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Applied Research On The Removal Of SO2by Acidithiobacillus Ferrooxidans

Posted on:2013-11-06Degree:MasterType:Thesis
Country:ChinaCandidate:H ZhangFull Text:PDF
GTID:2231330371487015Subject:Microbiology
Abstract/Summary:PDF Full Text Request
Sulfur dioxide gas not only harms human body health, and will cause serious environmental pollution, corrosion of industrial facilities, agricultural output, even the change of climate. At present, removal of sulfur dioxide mainly use the physical and chemical method, but these methods all has the disadvantages of high investment, low efficiency, high maintenance costs, and the secondary pollution on the environment. The rise of biological technology may helps to improve the situation recently. Acidithiobacillus ferrooxidans is a kind of heterotrophic eosinophilic bacteria, it can draw on energy through the oxidation of ferrous iron and reducible sulfur. The Acidithiobacillus ferrooxidans can oxide ferrous iron into ferric iron, and this character makes it to participate in the process of biological desulfurization, the ferric iron was reduced into ferrous ion by sulfur dioxide, and recycling. Usage of the biological desulfurization technology has the advantage of less investment, high efficiency, mild conditions, and green environmental protection, is an efficient desulfurization technology with high development potential. In this paper the efficiency strain with high activity was chose to make immobilized cell, and then apply to the bio-chemical double stage reactor, achieve effective desulfurization. The main conclusion was derived as followings in this systematic study.First, continuous domestication of the Acidithiobacillus ferrooxidans strain was done to improve the activity, reduce the by-products, and adapt to lower pH. The optimal pH of domesticated strain decline, from the first2.0fell to1.8, in this lower pH environment, the ferrous oxidation rate increased about40%, the formation of precipitation was reduced60%.Second, the use of acid resistant polyvinyl alcohol (PVA) as a basis embedding agent, choose the suitable catalyst, optimizing the performance of the immobilized cells. With suitable proportion of sodium alginate and PVA under high temperature to dissolve, then in the low temperature improve the solidification process. During the solidification process, sodium alginate form a gel firstly, this gel will help to the gel formation of polyvinyl alcohol (PVA). The low temperature promote the the formation of hydrogen bonds between PVA molecules, enhance the strength of mixed gel. In the acidic conditions, sodium alginate partly dissolved, making the pore structure of PVA nets optimized, the cells in the grid may have better survival.Third, use the immobilized Acidithiobacillus ferrooxidans to build biological reactor, detection of immobilized cells continuous operating performance, and optimize the reaction conditions. The experimental results show little pH and temperature changes in the process of continuous reactor operation with immobilized cells, cell activity has remained at a higher level, with the extension of time cell activity decline is not big. Light yellow precipitation was formed in the reactor operation process, and left the reactor with circulatory medium in the short term, but in a long time will have a small amount of accumulation, influence cell activity and the unobstructed reactor.Fourth, the biological reactor and chemical reactor were connected, and make the ferrous iron regenerated and circulated in the medium; at the same time sulfur dioxide dissolved in water was oxidized into sulfuric acid, enriched and recycled finally. Immobilized cells in the reactor has good tolerance to sulfur dioxide, the cell vitality is high, comparison to the traditional physical and chemical methods, this technology improve the desulphurization efficiency, reduce the cost, green initiative and won’t produce secondary pollution.
Keywords/Search Tags:Acidithiobacillus ferrooxidans, immobilized cell, sulfur dioxide, bio-chemicaldouble stage reactor, Fe2+/Fe3+
PDF Full Text Request
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