| Summary: | 碩士 === 國立宜蘭大學 === 環境工程學系碩士班 === 105 === In recent years, it is important to pay more attention for heavy metal removal due to increasing environmental awareness. In Taiwan, the sewage treatment plant produces about 4 million tons/year sludge (80% moisture) and nearly 60% of the sludge is not adequately treated. The main traditional treatment of sludge is direct burial. However, direct burial not only occupies the land, but also increases the possibility of groundwater pollution. The residue still needs to be further processed since it contains heavy metal, although some methods such as drying and burning can stabilize the nature of the sludge and reduce its volume. At present, the traditional heavy metal wastewater treatment is adsorption. The activated carbon is used very often because the activated carbon has a very high specific surface area and internal porous structure. In addition, the presence of functional groups on the surface will enhance the adsorption capacity. Activated carbonization sludge owns high porosity and high specific surface area. Furthermore, the operation cost of carbonated sludge is low since sludge is reused and recycled.
Domestic sewage sludge Carbon (DSSC) was prepared in this study to reduce the cost of adsorbent. The DSSC was activated with an activator, such as zinc chloride (ZnCl2). The activated DSSC has porous structure, high specific surface area and uniform pore distribution, and a good adsorption capacity. In this study, activated DSSC was used to adsorb heavy metals in wastewater and compare with AC. The prepared material characteristics were be analyzed with BET, SEM-EDS, FTIR, TGA, ICP-AES, UV-VIS. The results show that the maximum specific surface area is 490 m2 g-1. The isothermal adsorption/desorption curves belong to type Ⅳ curve with N2 isothermal adsorption/desorption instrument. The adsorption capacity of DSSC is 15.1, 28.9, 48.3 and 68.8mg g-1, respectively, when the Cr(VI) concentration of wastewater is 15, 30, 60 and 120 ppm. In contrast, the adsorption capacity of AC is only 0.04, 0.07, 0.12 and 0.17 mg g-1, respectively. The best ratio of DSSC and ZnCl2 was 1: 1, and the maximum adsorption capacity was 68.8 mg g-1. This study also aimed at effects of operation parameters, such as Cr(VI) concentration, pH, dosage and temperature, on Cr(VI) removal performance. The results also show the Cr (VI) removal efficiency was about 90% at a lower pH value (pH = 1.5-2), adsorption dose 1g L-1 under 35oC. In other hand, the mathematical models, such as adsorption kinetics model, isothermal adsorption mode, thermodynamic model and particle diffusion mode, were also obtained by means of model analysis for predicting the possible impact of the reaction.
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