Distribution Of Typical Heavy Metal On Black Soil,Colloid And Water

There is a consensus that the colloid is universal regarded as of the third phase in addition to soil and water,namely the solid,liquid phase and colloid phase.A lot of research has been done on the adsorption of heavy metals by separate components in soil,but has rarely been studied to explain adsorption of heavy metal on separate components at the same time.This article is designed to compare adsorption of heavy metal on single component of soil and distribution on soil,and to study dynamic distribution of heavy metal in soil column.The isothermal adsorption result show that the adsorbance of heavy metal on soil and colloid is sort as Pb>Cd>Zn.Adsorptivity of colloid was apparently higher than solid.Sorption isotherm of Zn on solid could be better described with Langmuir equation and Cd,Pb were better described with Freundlich equation.Sorption isotherm of Zn on colloid was better described with Langmuir equation,while Cd with Freundlich and Temkin equation,and Pb with Freundlich equation.The static distribution experiments show that three heavy metals in soil are mainly adsorbed on the colloid,which has proportion of Zn in 80.5%?86.9%,Cd in 80.1%?86.6%,Pb in 86.8%?95.4%.The partition coefficient koc showed that the koc of heavy metal on colloid was slightly higher than that on solid phase,and it showed that the "dominant" factor in the process of distribution.Temperature had little impact on the distribution of the Zn,miller effects on Cd,and large positive effects on Pb,but sorption on the solid phase changed little.The distribution of metals at different pH showed that the total amount of adsorption increased with the increase of pH,and the increase of pH under acidic conditions favor the distribution of heavy metals to colloid.In the colloid release experiment,the increase of ionic strength and the decrease of colloidal leaching rate were decreased.The release curve had little difference under pH of 5,7,8 and the release rate was significantly decreased at pH=3.In the dynamic allocation experiment,it was found that 99%of the heavy metal in the 10 cm soil column was retained by the soil column.Among these 90.75%of the Zn,95.26%of the Cd,and 88.08%of the Pb are adsorbed on the colloid,indicating that colloids remained "dominant" in dynamic distribution.In the leaching solution of Zn and Cd in different height,the amount of colloidal leaching of Zn and Cd was very little.The leaching amount of Pb decreased with the increase of the height,and the colloid could carry a certain amount of Pb in different height.After the concentration of the leaching solution was stable,Zn and Cd in the leaching solution were mainly in water phase while Pb was mainly in colloid phase.