| Summary: | 碩士 === 國立中山大學 === 海洋環境及工程學系研究所 === 103 === Due to increasing demand of food, extracting phosphate from rocks containing rich phosphorus as fertilizer to increase crop yields become necessary. However, the phosphorus cycle in nature has been destroyed by the high demand of extraction. Phosphorus from soil erosion, domestic, agriculture and industrial source transmitted through air or soil into nature water body, such as river, lake, ocean, provide nutrients to algae causing eutrophication and even algae blooms. These not only can deplete oxygen, even hypoxia, and can exhaust fishery resources.
In recent years, researches on using water treatment sludge or BFS to adsorb phosphate in laboratory or application in wetlands have been reported. Which open another way to reusing these two by-products. Although they can reduce the problem of eutrophication, the structure of water treatment sludge is loose and the BFS releases high alkalinity in water or soil. For sustainability these two materials can’t be reused when they reach saturation of adsorption.
In the study, we use the water treatment sludge from water supply treatment process by Zhitan Purification Plant and the BFS is a by-product from steel-making process by China Steel Corporation. Mixing these materials with different ratio and add DI-water for making the test composites. Increasing porosity of the composites by adding charcoal or hydroclay. The test sample’s strength will be stronger through the high temperature sinter process. After that put the sample into water sample for tests phosphate adsorptions. According to the sinter test results, we set the rate of raise temperature at 15°C/min, the final sinter temperature is 1100°C. The process can provide higher porosity, stronger strength and increase the adsorption and desorption efficiency of the test samples. The results of porosity test show that A、B、C、D sample is 28.44%、38.40%、31.49%、34.62%, respectively. The phosphate adsorption capacity is 1.88 mg/g、3.83 mg/g、2.10 mg/g、2.33 mg/g, respectively. The desorption capacity of phosphate in trickling test for 10 minutes each test(an average of repeat 7 times) in 24 hours (pH of the highest desorption capacity) is 0.037 mg/g (pH=4.5)、0.405 mg/g (tap water，pH=7.46)、0.054 mg/g (pH=6.0)、0.086 mg/g (pH=4.5), respectively. Results of this study show that the porosity dominates the absorption capacity and desorption capacity. B sample have the best efficiency in adsorption and desorption test, the mixing ratio is 20 g sludge, 10 g BFS and 10 g charcoal. The pH value of trickle water has no significant impact to the efficiency of phosphate desorption.
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