表面改性活性炭对铬污染土壤的稳定化研究

发布时间：2018-01-09 22:21

  本文关键词：表面改性活性炭对铬污染土壤的稳定化研究　出处：《武汉科技大学》2015年硕士论文　论文类型：学位论文

  更多相关文章： 铬污染土壤 活性炭 表面改性 稳定

【摘要】：随着工农业的快速发展,土壤中重金属污染日趋严重,其中铬元素存在形式复杂,六价铬离子毒性较强且容易迁移,已对生态环境造成严重威胁。在多种针对重金属污染土壤修复方法中,稳定/固化技术由于具有经济有效,适用范围广,操作简单等优势,已广泛用于底泥、淤泥、工业废渣和尾矿中重金属的稳定与重金属污染土壤的修复,但寻求经济高效稳定剂是稳定技术的关键。活性炭由于其具有丰富的孔隙结构与发达的比表面积且化学性质稳定,已广泛用于含有重金属气体体系及液相体系的吸附,而用于固相体系的研究较少。本论文将研究活性炭进行多种改性增强表面化学性质,用于铬污染土壤的修复,并探讨改性活性炭对污染土壤中铬的稳定机理。本文首先以商品活性炭(标记为AC)为原料,进行硝酸、氨气及赋硫改性分别制得含O、N和S官能团的活性炭(分别标记为OAC、NAC及SAC),并用BET、元素分析、FT-IR、Raman、XPS、Boehm滴定及pHpzc手段表征其理化性质。结果显示,OAC比表面积增加了27.0%,表面氧含量明显增加,C=O含量有所降低,生成了COOH,OH等含氧官能团;NAC比表面积增加了20.2%,表面引入含氮官能团,如吡啶、吡咯及吡啶氧化物等,活性炭碱性增强;SAC的比表面积下降了34.6%,改性过程中形成了-S-S-,噻吩,砜,O=S=O等含硫官能团。利用BCR连续浸提法考察了改性活性炭对铬盐厂区不同水平及垂直分布污染土壤中铬赋存形态的影响,探讨活性炭对污染土壤中铬的稳定作用。在可交换态总铬含量为2.41%~39.88%的供试土壤中,分别添加5%(w%)AC,OAC,NAC及SAC后,可交换态总铬与六价铬含量均有不同程度的下降,其中最优稳定效果试样中六价铬降低到未检出线,四种活性炭稳定总铬与六价铬的能力依次为SACOACACNAC。为了进一步研究活性炭对土壤中铬生物有效性的影响,向土壤中添加OAC与NBC(氨气改性生物炭),以辣椒为指示作物进行盆栽实验,观察生长状况,分析不同器官铬离子含量,发现OAC有效降低了土壤中铬离子的生物有效性及迁移能力,减少对辣椒的毒害作用,在铬离子浓度为300mg/kg的土壤中,铬在不同器官的富集程度呈现根叶茎果实的趋势,90%的铬富集在植株根部。研究了上述四种活性炭对Cr(VI)与Cr(III)的等温吸附及吸附动力学过程。结果表明,Langmuir模型比较吻合AC吸附Cr(VI)与Cr(III)的过程;由于表面改性增加的官能团使OAC、NAC及SAC表面不均匀,Freundlich模型对Cr(VI)与Cr(III)的等温吸附过程拟合效果更好。AC、OAC、NAC及SAC吸附Cr(VI)与Cr(III)动力学过程符合拟二级动力学方程,表明吸附Cr(VI)与Cr(III)是化学吸附过程。三种改性活性炭OAC,NAC和SAC对Cr(VI)的饱和吸附量qe,exp均较AC有较大幅度的增加,在298K下,OAC,NAC及SAC对铬离子的饱和吸附量分别增加了112.17%,120.73%和55.20%。结合FT-IR、Raman和XPS表面分析技术对吸附Cr(VI)与Cr(III)前后的活性炭进行表面性质分析,发现表面改性过程中引入活性炭表面的多种官能团(C=O,C-O-C,C-O或者O-S,吡啶,S-S,噻吩,O=S=O)均参与吸附过程,强化了化学吸附在吸附过程中的作用。
[Abstract]:With the rapid development of industry and agriculture, soil heavy metal pollution is becoming more and more serious, which exists in the form of chromium complex, six chromium ion toxicity is strong and easy to move, has caused a serious threat to the ecological environment. In a variety of the heavy metal contaminated soil remediation method, stable / solid technology because it is economical and effective, applicable to a wide range of operation simple and other advantages, has been widely used in the sediment, silt, repair and stabilization of heavy metal industrial waste residue and tailings in soil contaminated with heavy metals, but seek economic efficient stabilizer is key to stabilizing technology. Activated carbon due to its pore structure and developed specific surface area and stable chemical property rich, has been widely used for the adsorption of heavy metal containing gas system and liquid system, and used to study the solid system is less. This paper will study a variety of modified activated carbon enhanced surface chemical properties, for Remediation of chromium contaminated soil, and discusses the stability mechanism of modified activated carbon on pollution of chromium in soil. In this paper, commercial activated carbon (labeled AC) as raw materials, nitrate, ammonia and sulphur modification were prepared with O, N and S activated carbon functional groups (labeled OAC, NAC and SAC), and by BET, elemental analysis, FT-IR, Raman, XPS, Boehm and pHpzc characterization of titration means its physicochemical properties. The results showed that OAC increased by 27% than the surface area, surface oxygen content increased, C=O content decreased, the formation of COOH, OH and other oxygen-containing functional groups; NAC increased by 20.2% the specific surface area, surface into nitrogen containing functional groups such as pyridine, pyrrole and pyridine oxide, activated carbon enhanced alkaline; the specific surface area of SAC decreased by 34.6%, modified during the formation of -S-S-, thiophene, sulfone, O=S=O and sulfur functional groups. Use of BCR continuous extraction was investigated on different modified activated carbon chromate water Effect of chromium speciation in horizontal and vertical distribution of contaminated soil, the effect of activated carbon stable effect on the pollution of chromium in soil. The exchangeable chromium content of 2.41%~39.88% tested soils were added 5% (w%) AC, OAC, NAC and SAC, exchangeable chromium and chromium six. The content decreased to a certain degree, the stability effect of optimal six sample chromium reduced to unghecded qualify, ability of four kinds of activated carbon and stable total chromium chromium six followed by SACOACACNAC. in order to further study the effect of active carbon on the bioavailability of chromium in soil, add OAC and NBC to the soil (ammonia modified biochar), with pepper as the indicator plant pot experiment, observe the growth status, analysis of different organs of chromium ion content, found that OAC effectively reduces the chromium ions in the soil biological validity and migration ability, reduce the toxicity of chromium ion concentration in pepper. 涓，

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