Study On The Enrichment Process And Mechanism Of Imidazolium Ionic Liquids For Metal Chloro Complex Anions And Group VIB Oxygenate Ions

In this paper,we used imidazole-based ionic liquid as solid phase extractant,studied the enrichment process of trace heavy metals in the form of negative ions in water,and discussed various influencing factors in this process.Through the study of the structure of metal-containing chloro complex anions ionic liquids,the mechanism of enrichment was presumed.The paper is divided into the following four sections:1.In the introduction part,the main physicochemical property of heavy metal HgCl₄^2-and VIB group metal oxide ions,as well as the harm of their pollution on the ecological environment and human health were briefly described.The main sources of heavy metal pollution were also introduced.We introduced the traditional removal methods of Hg?II?,Cr?VI?,Mo?VI?,W?VI?,the advantages and disadvantages of these methods were compared and discussed.The property of ionic liquid and metal-containing ionic liquid were introduced,and the application and development of this material for enrichment and recovery of heavy metals were summarized.2.By polymerizing Styrene and p-chloromethylstyrene,then grafting N-methylimidazole,we designed and synthesized a hydrophobic imidazole-based polymeric ionic liquid.The basic structure of polymeric ionic liquids was determined by 1H Nuclear Magnetic Resonance Spectra?1H NMR?,infrared analysis?IR?and scanning electron microscop?SEM?.The effects of p H,polymer ionic liquid dosage,reaction temperature,interference ions and enrichment time on the enrichment of HgCl₄^2-were studied.The results showed that the polymeric ionic liquid can efficiently recover HgCl₄^2-from wastewater.The metal ions such as Cd2+,Zn2+,Cu2+ and Ni2+ have no interfere with the recovery of HgCl₄^2-.Polymeric ionic liquids showed an excellent selectivity for HgCl₄^2-.Enriching HgCl₄^2-under the optimal conditions,the concentration of Hg?II?was lower than the national emission standard and met the emission standard.3.The process of enrichment of low-concentration VIB group metal oxo acid ions in wastewater was investigated.The effects of solution p H,polymer ionic liquid dosage,reaction temperature,interference ions and enrichment time on the enrichment effect were determined.The results show that the polymeric ionic liquid can efficiently recover Cr?VI?,Mo?VI?and W?VI?from wastewater.The desorption of M?VI?by acid ascorbic acid solution and nitric acid solution has realized the reproducibility of polymeric ionic liquid.After treatment under the optimal enrichment conditions,the concentration of VIB group heavy metal ions in the solution was lower than the limits set by the national emission standard and met the emission standard.4.The metal-containing ionic liquid [Bzmim]2[HgCl₄] was synthesized and characterized by elemental analysis,nuclear magnetic resonance and thermal analysis.By NMR analysis,we found that [Bzmim]2[HgCl₄] has supramolecular effects in addition to the charge effect of HgCl₄^2-and [Bzmim]+.In addition,1,3-dibenzylimidazolium chloride [?Bnz?2im]Cl and its metal compounds [?Bnz?2im]2[MCl₄]?M=Cu,Co,Zn?and [?Bnz?2im][Au Cl₄] were synthetised.We determined the single crystal structure of [?Bnz?2im]2[MCl₄]?M=Cu,Co,Zn?and [?Bnz?2im][Au Cl₄].The structures of [?Bnz?2im]2[MCl₄]?M=Cu,Co,Zn?and [?Bnz?2im][Au Cl₄] were characterized by 1H NMR,IR,and thermal analysis.The results showed that the melting points of the four ionic liquids were all around 100°C and did not decompose under 200°C,they were relatively stable.Hydrogen bonds exist between the metal chloride anion and the benzene ring and the imidazole ring,these hydrogen bonds were very useful for stabilizing the structure of crystal.This result was a good explanation for the mechanism of enrichment of Au Cl₄-using imidazole double-grafted PVC,and laid the foundation for the subsequent work on the enrichment of metal anion with the imidazole double grafted styrene-p-chloromethyl styrene product.