臺灣博碩士論文加值系統

黏土礦物對於土壤中重金屬具有良好的吸附作用，然近來研究指出腐植質及環境參數均會影響黏土礦物對重金屬的遲滯力。本論文則進一步探討腐植酸含量、黏土礦物種類（日興土、蒙脫石、高嶺土與蛭石）以及環境因子如pH值等對鉛與鎘重金屬離子與黏土礦物的吸附現象之影響。並且從分析重金屬與腐植酸錯合反應、重金屬與黏土以及腐植酸與黏土吸附作用等單純系統中存在之機制推論腐植酸對重金屬在黏土礦物中吸附現象之影響。
黏土礦物對Aldrich腐植酸的吸附能力與其基本性質相關，而沈澱機制使腐植酸在黏土礦物表面形成一有機層，並藉由分配機制將更多的腐植酸分子吸附於黏土表面上。對重金屬與黏土礦物的吸附反應而言，黏土H+-溶液Mn+ 離子交換作用以及重金屬的沉澱機制推測為部分主要吸附途徑。
此外，本論文提出 1 : 2 修正模式用來替代傳統所使用的 1 : 1 錯合模式以符合二價重金屬離子與腐植酸之實際錯合情形，並透過此模式計算參與反應的腐植酸物種與濃度分佈以及求得鉛與鎘與腐植酸在 pH 6.5 以及離子強度0.01N 條件下的穩定常數，結果顯示鉛與腐植酸的錯合能力較鎘為佳；而腐植酸的錯合能力則隨腐植酸添加量的增加而下降；另鉛與鎘的競爭效應使穩定常數與腐植酸根濃度（At）皆呈現下降趨勢。但在添加較高濃度（> 300 mg/L）腐植酸時鉛與鎘的競爭效應則變得較不明顯。
若以離子交換平衡觀點視之，則可將 1 : 2 修正模式應用於重金屬、腐植酸與黏土礦物三者存在之吸附反應，結果發現三者存在之系統總吸附位址較二者存在之單純系統（重金屬-腐植酸＋重金屬-黏土礦物）吸附位址總和為多，暗示三者存在系統中之吸附機制比二者存在單純吸附作用複雜。此外，在不考慮重金屬沈澱機制下黏土礦物對於鉛的吸附能力仍較鎘為佳。一般而言，腐植酸對於黏土礦物吸附重金屬的影響程度亦受到競爭效應而降低。
本研究藉由修正傳統1：1錯合模式所得1：2修正模式來推求鉛與鎘在腐植酸存在之黏土礦物中時可能的反應機制以及重金屬競爭效應對黏土礦物吸附作用之影響。此成果對於評估受重金屬污染之含有機質土壤的擴散性與考量復育方式的選擇上有相當助益。建議未來在研選固體廢棄物處置場時的安全評估設計時可以依此成果推估場址中土壤有機質含量對於處置場緩衝能力設計之影響。

Clay mineral has excellent adsorption capability for heavy metal ions in general. However, recent studies showed that humic substance could affect the retardation capability of clay mineral for heavy metals. This study divided the main influence into three parts: organic content (Aldrich humic acid), clay minerals (Jishin bentonite, montmorillonite, kaolinite, and vermiculite), and the environmental parameter, such as the soil pH influence for further investigating the influence of humic acid on Cd and Pb adsorbed onto clay minerals.
The adsorption characteristics of humic acid onto clay minerals are related with the basic properties of clay minerals. In addition, clay H+- solution Mn+ ion exchange reaction was discussed to be one of the possible mechanisms. Moreover, the order of Kd values is consistent with average precipitated percentages of the humic acid on clay minerals, indicating that precipitation caused an organic film formed on the surface of clay, and substantially enhanced the adsorption capability of clay minerals by the organic partitioning.
The revised 1:2 complexation model, which was based on the traditional 1:1 complexation model, was evaluated to give the suitable description of the participating humic acid concentration and make connection to the evaluation of equilibrium constants of complexation (at pH 6.5, 0.01 N ionic strength, and 25℃). The binding capability of the Aldrich humic acid for Pb2+ was higher than Cd2+. Pb2+ generally has higher adsorption capability onto clay minerals than Cd2+ even without considering the precipitation.
In Cd2+ and Pb2+ co-existed condition, stability constants and total concentrations of deprotonated humic acid were influenced by the competitive effects. Less competitive effect of Cd2+ and Pb2+ occurred at higher amounts of aggregated deprotonated humic acid. Meanwhile, the influence extent of Aldrich humic acid was also depressed in the competitive system. By applying the concept of ion exchange equilibrium, heavy metal not only complexes with humic acid but also with other adsorption processes, such as partitioning, and the influence of Aldrich humic acid can only up to 10-1 meq/L degree.
The results of this study discussed the possible mechanisms and soil pH influencing the heavy metal sorption behaviors. The competitive effect and influenced extent of different concentrations of humic acid offer the information of estimating the trend of complicated environmental pollution, and more significantly, this perspective has significance for the use of biogeochemical safety assessment and the pollution retardation especially on the influence of organic content.

Chapter 1 Introduction 1-1
Chapter 2 Background and Theory 2-1
Chapter 3 Materials and Methods 3-1
Chapter 4 Results and Discussion 4-1
Chapter 5 Conclusion 5-1
References 6-1
Appendix 7-1

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