碱性低氧环境中pH对活性炭金吸附的影响

研究了常温碱性低氧环境中pH对活性炭吸附氰金络合阴离子Au(CN)₂^-的影响。等温吸附试验显示,该过程放热,从能级判断应属物理吸附。溶液化学计算和XPS分析显示,在常温碱性低氧的条件下,溶液中或活性炭上的金几乎都为Au(CN)₂^-或其离子对,金吸附过程无明显化学变化。吸附试验表明,金吸附量受pH与离子强度共同作用,且金吸附量随pH的变动规律受离子强度控制,即高离子强度下与pH负相关,反之则正相关。结合电动电位分析和离子对吸附理论推测,在低离子强度下,碱提供吸附紧缺的阳离子,虽然增大体系的电斥力,但整体上仍加强了吸附;而在高离子强度下,体系中阳离子充足,加碱则增大电斥力,削弱了吸附。研究结果表明,金吸附试验必须控制离子强度才能准确反映pH的作用。

The effect of pH on gold cyanide adsorption onto activated carbon at alkalinity with the absence of oxygen

This study presented the effect of pH on the adsorption of Au(CN)2- onto activated carbon at alkaline aqueous solution with the absence of oxygen. The isothermal adsorption tests indicated it was an exothermic physical process. The solution chemical calculation and XPS analysis proven that the most gold were Au(CN)2- in the solution and the activated carbon under the condition, where no obvious chemical change was detected and pH had little effect. The adsorption tests pointed that the variation of gold load with pH was controlled by ionic strength, i.e. they were negatively related at a high ionic strength, while positive at a low one. It was inferred that at low ionic strength, alkali provided the cation in short supply to facilitate the adsorption; at high ionic strength, cations were enough, the addition of alkali increased the repulsion between Au(CN)2- to the activated carbon, which deteriorated the process. Therefore, ionic strength must be controlled to reflect the effect of pH on adsorption correctly.