| dc.description.abstract | 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℃. | en_US |