Influence Of Root Exudates On Cadmium Adsorption Onto And Desorption From Yellow Soil And Iron Oxides

There are abundant minerals resources in Guizhou province, while the severe heavy metal pollution is the result of the long-term minerals exploit. Phytoremediation is an ideal remediation technology of heavy metal contaminated soil. The mobilization efficiency of heavy metal by root exudates is an important factor of phytoremediation. So this paper attempts to do some useful researches about heavy metal adsorption and desorption qualities of soil which affected by root exudates. The sunflower and maize are been selected as research objects because they are grown in large area in Guizhou. The typical soil and minerals are yellow soil, goethite and hydrous ferric oxide (HFO) in karst area, so they are selected too.The conclusions are as follows: The root exudates of sunflower can restrain the cadmium adsorption of yellow soil and goethite, but can promote the cadmium adsorption of HFO. The cadmium adsorptive quantities of goethite and HFO increase following the increase of temperature, the cadmium adsorptive quantities of yellow soil increases contrarily. The root exudates of maize can restrain the cadmium adsorption of yellow soil, but can promote the cadmium adsorption on goethite and HFO. The cadmium adsorptive quantities of three adsorbents increase following the increase of pH value. Langmuir model,Temkin model and Frenudlich model can primely describe cadmium adsorption on yellow soil and minerals. The root exudates of sunflower and maize can promote the cadmium desorption.The cadmium released quantities of three adsorbents decrease following the increase of pH value.The released quantities by maize's root exudates are bigger than sunflower's root exudates. The rise of temperature and the increase of root exudates concentration avail of cadmium desorption. The contact angles of yellow soil and HFO treaded with root exudates are bigger than the contact angles of untreated yellow soil and HFO. The contact angle increase following the increase of pH value. The Zeta potential of HFO decreases after treated by the root exudates of maize and sunflower.