不同来源生物质炭对汞的去除性能和固定机制研究

发布时间：2018-04-18 21:33

本文选题：生物质炭 + 汞　；参考：《南京师范大学》2015年硕士论文

【摘要】：目前,我国环境中汞污染日益严重。传统处理方法存在汞去除率低,费用昂贵、破坏土壤理化性质等缺点,因此迫切需要发展废水和土壤中除汞新技术。生物质炭作为一种新型的环境功能材料成为当前的研究热点。已有研究表明,生物质炭对溶液和土壤中重金属表现出良好的吸附性能,同时生物质炭在改良农业土壤、提高作物产量、固炭以及减少温室气体的排放等环境功能方面有着巨大的应用价值。本文以木屑、稻秆、稻壳及菹草为原料,600℃下热解制备生物质炭,运用扫描电镜和傅里叶红外光谱技术对四种不同原料制备的生物质炭的形态结构和表面化学特性进行表征。通过吸附实验和室内模拟实验,分别比较了不同生物质炭对水溶液中重金属汞吸附特性的差异及施加生物质炭对污染土壤环境质量和土壤中汞的形态变化的影响,并探讨了吸附动力学行为和汞的去除机理。主要研究结果如下：(1)四种生物质炭的产率、灰分含量、碱性强弱表现出了很好的一致性,均为：菹草炭稻壳炭稻秆炭木屑炭。其中菹草炭、稻壳炭和稻秆炭pH值高于10,属强碱性物质。生物质炭的含碳量大小为：木屑炭稻秆炭稻壳炭菹草炭。与其他材料相比,木材来源的生物质炭含碳量最高,灰分含量、矿质养分含量均较低。四种生物质炭表面形态有很大差异,但均具有丰富的孔隙结构,这对于改善土壤的持水能力有非常重要的意义。FTIR分析表明,不同原料制备的生物质炭均含有芳香基、羟基和一些含氧官能团,但吸收强度具有差异性。生物质炭的酸性官能团数量为：木屑炭稻秆炭菹草炭稻壳炭。(2)pH值对溶液中Hg2+的净化性能影响较大,当初始溶液pH值为5时,四种生物质炭对溶液中Hg2+的去除效果最佳。与其他三种材料相比,木屑炭对溶液中Hg2+的吸附相对较慢。Langmuir等温方程很好地描述了木屑、稻秆和菹草炭吸附Hg2+的过程,木屑炭吸附Hg2+的能力为60.2mg/g,优于其他三种材料。四种生物质炭对Hg2+的吸附动力学过程符合准二级动力学模型,且其吸附过程受内扩散和膜扩散共同控制。SEM-EDS分析结果表明,吸附之后所有生物质炭的能谱上均出现了汞峰,且吸附过程中存在离子交换作用；FTIR分析可知生物质炭羟基和羧基与汞的络合作用。同时生物质炭对Hg2+的吸附机制可能涉及还原作用和阳离子-π作用。(3)添加四种生物质炭后土壤的pH值、CEC和TOC含量均有不同程度地增加,说明生物质炭可以改良土壤的酸度,并增加土壤的肥力。在汞浓度为50mg/kg的土壤中,生物质炭没有表现出明显的稳定化作用。生物质炭对汞浓度为500mg/kg的污染土壤中的汞的稳定作用比较明显,添加生物质炭将土壤中可交换态和碳酸盐结合态汞转化为残渣态汞。菹草炭对汞的固定效果优于其他三种材料,而木屑炭、稻秆炭和稻壳炭对土壤中汞的修复效果不具有显著性差异。(4)固-液体系中,经典动力学吸附方程存在吸附剂浓度效应和参数的不确定性现象,在实际应用中存在局限性。SCA-准二级速率方程可以准确地描述木屑炭-Hg(Ⅱ)体系吸附动力学中的吸附剂浓度效应,得出不同时间点上的吸附量,预测值与实测值拟合较好,具有应用价值。
[Abstract]:At present, China's environmental mercury pollution is becoming increasingly serious. The traditional processing method is low, the removal rate of mercury is expensive, destroy the shortcomings of soil physicochemical property, so there is an urgent need for development of wastewater and soil mercury removal in new technology. The biomass carbon as an environmental functional material has become the hotspot. Studies have shown that biomass and soil carbon on heavy metal solution showed good adsorption properties, and biomass carbon in improving agricultural soil, increase crop yield and has great application value of solid carbon and reduce greenhouse gas emissions and other environmental functions. In this paper, sawdust, rice straw, rice husk and crispus as raw material, preparing the pyrolysis of 600 DEG C biomass carbon was characterized by scanning electron microscopy and Fourier transform infrared spectroscopy of four kinds of raw materials for the preparation of biomass carbon structure and surface chemical properties through adsorption experiment and application. The indoor simulation experiment, respectively. The effects of different biochar on mercury adsorption characteristics in aqueous solution and the morphological changes of soil environmental quality and pollution of mercury in soil by biochar, the removal mechanism of adsorption kinetics and mercury are discussed. The main results are as follows: (1) four kinds of biomass carbon the yield, ash content, basicity showed good consistency, are: rice husk rice straw carbon carbon potamogetoncrispus sawdust charcoal. The Potamogeton peat, rice husk and rice straw carbon pH value is higher than 10, strong alkaline substances. The size of carbon biomass carbon: rice straw sawdust charcoal carbon from rice husk carbon Potamogeton peat. Compared with other materials, the biomass carbon source of wood. The highest content of carbon, ash content, mineral nutrient content was relatively low. Four kinds of biomass carbon surface morphology are very different, but all have abundant pore structures, to improve The water holding capacity of soil is very important..FTIR analysis showed that the biomass carbon prepared by different raw materials contain aromatic radical, hydroxyl and oxygen containing functional groups, but the absorption intensity is different. The number of acidic functional groups of biochar: rice straw sawdust charcoal carbon rice husk carbon carbon crispus (2) pH value. Purification of Hg2+ in solution on the larger performance impact when the initial pH value was 5, the removal of Hg2+ in solution of four kinds of biomass carbon best. Compared with the other three kinds of materials, the adsorption of Hg2+ in solution on sawdust charcoal relatively slow.Langmuir isothermal equation well describes the process of rice straw and sawdust, Potamogeton Hg2+ adsorption capacity of peat, sawdust charcoal adsorption of Hg2+ is 60.2mg/g, better than the other three materials. The adsorption kinetics of four kinds of biomass carbon of Hg2+ follows a pseudo two order kinetics model, and the adsorption process is controlled by film diffusion and diffusion of common control .SEM-EDS analysis results show that the adsorption after all biomass carbon spectra showed peaks of mercury, and the adsorption ion exchange process in FTIR; analysis of complexation that biochar hydroxyl and carboxyl groups with mercury. At the same time the adsorption mechanism of biochar on Hg2+ may be related to the reduction and the Cation-n effect (3). Add four kinds of biomass carbon and soil pH, CEC and TOC were increased in different degrees, that biochar can improve soil acidity and increase soil fertility. The mercury concentration of 50mg/kg in soil, the biomass carbon did not show obvious stabilizing effect. The biomass carbon effect on the stabilization of mercury concentration for the pollution of mercury in soil 500mg/kg is quite obvious, adding biochar in soil exchangeable and carbonate bound mercury into residual mercury. The fixed effect is better than that of carbon on the mercury he crispus Three kinds of materials, and sawdust charcoal, rice straw and rice husk carbon restoration effect of carbon on mercury in soil has no significant differences. (4) solid - liquid system, uncertainty of the adsorbent concentration effect and the parameters in the classical kinetic adsorption equation, in the practical application of the limitation of the.SCA- can be accurately described sawdust charcoal -Hg quasi two level rate equation (II) adsorption dynamics in the adsorbent effect, the adsorption capacity of different time points, the predictive value of fitting well with the measured values, and has application value.

【学位授予单位】：南京师范大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：X505

【参考文献】