The Application Of Thiacalix[4]Arenetetrasulfonate In The Leaching Remediation Of Heavy Metal Contaminated Soils

Soils contaminated by heavy metals (Cu, Pb, Cd) were remedied by using leaching method with thiacalix[4]arenetetrasulfonate(TCAS). Removal mechanism, speciation analysis of heavy metals before and after leaching, the regeneration and reemployment of TCAS were also studied.Oscillation leaching method and soil column leaching method were applied in the remediation of heavy metals contaminated soils. The results demonstrated that when pH was11, TCAS concentration were0.3%0.7%and0.5%, respectively, liquid solid ratio was10:1, temperature range was in15-25℃, leaching time was24hours, almost all of the heavy metals were removed by TCAS, removal rates were85.5%(Cu)^69%(Pb)、92%(Cd). TCAS eluent could well remove Cu, Pb and Cd from the contaminated soil without influencing the nutrient elements such as K, Mg in the soil. The elution efficiency of TCAS eluent on heavy metals was significantly better than that of EDTA, DTPA, citric acid and hydrochloric acid.Target factor method in Chemometrics methods were used to analyze UV spectrum of TCAS-heavy metal complex with the different concentration ratio changes, complex constants of TCAS towards Cu, Pb, Cd were got to be11.34,7.64and9.68, respectively.Tessier sequential extraction method were used to study speciation changes of heavy metals before and after leaching and analyze biological availability of residual soil heavy metal. Test results show that compared with the original contaminated soil, the contents of heavy metals various speciation decreased in different degree after leaching, the contents of exchangeable state, carbonate combination state and iron manganese oxide combination state decreased most obviously. The removal efficiency of TCAS on biological available state of heavy metals were the highest and on potential available state of heavy metals were very ordinary. TCAS could carry on the multiple recycling. The results demonstrated that leaching efficiency was gradually declining with the increase of regeneration times. The removal efficiency of three times regenerative TCAS on Cu2+、Pb2+、Cd2+were relatively ideal. In all, it is feasible to remedy heavy metals contaminated soils by using TCAS.