【作者】 王忺；

【导师】 朱丽珺；

【作者基本信息】 南京林业大学 ， 生态学， 2008， 硕士

【摘要】 重金属污染一直是环境中的突出问题,它们在土壤和水体中的行为及归宿倍受人们的关注。锰氧化物是环境中最常见的矿物,对重金属污染元素的赋存、迁移和转化有着极其重要的作用。本文选择了最常见、最稳定且结构具有代表性的四种二氧化锰（α-MnO₂、γ-MnO₂、δ-MnO₂和无定形MnO₂）,研究了四者对重金属离子(Pb²⁺、Cd²⁺)的吸附行为,同时探讨了环境因素对其吸附行为的影响,并在此基础上,选择了吸附能力最强的一种二氧化锰,深入研究了其重金属离子的吸附性能。结果表明:（1）不同形态二氧化锰对Pb²⁺的吸附量均大于对Cd²⁺的吸附量,但对同一重金属离子吸附性能差异明显。对Pb²⁺的吸附能力δ-MnO₂﹥无定形MnO₂﹥α-MnO₂和γ-MnO₂,对Cd²⁺的吸附能力δ-MnO₂﹥α-MnO₂﹥γ-MnO₂﹥无定形MnO₂。（2）α-MnO₂和γ-MnO₂对Pb²⁺和Cd²⁺的等温吸附过程均最适合Freundlich等温方程。δ-MnO₂对Pb²⁺的等温吸附过程最符合Temkin方程,对Cu2+的等温吸附过程最符合Freundlich方程,对Cd²⁺的等温吸附过程最符合Langmuir方程。无定形MnO₂对Pb²⁺的等温吸附过程与Langmuir方程拟合度最高,对Cd²⁺的等温吸附过程与Temkin方程拟合度最高。（3）pH值对四种形态二氧化锰重金属离子的吸附影响相似。低pH值不利于重金属离子的吸附,随着pH值的增加,吸附量和吸附率上升,但变化规律因形态而异。吸附体系中盐浓度,总体上抑制重金属的吸附,且浓度越高,其阳离子化合价越高,抑制作用越明显。（4）在实验温度范围内,δ-MnO₂对Pb²⁺、Cu2+、Cd²⁺的饱和吸附量随温度升高而增大。且ΔG 0均为负,ΔH 0均为正,表明在该阶段三种重金属离子在δ-MnO₂上的吸附反应为自发吸热过程。（5）δ-MnO₂对Pb²⁺、Cu2+、Cd²⁺的吸附动力学特征有明显差异。δ-MnO₂对Pb²⁺和Cd²⁺的动力学吸附过程符合Elovich方程和双常数方程,对Pb²⁺Elovich方程拟合效果更优,对Cd²⁺双常数方程拟合度更高。而δ-MnO₂对Cu2+的动力学吸附过程仅符合双常数方程。（6）共存离子的存在影响重金属离子吸附效率。Pb²⁺与Cu2+共存时,Pb²⁺的竞争能力远大于Cu2+,δ-MnO₂表现出对Pb²⁺的“选择吸附性”。Pb²⁺与Cd²⁺共存时,Pb²⁺对Cd²⁺影响大于Cd²⁺对Pb²⁺的影响,竞争能力Pb²⁺﹥Cd²⁺。Cu2+与Cd²⁺共存时,Cd²⁺对Cu2+吸附的影响略大于Cu2+对Cd²⁺的影响,但从吸附量考虑Cu2+的竞争能力大于Cd²⁺。更多还原

【Abstract】 Heavy metal pollution was a great problem for a long time. The pollutant’s environmental behavior had attracted a lot of people’s attention. Manganese-oxides are widespread minerals. They can adsorb many kinds of heavy metals; oxidize some heavy metals. To a certain extent, Manganese-oxides control the bioavailability and toxicity of the heavy metals.α-MnO₂,γ-MnO₂,δ-MnO₂ and non-crystal MnO₂ are four kinds of Manganese dioxides which are widespread, stable and have typical texture. In this thesis, the behavior of Pb²⁺and Cd²⁺ adsorption on these four manganese dioxide was studied, and discussed the influence of surrounding factors, then gave further investigations of one manganese dioxides which has the highest adsorption capacity.（1） Adsorbing capacity of Pb²⁺ was higher than that of Cd²⁺ on all manganese dioxide studied by this thesis, but the adsorption capacity of the same heave metal ion on different manganese dioxide was otherness. For Pb²⁺ the adsorption capacity on different manganese dioxide was:δ-MnO₂﹥non-crystal MnO₂﹥α-MnO₂ andγ-MnO₂,for Cd²⁺ the adsorption capacity on different manganese dioxide was:δ-MnO₂﹥α-MnO₂﹥γ-MnO₂﹥non-crystal MnO₂（2）The equilibrium data of heave metal ion on different manganese dioxide was analyzed using the Langmuir, Freundlich, Temkin isotherms. The Freundlich isotherms provided the best correlation for both Pb²⁺ and Cd²⁺ onα-MnO₂ andγ-MnO₂. Forδ-MnO₂, the adsorption equilibrium data of Pb²⁺ fitted very well to Temkin isotherm, the adsorption equilibrium data of Cu2+ fitted very well to Freundlich isotherm, the adsorption equilibrium data of Cd²⁺ fitted very well to Langmuir isotherm. For non-crystal MnO₂, the Langmuir isotherms provided the best correlation for Pb²⁺; the Temkin isotherms provided the best correlation for Cd²⁺.（3）The effects of pH to adsorption of heave metal ion on different manganese dioxide were similar. The lower pH went against the adsorption of heavy metal ion. Along with the increasing of pH, both the adsorbing capacity and adsorption rate increased. The change of adsorbing capacity caused by pH value is related to the texture of manganese dioxide. Electrolytes in the singerle-component system inhibited the adsorption of heave metal ion, and the higher concentration or higher quantivalency of the cation of the electrolye made the inhibited effect more obvious.（4）In the studied temperatures range, the saturation adsorbing capacity of Pb²⁺, Cu2+and Cd²⁺ onδ-MnO₂ was increased when the temperature increased. The values ofΔG 0 andΔH 0showed that Pb²⁺, Cu2+and Cd²⁺ adsorbed byδ-MnO₂ is a spontaneous and endothermic process.（5）The process of the kinetics of Pb²⁺and Cd²⁺ adsorption onδ-MnO₂ can be well described with the models of Elovich and double constants. For Pb²⁺the adsorption kinetics can be best described by Elovich model, while the double constants model did for Cd²⁺. The process of the kinetics of Cu2+ adsorption onδ-MnO₂ can be described only by double constants model.（6）The competitive adsorption onδ-MnO₂ showed that the uptake of each metal was considerably reduced with increasing concentrations of the other. When both Cu2+and Pb²⁺were present in the solution together, the adsorption of Cu²⁺being more strongly influenced by Pb²⁺. When both Cd²⁺and Pb²⁺ were present in the solution together, the interference of Pb²⁺ with the Cd²⁺ uptake was more pronounced than the interference of Cd²⁺ with the Pb²⁺ uptake. The adsorption affinity is Pb²⁺﹥Cd²⁺. When both Cu2+and Cd²⁺were present in the solution together, the interference of Cd²⁺with the Cu2+ uptake was sub equal with interference of Cu2+ with the Cd²⁺uptake. Considering the adsorbing capacity, the adsorption affinity is Cu2+﹥Cd²⁺.更多还原