Please use this identifier to cite or link to this item: http://hdl.handle.net/11455/5483
標題: 以化學沈降法對重金屬離子共存時之處理控制探討
作者: 蔡永興
關鍵字: 化學沈降法;重金屬離子
出版社: 環境工程與科學系
摘要: 
化學沈降法在諸多處理重金屬廢水方法中,因簡易可行、處理成本較低,而廣為實際廢水處理所採行。目前國內外對於水及廢水中重金屬離子去除控制與錯合反應的影響,大都針對某一特定之重金屬種類來探討,對於兩種或兩種以上重金屬離子共存時物種平衡之競爭反應則少有涉獵,而在實際廢水處理上在某一特定pH操作條件下,無法使處理後放流水符合所有重金屬排放標準,因此本研究目的系以批分式實驗方法探討在化學沈降與混凝澱合併處理下,環境控制因子之改變(重金屬初始濃度、共存配比、pH、錯合劑存在等)對重金屬去除之影響,並結合水化學增平衡理論計算與背景試驗結果,尋找共存重金屬相關性及適當控制條件,提供實際廢水處理操作控制之參考。
由試驗結果發現,在銅、鎳與鋅、鎳共存廢水中,加入混凝劑FeCl3,控制pH值為9,以Fe(OH)3(s)產生”共沈澱-吸附”,並增加其不不溶性固體物沈降性,靜置後之上澄液皆可達到放流水標準;而就混凝劑加藥量多寡是以鎳為基準,在鎘、鎳共存時,混凝劑加藥量是以鎘為基準。
若在廢水中含強螯合劑(如EDTA)時,以FeCl3混凝劑而產生Fe3+“取代反應”及“共沈澱-吸咐”作用仍有一定限度,因此對於含高濃度強螯合劑重金屬廢水之處理,須注意本試驗方法處理上限;運用於連續流反應系統時,如能配合適當水力控制條件,加上後續固液分離處理,提昇化學混凝沈降法整體之成效。

Chemical precipitation is the most economic approach and is widely used for the treatment of heavy metal-laden wastewaters. In the past, most of the related references emphasized on the removel control and complexation effect for a certain kind of heavy metal ion in water and wastewater. However. However, study on the competitive reaction of various species due to the coexistence of several heavy metal sorts is quite scarce. Thus, the treated wastewater may not meet all the effluent standards of various heavy metals under a certain pH operational condiction. The prupose of this research is to investigate the effect of environmental controlled parameters(such as initial concentration of heavy metal, mole ratio between the coexitent species, pH value, and the presence of chelating agent) on the removal efficiency of heavy metals when the chemical precipitation followed by coagulative sedimentation process is used by batch type of experiments. It is expected that the relation between the coexistent heavy metals and the optimum controlled conditions can be observed through the theoretical calculations of aquatic chemcial equilibrium and the results of background experiments in order to offer the important information on treatment control.
It was found that the co-precipitation/adsorption by Fe(OH)3(s) is the major mechanism for the removal of heay metal ions with the coexistence of copper and nickel, ro, zinc and nickel, by the addition of FeCl3 as coagulant at pH9. The settling characteristic of the suspended particulates can be enhanced and the supernatant after quiescent settling meets the effluent standards. The requirement of coagulant dosage is based on nickel, however, the cadmium is instead in the cadmium/nickel coexistent wastewater.
In the presence of strong chelating agent (such as EDTA), the substitution reaction by Fe3+ and the co-precipitation/adsorption mechanism are significantly restricted by the addition of FeCl3 as coagulant. Thus, the limitation of treatment efficiency by this approach should be noticed when the heavy metal-laden wastewater with high strength chelating agent is treated. In the continuous-flow reaction system, the successive efficiency of chemical precipitation/coagulative sedimentation process can be enhanced by the proper hydraulic controlled conditions and solid-liquid separation treatment.
URI: http://hdl.handle.net/11455/5483
Appears in Collections:環境工程學系所

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