研究採取台灣電力公司火力發電廠燃煤飛灰，並將部分煤灰以高溫爐去除未燃碳作為研究用灰渣，探討礦物組成、比表面積、吸附反應pH值等因子對燃煤飛灰吸附水中銅離子之吸附能力、銅離子吸附於表面之鍵結型態與毒性萃取溶出特性。
研究結果發現燃煤飛灰樣品在不控制pH值條件下吸附去除水中銅離子，當吸附反應後溶液中pH>5.6，去除水中銅離子之反應機制應包括吸附及化學沈澱，推測以沈澱反應為主，且燃煤飛灰去除水中銅離子平均去除率達90%以上，燃煤飛灰之單位去除量平均在2.35~3.83 mg-Cu2+/g Ash之間。燃煤飛灰表面銅離子鍵結型態為碳酸鹽鍵結態與鐵錳氧化鍵結態。而氧化鈣及氧化鎂等鹼性物質含量大於20％之煤灰吸附銅離子後，進行毒性特性溶出程序，銅離子溶出濃度符合有害事業廢棄物認定標準中規定毒性特性溶出程序萃取溶液銅離子濃度須在15mg/L以下之標準，故無須進行脫附/無害化程序。
此外，控制pH=5.0條件下，燃煤飛灰樣品於不同添加劑量吸附去除水中銅離子平均去除率為46.3～57.2％，而燃煤飛灰表面銅離子之單位吸附量平均為1.45~1.96 mg-Cu2+/g Ash，燃煤飛灰吸附去除水中銅離子吸附量與比表面積、氧化鐵與氧化鈣含量成正相關。吸附於燃煤飛灰表面銅離子之鍵結型態分佈，於去除未燃碳的A～I燃煤飛灰樣品主要的鍵結型態大部分為碳酸鹽鍵結態。含有未燃碳的J～O燃煤飛灰樣品主要的鍵結型態為殘餘鍵結態。進行毒性特性溶出程序，結果發現A～O燃煤飛灰，須進一步以0.1N硝酸進行脫附/無害化程序方可符合有害事業廢棄物認定標準中規定毒性特性溶出程序萃取溶液銅離子濃度須在15mg/L以下之標準。 The coal-burn fly ash used in this study was collected from coal-burn power plants of Taiwan Power Company. Part of fly ash samples were decarbonized in a oven (550 ℃) to investigate the effect of minerals composition, specific surface area, and pH of the fly ash on the adsorption of copper ions from the aqueous solution . The binding species and leaching characteristics of copper ions adsorbed onto the surface of coal-burn fly ash were also discussion in the present work.
Research results based on adsorption experiments demonstrate that when solution pH was not controlled, most of aqueous copper ions were removed. The final solution pH was larger then 5.6 when the adsorption reaction finished. Removal of copper ions was attributed to chemical deposition and adsorption. The removal efficiency of copper ions by fly ashes were more than 90 %, with some cases 100%. Based on the results of adsorption isotherm experiments, the average specific adsorption capacity of copper ions was in the range of 2.35~3.83 mg- Cu2+/g-fly ash. Furthermore the major binding species of copper ions adsorbed onto the surface of coal-burn fly ash are carbonate bound and Fe-Mn oxides bound. After adsorption reaction, fly ashes with CaO and MgO content larger than 20% passed through toxicity characteristic leaching procedure, which means concentration of copper ions leaching from copper-leaden fly ash less than 15 mg/L limitation.
In addition, research result also shows that when solution pH was controlled at 5.0, the removal of copper ions was in the range of 46.3~57.2 %, with an average specific adsorption capacity of copper ions in the range of 1.45~1.96 mg- Cu2+/g-fly ash. The removal of copper ions was positively related to BET, Fe2O3, and CaO. Most of the binding species of copper ions adsorbed onto the surfaces of A~I coal-burn fly ashes was carbonate bound. The binding species of copper ions adsorbed onto the surfaces of J~O coal-burn fly ashes was residual. The copper-leached fly ash of A~O must be treated with 0.1N HNO3 for 24 hour to pass through the limitation of TCLP in Taiwan.
