柠檬酸存在下酸性土壤中铝溶解动力学的初步研究

Preliminary study on the kinetics of Al dissolution in acid soils in presence of citric acid

用一次平衡法研究了柠檬酸存在下砖红壤和红壤中铝的溶解动力学并与高岭石的结果进行比较,结果表明土壤铝的溶解速率比高岭石中的大得多,这主要因为土壤中交换态铝和无定形氧化铝的溶解速率较快,而粘土矿物中铝的溶解速率比较缓慢.红壤中硅、铝释放量的比较证明了这一假设,反应41.5 h,硅的释放量仅为铝的8%.48 h内铝的溶解动力学曲线可分为3个阶段:0～30 min的快反应阶段,主要是土壤交换态铝和结晶不良的氧化铝的溶解;30～120 min的较快反应阶段,主要是铝氧化物的溶解;120 min后的慢反应阶段,主要是氧化铝和粘土矿物中铝的溶解.

The kinetics of Aldissolution in a kaolinite, a red soil and a latosol in presence of citric acid was investigated with a batch method. The results showed that the dissolution rate of soil Al was much larger than that in kaolinite, which was attributed to high dissolution rate of exchangeable aluminum and amorphous Al oxides in soils. The dissolution of Al from clay minerals was very slow and this hypothesis was verified by the comparison between the release of Al and Si from the red soil. The quantity of Si released from the soil was only 8% of that for Al after 41.5 hours. The kinetics curve within 48 hours was divided into three stages: the first stage within 30 minutes was a fast one, in which Al dissolution primarily originated from the exchangeable Aland poorly crystallized Al oxides; a moderate stage was in the range of 30~120 minutes and the increase in soluble Al was mainly attributed to the dissolution of Al oxides in soils; and the last one after 120 minutes was a slow stage and the dissolution of Al chiefly resulted from Al oxides and clay minerals.