| With the development of the information age, more and more world-wide electronic and electrical equipment are eliminated, producing a huge amount of e-waste. Due to the imperfect dismantling techniques and equipment, heavy metals(e.g., copper, lead, and cadmium) and persistent organic pollutants(e.g., PCBs) have been released from the electronic waste(e-waste) to surrounding environment, leading to a special characteristic that these different types of pollutants coexist with each other in environmental systems. Therefore, it is necessary to remediate the e-waste contaminated soils. Previous studies on e-waste site soils mainly focused on pollution survey, exposure and risk assessment. However, there have been few reports on the remediation of e-waste contaminated soils.Chemical flushing technique is considered to be efficient and reliable, which can simultaneously remove high concentrations of organic matters and heavy metals from soils. This technique has some advantages on its simple, controllable, fast repair and restoration mild conditions, etc. Therefore, it is particularly suitable for electronic waste dismantling subject to this type of organic matter and other heavy metals and PCBs severe combined pollution, soil needs a quick fix.This paper used batch equilibrium shock method studies the effect of different chelate on heavy metals elution and different surfactants on the PCBs elution effect in complex contaminated soils, firstly. Several surfactants and chelating agents are filtered out to combined into kinds of composite eluent to achieve synchronization removal of heavy metals and PCBs in soil. In order to achieve the best leaching effect by least cost, ratio of two eluants, leaching time, p H are studied. Ultimate the soil biodegradability after the repair were discussed. using the germination rate, growth of seed, and soil microbial biomass.The main findings are as follows:1) Comparison of citric acid with TX-100, Tween 80, SDBS, β-cyclodextrin, respectively, we have found that a combination of Tween 80 and citric acid for heavy metals Cu, Pb, Cd, and PCBs eluting better, for contaminated soil of Cu: 5000mg/kg, Pb: 1967mg/kg, Cd: 51.0mg/kg, PCBs concentration: 12mg/g, respectively. In the composite shower when the concentration of the components in the lotion of 20g/L, respectively, can reach 95.90%, 61.71%, 63.05% and 60.10%, and not in a mutually inhibitory. By heavy metal speciation analysis have showed that the composite elution rate increase mainly through the soil acid extractable and reducible leaching.2) This chapter novel composite eluent Tween 80 and citric acid as the research object, the overall leaching of heavy metals and PCBs eluting effect, compared the three combinations leaching ways: adding Tween 80 firstly, adding Tween 80 after, and Tween 80 combined with citric acid, derived elution basically the same, therefore, using a combination of ways to add leaching.3) The new composite eluent of Tween 80 and citric acid as the research object, the order of addition different eluent, concentrations of two eluent, elution time, the lotion p H affect the elution rate were studied. Studies have shown that the formation of the composite shower lotion eluting PCBs in soil promoted a little, and the impact of heavy metals Cu, Pb, Cd vary. The overall effect was eluted from the perspective of heavy metals and PCBs, complex eluent in Tween 80, citric acid concentration was 10g/L, the elution time of 12 h, p H= 6, the soil Cu, Pb, Cd and PCBs four eluting contaminants effect higher, reaching 98.77%, 55.92%, 66.82%,58.01%.4) After use of new composite eluent, soil residual of Cu, Pb, Cd, PCBs were: 6.150, 812.6, 16.59, 5.039mg/kg. By ecology toxicity results indicate that contaminated soil ecotoxicity lower after elution, in particular in: test species of cabbage and rice germination rate; radicle and germ growth increased.Studies have shown that use of Tween 80 and citric acid compound drench lotion can be safe and effective to achieve synchronization to remove heavy metals in soil, with the purpose of the PCBs for actual electronic waste pollution of field soil repair provides a new train of thought. |
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