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首页> 外文会议>1998 Joint Conference on the Environment, 1998, Mar 31-Apr 1, 1998, Albuquerque, NM >Determination of Alfalfa Biomass Metal Binding by Amino ligands through Chemical Modification
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Determination of Alfalfa Biomass Metal Binding by Amino ligands through Chemical Modification

机译：氨基配体化学修饰法测定苜蓿生物量金属的结合

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Because of the severity of heavy metal contamination and the potential adverse health impact on the public, a tremendous effort has taken place to remediate lands and waters containing toxic metal ions. Traditional methods which have been employed, prove to be costly and prohibitive for low level waste remediation. Due to the economic barrier for remediation, there has been a great deal of attention to the use of both living and non-living biological materials for the economical remediation of toxic metal ions from industrial waste waters and mining effluents. Most recently, plant based biomaterials have been of interest. Unlike typical synthetic ion-exchange resins, plant based biomaterials do not require regeneration and conversion. Therefore, plant based biomaterial systems may be effective for the removal of heavy metal ions from the environment in a cost effective fashion. Biosorption or metal binding by inactivated biological materials occurs through the coordination of metal ions to different functional groups. Gardea-Torresdey et al. found that carboxyl groups were responsible for a great portion of copper(II) and aluminum(III) binding on algal cell walls as well as copper adsorption by sphagnum peat moss and its different humic substances. Chemical probe analysis to determine metal site binding was performed by both Rayson et al. and Majidi et al. using ~(113)Cd nuclear magnetic resonance (NMR) spectroscopy. Studies performed by Kuyucak et al. determined that carboxyl groups are responsible for the binding of cobalt to the nonliving biomass of the common seaweed Ascophyllum nodosum. Therefore, chemical functional groups have shown to be important to the binding of metal ions to biomaterials. Alfalfa has shown to be very effective at the removal and recovery of several heavy metal ions from aqueous solutions. Although much information has been gained on the binding of metal ions to the alfalfa biomass, relatively little information has been obtained in relation to the actual metal binding chemical groups. X-ray absorption spectroscopic studies previously performed indicated that some of the metal binding by alfalfa biomass may be occurring through an oxygen ligand (possibly carboxyl groups) for some metals, while other metals could be partially binding through nitrogen ligands. Consequently the metal binding mechanism in the alfalfa biomass is not completely understood. Therefore, additional investigation is necessary to determine what chemical functional groups are responsible for binding of different heavy metal ions and in what proportions. The objective of this study is to determine the extent of metal binding occurring through nitrogen ligands. This was accomplished by chemically modifying the available amino groups. Two methods of chemical modification were used; acetylation of the biomass, and succination of the biomass. Through acetylation of the biomass, the available amino ligands were blocked through the addition of acetic anhydride, thereby reducing the metal binding to the available nitrogen ligands. In addition, succination of the biomass was performed which would add a carboxyl group onto the modified nitrogen ligand. Since carboxyl groups have been shown to play an important role in metal binding, succination of the biomass should increase the metal binding and indicate the metal binding ability of available modified amino groups. A comparison of the metal binding capacities by the acetylated biomass, succinated biomass, and control biomass, will show the percentage of metal binding by amino ligands in the alfalfa biomass for the different metal ions studied. By determining the metal binding sites in the alfalfa biomass, a new treatment technology of heavy metal contaminated ground waters can be further understood and developed.
机译：由于重金属污染的严重性以及对公众的潜在不利健康影响，已经做出了巨大的努力来修复含有有毒金属离子的土地和水域。已被采用的传统方法被证明是昂贵的并且禁止低水平的废物修复。由于修复的经济壁垒，人们非常关注使用有生命和无生命的生物材料对工业废水和采矿废水中的有毒金属离子进行经济修复。最近，基于植物的生物材料受到关注。与典型的合成离子交换树脂不同，基于植物的生物材料不需要再生和转化。因此，基于植物的生物材料系统对于以成本有效的方式从环境中去除重金属离子可能是有效的。灭活的生物材料对金属的吸附或金属结合是通过金属离子与不同官能团的配位而发生的。 Gardea-Torresdey等。发现羧基是藻类细胞壁上大部分铜（II）和铝（III）结合以及泥炭藓泥炭及其不同腐殖质对铜的吸附的原因。 Rayson等人均进行了化学探针分析以确定金属位点结合。和Majidi等。使用〜（113）Cd核磁共振（NMR）光谱。 Kuyucak等进行的研究。认为羧基是导致钴与普通海藻Ascophyllum nodosum的非生物量结合的原因。因此，化学官能团已显示对于金属离子与生物材料的结合很重要。紫花苜蓿在从水溶液中去除和回收几种重金属离子方面显示出非常有效的效果。尽管已经获得了许多有关金属离子与苜蓿生物量结合的信息，但有关实际的金属结合化学基团的信息却相对较少。先前进行的X射线吸收光谱研究表明，苜蓿生物量的某些金属结合可能通过某些金属的氧配体（可能是羧基）发生，而其他金属可能通过氮配体部分结合。因此，尚未完全了解苜蓿生物质中的金属结合机理。因此，需要进行额外的研究以确定哪些化学官能团负责不同重金属离子的结合以及比例如何。这项研究的目的是确定通过氮配体发生的金属结合程度。这是通过化学修饰可用的氨基完成的。使用了两种化学修饰方法：生物质的乙酰化和生物质的琥珀化。通过生物质的乙酰化，可利用的氨基配体通过添加乙酸酐被封闭，从而减少金属与可利用的氮配体的结合。另外，进行生物质的琥珀酸化，其将羧基添加到改性的氮配体上。由于已显示羧基在金属结合中起重要作用，因此生物质的琥珀酸化应增加金属结合并表明可用的修饰氨基的金属结合能力。乙酰化生物质，琥珀酸化生物质和对照生物质对金属结合能力的比较将显示苜蓿生物质中氨基配体对所研究的不同金属离子的金属结合百分比。通过确定苜蓿生物量中的金属结合位点，可以进一步理解和开发一种新的重金属污染地下水处理技术。

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