性活性炭效果最好。掺硫改性后,活性炭的含硫基团增加,显著改善活性炭对Hg(Ⅱ)的吸附能力,但不同碳硫质量比对改性活性炭的吸附性能影响明显,以碳硫比为1:3制得的改性活性炭的效果最优。改性前活性炭的粒径大小也显著影响改性后的吸附性能,但吸附性能随粒径大小的变化没有趋势,以中等粒径(150μm)得到的改性活性炭表现最好。改性时间对改性活性炭的吸附性能没有明显影响。2.与未改性活性炭相比,改性活性炭显著地提高了对溶液中Hg(Ⅱ)的去除率,其吸附性能与溶液pH、初始浓度、吸附剂用量有关。改性活性炭受溶液的pH影响范围较未改性活性炭小,pH值在4左右,改性活性炭对Hg(Ⅱ)的去除率达到最大,而未改性活性炭的去除率随pH增加而增加。初始Hg(Ⅱ)浓度影响到吸附剂的去除率,相同初始浓度下,改性活性炭对Hg(Ⅱ)的去除率远大于未改性活性炭。Hg(Ⅱ)的去除率随活性炭用量增加而增加,但吸附量随用量增加而减少,在初始Hg(Ⅱ)浓度为30mg/L条件下,活性炭用量为3.0g/L时,改性活性炭对Hg(Ⅱ)的去除率达到99.8%,未改性活性炭仅为80%左右;吸附平衡时,改性活性炭的吸附量为33.10mg/g,远大于未改性活性炭的11.67mg/g。活性炭的吸附过程为吸热反应,但不同温度条件下,活性炭的吸附性能差异并不明显。活性炭对Hg(Ⅱ)的吸附符合Freundlich方程,吸附机制为多分子层吸附,吸附动力学符合Lagergren准二级动力学模型,吸附类型主要以化学吸附为主。3.改性活性炭对模拟含汞废水的处理效果受pH、接触时间的影响明显。在活性炭用量为4g/L,模拟废水Hg(Ⅱ)浓度为30mg/L的条件下,最佳处理pH为5,接触时间为5h,Hg(Ⅱ)的去除率为72%,工艺试验结果与实验结果有相当的差距。主要结论:秸秆活性炭经掺硫改性后,显著地改善了活性炭的表面吸附性能。改性活性炭对Hg(Ⅱ)吸附受pH、吸附剂用量和初始浓度的影响明显,但受温度的影响不大;活性炭对Hg(Ⅱ)的吸附过程符合Freundlich方程,吸附动力学符合Lagergren准二级动力学模型,吸附机理为多分子层吸附,吸附类型主要以化学吸附为主,吸附热力学为吸热反应。
[Abstract]:Mercury containing wastewater is a kind of heavy metal wastewater discharged from many industrial processes. Its harm has already been recognized by people, and many kinds of physical, chemical and biological treatment methods have been developed. However, the existing methods have restricted extensive engineering applications because of many disadvantages, and the mercury containing wastewater is still one of the important sources of mercury pollution in the present environment. With the international and domestic restrictions on environmental mercury emission standards further stricter, a large number of mercury containing wastewater treatment more and more need to develop high efficiency, low consumption, low cost treatment materials, processing technology and technology to ensure the standard discharge of mercury containing wastewater. In this paper, the straw activated carbon from agricultural crop straw was used as the material, and the modification was used to study the modification. The adsorption properties, adsorption mechanism and influencing factors of activated carbon on the solution, explore the technological parameters of treating mercury containing wastewater by modified activated carbon, and provide scientific basis for developing low cost, efficient and environmentally friendly mercury adsorption materials. The results show that the 1. modification conditions affect the adsorption properties of activated charcoal at 600, 800 and 1000. The adsorption rate of Hg (II) was significantly different from the modified activated carbon obtained under the temperature condition. The effect of the modified activated carbon obtained at 1000 temperature was the best. The sulfur content group of the activated carbon was increased, and the adsorption capacity of activated carbon to Hg (II) was obviously improved, but the adsorption properties of the modified activated carbon were obviously influenced by the different carbon and sulfur quality. The modified activated carbon obtained by the carbon sulfur ratio of 1:3 is the best. The particle size of the activated carbon before the modification also significantly affects the modified adsorption properties, but the adsorption property changes with the size of the particle, and the modified activated carbon obtained by the medium size (150 mu m) shows the best performance. The adsorption performance of the modified activated carbon is not clear. Compared with the unmodified activated carbon, the modified activated carbon significantly improved the removal rate of Hg (II) in the solution, and its adsorption performance was related to the solution pH, initial concentration and the amount of adsorbent. The modified activated carbon was affected by the pH of the solution less than that of the unmodified activated carbon, and the pH value was about 4, and the removal rate of Hg (II) was maximum by modified activated carbon. The removal rate of unmodified activated carbon increases with the increase of pH. Initial Hg (II) concentration affects the removal rate of adsorbents. Under the same initial concentration, the removal rate of modified activated carbon to Hg (II) is much greater than that of unmodified activated carbon (II). The removal rate of.Hg (II) increases with the increase of activated carbon, but the adsorption amount decreases with the increase of the amount of activated carbon, in the initial Hg (II). Under the condition of 30mg/L, when the amount of activated carbon is 3.0g/L, the removal rate of modified activated carbon to Hg (II) is 99.8%, and the unmodified activated carbon is only about 80%. When adsorption equilibrium, the adsorption amount of modified activated carbon is 33.10mg/g, which is much larger than the adsorption process of 11.67mg/g. activated carbon with unmodified activated carbon, but at different temperature conditions, the adsorption process of activated charcoal is much higher than that of unmodified activated carbon. The adsorption properties of activated carbon were not obvious. The adsorption of activated carbon on Hg (II) was in accordance with the Freundlich equation, adsorption mechanism was multi molecular layer adsorption, adsorption kinetics accorded with Lagergren quasi two kinetics model, and the adsorption type was mainly chemically adsorbed on.3. modified activated carbon for the treatment of simulated mercury containing wastewater by pH and contact time. The effect is obvious. Under the condition of 4g/L and Hg (II) concentration of simulated wastewater, the optimum treatment pH is 5, the contact time is 5h, the removal rate of Hg (II) is 72%, and the result of the process test is quite different from the experimental results. The adsorption of modified activated carbon on Hg (II) was obviously influenced by pH, the amount of adsorbents and the initial concentration, but it was not affected by the temperature. The adsorption process of activated carbon to Hg (II) was in accordance with the Freundlich equation. The adsorption kinetics accorded with the Lagergren quasi two kinetics model, the adsorption mechanism was multi molecular layer adsorption and the adsorption type was mainly chemical adsorption. The thermodynamics of adsorption is the endothermic reaction.

【学位授予单位】：四川师范大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：X703;TQ424.1

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