Research On The Stabilizing Agents And In Situ Stabilization Technology For Vanadium Contaminated Soil

The contamination of heavy metal in soil is serious in China.The vanadium contamination in soil can't be ignored,because of its progressively increasing application in steel and other industry.But there are few researches on the remediation of vanadium contaminated soil.The calcium-based and iron-based stabilizing agents and their in situ stabilization technology were studied.The main research results are as follows.The calcium-based stabilizing agents showed a higher stabilization efficiency in neutral environment.The effect of calcium hydroxide was the best with an efficiency of 69.4% under horizontal vibration extraction procedure.The soil p H increased after its stabilization.The vanadium concentration in leachates decreased with the increase of agent dosage.The calcium-based liquid agents promoted leaching of Cr,Cu,Cd,Zn,Pb,but there was no secondary pollution risk.The compound of calcium nitrate and sodium silicate showed a good synergistic stabilization effect,the optimal dosage of which was 0.4% and 1.6%,respectively.The stabilization effect of iron powder and ferrous sulfate was better than other iron-based stabilizing agents,with efficiencies of 97.7% and 98.8%,respectively.They performed well in both neutral and acid environment.After their stabilization,acid soluble of vanadium decreased significantly,and oxidizable increased.Cr was stabilized simultaneously.V and Cr concentration in leachates decreased with the increase of agent dosage.The optimal dosage of iron powder and ferrous sulfate was 1%.V and Cr concentration in leachates increased with time.Among iron-based liquid stabilizing agents,ferrous salt performed better than ferric salt.The V concentration in leachates decreased with the increase of agent dosage.The highest stabilization efficiency of ferrous salt was 100.0%.The Cr concentration in leachates decreased with the increase of ferrous salt dosage and increased with the increase of ferric salt dosage.The Cu,Cd,Zn,Pb concentration in leachates increased with the increase of agent dosage,higher with ferric salt.The best agent was ferrous sulfate,the optimal dosage(calculate by iron)of which was 0.5%.The V concentration in leachates increased,and then remained stable with time.The Cr concentration in leachates remained stable with time.The Cu,Cd,Zn,Pb concentration in leachates remained low or decreased with time,and was similar to the soil without stabilization at day 120.Iron-based liquid agents showed a long-term stability.Iron-based liquid agents acidified soil,but soil p H was neutral because of the buffer ability of soil at day 120.The Cu,Cd,Zn concentration in leachates was negatively to soil p H significantly.In-situ stabilization pilot scale tests were carried out by combining solid stabilizing agents with surface soil and pumping liquid stabilizing agents into deeper soil.The results showed that the effect of calcium hydroxide and iron powder on surface soil was similar to laboratory results.The effect of ferrous sulfate and combined calcium-based stabilizing agents on deep soil decreased a little.Ferrous sulfate showed excellent penetrability by stabilizing soil in horizontal range of 2 m.The liquid agents were able to be pumped through horizontal shallow wells or grooves.