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采用流动搅动法,在溶液p H、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p H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p H 3.0和p H7.0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298K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(E*a)为14.60 k J·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.
The characteristics of adsorption of arsenite on goethite were studied by using flow-agitation method under the conditions of solution pH, concentration and temperature.The results showed that under different conditions, the adsorption process of arsenite was divided into fast reaction and With the increase of solution pH, the adsorption capacity of arsenic gradually decreased, the apparent adsorption rate constant (k ’) gradually increased, and the half reaction time (t1 / 2) became smaller. The arsenic The shorter the equilibrium reaction time is reached and the constant b of the arsenic diffusion rate gradually decreases.The maximum adsorption of arsenic is 246.9 mg · kg -1 and 99.8 mg at p H 3.0 and p H 7.0 respectively · Kg -1. With the increase of arsenic concentration, the amount of arsenite adsorbed by goethite increased and the apparent adsorption rate constant (k ’) increased gradually. The arsenic concentration was 0.10 mg · L -1 ) And 1.00 mg · L ~ (-1), the maximum adsorption of arsenic was 96.5 mg · kg -1 and 249.1 mg · kg -1, respectively. The Kf value of Freundlich equation over time , And its adsorption capacity is gradually weakened.Langmuir equation distribution factor RL is between 0 and 1, which shows that the adsorption of arsenic on goethite is preferential adsorption.With the increase of temperature, The adsorption capacity increased, apparent adsorption The rate constant k ’also increased gradually, and the maximum adsorption of arsenic was 241.1 mg · kg -1 and 315.6 mg · kg -1 at 298 K and 313 K. The parabolic diffusion equation b (E * a) of 14.60 kJ · mol -1, the enthalpy change (ΔHθ) of arsenic diffusion decreased with the increase of temperature, and the activation energy of arsenic adsorption reaction ΔHθ are positive, the diffusion process for the endothermic reaction, the increase of temperature is conducive to the adsorption of arsenic; activation free energy change (ΔGθ) increases with increasing temperature, increasing the temperature is conducive to accelerating the diffusion process; ΔSθ values Is negative, indicating that the adsorption reaction increases the orderliness of the system.