【作者】 孙新元；

【导师】 张齐生；

【作者基本信息】 南京林业大学 ， 环境工程， 2010， 硕士

【摘要】 本文采用硝酸、氨水、微波三种改性方法对竹炭进行了表面改性,并研究了表面改性对微污染水中4种典型有机物指标的吸附效果。通过对改性前后竹炭基本吸附性能参数及微观结构的分析,探究了表面改性竹炭吸附效果变化的机理,结果表明:(1)表面改性竹炭中,在最佳吸附条件下,硝酸改性有利于对UV254、UV410的吸附,34%硝酸改性炭(O-2炭)使竹炭对两指标的去除率分别提高了28.18%和32.86%,但硝酸改性不利于对CODMn和2,4-DCP的吸附,高浓度硝酸改性条件对各指标的吸附均产生不利影响;低浓度氨水改性可以提高对各指标的吸附效果,但提高幅度不大,高浓度氨水使得改性效果降低;微波改性使竹炭对各指标的去除率均有所提高,且幅度大于氨水改性,微波改性对2,4-DCP的去除效果最优,相比于未改性炭,去除率提高了16.25%。(2)改性前后各竹炭对于有机物指标的吸附容量实验表明,改性前后竹炭对CODMn、UV254、UV410的吸附过程均可以Freundlich型吸附等温线表示;未改性炭、氨水、微波改性炭对于2,4-DCP的吸附过程均类似于单层吸附,适合用Langmuir型吸附等温线表示,而硝酸改性炭对2,4-DCP的吸附过程则适合用Freundlich型吸附等温线表示。(3)硝酸改性和氨水改性均导致竹炭碘值降低、灰分及水分含量减少,微波改性使竹炭碘值呈略增大趋势,也出现存在碘值减小的情况,灰分、水分含量随改性程度加深而减少。3种改性条件下,竹炭表面官能团含量发生明显变化:硝酸改性炭表面含氧官能团显著增加,总碱度下降;氨水改性炭表面总酸度下降,总碱度明显升高,含氮官能团增加;微波改性炭表面官能团含量总量减少,总酸度和总碱度略有增加。(4)综合采用SEM-EDS分析、XRD分析、红外光谱分析、拉曼光谱分析、TG-DSC分析等多种手段对改性前后竹炭的微观结果进行了分析。结果表明,硝酸改性炭氧含量明显增加,晶体结构趋于规整、有序,石墨化程度提高,使得硝酸改性炭有利于吸附较大的分子,使UV254、UV410得去除率明显提高,而碳结构表面含氧官能团的增加,使竹炭亲水性增强,总酸度增加,导致对CODMn和2,4-DCP去除率的下降;氨水改性炭表面总碱度增加,含氮官能团增多,疏水性增强,炭表面观察到被腐蚀的迹象,各指标去除率提高不大与微孔体积减小有关;微波改性使得竹炭微孔体积增大,从而有利于对各指标的吸附。表面改性提高了竹炭对有机物吸附的选择性。改性前后竹炭的吸附效果是由竹炭孔隙结构、表面性质及吸附质性质共同作用的综合结果,三种影响因素的强弱决定了最终吸附效果的趋势。更多还原

【Abstract】 In this paper, three kinds of methods were used on the surface modification of bamboo charcoal, nitric acid modification, ammonia modification and microwave modification. The adsorption effects of these modified bamboo charcoals on four organic pollutions were also studied in this paper. Through the modification of the basic adsorption parameters before and after the charcoal and the analysis of its microstructure, exploration on the causes in changes on adsorption effect of surface-modified charcoal was made. The result of the study reveals that:(1)Among the three kinds of surface modification bamboo charcoal, the nitric acid modification is benefit for the absorption of UV254 and UV410 in the best adsorption conditions. Bamboo charcoal 34% nitric acid modified carbon (O-2) makes the two indicators of carbon removal rates increased by 28.18% and 32.86%, but nitrate modified wasn’t conducive to the CODMn and 2, 4-DCP adsorption, high concentrations of nitric acid modification conditions on the adsorption of each index were negatively; low concentration of ammonia modification could increase the adsorption of each index but not obviously. High concentrations of nitric acid makes the modified lower; microwave modified to make bamboo charcoal for the removal of all indexes were improved, and larger than ammonia modification, microwave modification on the 2,4-DCP removal efficiency of the most excellent, compared to unmodified carbon, the removal rate increased 16.25%.(2)The adsorption capacity for organic results of the bamboo charcoal before and after the modification show that, the adsorption process for CODMn, UV254, UV410 both before and after modification can be illustrated by Freundlich-type adsorption isotherm. The adsorption process for 2,4-DCP of unmodified charcoal, ammonia modified charcoal, and microwave modified charcoal is similar to the single-layer adsorption, can be illustrated by Langmuir-type adsorption isotherm.(3)Modification of nitric acid and ammonia led their iodine adsorption value, ash and moisture content decreased. The iodine values of micro-wave modification charcoal tend to slightly increase combined with a little decrease. Along with the degree of deepening, the ash, moisture content reduced. The contents of surface functional groups in bamboo charcoal significant change in three kinds of modified conditions: The nitric acid modified carbon surface oxygen groups increased significantly with the total alkalinity decreased; The total acidity of the ammonia surface modification carbon decreased and total alkalinity significantly increased, with the contents of the nitrogen functional group become higher; microwave carbons reduced the total content of surface functional groups, and make the total acidity and total alkalinity increased slightly.(4)SEM-EDS analysis, XRD, infrared spectroscopy, Raman spectroscopy, TG-DSC analysis were used in the study of modified charcoal microstructure analysis results .The results showed that the oxide content in the nitric modified carbon was increased remarkably, the crystal structure became regular, orderly, and the degree of graphitization increased that make its removal rate of large molecules conducive to UV254, UV410 significantly increased. While the carbon structure of the surface oxygen functional groups increased, so that bamboo charcoal can improve its hydrophilic and acidity increased, resulting the removal efficiency of CODMn and 2,4-DCP decreased. Total alkalinity of ammonia surface modified carbon increased, along with the nitrogen-containing functional groups and the hydrophobic increased. It is beneficial for the adsorption of the organic pollution indicators, but signs of corrosion in the surface of the ammonia surface modified carbon were observed, making the micro-porous volume decrease and resulting in the removal of the index. Micro-wave modification makes the charcoal micro-pore volume increases, thus facilitating the absorption of various indicators.Surface modification of bamboo charcoal improves the adsorption selection to organic pollutions. The adsorption effect of bamboo charcoal before and after modification was combined with the bamboo charcoal pore structure, surface properties and adsorptive interaction. The most important factors determine the final adsorption effect of the bamboo charcoal.更多还原