| Summary: | 碩士 === 淡江大學 === 水資源及環境工程學系碩士班 === 96 === Accelerating limestone dissolution in fluidized limestone bed (FLB), modified from pulsed limestone bed (PLB) (Watten, 1999), within acid (sulfate, oxalate) environments were discussed in this research. The characteristics of acid neutralization and related mechanisms were monitored also.
In order to better understanding the phase reaction within limestone particles, carbon dioxide and acid solutions, simple vibration system (VS) were conducted for comparison in the first stage of the experiments. The differences of pH, alkalinity, acidity and calcium concentration between influent and effluent were tested. The results come out that the alkalinity mostly generated from limestone dissolution with the increment of longer reaction time in FLB system while not cleared seen in VS system.
Various pressure of carbon dioxide (0, 68 and 136 kPa) applied to the FLB system with sulfate (2.95 and 5.76 mM) and oxalate (5.76 mM) were conducted in the second stage of experiments for comparison of the effects due to the addition of carbon dioxide. The alkalinity generated (influent Acid plus effluent Alkalinity) were identical to the calcium disolved in the sets sulfate tests while more limestone dissolution with higher neutralization capacity and rapid precipitation of calcium oxalate were monitored in the system. The calcium dissolved from limestone (includes precipitated with oxalate) is half the amount of bicarbonate (HCO3-) which is calculated from the alkalinity generated.
The characteristics of limestone dissolution were also monitored using the real-time detection of the pH and the ambient pressure in the system. The hydrogen ion (H+) dominated the major surface reaction to the limestone and the present of carbon dioxide plays the role of enhancing limestone dissolution due to further hydrogen ion generated from CO2 dissolved in water.
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