生物炭负载纳米零价铁对有机污染物的去除研究

发布时间：2018-07-17 04:18

【摘要】：纳米零价铁具有较大的比表面积和较强的反应活性,能够有效地去除环境中的有机污染物,是目前最具有应用潜力的高效还原剂之一;但由于其在处理污染物时表现出易团聚的缺陷,限制了其工程应用。为了克服此缺陷,本研究以生物炭为载体,使用液相还原法制备生物炭负载纳米零价铁材料,并使用制备的生物炭负载纳米零价铁材料对甲基橙、三氯乙烯以及1,2,4-三氯苯进行降解研究。最后,为了拓宽材料的应用范围,使用生物炭负载纳米零价铁活化过硫酸盐,并研究了其对三氯乙烯的去除效果。主要研究内容与结果如下:(1)利用液相还原沉积法制备了生物炭负载纳米零价铁材料。材料的表征结果表明,生物炭的微观形态呈片状形态,且生物炭上出现的羟基、羧基、羰基等电负性官能团有利于纳米零价铁的负载;纳米零价铁颗粒的粒径主要分布在30-70 nm之间,且在负载前后,纳米零价铁的表面积由20.9 m2/g升高至126.6~138.1 m2/g。(2)使用生物炭负载纳米零价铁材料对甲基橙进行去除研究,结果表明,将纳米零价铁负载于生物炭上明显增加了甲基橙的去除效果,生物炭负载纳米零价铁对甲基橙的去除率均为93.26%以上,其中炭铁质量比为5:1的生物炭负载纳米零价铁对甲基橙的去除效果最好,达到98.51%。(3)污染物的初始浓度、反应溶液中生物炭负载纳米零价铁的投加量、反应初始pH以及共存阴离子等条件都会对降解反应的速率产生影响:随着反应初始浓度的升高,生物炭负载纳米零价铁材料对甲基橙的去除率及反应速率降低;增加生物炭负载纳米零价铁的投加量能够有效加快反应的速率;溶液中pH值的升高不利于反应的进行;向溶液中添加诸如氯离子、硫酸根离子及硝酸根离子等阴离子时,这些阴离子与污染物在纳米零价铁表面的活性位点上产生竞争吸附。同时也会减少溶液中氢离子的数量,因此,溶液中的共存阴离子会对反应的速率和降解的效果产生影响。(4)在自然条件下放置一个月后的生物炭负载纳米零价铁仍能够对甲基橙有良好的去除效果(比新鲜制备的生物炭负载纳米零价铁对甲基橙的去除率低3%),说明生物炭能够延缓纳米零价铁在自然条件下的氧化过程,有利于材料的工程应用。(5)使用生物炭负载纳米零价铁能够有效降解三氯乙烯和1,2,4-三氯苯。降解反应完成后使用正己烷对吸附剂进行脱附处理,结果表明,反应溶液中三氯乙烯和1,2,4-三氯苯浓度的降低主要是由于纳米零价铁的还原作用引起的。(6)为了拓宽生物炭负载纳米零价铁材料的应用范围,使用生物炭负载纳米零价铁活化过硫酸盐并研究其对三氯乙烯的降解,结果表明,该反应体系对三氯乙烯的降解反应过程在1 min左右基本达到平衡,使用炭铁质量比为5:1的生物炭负载纳米零价铁材料活化过硫酸盐对三氯乙烯的降解率最高,可以达到99.4%。
[Abstract]:Nanocrystalline zero-valent iron has a large specific surface area and strong reactive activity, which can effectively remove organic pollutants in the environment, so it is one of the most potential high-efficiency reductants. However, its engineering application is limited because of its easy agglomeration defect in the treatment of pollutants. In order to overcome this defect, the liquid phase reduction method was used to prepare biochar supported nanocrystalline zero-valent iron materials, and the biological carbon supported nano-zero-valent iron materials for methyl orange were used in this study. The degradation of trichloroethylene (trichloroethylene) and trichlorobenzene (4-trichlorobenzene) was studied. Finally, in order to widen the scope of application of the material, the activated persulfate was activated with nano-ferric oxide loaded with biological carbon, and the removal effect of trichloroethylene was studied. The main contents and results are as follows: (1) Nano-sized zero-valent iron materials supported by biological carbon were prepared by liquid phase reduction deposition. The characterization results showed that the micromorphology of biochar was flake, and the electronegativity groups such as hydroxyl, carboxyl and carbonyl on the biochar were favorable to the loading of nano-zero-valent iron. The particle size of nanocrystalline zero-valent iron particles is mainly between 30-70 nm, and the surface area of nano-zero-valent iron increases from 20.9 m2 / g to 126.6n 138.1 m2 / g before and after loading. (2) the removal of methyl orange by biochar supported nano-zero-valent iron nanoparticles is studied. The removal efficiency of methyl orange was obviously increased by loading nano-zero valent iron onto biochar, and the removal efficiency of methyl orange was more than 93.26%. Among them, the removal efficiency of methyl orange was the best when the mass ratio of carbon to iron was 5:1, which reached 98.51. (3) the initial concentration of pollutants and the amount of nano-zero-valent iron loaded by biological carbon in the reaction solution. The initial pH of the reaction and the coexistence of anions will affect the degradation rate: with the increase of the initial concentration of the reaction, the removal rate and the reaction rate of methyl orange are decreased with the increase of the initial concentration of biochar supported nanocrystalline iron. Increasing the amount of nano-zero-valent iron loaded with biological carbon can effectively accelerate the reaction rate; the increase of pH value in the solution is not conducive to the reaction; when the anions such as chloride ion, sulfate ion and nitrate ion are added to the solution, These anions and pollutants are competitively adsorbed on the active sites on the surface of nanocrystalline zero-valent iron. It also reduces the amount of hydrogen ions in the solution. The coexistence of anions in the solution will affect the reaction rate and the degradation effect. (4) after a month's storage under natural conditions, the nano-zero-valent iron supported by biological carbon can still have a good removal effect on methyl orange (compared with fresh preparation). The removal rate of methyl orange is 3% lower than that of the prepared biochar loaded with nanometer zero-valent iron, which indicates that biochar can delay the oxidation process of nano-zero-valent iron under natural conditions. It is beneficial to the engineering application of the materials. (5) trichloroethylene and 1-trichlorobenzene can be effectively degraded by using biochar supported nano-zero-valent iron. The adsorbent was desorbed with n-hexane after the degradation reaction was completed. The decrease in the concentration of trichloroethylene and 1-trichlorobenzene in the reaction solution is mainly caused by the reduction of nanometer zero-valent iron. (6) in order to widen the application range of nano-zero valent iron loaded with biological carbon, Activated persulfate with nano-zero-valent iron supported by biochar and studied its degradation of trichloroethylene. The results showed that the degradation process of trichloroethylene was basically balanced at about 1 min. The degradation rate of trichloroethylene by activated persulfate was the highest when the mass ratio of carbon to iron was 5:1, and the degradation rate of trichloroethylene was 99.4%.
【学位授予单位】：苏州科技学院
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：X505

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