Adsorption And Desorption Of Cadmium And Lead By Three Typical Soil Colloids And Tolerance Bacteria

In recent years,soil heavy metal pollution has become more and more serious which poses a great threat to ecological safety and human health.It is significance to study the transformation and migration of heavy metal ions into soil for the future treatment of heavy metal pollution.This study selected three representative Latosolic red soil Brown soil and Brown calcareous soil extract less than 1?m soil colloids and patience bacteria strains E-2 as adsorbents.The adsorption experiment of cadmium and lead ions by adsorbent was carried out.After adsorption experiments done desorption test was performed with EDTA.The adsorption and desorption characteristics of cadmium-lead ions by different colloids resistant bacteria and their complexes were studied.The effects of ion competition and organic matter on adsorption and desorption were also studied.Finally,the following conclusions were obtained:(1)The adsorption equilibrium of cadmium and lead by Latosolic red soil Brown soil and Brown calcareous soil colloids was reached after 8 hours.The adsorption of cadmium and lead ions by soil colloids was the result of the combined action of physical adsorption and chemical adsorption.The adsorption capacity of three colloids to cadmium is Latosolic red soil colloids > Brown soil colloids > Brown calcareous soil colloids.The adsorption capacity of three colloid to lead is Brown soil colloids >Brown calcareous soil colloids > Latosolic red soil colloids.The second order kinetic model and the Freundlich model had the best correlation of adsorption fitting for the three colloids and the correlation reached above 0.90.(2)The adsorption of cadmium and lead ions by E-2 resistant bacteria was good.The adsorption process was dominated by chemical adsorption,in which the affinityof tolerant bacteria to lead ions was stronger than that of cadmium ions.The adsorption capacity of E-2 resistant bacteria to the two heavy metal ions in the single solution system was larger than that in the mixed system and the adsorption effect was firm.so the heavy metal ions were not easy to be desorbed by EDTA.(3)The adsorption of two heavy metal ions by the complex was dominated by chemisorption.The complex of brown soil colloids and resistant bacteria had the strongest adsorption of cadmium and lead ions.In generally,the adsorption of the complex to heavy metal ions was not as strong as that of the single colloids and the resistant bacteria.(4)Competitive adsorption was occurred between cadmium and lead ions in mixed solution.The competitive action reduced the adsorption amount of lead and cadmium on the adsorbent.Organic matter also affected the adsorption of heavy metals.The adsorption of cadmium and lead on the soil colloids without organic matter was lower than that with the original colloids.(5)EDTA increased the desorption capacity of heavy metal ions with the increase of adsorption capacity.The adsorption of cadmium and lead by the complex was large and the desorption was also large.These conclusions are helpful for us to understand the adsorption and desorption characteristics of different types of soil colloids and their complexes with resistant bacteria to different heavy metals and provide certain theoretical basis for the prevention and treatment of heavy metal pollution in different areas in the future.