柠檬酸铝中铝含量测定方法研究

Determination of Aluminium in Aluminium Citrate

李 岩 谢 春 赵佳丽 毛三鹏

LI Yan XIE Chun ZHAO Jia-Li MAO San-Peng

柠檬酸铝在油田堵水、调剖和驱油作业中应用广泛。在生产和使用过程中需要对铝含量进行监测分析，但有关测定方法未见工业标准或研究报告。按常规络合滴定法测定时，柠檬酸会干扰铝含量的测定。若用加酸消解预处理消除柠檬酸根离子的干扰之后，可用络合滴定法准确测定柠檬酸铝中铝的含量。室内用体积分数大于50%的硫酸/硝酸消解预处理含柠檬酸的十二水合硫酸铝钾样品，滴定前先加入二甲酚橙指示剂，再加入适量氢氧化钠溶液使试液颜色由黄色变为紫色，最后用8%硝酸使试液颜色变至淡黄色，pH值为5.5~6.0，滴定终点明显，相对误差绝对值小于1%。该方法准确可靠，加标回收率为99.46%~100.28%，每次测定的相对误差绝对值均小于2%，平行性好，有效解决了柠檬酸铝产品生产中质量控制难题。

Aluminium citrate was widely used in water shut-off, profile control and oil displacement operation in oilfield. It was necessary to determine aluminum content during the process of producing and using. But the related determination method hadn’t been found in industrial standard or research report. Citric acid would interfere with the determination of aluminum when routine complexometric titration was adopted. The content of aluminum in aluminium citrate could be determined precisely by the way of complexometric titration if the interfere produced by citrate ions was removed by preprocessing with acids. The twelve hydrated aluminum potassium sulfate samples containing citric acid were treated with sulphuric acid and nitric acid whose volume fraction was more than 50% for digestion in the room. Xylenol orange had been put into the samples before titrated. Then an appropriate amount of sodium hydrate solution was added into the test solution whose color changed from yellow to purple. Finally 8% nitric acid solution was used for changing the color of test solution to light yellow. The pH value was between 5.5 and 6.0. Titration end point was clear, and the absolute relative error was less than 1%. The recovery rate with standard sample ranged from 99.46% to 100.28%, and the absolute value of relative error for every determination was less than 2%, which showed good parallelization and had solved the problem of controlling product quality of aluminium citrate timely and effectually.