| 摘要: | 本研究嘗試應用無機聚合物技術，探討都市垃圾焚化飛灰無害化，以及評估焚化飛灰型無機聚合物，作為吸附廢水中重金屬Cu(II)及Pb(II) 之材料可行性。無機聚合物製備實驗係以焚化飛灰與30%及40%偏高嶺土進行摻配，以期調整試驗材料之矽鋁比，同時以8M~12M KOH作為鹼活化劑，並分別控制恆溫恆濕(25℃及相對溼度65%)及快速加熱(60℃)兩種養護方式，期進一步評估無機聚合反應之最佳條件。此外，吸附試驗之實驗規劃，依序針對吸附劑劑量(1.5、5、10及20 g/L)，重金屬溶液pH值(2、3、4、5及6)，吸附接觸時間(15、30、60、180、360、720及1,440分鐘)，以及重金屬初始濃度(100、150、200及250 mg/L)等參數，除評估最佳操作條件外，亦藉由吸附接觸時間及重金屬初始濃度之試驗結果，建立相關吸附之動力參數及重金屬之理論吸附容量。
研究結果顯示，在8M KOH鹼活化及恆溫恆濕養護28天條件下，添加30% 偏高嶺土(Si/Al=1.89)之反應條件，無機聚合物具有較佳的抗壓強度，約可達4.59 ± 0.43 kgf/cm2。根據無機聚合物之FTIR、XRD及SEM等分析結果顯示，試驗材料間具有Si-O-Si與Al-O-Si等官能基之鍵結型態，以及石英與鋁矽化合物等晶相物種，均可驗證無機聚合反應之發生。另根據TCLP之重金屬毒性溶出濃度分析結果可知，焚化飛灰中重金屬鉛之溶出濃度，已由36.20 mg/L降低至0.05 mg/L，已符合法規溶出濃度之管制標準，達到焚化飛灰無害化之目標。為進一步瞭解無機聚合物作為吸附劑之可行性，根據BET分析結果，其比表面積為25.21 m2/g，應屬於中孔型吸附材料。
吸附試驗結果顯示，試驗控制在固液比為5 g/L及重金屬Cu(II)與Pb(II) 溶液之pH值分別為6及5條件下，吸附接觸時間為720分鐘時，重金屬Cu(II)及Pb(II) 之最佳去除效率分別為99.91%及99.93%。當重金屬初始濃度為250 mg/L時，重金屬Cu(II)及Pb(II)之最佳吸附容量，分別為20.90 mg/g及25.96 mg/g。根據吸附動力學結果顯示，擬二階動力學模式可良好模擬吸附試驗結果，並以Freundlich等溫線模式較為符合。根據重金屬物種XRD鑑定及物種模擬之分析結果，證實無機聚合材料之強鹼性，促使重金屬溶液之pH值上升，並形成重金屬Cu(II)及Pb(II)之沉澱物，進而增加重金屬之吸附去除效果。整體而言，根據本研究初步之成果證實，無機聚合物技術可有效達到焚化飛灰無害化之目的，同時亦能有效吸附去除廢水中重金屬Cu(II)及Pb(II)。因此，焚化飛灰型無機聚合物作為吸附材料，除具焚化飛灰資源化再利用之價值外，亦極具有應用於含重金屬廢水處理與發展之潛力。
;This research investigated the effect of converting the municipal solid waste incinerator (MSWI) fly ash to the non-hazardous material by geopolymer and the feasibility of fly ash-based geopolymer on the adsorption of copper and lead in the aqueous solution. The geopolymer preparation experiments used 8~12M of KOH as the alkaline activator and designed MSWI fly ash blending with 30% or 40% metakaolin to adjust the suitable Si/Al ratio. The curing conditions, including natural (25℃and 65% of humidity) and accelerated curing (60℃), were also discussed. On the other hand, the adsorption experiments were conducted by controlling the adsorbent dosage (1.5, 5, 10, and 20 g/L), the pH value of the heavy metal solution (2, 3, 4, 5, and 6), the contact time (15, 30, 60, 180, 360, 720, and 1,440 minutes), and the initial concentration of the heavy metal solution (100, 150, 200, and 250 mg/L). The adsorption kinetics and tested metal adsorption capacity were determined by controlling the contact time and the initial concentration of the heavy metal solution.
The experimental results showed that the fly ash-based geopolymer could provide enough compressive strength (4.59 ± 0.43 kgf/cm2) to ensure the geopolymerization in the case of 8M KOH and 30% metakaolin addition (Si/Al ratio=1.89) by the natural curing condition. The presence of Si-O-Si, Al-O-Si, quartz crystal, and aluminosilicate speciation of geopolymer were identified by FTIR, XRD, and SEM. It implied that the geopolymerization had occurred during the preparation process. On the other hand, toxicity characteristics leaching procedure (TCLP) concentrations of the tested metals in the geopolymer were all in compliance with current regulation thresholds. Especially for the lead (Pb) TCLP concentrations, it was decreased from 36.20 mg/L in the original MSWI fly ash to 0.05 mg/L in the geopolymer. The TCLP analysis results indicated that the non-hazardous treatment of MWSI fly ash had been successfully developed by geopolymer. To further understand the feasibility of adsorbent application in geopolymer, the BET analysis results of geopolymer indicated that the specific surface area was approximately 25.21 m2/g and belonged to the mesoporous adsorbent materials.
According to the adsorption test results, in the case of solid-liquid ratio was 5 g/L and the pH values ranging from 5 to 6, the Cu(II) and Pb(II) removal efficiencies were 99.91% and 99.93%, respectively, when the contact time was controlled at 720 minutes. However, when the initial concentration of heavy metals was 250 mg/L, the adsorption capacities of Cu(II) and Pb(II) were 20.90 mg/g and 25.96 mg/g, respectively. The adsorption kinetics results showed that the pseudo-second-order model could fit well in the adsorption test, and the Freundlich isotherm model also matched the tested metals adsorption phenomena. According to the results of metals speciation identified by XRD and simulated by the HSC model, the strong alkali geopolymer could increase the pH value of the heavy metal solution, resulting in the precipitation of tested heavy metals. It will enhance the tested Cu(II) and Pb(II) removal efficiency. In summary, this research confirmed that the MSWI fly ash-based geopolymer was both a non-hazardous material and a promosing adsorbent for effectively removing Cu(II) and Pb(II) from aqueous solutions. Therefore, MSWI fly ash-based geopolymer as the adsorbent materials will be valuable recovered materials and have good potential for practical application in the wastewater containing heavy metals treatment plant. |
