Research On The Principle Of Electro-Remediation Technology And Application In Removal Of Heavy Metal In Sludge And Tailings

Soil contaminated by heavy metals is one of the environmental problems that should be resolved urgently. Soil pollution is accumulative, lagging, dormant, and irreversible, therefore, soil pollution is usually difficult to be remedied and treated. This paper mainly studied phytoremediation and electroremediation of lead contaminated red soils. The studies based on the researches of at home and abroad and combined actual conditions.Electroremediation technique is an advancing task of global environment science and technology. Its principle is that: application of direct electric current via electrodes immersed in a saturated soil results in oxidation at the anode, generating an acid front that cause desorption and dissolution of heavy metals. The desorped and soluted heavy metals are migrated toward cathode reservoir by electric field and ions concentration grads by the means of electromigration, electroosmosis and diffusing.Firstly, a series of tests about lead spiked red soil sample are conducted, the results show: the electroremediation technology is efficient to remedy Pb contaminated red soil; pH value of red soil is the major factor of dominating electroremediation efficiency: pH value of red soil can not only lead to high tank voltage and high temperature of red soil by means of decreasing electro-conductivity of soil, but also reduce remediation efficiency by precipitating Pb and then decreasing mobility of Pb. Hence, electroremediation techniques should be enhanced so as to efficiently remove Pb from contaminated red soil; control pH value of the cathode reservoir with HNO3 can improve the removal efficiency. The enhanced test removal efficiency of Pb is 79.5%, and the energy consumption is 285kw/m3.soil; 10 A/m2 is the suitable current density for electroremediation.Secondly, a series of experiments used sludge samples are conducted to research and explore electroremediation. Experiment I showed the curve of removal efficiencies of different speciation Cd and Zn. The total removal efficiencies of Cd and Zn in municipal sewage sludge were 64.5% and 52.36% after five days electroremediation. The removal efficiencies of labile state fractions of Cd and Zn were 68.6%, 60.6% correspondingly. The labile state fractions that could be easily absorbed by plants included the exchangeable, carbonate and Fe and Mn oxides fraction. The electroremediation technique was fitted for removing heavy metals from municipal sewage sludge, and the electro remedied sludge was favorable to land utilization.Experimentâ…¡showed pH value of municipal biosolids is the major factor of dominating electroremediation; pH value of red soil can not only lead to high tank voltage and high temperature of municipal biosolids by means of decreasing electro-conductivity of soil, but also reduce remediation efficiency by precipitating Pb and then decreasing mobility of Pb. Hence, electroremediation techniques should be enhanced so as to apply to remedy heavy metals contaminated municipal biosolids. Control pH value of the cathode reservoir with HNO3 can improve the removal efficiency, decrease cost of remediation and shorten duration of remediation.The influence of thiobacillus ferrooxidans on the Speciation of Heavy Metals in the Sewage were analyzed and the removal efficiencies of heavy metals from sewage sludge by electrokinetics in experimentâ…¢.The pH value of the sludge sample which was pretreated by thiobacillus ferrooxidans reduced. Because of this, the heavy metals of the sewage sludge transformed from stable state to labile state. The samples pretreated by thiobacillus ferrooxidans and pretreated were electroremedied under the same conditions, the results were that the removal efficiencies of Cd raised from 61.85% to 72.54%,Cu from 34.26% to 63.51%, and Zn from 65.06% to71.22%, after pretreated. The effect of pretreated by thiobacillus ferrooxidans on Cu was much obviously than Cd or Zn. The sewage sludge pretreated by thiobacillus ferrooxidans could effectively enhance the removal efficiency of Cu while it is exceeded the control standards of land utilization. The electroremedied sludge which was pretreated by thiobacillus ferrooxidans was favorable to land utilization.Based on foregoing results, sampled with nonferrous tailings, the expectation of electroremediation technique to dispose tailings are conducted using electrokinetic's, middle recycle washing technology, bioleaching-electroremediation technology, respectively. The results shows: the removal efficiency of Cu, Pb and Zn is 75.8, 37.8 and o% in test 1, respectively; the removal efficiency of Cu, Pb and Zn is 81.4%, 48.6% and 36.3% in test 2, respectively; the removal efficiency of Cu, Pb and Zn is 82.8%, 56.1% and 47.5% in test 3, respectively.