Research On The Total Content And Speciation Analysis Of Hg And Cr In Environmental Samples And Removal Of Cr(Ⅵ) From Water

As an essential component of human survival,the contents and forms of heavy metals in environmental samples have a direct impact on the normal life activities.Accurate determination methods of typical heavy metals as Hg and Cr,methylmercury（MeHg）and hexavalent chromium（Cr（Ⅵ））in soil/sediments and water samples were investigated.The different influence parameters and reaction mechanism on the removal of hexavalent chromium from water by AlFe20 bimetallic materials were researched.The main works were as follows:1.The contents of Cr and Hg in soil/sediments were determined by isotope dilution-inductively coupled plasma mass spectrometry（ID-ICP-MS）.Primary standard solutions of Cr and Hg were used to calibrate the concentrations of 53Cr and 202Hg enriched isotope,respectively.The samples were mixed with 53Cr and 202Hg spikes and digested by acid in PTFE vessel separately.Interference from sample matrix was explored,and the results of Cr under the two modes of H2 and He were compared.5 mg/L EDTA,2.5 mg/L Au solution and 3%HNO₃ were used to flush piping system by turns in order to avoid memory effect of Hg.The calculation results by ratio of 200Hg/202Hg and 199Hg/202Hg were compared.2.The extraction conditions of MeHg in soil/sediments were optimized,accurate determination methods such as ID-GC-ICPMS after purge and trip technique and ID-HPLC-ICPMS were established after method validation by CC580 sediment certified reference material.At the same time,the two methods were used to characterize the content of MeHg in the candidate lake sediment reference material.For the trace MeHg,the purge and trip-GC-ICPMS based on IDMS method has a higher sensitivity and precision compare with ID-HPLC-ICPMS.The contents of Cr（Ⅵ）in soil and water samples were determined by methods of spectrophotometry,Ion chrotography（IC）and（ID）-HPLC-ICPMS.3.The effects of Cu²⁺ and NO₃-to Cr（Ⅵ）removal under the protection of the inert gas by AlFe20 bimetallic materials were studied.It was found that the introduction of a certain amount of CuCl2 salt in water sample could effectively promote the removal of Cr（Ⅵ）pollutants when the pH was not less than 4.2.The mechanism of removal reaction may be due to the active sites of the bimetallic material were strengthened and the surface of the oxide passivation film destroyed through the addition of Cu²⁺,which facilitated the completion of the reaction.