| With great complexation and current-boosting effect, Surfactant is one of the significant measures in the remediation for the heavy metal pollution. Biosurfactant is promising in the remediation for the heavy metal pollution, featuring low critical concentration, low toxicity and environmental benign. However, the relative research in the application of synergistic electric repair of heavy metal contaminated soil is blank now.This thesis evaluates and discusses the feasibility of sophorolipid biosurfactant in the remediation for the heavy-metal polluted soil. Before applying the sophorolipid to the electrokinetic remediation of the heavy-metal polluted soi, the complexation constants and influence factors between sophorolipid and copper, lead, zinc, cadimium, calcium and magnesia are measured, and the adsorption and desorption of sophorolipid and cadimium are observed. The main research results are as follows:(1) With equimolar series method, the complex-ratio between sophorolipid and Pb2+、Cd2+、Cu2+、Zn2+、Ca2+、Mg2+ is fixed. According to the complexation constants between the six metals and sophorolipid, the following sequence is obtained:Cu2+>Pb2+>Cd2+>Zn2+>Ca2+>Mg2+. The result shows that sophorolipid has greater complexation tend with these four heavy-metal ions. And further research shows that as ionic strength increases, The complexation constants between Pb2+、 Cu2+、Zn2+ and sophorolipid decreases, which shows that the increase of ionic strength is not good for the complex reaction between heavy metal and sophorolipid. As pH increases, the complexation constants between Pb2+、Cd2+、Cu2+、Zn2+ and sophorolipid increases obviousl. In 288-303K, the change of complexation constants between Pb2+、Cd2+、Cu2+、Zn2+ and sophorolipid is not obvious.(2) The adsorption types between sophorolipid and heavy metals are different. The adsorption isothermal curve of sophorolipid on the soil conforms to Langmuir and the biggest adsorption amount is 11.228mg/g. The adsorption isothermal curve of lead on the soil conforms to the Langmuir formula and the biggest adsorption amount is 5309.65mg/kg. The adsorption isothermal curve of cadmium on the soil conforms to the Freundlich formula. Potential of hydrogen restrains the adsorption capability of sophorolipid but stimulates the adsorption capability of lead and cadmium. The increase of ionic strength is good for the adsorption of sophorolipid but not good for lead and cadmium ion. When the sophorolipid concentration is 750mg/L, the removal rate of lead and cadmium removal rate is 16% and 21% respectively. When the sophorolipid concentration is in 100mg/L-1000mg/L, the removal rates of the two metals all increase as sophorolipid concentration increases. When pH is in 4-8, it has positive influence on the removal rate. When the temperature is in 288-308K, The removal rate of lead and cadimium decrease as temperature increases and the decrease. As the eluent ion strength increases, the removal rate of lead increases while is the removal rate of cadimium decreases.(3) By adding sophorolipid synergistic electric repair process, and observing the processing time, voltage, organic matter content, the cathode pH control impact on removal efficiency, t, he following results are gained. With sophorolipid (750mg/L), the disposal under 15V and lasting 96h, the removal rate of lead is 44.0% and the removal rate of cadimium is 38.9%, which is improved by 32.8% and 20.3% when it is without sophorolipid. The result owes to the complexation effect of sophorolipid. When the repair time is among 2 days to 11 days, the removal rate of cadimium increases as the voltage increases while the removal rate of reaches its highest level under 15V. Taking the economic cost and the overall removal rate of lead and cadimium into account, the disposal time is 96h and voltage is 15V.when the concentration is among 1.348-2.695%, the removal rate of cadimium and lead increase as organic content increases. With 0.01M acetic acid, the removal effect of lead and cadimium can reach their best level and the removal rates is 52.2% and 88.7% respectively. In conclusion, the optimization condition of electrokinetic remediation is asfollows:sophorolipid (750mg/L), voltage (15V), pH (0.01M acetic acid) and processing time (96h). |
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