| 摘要: | 本研究針對都市下水污泥灰渣去除水溶液中銅離子，進行初步實驗探討。污泥灰渣來源係採自台北民生廠與八里廠之脫水污泥餅，並以小型模組式焚化爐加以焚化而得。在本研究中，灰渣特性的分析包括基本物化性質、比表面積、等電位點、pH值、界達電位及陽離子交換容量等。且以恆溫吸附試驗，在不同灰渣劑量、溶液pH值、離子強度、反應溫度及銅離子濃度等操作條件下，瞭解污泥灰渣對銅離子之吸附行為。最後並以灰渣粒徑大小、污泥焚化溫度、及淘洗等不同備製條件，探討其對污泥灰渣吸附行為之影響。 經由以上實驗結果發現，下水污泥灰渣表面具孔隙結構，其化學組成以矽、鋁及鐵等氧化物為其主要構成(約佔70%)。在表面特性方面，民生廠與八里廠污泥灰渣，其比表面積分別17.51與10.66m2/g，而pHzpc則介於3.1∼3.4，有利於去除水中之陽離子。陽離子交換容量約為24∼25meq/100g，可視為一吸附性質頗佳之灰渣材料。根據恆溫吸附實驗結果，民生廠與八里廠污泥灰渣，對銅離子之吸附速率常數分別為0.004與0.005min-1，而在灰渣劑量10g/L、銅離子初始濃度50mg/L、溶液pH值4.0、離子強度0.01N及溫度30℃條件下，其對銅離子之最大吸附容量，分別可達2.79mg/g與3.04mg/g。且在低離子強度及高反應溫度(40℃)條件下，污泥灰渣吸附銅離子，呈現較高的去除效率。唯污泥灰渣在溶液pH值較低的情況下，銅離子脫附百分率有增加之趨勢。此外污泥灰渣對銅離子去除之機制，應為污泥灰渣表面提供可吸附或可交換之位址，以靜電吸引與離子交換等方式，去除溶液中銅離子。而改變備製條件發現，污泥灰渣經水洗，以及在較低溫度(700℃)下焚化，具有較高的銅離子去除能力，推測其原因，可能為水洗過程中可將灰渣表面之雜質洗去，故灰渣可提供更多可吸附或可交換之位址；相反地，提高污泥焚化溫度，則由於灰渣顆粒與顆粒間，發生局部燒結現象，使得污泥灰渣之比表面積與陽離子交換容量均降低，故不利於銅離子之去除。 This study used sewage sludge ash (SSA) as an adsorbent to remove copper ions in aqueous solution. The sewage sludge cake was first sampled from Min-Shen Community Wastewater Treatment Plant (WWTP) and Pa-Li WWTP in Taipei. Then the SSA was prepared from the sampled sludge cake in a modular incinerator. The chemical, physical, and surface properties of the SSA samples were analyzed. Thereafter the adsorption capability of SSA to copper ions was evaluated through equilibrium and kinetic isotherm tests. The effect of adsorbent and adsorbate parameters on adsorption behavior of SSA was also investigated. These adsorbent and adsorbate parameters included SSA dosage, initial copper concentration, initial solution pH, ion strength, and ambient temperature. In addition, the effect of SSA preparation factors on its adsorption behavior was also investigated. The factors of SSA preparation included SSA particle size, temperature of incineration, and washing procedures. According to test results, the SSA samples in this study are found porous and irregular-shaped particles with significant surface area. The predominant compositions of SSA include silicon, aluminum, and iron oxides. The overall weight content of these three compositions in SSA is approximately 70%. In addition, the BET specific surface area of SSA is primarily between 17.51 and 10.66 m2/g. The pH value at zero-point-of-charge (pHzpc) of SSA is primarily between 3.1 and 3.4. The cation exchange capacity (CEC) of SSA is primarily between 24 and 25 meq/100g. The specific surface area, pHzpc, and CEC are three favorable properties of SSA for copper ion removal. According to kinetic isotherm tests, the adsorption rate constant of Min-Shen and Pa-Li WWTP SSA is 0.004 and 0.005 min-1 respectively. According to equilibrium isotherm tests, the specific adsorption capacity of Min-Shen and Pa-Li WWTP SSA is 2.79 and 3.04 mg/g respectively. The conditions of above testes include 10 g/L of SSA dosage, 50 mg/L of initial copper concentration, 0.01 N of solution ion strength, 4.0 of initial pH value, and 30℃ of ambient temperature. The above test results reveal that the copper ions are removed by mechanism of electrostatic attraction and cation ion exchange occurred in SSA surface. Regarding the effect of SSA preparation, this study found that the water-washed ash and the ash incinerated at 700℃ exhibit higher copper adsorption capacity than those ashes prepared in different conditions. This result reveals that the water washing can remove impurities on SSA surface and provides more available sites for copper ion. On the other hand, the high incineration temperature results in partial sintering between SSA particles. Both of the specific surface area and CEC of SSA decreases when incineration temperature increases. For this reason, SSA incinerated at 700℃ exhibits higher copper removal capability than that of SSA incinerated at 800 and 900℃. |
