向日葵根分泌物对土壤水合铁氧化物(HFO)吸附Cd^(2＋)的促进效应

Effect of Exudates from Helianthus annuus Root on Cd^(2+) Adsorption by Hydro Ferric Oxide

研究了向日葵(Helianthus annuus)根分泌物对水合铁氧化物(HFO)吸附Cd2+的行为的影响.结果表明,向日葵根分泌物具有促进HFO吸附Cd2+的作用.随着pH升高,HFO对Cd2+的平衡吸附量增加,向日葵根分泌物促进了HFO对镉的吸附.Langmuir方程和Freundlich方程可用来描述HFO对Cd2+的等温吸附行为,拟二级速率方程可描述HFO对Cd2+的吸附动力学.等温吸附参数和吸附动力学参数表明向日葵根分泌物增加了HFO吸附Cd2+的速率、强度及吸附容量.HFO吸附Cd2+是一个熵增的吸热反应.向日葵根分泌物的存在使HFO对Cd2+的吸附更容易自发.

The effect of root exudates from Helianthus annuus on adsorption of Cd2＋ by hydro ferric oxide（HFO） was investigated.It was demonstrated that the adsorption of Cd2＋ by HFO was enhanced when the root exudates from H.annuus existed.The adsorption capacity of Cd2＋ by HFO increased with increasing of initial solution pH.The root exudates increased the Cd2＋ adsorption capacity when pH varied from 3 to 8.Both the Langmuir and Freundlich isotherms well represented the experimental data,and the pseudo-second order equation well described the kinetic data.Isothermal and kinetic studies showed that the root exudates increased the adsorption strength and adsorption rate.The adsorption of Cd2＋ by HFO was an endothermic process whereas the spontaneity of the reaction was enhanced in the presence of the root exudates.