Experimental Study On Strengthening Electrokinetic Remediation Of Pb Polluted River Sediment

With the development of urbanization and industrialization,heavy metal pollution in river sediment becomes increasingly serious.As a new soil remediation technology,electric remediation technology has developed rapidly in the field of soil pollution remediation due to its high efficiency and low cost.At present,there are few studies on the application of electric remediation technology to the special soil of river sediment.Therefore,in this paper,the simulation of Pb contaminated sediment was used as the research object to carry out electric remediation,and the influence of different electrolytes,voltage gradient,remediation cycle and a series of enhancement technologies on the remediation effect and energy consumption of Pb contaminated river sediment was explored.Combined with the factors such as p H of sediment,remediation current,Pb migration effect and valence change in sediment,the restoration mechanism of polluted river sediment by electrokinetic remediation was explored.The following conclusions are drawn:(1)For the simulated lead-contaminated river sediment,the extraction effect of Pb was hydrochloric acid(83.33%)>EDDS(69.65%)>acetic acid(51.16%)>citric acid(44.3%)>deionized water(3.14%).Although hydrochloric acid has a better effect on Pb extraction,the physicochemical properties of the sediment sediment after hydrochloric acid extraction are seriously damaged.The sediment p H decreased from8.36 to 2.19,and the organic matter decreased from 68.36g/kg to 28.65g/kg.Therefore,the exclusion was made after comprehensive consideration.(2)0.02mol/LEDDS solution and 0.20mol/L acetic acid solution selected in the extraction experiment were used as the electrolyte and deionized water was used as the control for electric repair,The results showed that because Pb migrated weakly in a neutral environment,so using deionized water as the electrolyte,the removal rate of Pb was only 2.96%,The high acid and base buffer performance of the river sediment itself makes the acetic acid solution have poor acidification effect.The removal rate of Pb is 11.72%.As EDDS is a natural degradable environmentally friendly chelator,it can react with Pb under neutral conditions to form metal chelates,which improves the migration ability of Pb,and the Pb removal rate is increased to 21.13%.(3)With EDDS as electrolyte to explore the effect of voltage gradient and repair cycle on the effect,the results show that increase voltage gradient and extend the repair cycle can improve the migration ability of Pb,Pb enrichment in the anode side,comprehensive energy consumption and removal rate,using EDDS as electrolyte applied 2V/cm voltage after 6d power effect is better,Pb removal rate reached27.91%,unit energy consumption of 200.89k Wh/m~3.(4)Under the condition of the optimal repair using coupled techniques to explore its influence on electric repair effect,the results show that the EDDS as saturated liquid instead of the saturated sediment deionized water,electric-leaching composite repair technology,can improve the system current and the increase of capability of migration of Pb,sediment concentration degree of enrichment area from 1.20 to 1.39,The removal rate of Pb in sediment increased from 37.72%to 53.53%;The addition of PRB can absorb Pb in the enriched area,reduce the enrichment degree of Pb in S1area from 1.39 to 0.84,and the permeable reaction wall can strengthen the system current and enhance the migration ability of Pb.The Pb removal rate in the non-enriched area of the sediment chamber reaches 59.67%,the total Pb removal rate is 33.39%,and the unit energy consumption is 219.26k Wh/m~3;Although the Intermittent power-on technology reduces the system energy consumption,the Pb migration in the sediment is not sufficient to enhance the removal rate of Pb;the exchange polarity technology can weaken the focusing effect of the alkaline zone of the sediment and keep the sediment p H in a stable state.However,the sediment p H fails to fall to the suitable conditions for Pb migration,so the Pb removal rate is not enhanced.(5)The p H and organic matter of the bottom mud after the enhanced electric restoration experiment of the four groups were measured.The p H of the bottom mud decreased from 8.36 to 7.45～8.01,and the organic matter decreased from 68.36g/kg to 56.39g/kg～61.93g/kg.The results show that the electrokinetic remediation technology has little change on the physical and chemical properties of river sediment,and it is a green and clean remediation technology.