温度对潮土和褐土钾吸附动力学的影响

K^+ Adsorption Kinetics of Fluvo-Aquic and Cinnamon Soil Under Different Temperature

研究了潮土、褐土在 3 种温度下吸附K+的动力学。结果表明,当 K+浓度恒定时,在不同温度下一级动力学方程均是描述K+吸附表观动力学过程的最优模型,温度对其适宜性没有明显影响,Elovich方程的适宜性随着温度的升高而变好,幂函数方程和抛物线扩散方程的适宜性随着温度的升高而变差;一级动力学的表观平衡吸附量q 随温度的升高而减小,表观吸附速率常数k 及其与q 的乘积随温度升高而增大;温度对 K+浓度项的反应级数 ∞a∞和吸附位的反应级数均没有明显影响,皆为1,如果同时考虑浓度和吸附位,潮土和褐土对K+的吸附为二级反应动力学;潮土、褐土吸附 K+的自由能变在-4 444.56～-2 450.63 J·mol-1之间,而且随着温度升高而增大;潮土、褐土对K+的吸附是放热过程和熵减过程,其表观吸附活化能不随温度变化而变化,但0.1 mmol·L-1 K+浓度下的表观吸附活化能是1.0 mmol·L-1 K+浓度下的2.4～2.7倍。不依赖K+浓度的吸附活化能、解吸附活化能、焓变、熵变也不随温度变化而变化,对于所试潮土、褐土,吸附活化能分别为1 730.93和3 260.81 J·mol-1,解吸附活化能分别为22 918.97和18 088.91 J·mol-1,焓变分别为-21 188.04和-14 828.10 J·mol-1,熵变分别为-60和-36 J·k-1·mol-1。

The K+ adsorption kinetics of Fluvo-aquic soil and Cinnamon soil under different temperature were studied. The results showed: 1) the first order equations were the most suitable for fitting the adsorption under various temperature, with temperature increasing, the suitability of Elovich equation increased, while those of power equation and parabolic diffusion equation decreased; 2) the apparent adsorption rate constant ka and the product of ka multiplied by the apparent equilibrium adsorption q∞ increased when temperature increased, while q∞ reduced; 3) temperature influenced hardly the reaction order, the order of concentration and adsorpton site were always 1 respectively under various temperature; 4) the Gibbs free energy change △ G of potassium adsorption increased with temperature increasing, while enthalpy change △ H, entropy change △ S and activation energy Ea were independent of temperature; 5) the sorption were spontaneous process with heat releasing and entropy dropping, Fluvo-aquic soil release more heat than Cinnamon soil.