纳米碳对重金属镉和铜的吸附特性及对烟草吸收重金属的影响

Adsorption characteristics of nano-carbon on heavy metal cadmium and copper and its effects on tobacco absorption of the two heavy metals

为明确纳米碳对重金属的吸附性能,在液/液吸附体系下研究了纳米碳对镉和铜的吸附特征,并探讨了土培条件下对土壤有效态镉含量(质量分数)及烟草吸收镉的影响。结果表明,纳米碳对镉和铜的等温吸附曲线可以用Freundlich和Langmuir方程较好地拟合。纳米碳对镉和铜的吸附符合准二级动力学方程,且吸附速度较快。当溶液的初始浓度为2 000 mg/L,10 min时镉的吸附量可达到平衡吸附量的80%以上;而铜相对较快,3 min即可达到平衡吸附量的80%。随着温度的升高,纳米碳对镉和铜的吸附量降低,表明纳米碳的吸附是放热反应;随着p H值的增加,其吸附量增大。该试验条件下,随着纳米碳用量的增加,土壤有效态镉含量及烟叶中镉含量均降低。当纳米碳用量为4.0 g/盆时,效果最好。

In order to clarify the adsorption characteristics of nano-carbon on heavy metals, the adsorption characteristics of nano-carbon on Cd and Cu were investigated in a liquid-liquid system. The effects of nano-carbon on the available Cd content in soil and the Cd absorption of tobacco cultured in soil were discussed. The results showed that the Cd and Cu isothermal adsorption curves of nano-carbon could be fitted by Freundlich and Langmuir equations. The Cd and Cu adsorption by nano-carbon agreed with a quasi-two stage kinetic equation, and its adsorption rate was fast. At the initial solution concentration of 2 000 mg/L, the Cd adsorption amount was more than 80% of the equilibrium adsorption amount after 10 min, while it only took 3 min to reach that level for Cu adsorption. With the rise of temperature, the adsorption amounts decreased, which indicated that the adsorption by nano-carbon was an exothermic reaction. With the increase of pH, the adsorption amount by nano-carbon raised. Under the condition of this experiment, both the available Cd content in soil and the Cd content in tobacco leaves decreased with the increase amount of nano-carbon, and the optimal nano-carbon addition rate was 4.0 gram/pot.