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Removal of Zinc and Copper from farmland soil by electrokinetic technology: effect of electrolyte circulation
YAO, HUNG CHING
|關鍵字:||Circulating Electrical Kinetics;迴流式電動力法;acidification;heavy metals;酸化現象;重金屬||出版社:||環境工程學系||摘要:||
To ameliorate the toxication caused by heavy metals within a polluted soil, the electrical kinetics is a good restorative means to cope with this hardship along with its efficacy and efficiency. However, the process of electrical kinetics has three inevitable disadvantages. First, the process itself is usually halted by the emergence of the acidification and the polarization effects caused by the hydrogen ions coming from the anode due to the electrolysis. Second, the accumulations of metal deposits throughout the processing usually lie around the middle or rear parts of the apparatus. Such accumulations have massively negative drawbacks on the whole efficacy. Third, we need extra cost and efforts to handle the huge amount of washing fluid coming directly from the cathode.
In this research, by devising a system of horizontal tube combined with circulating currents, we can lead the cathode electrolyte to circulate around the various specific spots of the conduit. Afterwards, by investigating those different processing effects of the aimed and intensified washing action,we hopefully can discover the best circulation spot to maintain the balance of pH value within the processing system. Furthermore, with the help of re-utilization of the electrolyte, this devised process can also approach the other two ultimate targets: the economical benefit and the reduction on the secondary pollution.
Proceeding the fundamental Electrical Kinetics experiments, using three processing fluid: tap water, 0.5M citric acid, and 0.1M EDTA, we come into the results of the removal rate on copper and zinc are: 13.77%, 35.27%, 23.53% and 12.73%, 28.85%, 65.45% respectively. In the meanwhile, when taking EDTA as the processing fluid, we can have the longest duration of treatment.Hence, we choose the 0.1M EDTA as anode electrolyte and the 0.01M citric acid as cathode electrolyte. Subsequently, we manipulate the Circulating Electrical Kinetics (CEK) experiments on the circulating rate of 0.2ml/min during the acidification phase.
According to the CEK experiments, the results show that if we circulate the cathode flowing fluid to the acidification spots of soil, the improvement on the processing benefits will advance significantly. For the copper, the removal rate can remarkably lift to 72.95%. For the zinc, the removal rate slightly lower to 56.12%. This outcome should have relevance with the competition with EDTA between copper and zinc. As for the entire ameliorating achievements on the polluted soil, the CEK ought to have vital enhancement toward resuscitating the salubrity of such soil to some great extent.
Keywords: Circulating Electrical Kinetics, acidification, EDTA, heavy metals
|Appears in Collections:||環境工程學系所|
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