电位滴定法测定Ruthner法盐酸再生工艺流程酸洗液中游离盐酸浓度

采用Ruthner法盐酸再生工艺对酸洗液进行再生处理时,需要及时测定其游离盐酸浓度。当采用通过电位滴定法测定酸洗液中游离H⁺浓度得到游离盐酸浓度的方法时,酸洗液中Fe²⁺和Fe³⁺的存在会干扰测定。实验利用Ca-CaY(0.1mol/L EDTA-0.150mol/L CaCl₂溶液)作为掩蔽剂消除了酸洗液中大量Fe²⁺和少量Fe³⁺的干扰,实现了电位滴定法对Ruthner法盐酸再生工艺流程酸洗液中游离盐酸浓度的测定。试验结果表明,Ca-CaY掩蔽剂的加入不仅对游离酸的测定无影响,且可使pH值的突跃范围变窄;在采用电位滴定法时,设定终点判断阈值为10、终点判断范围pH=7~10、终点识别为最大,可避免pH=6附近的突跃对终点的影响从而获得准确的滴定终点。优化后确定Ca-CaY掩蔽剂用量为10mL。从Ruthner法盐酸再生工艺不同流程中各取1个酸洗液样品,按实验方法测定游离盐酸浓度,并采用间接法进行方法对比。结果表明,采用t检验验证,t为0.51~1.18,小于t_(0.05,9)=2.26,说明实验方法和间接法测定结果无系统差。实验方法测定结果的相对标准偏差(RSD,n=10)在1.5%~2.6%之间。选取Ruthner法盐酸再生工艺流程中的不同酸洗液样品,按照实验方法进行测定,并加入一定量0.1mol/L盐酸标准滴定溶液进行加标回收试验,回收率在96%~103%之间。

Determination of free hydrochloric acid concentration in pickling solution in hydrochloric acid regeneration process of Ruthner method by potentiometric titration

It was necessary to timely determine the concentration of free hydrochloric acid during the regeneration treatment of pickling solution with hydrochloric acid regeneration process of Ruthner method. When the concentration of free hydrochloric acid was obtained with the concentration of free H⁺ in the pickling solution which was determined by potentiometric titration, the presence of Fe²⁺ and Fe³⁺ in pickling solution would cause the interference. After the interference of a large amount of Fe²⁺ and a small amount of Fe³⁺ in pickling solution was eliminated with Ca-CaY solution (0.1mol/L EDTA-0.150mol/L CaCl₂) as the masking agent, the determination of free hydrochloric acid concentration in pickling solution in hydrochloric acid regeneration process of Ruthner method was realized by potentiometric titration. The experiment results showed that the addition of Ca-CaY masking agent had no influence on the determination of free acid. Meanwhile, the jump range of pH narrowed. During the potentiometric titration, the influence of sudden jump near pH=6 on the end-point could be avoided, when the end-point judgment threshold value was set at 10, the end-point judgment range was pH=7-10, and the end-point recognition was maximum. Meanwhlie, the accurate end-point of titration could be obtained. The dosage of Ca-CaY solution was optimized and 10mL of Ca-CaY solution was used in experiments. One sample in each process of hydrochloric acid regeneration of Ruthner method was selected and determined by the proposed method. Moreover, the indirect method was also used for comparison. t test indicated that t (0.51-1.18) was lower than t_(0.05,9)=2.26. In other words, there was no system error between the determination results by experimental method and indirect method. The relative standard deviations (RSD, n=10) of the determination results by experimental method were between 1.5% and 2.6%. Different pickling solution samples in the hydrochloric acid regeneration process of Ruthner method were selected and determined according to the proposed method, then certain amount of 0.1mol/L hydrochloric acid standard titration solution was added into samples for standard recovery test. The recoveries were between 96% and 103%.