电感耦合等离子体发射光谱(ICP-OES)法测定含碘附银硅胶样品中碘含量

Determination of Iodine Content in Silver-coated Silica Gel Loaded with Iodine by Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES)

附银硅胶可以吸附放射性碘,形成含碘的附银硅胶,是后处理厂中常用的碘废物吸附材料。含碘附银硅胶样品中碘含量的准确测定能够验证碘的吸附效率,为后处理过程提供数据支持。含碘附银硅胶样品中银离子和碘离子形成难溶的碘化银,在溶解过程中难以将碘化银中碘离子定量转化为可溶解的碘离子、碘单质或者碘酸根,因此含碘附银硅胶样品中碘含量的测试方法比较困难。通过查阅银化合物的溶度积常数,考虑掩蔽银离子对碘离子的影响,在实验中采用加入硫离子的方法,生成比碘化银更难溶的硫化银沉淀,从而消除银离子的干扰。置换出的碘离子能够在碱性溶液中稳定存在,因碘含量较高,可采用电感耦合等离子体发射光谱法(ICP-OES)测定其含量。实验过程中考察了硫化钠加入量、氨水浓度、超声时间等对结果的影响。结果表明,硫化钠加入量与样品中银的含量有关,需要加入过量的硫离子沉淀银离子,不同的氨水浓度影响碘的灵敏度,而超声时间对结果基本无影响,优化实验条件后得到方法的检出限为0.52 mg/g,分别测量两个不同含量的含碘附银硅胶样品,平均值(n=6)为34.8 mg/g和59.3 mg/g,相对标准偏差为2.7%和2.0%,加标回收率为95.0%~103%。方法能够满足含碘附银硅胶样品中碘含量的测定。

Silver-containing silica gel is a commonly used iodine waste adsorption material in post-treatment plants,and can be formed by adsorbing iodine with silver-containing silica gel,which provides a feasible method for treatment of radioactive iodine.The accurate determination of iodine content in iodine-containing silica gel samples can verify the adsorption efficiency of iodine and provide data support for the post-processing process.Silver ions and iodide ions in the iodine-containing silica gel samples form insoluble silver iodide during the dissolution process,it is difficult to quantitatively convert the iodide ions in silver iodide into soluble iodide ions,iodine elements or iodate ions.Therefore,it is difficult to measuret the iodine content in iodine-containing silica gel samples.During the experiment,the effects of masking silver ions on iodide ions were considered.By checking the solubility product constant of the silver compound,the method of adding sulfide ions was used to generate a silver sulfide precipitate that was more difficult to dissolve than silver iodide,thus eliminating the interference of silver ions.The displaced iodide ions existed stably in alkaline solutions,and because of the high iodine content,inductively coupled plasma spectrometry(ICP-OES) was used to measure its content.During the experiment,the effects of sodium sulfide addition,ammonia concentration,ultrasound time,etc.on the results were investigated,and the ICP-OES method was used to measure the iodine content in the samples.Experimental results showed that the amount of sodium sulfide added was related to the silver content,excessive sulfide ions needed to be added to precipitate silver ions.Different ammonia concentrations affected the sensitivity of iodine,while the sonication time had little effect on the results.The detection limit of the method was 0.52 mg/g after optimizing the experimental conditions,and two silica gel samples containing iodine and silver were measured 6 times,with an average value of 34.8 mg/g and 59.3 mg/g.The relative standard deviations were 2.7% and 2.0%,and the recovery of the spiked was 95.0%—103%,which could meet the determination of iodine in iodine-containing silica gel samples.