| The chromium (Cr) is a necessary trace element in body of human and of animals. Cr exists in the water with the trivalent chromium (Cr3+) and hexavalent chromium (Cr6+). Trace amounts of Cr3+is beneficial to human, but too high amounts is harmful to human and animal body. The toxicity of Cr6+is giant strong, which is100times higher than Cr3+. If more than a certain concentration of Cr6+is ingested directly or indirectly into human and animal body, it generally cause damages such as carcinogenic, teratogenic, mutagenic three-induced hazards effects to human and animal body.Contamination of Cr is mainly produced by discharge of wastewater from electrolytic plating and chemical companies. Currently, according to the action principle, the methods removing chromium from waste water are classified into these sorts: chemical reduction precipitation, adsorption, electrolysis, filtration membrane method, photolysis, and other methods using multi-disciplinary approach and technical applications. However, there is a higher cost and long treatment period and other drawbacks for all the above methods. Based on the recent work on containing arsenic and phosphorus wastewater of our group, the removal research using pulsed electric field for high concentration of Cr6+from industrial waste water was carried out.The main contents of the thesis were to explore the mechanism, law and efficiency of the removal of Cr6+pulsed electric field (PEF) method using Fe-C heterogeneous plate from industrial waste water which content high concentration of chromium, and the PEF-co-precipitation method was studied to remove Cr6+.It was a innovation for the combined method of PEF and co-precipitation using the Fe-C heterogeneous plate to remove Cr6+of industrial waste water which content high concentration of chromium. And the law and efficiency of this combined method were investigated. In order to obtain new thinking and method with high efficiency, reducing secondary pollution, simple process, low cost, pure co-precipitation method and PEF-co-precipitation method were compared on removal of Cr6+.The Cr6+removal mechanism by PEF method using Fe-C heterogeneous plate was summarized as "three effects four process" in this thesis. The three effects include enrichment effect, precipitation effect, adsorption precipitation effect. The four processes include ion-directional movement process, oxidation-reduction process, co-precipitation process, adsorption precipitation process.The results showed that:1. Cr6+removal efficiency was up to31.2%in pulsed electric field, when the pulse peak voltage of300V, the reaction time was40min, and plate spacing distance of20cm.2. The contain of Cr6+was up to0.001mg/L in PEF-co-precipitation method, when the pulse peak voltage of80V, reaction time of10min, plate spacing distance of10cm.3. The removal rate of Cr6+was up to99.93%in co-precipitation method, when mFeSO·7H2O:mCr6+=20:1, and the treated waste water was adjusted by NaOH solution to a pH value of about8. PEF-co-precipitation method was better than the other two methods.It was suggested that, Cr6+removal by PEF-co-precipitation method has characteristics of high efficiency, environment-friendly, simple process, great application potential and so on. PEF-co-precipitation method was better than the other two methods under the same conditions. |
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