核桃壳吸附水中锰离子的特性

 采用农林废弃物核桃壳作为吸附剂处理水中的Mn²⁺,研究固体投加量、吸附时间、溶液初始质量浓度以及pH值等因素对吸附效果的影响;并进行动力学、热力学研究。结果表明,最佳投加量为50g/L;最佳吸附时间为90min;溶液初始质量浓度为0.32—2.17mg/L时,随着初始浓度的增加,水中Mn²⁺的去除率也增加;pH值为7—9时去除率可达80%以上。核桃壳对Mn²⁺的吸附过程符合准二级反应动力学方程。这说明初始阶段核桃壳对Mn²⁺的吸附受界面扩散控制,之后吸附受粒子内扩散控制。Freundlich等温线模型与实验数据的符合程度比其他的等温线模型要好,这表明发生的是物理吸附。而且对于Freundlich常数n,1/n<1,说明吸附过程较易进行,对于Mn²⁺来说核桃壳是一种适宜的吸附剂。

The Sorption of Manganese Ion in Water onto Walnut Shell

The sorption of Mn²⁺ onto walnut shell is investigated by batch experiments. The recycle of walnut shell as main agriculture and forestry wastes in the wastewater treatment is estimated. The effects of factors, including soil/water ratio, sorption time, initial concentration of Mn²⁺, and pH value on the sorption of Mn²⁺ onto walnut shell are carried out. Furthermore, the dynamics and thermodynamics of the sorption are discussed. The results show that the optimal ratio of soil (g) to water (L) is 50:1. And the optimal sorption time is 90min. When the initial concentration of Mn²⁺ is in the range of 0.32mg/L-2.17mg/L, the removal rate of Mn²⁺ in water increases with increasing initial concentration of Mn²⁺. Above 80% of Mn²⁺ is sorbed onto walnut shell, when pH value is between 7 and 9. The sorption of Mn²⁺ onto walnut shell fits in pseudo-second-order kinetics equation. The fact suggests that the initial sorption is controlled by interfacial diffusion, following by intraparticle diffusion. In addition, the sorption of Mn²⁺ onto walnut shell fits better with Freundlich equation with higher R² value. For the Freundlich constant, 1/n is less than 1. It is indicated that the sorption energy decreases with increasing initial concentration of Mn²⁺. The sorption of Mn²⁺ onto walnut shell likely occurs. In general, the walnut shell is a cost-efficient sorbent for Mn²⁺.