| 流动搅动法研究针铁矿对亚砷酸盐的吸附特征 |
| 摘要点击 1735 全文点击 687 投稿时间：2016-01-28 修订日期：2016-03-22 |
| 查看HTML全文
查看全文 查看/发表评论 下载PDF阅读器 |
| 中文关键词 流动搅动法 针铁矿 亚砷酸盐 吸附 反应动力学 |
| 英文关键词 flow stirring method goethite arsenite adsorption reaction kinetics |
|
| 中文摘要 |
| 采用流动搅动法，在溶液pH、浓度和温度影响条件下，研究针铁矿对亚砷酸盐吸附的特征.结果表明，在不同条件下，亚砷酸盐的吸附过程分为快反应和慢反应这2个阶段.随溶液pH的升高，砷的吸附量逐渐降低，表观吸附速率常数（k'）逐渐增大，半反应时间（t1/2）也就越小，砷的吸附反应达到平衡时间就越短，且砷的扩散速率常数b值也逐渐降低.溶液pH 3.0和pH 7.0时，砷最大吸附量分别为246.9 mg·kg-1和99.8 mg·kg-1.随着砷浓度的升高，针铁矿对砷的吸附量增加，表观吸附速率常数（k'）逐渐增大；砷浓度为 0.10 mg·L-1和1.00 mg·L-1时，砷的最大吸附量分别为96.5 mg·kg-1和249.1 mg·kg-1.Freundlich方程中吸附常数Kf值随着时间的延长逐渐降低，其吸附能力是逐渐减弱的.Langmuir方程分配因子RL在 0~1之间，表现为针铁矿上砷的吸附为优惠吸附.随着温度的升高，针铁矿对砷的吸附量增加，表观吸附速率常数k' 值也逐渐升高.温度为298 K和313 K时，砷最大吸附量分别为241.1 mg·kg-1和315.6 mg·kg-1.用抛物线扩散方程b值来计算扩散过程的伪热力学常数，砷吸附反应的活化能（Ea*）为14.60 kJ·mol-1.砷扩散活化焓变（ΔHθ）随着温度的升高有所降低，ΔHθ 均为正值，扩散过程为吸热反应，升高温度有利于砷的吸附；活化自由能变（ΔGθ）随着温度的上升而升高，升高温度有利于加快扩散过程；ΔSθ 值均为负，说明吸附反应使体系有序度增加. |
| 英文摘要 |
| Adsorption characteristics of arsenite on goethite under the effects of the solution pH, concentration and temperature were investigated using a flow-stirring dynamic device. The results showed that the adsorption process of arsenic could be divided into rapid and slow reactions under different conditions.The maximum of arsenite adsorption fitted by the first order equation remarkably decreased with increase in the solution pH, for example, 246.9 mg·kg-1 at pH 3.0 and 99.8 mg·kg-1 at pH 7.0, respectively. The rate constant(k')of the apparent adsorption increased gradually along with the increase of solution pH, and so the half reaction time(t1/2)was smaller, and the equilibrium time of arsenic adsorption was shorter. At the same time, the b values of diffusion rate constant were reduced gradually. With the increase of arsenic concentration, the amounts of arsenic adsorption and the k' values increased gradually. The maximum amount of adsorption of arsenic was 96.5 mg·kg-1 and 249.1 mg·kg-1 when the arsenic concentration was 0.10 mg·L-1 and 1.00 mg·L-1, respectively. Adsorption constant(Kf)by the Freundlich equation decreased gradually with the extension of the reaction time and its ability of adsorption was gradually weakened. Distribution factor(RL)by Langmuir equation was between 0-1, and the adsorption of arsenic on goethite was accounted for the preferential adsorption. With the increase of temperature, the maximum amount of adsorption of arsenic was increased, for example, 241.1 mg·kg-1 at 298 K and 315.6 mg·kg-1 at 313 K, respectively. And the k' values of the apparent adsorption rate constant gradually rose in the meantime. The false thermodynamic constants were calculated using the b values of the diffusion rate by the parabolic diffusion equation. The reaction activation energy(Ea*)of Arsenic adsorption was 14.60 kJ·mol-1. The change of arsenic diffusion activation enthalpy(ΔHθ)decreased with the increase of temperature, and ΔHθ was positive in values and on behalf of the endothermic process. So the rising temperature was beneficial to the diffusion of arsenic. ΔGθ of activation free energy was increased as the temperatures rose, and helpful to accelerate the diffusion process. Entropy of activation(ΔSθ)was negative in all cases, suggesting that the system could improve its degree of order. |
|
|
|
