Studies of Microwave Stabilization Processes for The Copper-contaminated Sludge after Acid Extraction
|關鍵字:||含銅污泥;污泥安定;微波程序;微波燒結;鐵粉;氧化鐵;硫化鈉;copper-contaminated sludge;sludge stabilization;microwave process;microwave sintering;iron powder;ferric oxide;sodium sulfide||公開日期:||2008||摘要:||含銅污泥為台灣產量甚大之有害事業廢棄物之一，這些污泥經由酸萃取等再利用技術回收其中大部分的銅離子後，殘餘固體經過毒性特性溶出程序後其銅溶出量仍可能超過法規標準，因此仍有危害環境的風險存在。對於有害事業廢棄物，在台灣固化法是最常被採用的安定技術，由於固化法是使重金屬穩定地存在於他種物質如水泥中，因此固化後污泥的體積會增加，故當以掩埋最為最終處置時，會因此而減少掩埋場的壽命。因此本研究應用微波能量之特性來做為酸萃取後含銅污泥的新技術，避免水泥固化法增加污泥體積的缺點。 微波安定技術為一系列以微波程序為核心的安定技術之總稱，這些技術包含直接微波安定技術、安定劑之微波安定技術、微波混成技術、鐵粉之微波安定技術與微波燒結技術。藉由微波功率、反應時間、添加劑的使用、反應氣氛之改變與操作流程等方面之控制參數來增加污泥安定之效果。另外，更進一步地使用微波程序進行污泥之燒結使其成為塊狀資材，使含銅污泥安定之同時，能產生塊狀之燒結體以做為公共工程之基材或骨材。 結果顯示，以微波安定技術處理含銅污泥具有快速去除污泥中的水分，同時能去除污泥中的有機物，達成污泥礦化的能力。於污泥安定方面，直接微波安定技術安定污泥的效果受到污泥性質的影響很大，僅部分批次污泥直接進行微波安定技術即可達成安定化。當污泥進行安定劑之微波安定技術時，於短時間內即可被安定，且所使用之安定劑量少於僅使用安定劑來安定含銅污泥的。不過安定劑之微波安定技術在反應時間較長時會有銅再溶出的情形發生，而這個現象可由安定劑-惰性氣體之微波混成技術來消除，且當使用硫化鈉-氮氣之微波混成技術進行污泥安定時，硫化鈉的使用量比安定劑之微波安定技術中使用的更少。鐵粉之微波安定技術亦能有效地安定酸萃取後含銅污泥，所需之反應時間略長，不過即使無惰性氣體之導入亦不會有再溶出的現象發生。 污泥微波燒結技術的結果顯示，當以改良式微波燒結技術來處理高濃度之含銅合成污泥時，可得到紮實的燒結體。不論污泥是添加鐵粉或是氧化鐵，經改良式微波燒結技術後所得燒結體之XRD分析結果皆顯示有含銅鐵氧磁體 CuFe2O4的生成，且添加鐵粉之合成污泥所製成的燒結體經毒性特性溶出程序之後其銅溶出量可以通過法規標準。
Copper-contaminated sludge is hazardous industrial waste yielded in huge quantities in Taiwan. After the copper-contaminated sludge passed through an acid-extraction process to reclaim most of the copper ions in it, the residue, called the low copper-contaminated sludge, may still need to be treated by stabilization technologies. The common method for stabilization of the hazardous waste in Taiwan is by cement solidification. However, this method has the disadvantage of an increase in waste volume, which will shorten the service life of a landfill. In this study, the characteristics of microwave energy were used to offer a new method that can avoid this disadvantage of the cement solidification. Microwave stabilization processes used in this study include the direct microwave process, the microwave process with stabilizers, the stabilizer-inertia gas-hybrid microwave process, the microwave process with iron powder, and the microwave sintering process. The stabilization effects of these processes were promoted by changing the microwave power and reaction time, adding some agents, leading inert gas, and altering operating procedures. Furthermore, the microwave sintering process was used to transform copper-contaminated sludge into a sinter, thus stabilizing it and producing a material for public construction at the same time. From the results, it was found that the moisture in sludge was removed quickly and that organic matter was burned by a microwave heating. At the point of stabilization of the low copper-contaminated sludge, the direct microwave process could stabilize only some batches of sludge. When the microwave process with stabilizers was performed for sludge stabilization, it was effective and a short reaction time was required. In addition, the stabilizer amount used in this method was less than that without any assisting process. However, when the reaction time was longer, the leaching concentration of copper ions from the treated sludge increased suddenly. The stabilizer-inertia gas-hybrid microwave process could overcome the disadvantage of the microwave process with stabilizers at the long reaction time. Moreover, the dosage of sodium sulfide as a stabilizer required in the former was smaller than that in the latter. The microwave process with iron powder was also effective in the stabilization of the low copper-contaminated sludge and the reaction time required in this method was little more than those in the later methods. However, re-leaching of copper ions from the sludge treated by the microwave process with iron powder did not occur, even when the reaction time was long and inertia gas was not used. The results of the microwave sintering process show that a hard sinter could be acquired after synthetic sludge of high copper concentration passed through the improved microwave sintering process. No matter whether ferric oxide or iron powder was used in this method, the XRD results showed that cuprospinel (CuFe2O4) was formed in sinters. Besides, the leaching concentration of copper ions from the sinter transformed from synthetic sludge with iron powder by the improved microwave sintering process was lower than the limit value specified in the Toxicity Characteristic Leaching Procedure.
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