改性栗壳吸附重金属离子的动力学及热力学研究

对改性板栗壳吸附Cr(VI)、Cu(II)及Ni(II)3种重金属离子过程的动力学和热力学进行研究。结果表明:改性板栗壳吸附Cr(VI)、Cu(II)和Ni(II)3种混合离子时存在拮抗的竞争关系,竞争吸附顺序为Cu(II)﹤Ni(II)﹤Cr(VI);与单独吸附过程相比,混合吸附平衡时,改性板栗壳对3种离子相应的去除率均有所降低,Cr(VI)去除率比单独吸附时降低20.2%,Cu(II)和Ni(II)分别降低40.7%和35.6%;拟二级动力学方程能很好地描述Cr(VI)、Cu(II)和Ni(II)在改性板栗壳上的单独和混合吸附过程,结果表明此3种重金属离子在改性板栗壳表面以化学吸附为主;热力学研究数据表明:改性板栗壳对Cr(VI)的吸附为吸热反应,对Cu(II)和Ni(II)的吸附为放热反应。

Study of Dynamics and Thermodynamics of Competitive Adsorption of Heavy Metal Ions by Modified Chestnut Shell

In this paper,dynamics and thermodynamics of the mixed adsorption of Cr(Ⅵ),Cu(Ⅱ) and Ni(Ⅱ) by modified chestnut shell was studied.The results showed that antagonism competition relation existed among Cr(Ⅵ),Cu(Ⅱ) and Ni(Ⅱ) when the ions were absorbed onto the modified chestnut shell,with the order in competitive adsorption of Cu(Ⅱ)＜ Ni(Ⅱ)＜Cr(Ⅵ).In comparison to the separate adsorption process,when the mixed adsorption reached equilibrium,the removal rate of the three ions in the mixed adsorption declined.The removal rate of Cr (Ⅵ) decreased by 20.2％ and that of Cu (Ⅱ) and Ni (Ⅱ) decreased by 40.7％ and 35.6％ respectively.The quasi secondary dynamic equation described well the separate and mixed adsorption of Cr (Ⅵ),Cu (Ⅱ) and Ni (Ⅱ) on the modified chestnut shell,indicating that the three heavy metal ions on the surface of modified chestnut shell were given priority to chemical adsorption.Data from the thermodynamics research showed that the adsorption of Cr (Ⅵ) on modified chestnut shell was endothermic reaction,while that of Cu (Ⅱ) and Ni (Ⅱ) was exothermic reaction.