本研究以飛灰吸附、Fenton oxidation及結合Fenton oxidation與飛灰吸附對鹼性染料Rhodamine B(RhB)去除率影響。研究內容可分為二部分，第一部分：單一處理方式對於染料RhB去除效率評估，(1)以飛灰吸附未經處理的染料，探討其吸附去除效果，並結合等溫吸附曲線Langmuir isotherm與Freundlich isotherm，評估飛灰對染料的吸附行為模式。(2)以Fenton oxidation降解染料RhB，以色度及COD探討其染料降解程度。第二部分：染料RhB以Fenton預先氧化後，再以飛灰吸附，探討染料RhB降解情形。
結果顯示，即使提高飛灰劑量至80 g L-1，其對染料色度移除僅有54%。而不同pH值對於飛灰吸附染料結果，在吸附時間拉長至8小時後，不同pH對於吸附的影響不大。等溫吸附曲線評估Langmuir isotherm與Freundlich isotherm，其R2分別為0.98及0.866，飛灰吸附RhB行為較符合Langmuir isotherm的單層吸附模式。單純以Fenton oxidation法處理染料RhB，溶液起始pH 3，添加H2O2劑量為6×10-3 M與Fe2+濃度為6×10-4 M，在實驗反應兩分鐘時，染料色度移除率可以達到97%，幾乎可完全去色，在COD部分則僅可移除31%，時間即使拉長至30分鐘，色度移除率提升至99.5%，其COD移除效率則僅至72%，仍有部份中間產物無法完全達到降解。圖譜偵測指出在吸收光譜200-400 nm處仍有大面積範圍，顯示去色溶液仍含有大量有機物未被降解。
結合Fenton預先氧化(H2O2與Fe2+濃度分別為6×10-3 M及6×10-4 M)與飛灰吸附(1 g L-1)染料Rhodamine B，可移除COD達98%以上，圖譜偵測結果顯示，經Fenton預氧化後染料以飛灰吸附2小時，在波長200-400 nm間有大面積區域消失。以飛灰吸附經Fenton oxidation處理的染料比未經處理的染料，其每單位重量飛灰對於染料之COD移除效率可提升41.6倍。本研究結果指出，結合Fenton預氧化與飛灰吸附，可以有效去除鹼性染料RhB，並可降低飛灰吸附時的使用量，大量減少污泥產生，在染料移除效率部分為一深具潛力的技術。
The removal of a basic dye, Rhodamine B (RhB), by fly ash adsorption, Fenton oxidation, and combined Fenton oxidation-fly ash adsorption were investigated. First, the effects of fly ash alone on RhB removal were studied. Two common isotherms, Langmuir and Freundlich models, were employed to evaluate the sorption behavior of RhB onto fly ash. Second, influences of Fenton oxidation alone on RhB removal were also examined. Finally, the combined Fenton pre-oxidation and fly ash process was carried out to investigate its effects on RhB removal.
When 80 g L-1 of fly ash was used alone, only 54% of RhB was removed after 8-h adsorption time. The changes of solution pH did not obviously influence RhB adsorption onto fly ash. The R2 values for the Langmuir and Freundlich model fitting results were 0.98 and 0.87, respectively. This suggests that the homogenous surface was responsible for RhB adsorption onto fly ash. When pH0 of 3, H2O2 of 6×10-3 M, and Fe2+ of 6×10-4 M were applied, the decolorization of RhB was rapid. 97% of decolorization and 31% of COD removal were achieved at treatment time of 2 min. Prolongation of reaction time of Fenton oxidation further increased RhB removal. 99.5% of color removal and 72% of COD removal were obtained after 30 min. Spectrum analysis result showed that a large area of UV spectrum at 200-400 nm remained after Fenton oxidation. This implied that there were still UV absorption-related intermediates presented in the Fenton-treated RhB solution.
The combined Fenton pre-oxidation (H2O2 of 6×10-3 M and Fe2+ of 6×10-4 M) and fly ash (1 g L-1) effectively removed more than 98% of COD of RhB. UV–vis spectra showed that fly ash obviously diminished UV absorption bands at 200-400 nm in the Fenton-treated RhB solution. The COD removal capacity of fly ash for Fenton-treated RhB solution was 41.6 times higher than that for untreated RhB solution. The results indicated that the combined process is a potential technique for RhB removal.
