本研究目的為探討二維平板式電極三維電解槽搭配批式循環系統，改變不同操作條件及填充材，探討本設備對含銀廢液中銀離子去除的可行性。
實驗結果顯示在含高濃度銀離子( > 3000 mg/L)之照相沖印廢液電解還原時，銀離子去除率隨電流密度增加而升高，而且增加循環流量並不能有效提高去除率。顯示當電解還原高濃度銀離子時，反應並不受質傳限制。但當去除率達80%後去除率之提升逐漸減緩，顯示當濃度變低時，質傳限制開始主導反應進行，提供太高的電流密度無法有效率去除廢液中銀離子。模擬低濃度含銀廢水之電解還原過程中，質傳限制為最主要之影響因子，降低操作之電流密度及提高流量可得到較高銀離子去除率。當電量負荷控制在5 Coul/L時，分別以銅電極與不銹鋼電極操作處理100 mg/L之低濃度模擬含銀廢水，銀離子去除率皆可達到80%以上。若電量負荷降低至2.5 Coul/L，去除率可進一步提升至95%。在較低pH時(pH<4)或較大電流密度(2.0 mA/cm2)之操作下，會導致產氫之側反應發生，銀離子去除率會因此而降低，此現象在使用不銹鋼電極時更為明顯，去除率僅達35%。低濃度實際廢水與模擬廢水在電解還原時同樣受到質傳限制影響，在適當之電量負荷下，可以得到70%以上之銀離子去除率。對於低濃度實際廢水在填充珠子後，去除率有隨電流密度增加而提升之趨勢，顯示對於低濃度實際廢水之電解還原反應，在填充玻璃珠與塑膠珠後可降低質傳對電解還原反應之影響，填充珠子對於低濃度銀離子電解還原之質傳限制具正面改善效果。
綜合以上結果可知，電解還原高濃度銀離子時，銀離子去除率隨電流密度增加而有上升之趨勢，但去除率80%後質傳限制開始主導反應進行，模擬之含銀廢水與實際低濃度廢水則同樣受到質傳之限制。添加填充材則可提高銀離子還原之極限電流，減少低濃度含銀廢水電解還原反應時之質傳限制。

In this research, a 3-dimensional reactor in combination with paralleled plate electrodes was used for the removal of silver ions from diluted aqueous solution in the batch recirculation system. Influences of operating conditions including current density, flow rate, initial pH, electrode and packed material on the removal efficiency were investigated respectively.
Silver ion (>3000 mg/L) removal efficiency from photographs developing waste stream increased as the current density increased. In addition, the increase in recirculation flow rate couldn’t promote the removal efficiency effectively. At the same time, the removal percentage increased linearly with operating time until 80% of removal ratio was attained. These results indicate that removal of silver ions at high concentration waste stream would not be limited by mass-transfer. These results indicate that whenever silver concentration drops to an extent that silver concentration gradient between liquid (solution) –solid (plate) becomes small, the effect of mass-transfer is weak, and therefore silver removal efficiency drops. The same phenomenon was also found in both sampled and simulated diluted solution (Ag+ concentration <100 mg/L). The removal efficiency could be improved by lowering current density and promoting recirculation flow rate. When the system was operated at charge loading of 5 Coul/L with copper cathode or stainless steel cathode, the removal percentages could be higher than 85% for simulated solution and 70% for sampled solution. If the system was operated at smaller charge loading (2.5 Coul/L), silver removal percentage could increase to 95%. Nevertheless, when system was operated at low pH value (pH<4) or higher current density (2.0 mA/cm2), hydrogen generating side-reaction would happen and led to poor silver removal. In stainless steel cathode system, the removal percentage was merely 35%. In order to improve the poor mass-transfer in diluted solution, various packing material was packed in the reactor. In experiments with packing to remove silver in diluted solution, the removal percentage could be promoted with in creasing current density. These results indicate that mass-transfer is no more the most important factor in the removal of silver ions. System with packing could improve the poor mass-transfer condition while removing diluted silver from the solution.
In condition, the removal percentage of silver in dense solution could be improved with increasing the current density. Nevertheless, the removal percentage would be limited due to poor mass-transfer in the diluted solution. The system developed in this study can improve the mass-transfer efficiency and can have potential to be applied in the future.

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