Analysis Method And Formation Of Halogenated Organic Compounds In Water

Halogenated organic compounds（HOCs）exist widely in environmental water bodies,which can seriously threaten the safety of ecological environment and human health due to their carcinogenicity,mutagenicity,reproductive toxicity and bio-enrichment amplification effects.However,it is difficult to identify and quantify all HOCs with current analytical techniques,which hinders the understanding of their toxicity and risk.As an alternative to qualitative and quantitative analysis of HOCs,total organic halide（TOX）aims to quantify the overall HOCs content in environmental water bodies,and has important implications for understanding the generation and toxicity of unregulated and unknown HOCs in water environments.Overall,current TOX assay methods are faced with many problems such as cumbersome operation,complex halogen recovery assay factors,high monitoring cost and low automation.Therefore,it is necessary to improve and develop new TOX assay methods to improve the efficiency of HOCs analysis.Based on solid phase extraction（SPE）separation and enrichment and UV/VUV photolysis,the pre-treatment processes of TOX were studied in this paper with Br-DBPs and I-DBPs.The recovery and retention of SPE to TOX and the conversion efficiency of HOCs to inorganic halide（IX）in UV/VUV photolysis system were measured by high performance liquid chromatography inductively coupled plasma mass spectrometry（HPLC-ICP-MS）.Combined with optimized SPE pretreatment method and Fourier transform ion cyclotron resonance mass spectrometry（FTICR-MS）,the total amount and composition of X-DBPs generated in disinfected water were analyzed.Specific research contents include the following three aspects:（1）SPE was used to separate and enrich HOCs,and HPLC-ICP-MS was used to determine the recovery and retention rates of Br-DBPs and I-DBPs.The recoveries of total organic bromine（TOBr）and total organic iodine（TOI）of five SPE fillers,including HLB and PPL,were investigated.It was found that the recoveries of total organic bromine（TOI）and total organic iodine（TOI）were not more than 45%.The optimization of SPE loading and elution conditions failed to improve the recovery of SPE samples.Further analysis of TOX content before and after column showed that SPE filler had good retention rate for bromine disinfection byproducts（Br-DBPs）and iodide disinfection byproducts（I-DBPs）.At p H=0.5 and 2.0,the retention rates of Br-DBPs and I-DBPs on HLB column could reach more than 90%and 85%,respectively,indicating that the strong adsorption of SPE fillers on some HOCs resulted in low recovery rates of Br-DBPs and I-DBPs,which provided a possibility for the determination of TOX by SPE method.（2）The conversion efficiency of HOCs adsorbed by HOCs and SPE to IX in UV/VUV photolysis system was studied.First,UV-Na₂SO₃,VUV and VUV-Na₂SO₃systems were used to convert the halogenated disinfection byproducts（X-DBPs）generated in the simulated disinfection system into IX,and the corresponding conversion efficiencies were 60.65%,70.43%and 90.72%,respectively,within 30 min.These results indicate that VUV-Na₂SO₃ is more favorable to the conversion of X-DBPs to IX.Under this system,85%of X-DBPs in actual water samples can be converted to IX.Subsequently,SPE packing and its adsorbed X-DBPs were placed in VUV-Na₂SO₃ for photo-dehalogenation.However,due to the light weight of the packing floating on water,the conversion efficiency of X-DBPs was very low.Therefore,it was necessary to reset the reaction system to improve its conversion efficiency.（3）Differential TOX and FTICR-MS assay were used to characterize X-DBPs generated in simulated disinfection systems and X-DBPs that were difficult to elution on SPE.The results showed that in the simulated disinfection system containing 10.0μM Br^–,and 1.0μM I^–,the yield of Br-DBPs and I-DBPs reached 7.31μM and 0.65μM,respectively,after 5 days.Based on FT ICR-MS,572 kinds of Cl-DBPs,121 kinds of Br-DBPs and 222 kinds of I-DBPs were detected,respectively,containing 1 halogen,belonging to tannic acid and lignin organic matter,containing carboxylic acid,phenolic hydroxyl and other functional groups.In terms of element composition,CHO was the most common substance,accounting for 96.68%,74.38%and 45.04%,respectively.The H/C and O/C ratios of Br-DBPs and I-DBPs are significantly different from those of Cl-DBPs,H/C values are specifically I-DBPs>Br-DBPs>Cl-DBPs,and O/C values show a trend of Br-DBPs≈Cl-DBPs>I-DBPs.The X-DBPs components that were difficult to eluate were mainly lignin and tannic acids,mainly polyphenols,phenols and highly unsaturated compounds,and the CHONs showed a trend of decreasing first and then increasing with the increase of p H,from 46.51%to 44.90%and then to 53.06%.However,241 I-DBPs were detected in the actual water samples,mainly containing 1 halogen element,and CHONs and CHOSs were the main elements.Polyphenols,phenols and highly unsaturated compounds were the main types of I-DBPs that were difficult to eluate.